Eric's Weather Library

Hurricane Katrina – 10 Years Later

Posted on August 31, 2015 by hippiedippyweatherman

Incredible aerial shot of the flooding in New Orleans after Katrina.
Source: US Coast Guard

I vividly remember the horrible, sick feeling I got as I watched Hurricane Katrina take aim at the Gulf Coast ten years ago. It was like watching a train wreck in slow motion. You knew lots of people were going to die and there was nothing you could do to stop it. It’s a horrible, helpless feeling. Watching the news coverage of the devastation was incredibly surreal. It reminded me of how I felt on 9/11. You feel almost detached, almost as if your mind refuses to believe what your eyes are seeing. “This can’t possibly be happening,” but it is. I’ve often said meteorology is a very humbling field. As meteorologists, we try very hard to see these things coming, but no matter how good technology gets, we can only do our best to predict and understand these events…we can’t stop them. Nature and its fury never fail to remind us of our humanity and our mortality.

A map of the original French settlement at New Orleans, centered on the modern-day French Quarter.
Source: US Census Bureau

Scientists had been warning for years that New Orleans was at serious risk for a major disaster. The handwriting was arguably on the wall. The city was founded in 1718 by French colonists. It was a strategic location along the Mississippi River and was in fact on comparatively high ground compared to the surrounding area. It’s worth pointing out that the elevated area in and around the French Quarter, which was originally the primary settlement, escaped the worst of the flooding in Katrina and sustained relatively little damage. The city’s first major storm hit in 1722, when the Mississippi River rose eight feet and numerous buildings were destroyed. At the time, Biloxi, Mississippi was the capital of France’s Louisiana colony but there was a push to move it to New Orleans because of its strategic location and its rise as a port of importance. The destruction of the hurricane of 1722 led to serious fears about the city’s future and there was significant opposition to the move. Nevertheless, the capital was moved to New Orleans just two years later.

Explorer and astronomer William Dunbar made revolutionary observations during the hurricanes of 1779 and 1780 in New Orleans.

In 1779, 190 years to the day before Hurricane Camille obliterated the Mississippi coast, another significant hurricane struck New Orleans. Louisiana had come under Spanish rule 17 years earlier and Spain had just declared war on Britain. An entire fleet of Spanish ships (save for one) was sunk offshore and numerous ships in New Orleans harbor were thrown well inland. Numerous buildings were leveled, but the city escaped widespread flooding. Scottish explorer and astronomer William Dunbar made a groundbreaking discovery during this storm, correctly theorizing that a hurricane was an independent, progressive-moving storm that rotated around a central vortex. It took a while before this theory was accepted by mainstream science, but Dunbar’s observations proved to be a pioneering meteorological discovery. Another, even worse hurricane hit the following year, sinking every ship on area waters and leveling much of the city. During that storm, Dunbar first observed that hurricanes can produce tornadoes and that such tornadoes tend to be short lived. Just eight years later, much of the city would be destroyed by fire.

A modern reconstruction of the track of the 1812 hurricane based on historical observations.
Source: Mock et. al. (2010)

In 1812, as the eponymous War of 1812 was getting started, an estimated Category 3 hurricane slammed into the delta southeast of New Orleans. Up to 15 feet of water flooded parts of New Orleans and adjacent Plaquemines Parish (where 45 people drowned). However, the 1812 hurricane was much smaller and weaker than Katrina, and rising sea levels and erosion of the delta have greatly increased the danger to the city. In 1831, a powerful hurricane struck central Louisiana, wiping out the village of Barataria south of New Orleans. Lake Pontchartrain burst its banks and flooded northern sections of New Orleans proper. 260 people were killed in the state, 150 in Barataria alone. Six years later, a Category 2 hurricane dubbed “Racer’s Storm” raked the southern Louisiana bayous on an almost west-to-east path. An eight-foot surge into Lake Pontchartrain caused 1-2 feet of water to flood most of New Orleans. Damage in the city was extensive in places, but not major.

The Bruning Grocery store near the shore of Lake Pontchartrain inundated by four feet of water following the 1909 hurricane.
Source: New Orleans Daily Picayune

New Orleans largely escaped the devastating 1856 hurricane that wiped out the resort island of Isle Derniere (Last Island), 75 miles southwest of New Orleans, and killed 400 people. The city again escaped when the state’s worst hurricane in history devastated the bayous of Jefferson and Plaquemines Parishes south of the city in early October, 1893. Several towns were completely wiped out. The village of Chenier Caminada was particularly hard hit, with 779 of its 1,500 residents being killed. In 1909, the city wasn’t so lucky. On September 20, a Category 3 roared over the bayous of Terrebonne Parish southwest of the city. The hurricane devastated rural communities across coastal Terrebonne Parish, where 200 people were killed. Grand Isle has been mistakenly reported to have been destroyed by this hurricane. Storm surge flooding of up to two feet was reported on the island but damage was minor. Lakes around New Orleans burst their banks, flooding the city. The city’s low-lying west side saw the worst of it, with some areas flooded in up to ten feet of water. At the time, however, those areas weren’t heavily developed. That combined with timely warnings (forecasts ahead of this storm were exceptionally good for that day and age) prevented a more devastating human catastrophe. 353 people died in the hurricane in Louisiana.

Wind damage from the 1915 hurricane was severe.

In 1915, the city was hit again. A strong Category 3 not much weaker than Katrina slammed into the southern coast west of Grand Isle on September 29. Plaquemines Parish was devastated. Over 200 people died in the parish, many of whom were never found, and miles of levees were wiped out. In Lafourche Parish, the town of Leeville was leveled and surrounding areas also suffered major damage. A 13 foot storm surge rushed into Lake Pontchartrain and caused parts of New Orleans to flood. It wasn’t as bad as the 1909 storm. The worst of it was in the Mid-City neighborhood after pumps failed. Worse flooding occurred east of New Orleans in St. Bernard Parish. However, the city was rocked by winds that gusted up to 98 mph, causing widespread major wind damage.

Moissant Airport was underwater after the 1947 hurricane.
Source: US Army Corps of Engineers

After that, things got quiet. The city grew and developed, with residential neighborhoods sprawling down off the high ground and into the flood plains surrounding the old city. After the 1915 hurricane, the levees were strengthened and no more floods came. Residents of New Orleans had faith that the levees would hold. The first warning came in 1947. After striking south Florida as a Category 4, a Category 2 hurricane plowed into Black Bay southeast of New Orleans. Low-lying areas of the city suffered relatively minor but widespread flooding. Moissant Airport on the shore of Lake Pontchartrain was under two feet of water. The warning was heeded and again the levees were strengthened, this time with help from Congress. The lakeshore levee and the Orleans Seawall were both increased in height and a new eight foot levee was built along the Jefferson Parish lakeshore. But it wasn’t enough.

This spectacular aerial view of the Lower Ninth Ward after Betsy bears a chilling resemblance to the aftermath of Katrina.
Source: Lyndon B. Johnson Presidential Library

The most terrifying foreshadowing came in 1965. Hurricane Betsy slammed into southeastern Louisiana as a strong Category 4 on September 10. A ten foot storm surge rushed into Lake Pontchartrain, causing the lake and the city’s deepwater canal (called the Mississippi River Gulf Outlet) to burst their banks. Levees along the Outlet and the Industrial Canal failed and large sections of the Ninth Ward and Gentilly were inundated…exactly what happened during Katrina 40 years later. On the south side, the Mississippi River rose over ten feet, causing additional flooding. New Orleans Mayor Vic Schiro was widely hailed for his actions in preparation for Betsy as well as during relief efforts that helped prevent an even more devastating disaster. In the aftermath of Betsy, the levees were heavily renovated by the Army Corps of Engineers. The levees were rebuilt of a stronger material and up to twelve feet higher. They were also expanded in many areas. The Corps had planned to build a large hurricane barrier on the south side of Lake Pontchartrain as an extra measure of protection for the city, but they were sued by an environmental group concerned about preserving area wetlands. To avoid a protracted legal battle, the Corps scrapped the project. It was a decision that would haunt them.

This graphic shows how the storm surge caused the levees and floodwalls in New Orleans to fail.
Source: Tulane University

The reinforcements made after Betsy were in line with the available technology at the time but did not account for the exacerbating effects of a slow-moving storm. Betsy was powerful but moved very quickly. Surge is less driven by the force of the winds and more by the size of the storm, speed of motion, direction to the coast, and the shape of the coastline. This destructive potential was made abundantly clear by Hurricane Georges in 1998, which despite being only a Category 2 and hitting east of New Orleans in Mississippi (keeping the city on the storm’s weaker west side), floodwaters nearly overtopped the levees in places.

In 2001, FEMA commissioned a number of studies on hypothetical disasters, among them a terrorist attack in New York City and a hurricane disaster in New Orleans. The idea of the hurricane barrier was revisited, but the cost was considered prohibitive and the belief was that it would take a 500-year event to breach the existing levee system. Whenever there is a major disaster, it’s always easy to look back and see the warning signs and what we should or should not have done. Hindsight, as they say, is 20-20. FEMA’s greatest failing was most likely its philosophy of reactivity versus proactivity. There wasn’t a system in place for responding to 500-year events or enough emphasis on coordination between local governments and the federal government. However oftentimes our harshest lessons are also the most valuable.

The hard lessons from Katrina prepared us for the havoc unleashed by Sandy.
Source: Daily Mail (UK)

In the years after Katrina we applied those lessons and in October of 2012, those changes were put to the test. Hurricane Sandy was an unprecedented event. Meteorologists who’d been in the business for 50 years had never seen anything like it. Like New Orleans, scientists had been warning for years about the dangers of a hurricane impacting New York City and the Jersey Shore. NYC sits at the peak of a concave coastline, which acts to greatly enhance the storm surge by focusing it on a single point. And there you have tens of millions of people all crammed together on low-lying, flood-prone coastline. It was a worst-case scenario. The Jersey Shore was devastated and New York City saw unprecedented flooding, with damage estimated at $68 billion, making it the second costliest hurricane in history behind Katrina. The death toll in the US was 157, which to me is a borderline miraculous number. I don’t think people appreciate just how easily that number could’ve been in the thousands. Outstanding local leadership and governmental cooperation saved untold lives. I think a lot of that can be attributed to the fundamental changes made in the wake of Katrina. Sandy was a beautiful example of hard lessons beautifully applied to prevent another cataclysm. The material damage was great, but most people lived to pick up the pieces. Things can be replaced, lives can’t. And at the end of the day, that’s one of meteorologists’ greatest responsibilities: keeping people safe from the worst nature has to offer.

Posted in Uncategorized | Tagged Hurricane Katrina, hurricanes, science, weather | Leave a comment

Meteorology’s Magic 8-Ball

Posted on August 24, 2015 by hippiedippyweatherman

The Farmers’ Almanac was first published in 1792, with articles and predictions for 1793.
Credit: Old Farmers’ Almanac

When I was a kid, and a blossoming weather nerd, I used to love reading the Farmers’ Almanac. They always had these cool little tidbits about past weather events and I was always amazed at how they projected tides and moon phases and things like that a year in advance. However, I never paid much attention to their wild weather predictions, as fun as they were. Whenever their predictions panned out though, it always felt like magic. The truth is, however, that there was little science behind this magic. The Farmer’s Almanac is a vestige of a time when meteorology was in its infancy. When the Farmers’ Almanac was first published in 1792 (a competing publication with the same name was published in 1818), we understood very little about how weather worked. In the 19th Century, astrology was quite popular and a common theory was that weather could be predicted well in advance by studying the alignment of planets, the Moon, and the stars.

Stephen Saxby’s prediction of the hurricane that hit New England in 1869 earned him much acclaim but they were based on flawed astrological principles.
Credit: Albert County Museum

On Christmas Day, 1868, British Royal Navy lieutenant and amateur astronomer Stephen Saxby submitted a letter to the editor of the London Evening Standard, predicting severe high tides in the North Atlantic on October 5 of the following year. Nine months later, on September 16, 1869, Saxby submitted another letter, this time warning of an “atmospheric disturbance” between October 5th and 7th at an undetermined location. Lo and behold, on the evening of October 4, a Category 2 hurricane clobbered New England, killing more than a hundred people. Saxby received considerable acclaim for his predictions, and it seemed to vindicate proponents of the theory that the alignment of celestial bodies affected the weather. It was one of the first successful forecasts, but based on flawed principles.

Before modern meteorology, people had to live with the fear that they could be struck with terrible devastation virtually without warning.

Saxby’s ideas were not as outlandish as you may think and it was the source of intense debate at the time. Even in the 19th Century, science had known for centuries that the moon affected the tides. Also, solar activity has now been found to have a major effect on climate. So the belief among many scientists at the time that the answer to our weather lay in outer space was not a farfetched one. Now we know better, and even then Saxby’s ideas were met with substantial criticism, but in the 19th Century, scientists didn’t have a lot to go on. There were no satellites or radar or even airplanes. The only warning came when some other poor sap got hit without warning, be it on land or a ship at sea, and hopefully survived to get the word out to places that might be in its path. This uncertainty understandably led to a lot of fear and people looked desperately for someone to find the answer to the great biblical mystery that was weather and its terrible “Acts of God”. That’s where publications like the Farmers’ Almanac came in. Every year, they came out with predictions based on secret knowledge that at least seemed to get it right a lot. This perception probably had more to do with people being so amazed with the successful predictions that they forgot about the not-so-successful ones, than it did with good science.

The US Weather Bureau, the precursor to the National Weather Service, was founded in 1870 and began regularly producing weather maps, which debuted in the 1860’s. They were part of the wave of scientific innovations in the field of meteorology that took place in the latter half of the 19th Century.
Credit: NWS

But times have changed. Modern technology has allowed meteorology to step out of the realm of mysticism and into real science. Weather radar was born out of the aftermath of World War II and he first weather satellite, TIROS I, was launched in 1960. Innovations such as these revolutionized the field of meteorology and enabled drastically improved forecasts. Also, the 1960’s saw an increase in climatological and statistical research and improvements in modeling. The first forecasting model came out in 1955 and was very primitive by today’s standards but it was a dramatic improvement over what really amounted to educated guesswork. Improved models began to be introduced in the 1970’s. The fear and the uncertainty that the Farmers’ Almanac assuaged began to ebb. The publication has now become more of an amusing oddity than an impactful weather publication, and while its ability to attract young people such as my younger self to weather is admirable, it no longer has the public influence it once did. It has become the magic 8-ball of meteorology. It’s fun to shake it and see what it says about the future, but it would be foolish to take any of it seriously. Reading the Farmers’ Almanac is a bit like reading your horoscope in that as unsubstantiated as the science is, it does raise awareness of things that could potentially happen and may make people pay more attention to real forecasts. That’s what I hope anyway.

I think the Farmers’ Almanac has hung on largely because long-range forecasting remains an area where skill is very poor. We’ve gotten a lot better (and even with all its problems, I’d say current long-range forecasts are still better than Farmers’), but there are still high error rates in products like monthly and seasonal forecasts. As long as there’s that area of uncertainty, I think Farmers’ will find a niche. But more than that, it’s just fun to read, just like anything claiming a magical ability to predict the future. Just be glad we no longer live in a time where the Farmers’ Almanac is all we have.

Posted in Uncategorized | Tagged farmers almanac, forecasting, meteorology, science, weather | Leave a comment

Heat Bursts

Posted on August 12, 2015 by hippiedippyweatherman

Temperature and dewpoint graph from the dramatic heat burst in Sioux Falls in 2008.
Credit: KELO-TV

Heat bursts are rare and intriguing phenomena where air temperature spikes suddenly and dramatically. They are most common at night or during the early hours of the morning. These spikes are often accompanied by severe wind gusts and significant drops in dewpoint (which means the air is drying out significantly). Typically temperature jumps are roughly ten degrees in less than 30 minutes, but extreme cases have been reported. At 3 a.m. on July 11, 1909, the temperature spiked to 136 deg F over a small area south of Cherokee, Oklahoma. Crops were said to have instantly desiccated. Great Falls, Montana experienced a spike of +26 deg F in 15 minutes in the pre-dawn hours of September 9, 1994, topping out at 93 deg F and matching the record high for that day. The temperature was back down to 68 deg F just 20 minutes later. Two of the most well-documented heat bursts took place in Sioux Falls, South Dakota on August 3, 2008 and Wichita, Kansas on June 9, 2011. In Sioux Falls, the temperature rose from 74 deg F to 101 deg F in a matter of minutes in arguably the most dramatic heat burst ever reliably documented. Three years later in Wichita, the temperature went from 85 deg F to 102 deg F in 20 minutes between 12:22 a.m. and 12:42 a.m. This event was recorded by both the National Weather Service and numerous amateur weather stations in the Wichita area.

Temperature graph from the Wichita heat burst of 2011. This was a more prolonged event than the one that hit Sioux Falls three years earlier.

The most infamous heat burst, however, was the one that struck Kopperl, Texas on the night of June 15, 1960. Kopperl is a small town on the north side of Lake Whitney up the Brazos River about fifty miles southwest of Fort Worth. In the hours preceding the event, lightning flashes were seen in the far distance without any thunder being reported (commonly known as “heat lightning,” which is a misnomer…the lack of thunder has nothing to do with heat and everything to do with one simply being too far away to hear it). The temperature was about 70 deg F. Suddenly, just after midnight, the town was hit with a hot blast of wind in excess of hurricane force, reportedly knocking down trees and tearing the roof off a store. The wind was accompanied by a dramatic spike in temperature, surging well over 100 deg F. Thermometers capable of measuring up to 140 deg F reportedly broke as the alcohol inside rapidly expanded. The power in the town failed and people were awakened as their homes were suddenly sweltering and ran outside thinking the homes were on fire. People reported it was so hot, they had difficulty breathing. The next morning, cotton fields were found to be carbonized; burnt to the stalk. The event became known in local lore as “Satan’s Wind” or “Satan’s Storm.”

This story has been told many times and is often repeated in local newspaper articles on anniversary events and in articles posted about heat bursts. How much truth there is to the story is not clear. It was first published in a book about Texas weather by meteorologists Harold Taft and Ron Godbey from the NBC station in Dallas in 1975 and likely comes from local records and community tales. As with many oft-retold stories, over time, legend begins to replace facts. As the old saying goes, “everything gets better in the retelling.” It certainly seems that something dramatic happened there that night, however there is no record in the National Weather Service database of a severe wind event in Bosque County that night (although there was a tornado reported in far north Texas near the Oklahoma Panhandle that afternoon). What is definitively clear is that in the days that followed, a major heat wave struck that area of Texas.

A graphical depiction of how a heat burst occurs.
Source: MeteorologyNews

Other wild stories of heat bursts have come from abroad. Near Lisbon, Portugal, the temperature supposedly rose from 100 deg F to an insane 158 deg F in two minutes on July 6, 1949. In Abadan, Iran, in June of 1967, a ridiculous shade temperature of 188 deg F was reported. Dozens of people supposedly fell dead and the streets and asphalt roads liquefied. These reports are likely both apocryphal. A report of 152 deg F from Turkey in 1977 also seems dubious. There is more support, however, for a report from Kimberley, South Africa of a 43 degree spike in just five minutes during a squall. The report comes from an observer at a local weather station but may be the result of faulty equipment. A significant heat burst likely did occur, however. At Gretna, Manitoba in Canada, there were two successive heat bursts in the early morning hours of July 21, 1960. The temperature spiked 16 degrees Fahrenheit in 15 minutes between 12:25 a.m. and 12:40 a.m. Then, just an hour and a half later, another, even stronger heat burst occurred, surging from the 70’s to 97 deg F also in just 15 minutes. Just last year, in January of 2014 in Melbourne, Australia, the temperature rose from 86 deg F to 102 deg F in roughly an hour. At the same time at the nearby Cerberus naval base, the temperature rose from 76 deg F to 90.5 deg F in just 30 minutes.

This animation shows a traditional “wet” downburst, which is far more visible and gives a good depiction of how powerful these events are.
Source: NWS

So what causes these events? Well, if you have an environment where there is cooler, moist air near the surface and a layer of hot, dry air up higher, what can happen is a thunderstorm moves into that environment and dies. In a thunderstorm, warm air rises in the updraft and cooler air (often accompanied by heavy rain, hail, and all that other fun stuff) comes down in the downdraft. When a thunderstorm dies, its updraft is choked off and it collapses as the downdraft dominates. This collapse can be quite violent, occasionally resulting in a phenomenon known as a “downburst.”

A downburst is a blast of wind caused by the downward surge of air as a thunderstorm collapses, frequently accompanied by heavy rain. When you have hot, dry air in the mid-levels above the surface, there’s no moisture to evaporate to cool the air and what happens is something called “compressional heating.” When air sinks down, it increases in density and causes compression of the molecules in the air, which generates heat. Normally this is offset by evaporating moisture, which has a cooling effect (this is what happens to your body when you sweat). However if there’s no moisture to evaporate, this cooling doesn’t occur. So, not only is the much warmer air aloft thrust down to the surface by the downdraft, the heat is dramatically increased because of the compression effect. This what causes a heat burst. This situation is most common in desert environments, where heating is stronger and that warm, dry layer in the mid-levels is seen more often.

Posted in Uncategorized | Tagged climate, extreme weather, heat, science | Leave a comment

Great Balls of Fire – The Mystery of Ball Lightning

Posted on August 4, 2015 by hippiedippyweatherman

This spectacular image is believed to be the first time ball lightning was ever captured on film. It was taken in Japan in 1988.
Credit: Warren Faidley et. al., Weatherstock.com

It’s among the most bizarre and mysterious natural phenomena that has ever been observed. “Ball lightning” is reported as a fiery ball of light that moves horizontally across the sky. Reports of ball lightning date back to the Middle Ages. In 1638, ball lightning supposedly struck the church of St. Pancras in Widecombe-on-the-Moor, England during a terrific thunderstorm. It crashed through a window, knocked the minister off his feet, singed clothing, and melted metal, but left the wood unharmed. This incident spawned numerous legends about how a local man made a deal with the devil where Satan could have his soul if he fell asleep in church. Supposedly he fell asleep that day. It’s easy to see why the people of that time would see something like that as the work of the devil. It was a ball of fire that smelled of sulfur and tore through the heart of the church.

Numerous ships reported seeing balls of fire in the sky. In 1726, the Catherine and Mary reported that a large fireball blew its mast into “ten thousand pieces.” In 1809, the HMS Warren Hastings reported three “balls of fire” struck the ship, killing two of their crew and setting their mast on fire. Tsar Nicholas II also reported seeing ball lightning as a child during a church service. These events were so rare and so spectacular (and terrifying) that a layer of mythology cloaked the real science, making it hard to separate fact from fiction.

Numerous spectacular tales of ball lightning entering buildings and other structures and causing all sorts of mayhem have been reported. In many of these cases, where the truth ends and the legend begins is murky. However ball lightning has been positively observed passing through the cabin of a plane.

With all this in mind and given the dearth of hard evidence, up until the 1960’s, scientists believed that ball lightning was just an urban legend, despite numerous credible reports. Then, in 1963, a group of scientists flying from New York to Washington, DC saw a bright ball of light move down the aisle and exit out the back of the plane. This incident sparked renewed scientific interest in the phenomena and a number of studies followed. A report in 1972 identified numerous distinct characteristics about it. One thing that is clear is that ball lightning is not very consistent. It almost always occurs during or immediately following a cloud-to-ground lightning strike. Their size varies widely but they’re typically about the size of a grapefruit. It’s about as bright as your standard floor lamp and virtually every color in the rainbow has been reported, with yellow, red, and orange being the most common. They last anywhere from a second to over a minute.

Given that it took decades for scientists to even prove that ball lightning exists, it’s not surprising that its cause remains a mystery. A number of theories have been proposed. The most popular theory is ball lightning is in fact vaporized silicon. Earth’s soil is very rich in silicon dioxide, or silica, and the theory goes that when lightning strikes the ground, that silica is vaporized and split from the oxygen, turning it into pure silicon vapor. This vapor condenses into dust as it cools and is pulled together by the electric charge imparted by the lightning strike. The resulting “ball” of silicon-rich dust recombines with the oxygen in the air, a process (known as oxidization) that generates heat, causing the ball to glow. When the silicon burns out, the ball dies.

A spectrograph showing the mineral composition of ball lightning based on data from the Chinese team.
Credit: Olli Niemintalo

Science has only recently started to get a handle on the phenomenon. Most recent experiments have focused on the vaporized silicon theory. In 2007, researchers from the Federal University of Pernambuco in Brazil were able to replicate this process. They shocked samples of silicon with electricity and were able to produce glowing balls about the size of a golf ball. Eli Jerby and Vladimir Dikhtyar of Tel Aviv University created ball lightning by accident while using a powerful microwave beam to drill into a chunk of silicon. Then, in January, 2014, scientists from Northwest Normal University in Lanzhou, China dropped a bombshell. In July, 2012, a scientific team from Northwest Normal was conducting a study of traditional lighting on the Tibetan Plateau when they observed a glowing ball streaking across the sky just 3,000 feet away from them, lasting approximately two seconds. Their proximity to the event allowed them to capture it with their instruments, including several high tech cameras and spectrographs.

A rare image of ball lightning taken in the Netherlands. Credit: Joe Thomissen

This image believed to be of ball lightning was taken in the Netherlands in 2011.
Credit: Joe Thomissen

Using this data, they were able to determine the composition of the ball’s emissions, which they published in a detailed report in 2014. With traditional lightning, usually only ionized nitrogen is observed. With ball lightning, however, scientists found atomized nitrogen, oxygen, calcium, iron, and…you guessed it…silicon. Calcium, iron, and silicon are all minerals that are common in soil. This is a big win for the theory that ball lightning is a chemical reaction caused by minerals in the ground that are vaporized and electrified by a lightning strike.

There are still many things we don’t understand about this amazing and bizarre phenomenon. How does it go through walls and manifest in enclosed spaces? If it’s caused by lighting hitting the soil, why is it so rare? Are there different types? Many, many questions still remain. But we are getting closer. After hundreds of years of mysterious tales, ball lightning is finally stepping out of the realm of legend and into the realm of science. And I think that’s pretty exciting.

Posted in Uncategorized | Tagged extreme weather, lightning, science, weird weather | Leave a comment

Nature’s Light Show – The Science of Lightning

Posted on July 25, 2015 by hippiedippyweatherman

A spectacular lightning display over Quebec.
Source: JP Marquis

Among nature’s most spectacular phenomena is lightning. Lighting up skies throughout the world millions of times per day, coming in bright flashes and brilliant bolts. What causes this amazing spectacle? It’s all about electrical energy. There remains some debate about exactly what happens, but the basic theory is that essentially an electrical circuit develops between the thunderstorm and the ground, as well as within the cloud itself. Inside a thunderstorm, strong updrafts heave water droplets high into the air, where they freeze into ice pellets. Downdrafts then hurl these ice pellets back down toward the surface. On the way, they run into other water droplets that then freeze on contact as well as other ice pellets that freeze together. This is how hail forms. These collisions cause electrons (which have a negative charge) to break off of drops going up in the updraft and collect on the ones coming down in the downdraft. This gives you a positive charge at the top of the cloud and a negative charge at the bottom of the cloud.

In this graphic, you can see how the most common forms of lightning develop and how the charges are distributed.
Source: University of Alaska-Fairbanks

Remember from high school science class: opposites attract. When you have a difference in charges, it can form an electric field. This is what happens in storm clouds. An electric field develops between the top and the bottom of the cloud. Fortunately for us, the atmosphere is a pretty good insulator, which prevents the sky from lighting up like a Christmas tree with every shower (during the Carboniferous Period roughly 300 million years ago, the atmosphere was much more oxygen rich than it is today, which made the atmosphere much more sensitive to electric charge, producing frequent spectacular thunderstorms unlike any we see today). Because of the insulating effects of the modern atmosphere, an incredible amount of charge has to build up in order to produce lightning. As the updraft strengthens, the charge increases. Eventually it builds up enough to overcome the insulation and you get lightning. This is of the intracloud variety where lighting occurs within the could itself. Lighting can also run between two different thunderstorm clouds, between the positively charged top of the cloud and negatively charged bottom of another. This is cloud-to-cloud lightning; bolts that snake across the sky.

An animation showing how traditional cloud-to-ground lightning forms.
Source: Science Joy Wagon

How does that lightning get to the ground? As the thunderstorm moves, a positive charge builds up on the ground underneath it. Meanwhile, a string of negative charge begins to descend from the cloud. This is called a “stepped leader.” As the charges strengthen, the positive charge on the ground envelopes ground features such as trees, telephone poles, even houses. The charge climbs up as the leader drops down until they meet in a brilliant bolt of lightning.

The reason prominent objects, like trees and tall buildings, are at higher risk is because they effectively decrease the distance between the cloud and the ground, thus requiring less energy to produce a lightning strike. Lightning, as with many things in nature, tends to take the path of least resistance. That doesn’t mean lightning will always strike the tallest object. Exactly what causes lightning to strike a specific place at any given time is something of a mystery, but it’s always where the charge is the strongest, be it a tall tree or a flat field. There are some objects, like metal poles, which are better conductors of electricity and may be more likely to get struck even though there might be, for example, a much taller tree nearby. After an initial lightning strike, if there’s enough charge left over, additional strikes can follow the same path. If you’ve ever seen a lightning bolt that flashed more than once, that’s what’s happening. Sometimes little pieces of charge can extend out, away from the main channel, which is what causes the little forks of lightning we occasionally see.

This spectacular image taken by the late meteorologist Al Moller in 1976 is an excellent example of a positive lightning strike.

There are several different types of lightning. Described above is the most common form, known as negative lightning. However, there is another type called “positive lightning.” Unlike negative lightning, which tends to come out of the base of the thunderstorm, positive lightning comes from the top of the cloud and is positively charged. What happens is that a negative charge builds up on the ground in the wake of a thunderstorm, and on rare occasions the positive charge at the top of the cloud and the negative charge on the ground become powerful enough for their leaders to meet in a bright, long, incredible bolt. These events make up less than 5% of all lightning strikes. The reason is that it takes an incredible amount of energy for them to overcome the much greater distance through the atmosphere. As a result, however, these bolts (sometimes referred to as “Superbolts”) are extremely powerful and dangerous. Superbolts are up to ten times more powerful than average lightning, producing up to one billion volts. Yes, BILLION, with a “B.”

Diagram showing a typical example of a positive lighting strike.

Adding to the danger is that the nature of the charge means that most positive strikes occur well away from the thunderstorm, sometimes as much as ten miles away. They have been reported in areas where no thunder was audible…a proverbial “bolt from the blue.” Positive lighting is also many times brighter, hotter, and longer-lasting than negative lightning, and release a large amount of VLF (Very Low Frequency) and ELF (Extremely Low Frequency) radio waves. They are believed to be responsible for a large percentage of lightning-caused forest fires. They may also be the source of a strange phenomenon called “sprites,” which are little electric discharges observed high in the atmosphere above the tops of thunderstorms. They are often seen by satellites and orbiting astronauts. Sometimes lightning can change polarity (turning from positive to negative and vice versa). This is called “bipolar lightning.”

Another incredible shot of a positive lightning strike.
Source: Kara Swanson/National Geographic

There are some incredible reports about the power of “superbolts.” In 1838, the top-gallant mast of the HMS Rodney was struck and “instantly converted to shavings. The sea looked as if the carpenters had swept their shavings overboard.” A church belfry in England was struck with a bolt so powerful that a stone weighing 350 pounds was thrown 60 yards over the roof and another stone of unknown size was tossed a quarter of a mile. No date was given with this event. In 1959, farmers in Leland, Illinois reported a blinding flash and deafening thunder that shook houses violently enough to break windows and throw loose objects to the floor. Many of them thought they’d been directly hit, but in fact it was an incredibly powerful bolt that struck three quarters of a mile away in a cornfield, leaving a crater roughly ten feet wide and a foot deep. (Extreme Weather, Christopher Burt, 2003, p.149)

What about thunder? How is that created? Well, lightning is extremely hot, as much as 30,000 degrees Celsius (54,000 degrees Fahrenheit)…five times as hot as the surface of the sun! The air we breathe is a gas, and when you heat gas up, it expands. A lightning flash superheats the air around it instantaneously, causing the air to explosively expand beyond the speed of sound and create essentially a sonic boom. Light travels WAY faster than the sound, which is why you see lightning long before you hear it. When the lightning strike is close by, it sounds like a loud boom or crack. This means you’re close enough to hear the single initial shockwave. When you’re farther away, the sound waves blend together and create more of a prolonged rumble. Temperature also makes a difference. If it’s warmer outside, the sound waves travel faster and thus you will hear thunder sooner. When it’s cold out, the sound waves are slower and take longer to reach your ears. The above video shows a lightning strike slowed down frame by frame. You can see the initial strike with branching, followed by a return stroke (the secondary flash).

Credit: William Curstinger

Roughly a hundred Americans are killed by lightning every year. How do you stay safe? Well first, I know it sounds kind of obvious, but don’t be outside in a thunderstorm if you don’t absolutely have to be. All that does is add risk. If thunder roars, go indoors! If you hear thunder, you need to find your way to a safe place. If you are outside and there’s no public building or other shelter nearby, getting in your car is the best option, but any sort of open vehicle like a convertible or golf cart isn’t safe. But most importantly, always keep an eye on weather forecasts whenever you’re planning outdoor activities and always have an idea of what you will do if there’s a lightning threat. Lighting is spectacular display but it is also very dangerous and must always be treated with respect.

Posted in Uncategorized | Tagged lightning, nature, science, weather | Leave a comment

What is the Sea Breeze?

Posted on July 8, 2015 by hippiedippyweatherman

The black arrows point to developing sea breeze thunderstorms. On two of them, you can clearly see a line of small clouds adjacent to the thunderstorms that mark the location of the sea breeze front.
Source: University of Wisconsin

Have you ever been at the beach and noticed thunderstorms build in off the water during the afternoon? That is frequently the result of the sea breeze. You may have heard forecasters on TV use the term before. What is it? It’s all about temperature differences. The ocean absorbs heat from the sun much more effectively than land. The land surface gets hot during the day and cools significantly at night, resulting in large diurnal (day-night) temperature differences. The ocean, meanwhile, has a much smaller day-night temperature fluctuation. During the day, the ocean is significantly cooler than the land. During the summer, this difference is magnified and can cause a circulation to develop.

Schematic showing the sea breeze circulation and the development of the sea breeze front.
Source: NOAA

Physics tells us that warm air rises and cold air sinks, right? Well, what happens during a hot summer day is that warm air rises off the hot land, leading to relatively low pressure at the surface. Higher up in the atmosphere, the air cools and settles, leading to higher pressure aloft. Over the water, the air remains cooler and sinks down to the surface and spreads out (diverges), creating relative high pressure at the surface and low pressure aloft. A basic rule of meteorology is that air wants to move toward areas of lower pressure, so in this situation, the differential pressure causes a circulation. The cooler, denser air mass over the water moves toward the lower pressure on land, clashes with that warmer air mass, and you get a small-scale front. As with a large-scale front, warm air is lifted over it and can generate thunderstorms in the right conditions, with the ocean providing a constant source of moisture to fuel the storms. As the front moves inland farther away from the coast, the temperature difference (or “gradient”) weakens and the front dies out, taking the thunderstorms with it.

Schematic showing the land breeze circulation and the development of the land breeze front.
Source: NOAA

At night, this process is reversed. The land loses heat much more quickly than the ocean, which results in the land being cooler than the oceans. This allows high pressure to develop over land and low pressure over the water, flipping the circulation and forming what is known as a “land breeze”. A land breeze is just like a sea breeze, except the front pushes off the land out over the water. Land breezes are typically weaker and don’t produce thunderstorms. This is because land breezes form in a more stable environment. The cooling land surface doesn’t allow for the lifting necessary for thunderstorm development and the temperature gradient in a land breeze situation is not as strong as with the sea breeze. There is also very little heating present and terrain features of the land surface (trees, buildings, etc.) block air flow from the land to the water. They can, however, result in cloud development. Unlike sea breezes, which occur predominantly in summer, land breezes are more common in the fall and winter, when nighttime temperature differences are the greatest.

A radar image of a lake breeze event over the Chicago metro area. The lake breeze front is clearly visible as the blue line along with its attendant thunderstorms. This event was aided by a large-scale cold front and outflow from previous thunderstorms.
Source: NWS Chicago

The strength of sea breezes is significantly affected by the strength and direction of the prevailing wind. Prevailing winds off the water during a summer afternoon can strengthen the sea breeze and help it penetrate farther inland. Light winds off the land, or opposite the direction the front is moving, can pin the sea breeze near the coast but also allow much more significant and widespread thunderstorm development. Stronger opposing winds, however, can keep the sea breeze over the water, thus preventing thunderstorms from developing at all. On smaller peninsulas, opposing sea breezes can actually collide and lead to very intense, though short-lived, thunderstorms. On larger peninsulas, the opposing sea breezes typically weaken before they reach each other.

This phenomena isn’t restricted to oceans. Any large body of water can experience sea and land breezes. On the Great Lakes, they are known as “lake breezes” and can have exactly the same effects as their oceanic counterparts. Lake breeze thunderstorms are quite common during the summer along the Great Lakes and can be very persistent, due in part to the geography and wind patterns of the Great Lakes region.

So, the next time you go to the beach, keep an eye out for this neat little phenomena. But remember to be safe about it. These storms don’t usually last long but they can be pretty nasty. “When thunder roars, go indoors.” You can always come back later.

Posted in Uncategorized | Tagged educational, science, summer, weather | Leave a comment

Anatomy of a Heat Wave

Posted on June 24, 2015 by hippiedippyweatherman

Man, it’s hot out there! Summer is in full swing and many parts of the US are experiencing their first significant heat wave of the season. That begs the question: what causes a heat wave? Well, the short answer to that is generally a large, tropical high pressure system. A high pressure means air is converging high in the atmosphere and sinking down to the surface, where it spreads out, or diverges. This sinking air has a drying effect, clearing out clouds and leaving us to roast in the summer sun. High pressure systems can also bring in much warmer air from the south, further intensifying the heating. It also has a bad habit of killing off any cooling breezes. In the southeast, however, the drying effect of the sinking air is limited by the tropical influence of the Gulf of Mexico and Atlantic Ocean, with moist air coming off the water. This limits how high temperatures will climb and allows some cloud formation, but it also greatly increases dewpoints and relative humidity. This causes much higher heat indices, or apparent temperatures. In the desert southwest, this tropical moisture is absent, which keeps the relative humidity down but allows temperatures to soar well into the hundreds.

Today’s high temperatures, showing the heat spread across the southeast and southwest, as well as the plains of Kansas.
Source: NOAA

The traditional setup for a heat wave is much like the reverse of a cold wave. In the winter, big Arctic high pressures sweep down from Canada, bringing frigid Arctic air with it. The lack of cloud cover allows the Earth’s surface to lose a lot of heat at night through radiative effects and causes temperatures to plummet. In a heat wave, strong tropical high pressures build in from the south (in the southeast, they can also come from the west or southwest, or the Atlantic to the east), bringing in warmer air from the deserts of northern Mexico, or the tropical Atlantic or Gulf of Mexico. As I mentioned earlier, the clearing of clouds during the peak of the day allows for vastly increased solar radiation. In the Deep South, temperatures closest to the coast are moderated by the presence of the ocean. However, once you move farther inland, there is a stronger continental influence with just enough tropical air to strongly impact heat indices. What you end up with over the interior Deep South is hot and sticky weather with the ever-present chance of thunderstorms.

So what’s happening now? The heat wave in the southeast is cresting today and into tomorrow and is expected to break by the weekend as the high pressure begins to break down. Heat index values as high as 110 can be expected over portions of the South. This intense heating plus the presence of tropical moisture brings with it the possibility of thunderstorms, particularly in the peak of the afternoon. These thunderstorms can develop quickly and are very difficult to predict.

The west is about to really heat up as a high pressure moves north and sets up an intense heat wave.
Source: The Weather Channel

While the South may be cooling off this weekend, the west will be getting even hotter. This one may set records. A high pressure is moving north-northwest from Mexico and bringing intense heat with it. The high temperature in Boise, Idaho is expected to be 107 deg F both Sunday and Monday. Parts of eastern Washington, Oregon, and Idaho could approach 110 deg F. Missoula’s June record of 100 deg F, which has stood for 97 years (it was matched in 1937), is expect to fall, with 102 deg F forecast for Sunday. Nearby Kalispell has never seen triple digit temperatures in June. They’re expected to reach 101 on Sunday. Spokane, Washington’s all time record is 108 deg F. It’s expected to reach 105 on Sunday. Portland, Oregon’s June record is 102 deg F, set in 2006. They’re forecast to reach 101 on Saturday. That record could be in jeopardy. Reno, Nevada’s June record is 104 deg F and they could hit 102 both Friday and Saturday. Salt Lake City’s June record is 105 deg F and they are expected to see 102 on Monday and Tuesday, the final two days of June. Many areas could see one hundred degree temperatures for several consecutive days, threatening further records. Triple digit heat is expected to reach as far north as southern Canada.

So how do you beat the heat? Stay inside as much as possible, but if you must be outside, drink lots of water and take plenty of breaks. Limit time outside as much as possible. Also remember to wear plenty of sunscreen. And watch out for thunderstorms. Remember, when thunder roars, go indoors!

Posted in Uncategorized | Tagged heat, summer, weather | Leave a comment

What El Nino Means for the Atlantic Hurricane Season

Posted on June 16, 2015 by hippiedippyweatherman

Evolution of the present El Niño pattern. This chart shows changes in Pacific Ocean temperature anomalies over the past year, with longitude along the x axis and time on the y axis.
Source: NOAA

Well, after months of indecision, El Niño has finally decided to establish itself. Simply put, El Niño is when the waters of the Pacific Ocean become abnormally warm. This has far-reaching effects on tropical and even global climate. The primary effect of El Niño is drastically increased rainfall across the Eastern Pacific Ocean and the southern United States. We’ve already seen this with the devastating floods in Texas and Oklahoma. By contrast, in the Western Pacific, rainfall is drastically reduced, often leading to drought and wildfires in Australia.

So, what does this mean for the hurricane season? Well, during El Niño years, the spike in ocean temperatures typically increases tropical cyclone activity in the Eastern Pacific. Outflow, the stream of high-level clouds and winds, from these storms combined with enhanced westerly flow aloft into the Atlantic Ocean, typically leads to unusually high wind shear, or change in wind speed and direction with height, across the Atlantic Basin during the heart of hurricane season. High wind shear is a death sentence for a tropical cyclone. It tears them apart from the top down. This is why El Niño years typically see much fewer hurricanes in the Atlantic. A major El Niño event in the early 1980’s effectively knocked out two Atlantic hurricane seasons. There were just ten storms in 1982 and ’83 combined, with a record low four in 1983.

However, El Niño isn’t a guarantee that we’ll get off scott free. One of the four storms in 1983 was Hurricane Alicia, which caused major destruction in the Galveston area of Texas, killing 21 people and causing $2.6 billion in damage ($6.2 billion in 2015). In 1992, just seven storms formed the entire season following a strong El Niño the previous winter. However, one of those storms just so happened to be Hurricane Andrew, which was the most destructive hurricane in US history at the time, causing damage conservatively estimated at $26.5 billion ($44 billion in 2015). Some estimates run as high as $34 billion ($57 billion in 2015). Up to 62 people died.

Hurricane Betsy, in an eerie foreshadowing of Katrina, left large portions of New Orleans underwater. Betsy struck near the peak of a strong El Niño, with +1.7 deg C ocean temperature anomalies present in the Pacific.
Source: University of Texas

El Niño statistically reduces the number of storms in the Atlantic, but how much does it really reduce the risk of a destructive hurricane? The fact is Mother Nature doesn’t follow a rule book. Since 1950, ten Atlantic hurricanes have killed at least 60 people during El Niño conditions. Nine caused over $1 billion in damage, a number that grows to eleven when inflation is taken into account. Audrey devastated southwestern Louisiana during the El Niño of 1957. Flora caused catastrophic floods in Haiti and Cuba that killed over 7,000 people in October, 1963 during a moderate El Niño event, making it one of the deadliest hurricanes in Atlantic history. Betsy became the first hurricane to cause over $1 billion in damage during the heart of a strong El Niño event in 1965 that resulted in just a six-storm season. Camille occurred during a weak El Niño and Agnes, which caused devastating floods across the eastern United States that killed 129 people and was the costliest hurricane in history at the time ($3 billion, $17 billion today), occurred during an even stronger El Niño. Gordon killed 1,100 people in Haiti during the El Niño of 1994.

Damage in Haiti from Hurricane Flora. Flora was the worst hurricane in Haiti’s history and the sixth deadliest Atlantic hurricane on record. It occurred with a +1.2 Pacific Ocean temperature anomaly.
Source: HistoryMiami

Most surprisingly, however, all of the incredible devastation of the 2004 season occurred under weak El Niño conditions that peaked at 0.8 deg C of Pacific warming during the August-September-October time frame. This may explain why the 2004 season became remarkably quiet after mid-September. However, that still didn’t stop Jeanne from plowing into Florida as a major hurricane on September 26. It’s also worth noting that Hurricane Sandy occurred during a brief spike in Pacific Ocean sea surface temperatures (a +0.6 anomaly) that, while not officially classified as an El Niño, was within El Niño parameters for approximately 3-4 months from August into November. The most common examples of major storms in inactive years that I mentioned earlier, Alicia and Andrew, in fact occurred on the backside of weakening El Niños. When Alicia formed, conditions were in fact transitioning to La Niña. All of the others I just mentioned happened with at least 0.5 deg C of Pacific warming, the official boundary of El Niño. Betsy occurred with an astonishing +1.7 deg C warm anomaly present in the Pacific. That year’s El Niño reached peak intensity just a couple of months later.

Looking at the statistics, there have been a total of 45 billion-dollar hurricanes in recorded history. Nine of them, 20% of the total, occurred during El Niño (+0.5 deg C or greater). Nineteen happened during neutral conditions (+0.4 to -0.4 deg C), and 17 were during La Nina (-0.5 deg C or lower). Of the 35 storms that have killed at least 100 people since 1950, 28.6% of them (10 in total) happened during El Niño. Nine storms have caused at least $1 billion in damage and/or 100 deaths in the United States during El Niño (Audrey, 1957; Betsy, 1965; Camille, 1969; Agnes, 1972; Bob, 1991; Charley, 2004; Frances, 2004; Ivan, 2004; Jeanne, 2004) out of 33 total events (28%, expanding the data set to storms with 50+ deaths for the purpose of the chart above adds only two storms…Carol and Hazel of 1954…but reduces the El Niño percentage down to 26%). That means over a quarter of major destructive tropical events happened when conditions were climatologically unfavorable for tropical cyclone development.

Since 1950, there have been 409 hurricanes in the Atlantic Ocean. 33 of them ultimately produced major destructive events in the United States (50+ fatalities and/or $1 billion in damage), or approximately 8%. Eleven of those events occurred under La Niña conditions (2.7%), while nine occurred under El Niño conditions (2.2%). So, based on the past 64 years, El Niño’s presence has reduced the chances of a devastating tropical event by a whopping 0.5% over the dreaded La Niña. Yee ha!

All this highlights the danger of writing off an El Niño year. The tropics, like nature in general, are fickle. You simply cannot expect any particular hurricane season to simply pass quietly into the night. It only takes one.

Posted in Uncategorized | Tagged El Nino, hurricanes, weather | Leave a comment

Dixie Alley

Posted on April 27, 2015 by hippiedippyweatherman

Climatological tornado alleys across the United States. Research has identified at least four significant hot zones of tornado activity. Source: University of Akron

Climatological tornado alleys across the United States. Research has identified at least four significant zones of tornado activity. This is probably a more precise depiction of where these active regions really are.
Source: University of Akron

The vast expanse of the southern Great Plains from central Texas through Oklahoma, Kansas, and Nebraska have become synonymous with tornadoes. The legend of “Tornado Alley” has become ingrained in the American consciousness. This association has been fed by popular culture, with Hollywood movies from the Wizard of Oz to Twister. It’s not without merit either; this region sees more tornadoes than anywhere else in the world, statistically. However, in reality, there isn’t just one “Tornado Alley.” In fact, the two largest and most significant tornado outbreaks in recorded history happened not in the Great Plains, but in the Ohio and Tennessee River Valleys. In the south, there is an intense tornado hot zone that runs from northeastern Louisiana through central and northern Mississippi, northern Alabama, and northwestern Georgia (and sometimes portions of Tennessee are also included). This region doesn’t get any Hollywood movies made about it, but throughout history it has been ravaged by tornadoes.

Devastation in Albertville, Alabama after an F4 tornado struck the town during the Dixie outbreak of April 24, 1908. This tornado killed 35 people and 324 died during the outbreak, which took place almost entirely within Dixie Alley. An outbreak on the Plains the previous day produced an F5 in Nebraska.
Source: NOAA

Plains Alley, the traditional “Tornado Alley,” is nearly twice as large as Dixie Alley, but between 1950 and 2003, Dixie Alley had over a hundred more strong tornadoes (EF3 or greater) than its more well-known counterpart, or roughly 25% more, and 43% of the total tornadoes between the two regions. Since that time, 26 violent tornadoes (EF4 or greater) have struck Plains Alley. Dixie Alley has had 31. The state of Texas has not had an F5/EF5 tornado since 1997. Since that time, Alabama has had at least three (granted, Oklahoma has had at least four…Oklahoma has been the dominant hot spot west of the Mississippi over the past 12 years). However, in the Great Plains, the activity is more widely spread. In Dixie, the intensity is relatively focused on a small area. According to a study by Mississippi State University, south-central Mississippi has the highest likelihood of a tornado hitting within 25 miles of any given point than anywhere else in the country.

Total destruction in the Stacy Hollow neighborhood near McDonald Chapel after the April 15, 1956 tornado.
Source: NOAA

However, the most dramatic difference between Dixie Alley and Plains Alley is the devastation. Dixie Alley is half the size of Plains Alley but is home to seven million more people. Four of the top ten deadliest tornado outbreaks took place almost entirely in Dixie Alley. Three others had at least two strong tornadoes kill at least 20 people in Dixie Alley. Between 1950 and 2013, 716 people died in tornadoes in the state of Alabama, far and away the highest toll of any state. There is a particularly severe section that includes central and northern Mississippi and Alabama, and extreme south-central Tennessee. This region has been ravaged by an astonishing 13 F5/EF5 tornadoes (not counting Tuscaloosa) all time and 50 F4/EF4s since 1950 alone, with major outbreaks also occurring in 1908, 1920, and 1932. This compares favorably to a similar section from central Oklahoma north into central Kansas (along the I-35/135 corridor I like to call “F5 Alley”). Also, interestingly, seven of the top 11 longest-lived tornadoes ever reliably documented occurred in Dixie Alley.

Homes in the Smithfield neighborhood on the north side of Birmingham vanished during the 1977 F5 tornado.
Source: NOAA

The cities of Birmingham, Alabama and Moore, Oklahoma are the only cities to have been struck by an F5 tornado twice. The community of Tanner, Alabama, has been impacted by as many as three (including two in the span of 45 minutes during the Super Outbreak of April 3, 1974…the monstrous Hackleburg tornado of the April 27, 2011 Super Outbreak caused high-end EF4 damage just SE of Tanner, however the rating of the second 1974 tornado is controversial). Jefferson County, Alabama has been struck by five violent tornadoes since 1950, tied with Cleveland County, Oklahoma for the most of any county in the country. Oklahoma City is synonymous with powerful tornadoes. The principle metro area of OKC has been hit by five violent tornadoes in recorded history (1912, 1930, 1942, 1945, 1999), and only one since 1950. Birmingham (which, for the record, is four times smaller than OKC) has also been hit by five violent tornadoes, all of them since 1950 (1956, 1963, 1977, 1998, 2011). Moore, which has been hit by two F5/EF5s and and F4 in the past 16 years, only had one significant event prior to 1999 (1893). Yet Oklahoma, Texas, and Kansas are the areas iconically associated with tornadoes, not Alabama.

Aerial view of the devastation in Phil Campbell after the April 27 tornado.
Credit: HBTV

The point of all this is that it’s a fallacy to select any single area as THE tornado alley. The truth is, there are several “tornado alleys” and there’s limited statistical discontinuities between them. A region encompassing most of Indiana, central and northern Kentucky, western Ohio, and southern Michigan is sometimes referred to as “Hoosier Alley”. The upper Midwest of Iowa, southern and central Minnesota, most of Wisconsin, and northern Illinois is a particularly active area. Portions of it are sometimes incorporated into Plains Alley or Hoosier Alley. Pretty much anywhere between the Rockies and the Appalachians has a statistically significant risk of tornadoes. It’s important to bring awareness to all of these areas, not just the one’s we see in movies. It’s worth pointing out that only half of the ten deadliest tornadoes in recorded American history (plus ties) occurred in either Plains Alley or Dixie Alley. The big ones don’t just happen on the Plains, they can happen almost anywhere, so it’s important to know the risks no matter where you live.

Today marks four years since the April 27, 2011 outbreak and we should never forget that it could happen again, but for our awareness, preparedness, and vigilance.

Posted in Uncategorized | Tagged extreme weather, the South, tornadoes | Leave a comment

The Year Summer Never Came

Posted on April 22, 2015 by hippiedippyweatherman

Tambora today. Source: Smithsonian Institution

Satellite image of the volcano as it is today.
Source: Smithsonian Institution

200 years (and 17 days) ago, the Earth was visited by a terrifying slice of prehistoric oblivion. Mount Tambora sits on Sumbawa Island, a member of the Sunda Islands in Indonesia. Indonesia is a string of volcanic islands that lie along the southwestern edge of the Pacific Ring of Fire. It is home to 141 volcanoes, including the legendary Krakatau (better known as Krakatoa), and the supervolcano Toba that reportedly nearly drove humanity to extinction 74,000 years ago. Tambora made Mt. St. Helens look like a mouse fart. St. Helens spat out roughly 0.3 cubic miles of ash. Tambora released 38 cubic miles of ash. That’s enough to bury the entire state of New York, all 54,555 square miles of it, in 3.7 feet of ash. Its initial explosion was like an 800 megaton nuclear bomb. That’s 61,500 times more powerful than Hiroshima. Think about that for a second. The Hiroshima bomb made a major city disappear, seared people’s shadows into concrete and fused clothes to people’s skin. The Tambora eruption was 61,500 times more powerful than that.

A contemporary etching of the eruption.

Before 1815, Tambora hadn’t erupted in a thousand years. Many scientists believed it was extinct. Volcanism in Indonesia in general had been remarkably quiet for over a century. The country hadn’t had a major eruption since a relatively modest VEI 4 eruption (on a 0-8 scale, St. Helens was a 5, Tambora a 7) reportedly killed 3,000 people on the island of Halmahera and nearby islands in 1760. No eruption more powerful than that had happened there since the 1600’s. People simply stopped thinking about it. Beginning in 1812, however, things began to change. Residents heard rumbling coming from the mountain and periodic earthquakes occurred. Occasionally, a dark cloud wafted up from the mountain’s summit. For a while, nothing happened, but as the months passed, the earthquakes grew more frequent. Then, three years after the volcano awakened from its slumber, the unthinkable happened.

On April 5, 1815, Tambora exploded. Massive booms reverberated for hundreds of miles. People on Sumatra, 1600 miles away, heard what sounded like gunshots. British troops on nearby Java, which had been temporarily seized by the British to prevent it from falling to Napoleon after Indonesia’s colonizers, the Dutch, lost their homeland to the French, were mobilized because it was initially thought they were being attacked by naval cannon. Five days later, on the evening of April 10, the eruption intensified. Witnesses reported seeing three columns of ash and flame swell and merge together, towering high into the sky. Lava began to pour down the mountainside toward the villages below. Ash and pumice rained down and began to bury the landscape. Thick clouds of ash covered the sky as far away as Jakarta, nearly 800 miles away. People in Jakarta (then called Batavia) reported smelling a “nitrous” odor as a dark, ash-filled rain began to fall.

The pyroclastic flow from the Mt. Pinatubo eruption in 1991. The Tambora eruption was 14.5 times more powerful.
Source: PBS

Back on Sumbawa the situation was dire. Huge clouds of intensely hot rock, ash, and gas called pyroclastic flows surged down the mountain at very high speed, annihilating everything in their path, spreading out up to 12 miles from the summit. Pyroclastic flows are one of the volcano’s greatest killers. Much like a nuclear blast, exceptionally few of those caught in one live to tell about it. It was the pyroclastic flow that wiped out the people of Pompeii, many of them killed where they stood, frozen in horrifying repose before being entombed in ash for 1800 years before being excavated. Roughly 10,000 people met the same fate on Sumbawa. 38,000 more starved as all the island’s crops were wiped out. The entire island was stripped of vegetation. Everywhere within up to 370 miles of the summit was plunged into pitch darkness for up to two days.

A British military officer sent to the island by the Lieutenant-Governor of Java reported that bodies were strewn neglected by the sides of the roads. Virtually every survivor had been left homeless and they scrounged desperately for food. Water sources were contaminated by toxic ash and diarrhea was rampant, drastically increasing the death rate. It wasn’t much better on neighboring islands, as ashfall wiped out crops and created widespread famine. In those days, information traveled slowly, and with all the world’s major powers just coming out of major warfare, few resources were available to provide relief. On Sumbawa and surrounding islands, at least 71,000 people are believed to have died, making it the deadliest volcanic eruption in recorded history.

Temperature anomalies for the summer of 1816 in Europe.
Source: NOAA

The volcano’s effects were felt worldwide. The dust and ash from Tambora soared high into the atmosphere and was carried around the world by the jetstream, plunging the planet into a volcanic winter. Skies over England filled with dust and spectacular sunsets were reported across Europe and North America. Portions of central Europe experienced brown and red snow, tinged by the ash high in the atmosphere. August frosts were reported. Switzerland was particularly hard hit. Over the succeeding two years, the country’s average mortality rate doubled. It was so cold that an ice dam formed at the edge of Gietro Glacier, which then catastrophically collapsed in 1818, killing 44 people. Unusually heavy rains caused floods on Europe’s major rivers.

The eerie color of the sunset in this painting of the Chichester Canal in England by J.M.W Turner is believed to have been inspired by the atmospheric phenomena occurring across Europe and North America during the summer of 1816.

A persistent fog or mist shut out the sun across the United States and Canada. In 1816, throughout much of the northern hemisphere, summer never came. Portions of upstate New York reported sub-freezing temperatures throughout May. It snowed as far south as Pennsylvania in early June. Quebec City, Canada and the higher elevations of Vermont and New Hampshire received a foot of snow between June 6 and June 8. Lake and river ice was reported as far south as northwestern Pennsylvania throughout the summer. Frosts were reported as far south as Virginia on August 20/21. The Berkshire Hills of Massachusetts and Connecticut reported frost on August 23. Some areas recorded major frosts every month of the year. All of that from something that happened on the other side of the world. However, normal or even above normal summertime temperatures were reported at times, with the cold extremes happening at the end of wild temperature swings. Curiously, the Atlantic hurricane seasons of 1815 and 1816 appear to have been quite active, despite the record-cold summers (indeed, a hurricane struck the Florida Keys in early June, 1816 as snow was falling in New England). The 1817 season was much less active but it’s not clear if the aftereffects of the eruption had anything to do with that.

Sunset in Hong Kong nine months after the Pinatubo eruption in the Philippines, giving us a glimpse at how the skies over Europe and North America may have looked after the Tambora eruption. Note the low, dense veil of dust hanging over the water like smog.
Source: Wikipedia

Outside the Western Hemisphere, snow also fell on tropical Taiwan. Wintry precipitation was also reported in eastern China at latitudes comparable with the southeastern United States…in summer! Crops across China were wiped out. A severe monsoon season led to widespread devastating floods in China and India. Even when the winter finally abated, the weather remained miserable. Much of the northern hemisphere was mired by chilly weather and persistent rain and cloudiness.

The weather inspired a group of young authors and friends, Mary Godwin, John William Polidori, and Lord Byron, to challenge each other to see who could write the scariest story. Godwin, together with her future husband Percy Shelley, wrote Frankenstein, and Byron wrote a piece called A Fragment. Byron’s work inspired Polidori to write The Vampyre a few years later, which in turn inspired Bram Stoker’s Dracula as well as Alexandre Dumas’ The Count of Monte Cristo and is considered one of the founding works of the vampire genre and a hallmark of Gothic literature. Byron also wrote the poem Darkness about the persistent gloom. Oats to feed horses were so scarce that a German inventor, Karl Drais, came up with human-powered wheeled machines that were the precursors to the modern bicycle so that people could get around without horses.

Another Pinatubo sunset, this one was taken in Hawaii in the summer of 1991. Long after the sun had gone, the sky turned an intense red that lingered long after the usual twilight. This exact same phenomena was reported in Europe and the US after Tambora.
Source: Richard Fleet

Widespread crop failures brought on by the bitter cold of 1816 and 1817 had devastating effects on Europe and North America. Europe saw its worst famine of the 19th Century. Riots and looting were common as food prices soared. In the US, the famine was exacerbated by poor transportation networks (the Transcontinental Railroad was still nearly 40 years away), making it hard to import food. A typhus outbreak ravaged Ireland, killing 100,000 people. At least another 100,000 are believed to have died in Europe from the extreme conditions. In China, thousands starved. The exact death toll will likely never be known. Gillen D’Arcy Wood’s book Tambora: The Eruption that Changed the World paints a very dramatic picture of the dire conditions in some parts of China. “Famished corpses lay unmourned on the roads; mothers sold their children or killed them out of mercy; and human skeletons wandered the fields, feeding on white clay.” Local poets spoke of barren fields; never-ending rains; and desperate, starving people.

Modern researchers have questioned whether Tambora was the sole culprit of the upheavals of 1816 and 1817. Four VEI 4 eruptions had happened worldwide in the preceding three years and the Tambora eruption occurred during a period of low sunspot activity called the Dalton Minimum. All of these probably contributed to the severity of the climate impacts caused by the Tambora eruption.

Today, Tambora is quiet. The volcano hasn’t had an explosive eruption since 1880 but remains active. The area’s population has dramatically increased, and Tambora’s terrifying history earns it considerable attention from scientists. In recent years, periodic seismic activity around the mountain has been reported, just more reminders of the threat the volcano still poses.

The Tambora caldera as it looks today. The caldera was formed by the massive 1815 eruption.

Volcanic cataclysm of this magnitude is typically only found in ancient rocks and sediments of long-quiet craters, evidence of a hostile Earth whose ravages were wrought long before humans ever walked upon it. Today, we fear more the havoc we might wreak upon the Earth than the havoc it might wreak upon us. The pursuit of softer footprints and more conscientious stewardship is a noble one, but we should never forget how powerful this great planet is. It can uproot our peaceful existence and throw our society into turmoil at a moment’s notice. Events like Tambora, if nothing else, should remind us to appreciate today, because tomorrow isn’t guaranteed.

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