Dr. Jeff Masters' WunderBlog

New Orleans' Achilles Heel: a Storm Surge on the Mississippi River?

By: JeffMasters, 7:23 PM GMT on June 27, 2013

In the wake of the unthinkable devastation wrought by Hurricane Katrina in New Orleans in 2005, Congress approved a $14.5 billion upgrade to the city's flood defenses--the Hurricane and Storm Damage Risk Reduction System (HSDRRS), a 139-mile system of levees, walls and gates designed to protect against a 1-in-100-year storm surge, equivalent to what a Category 3 hurricane would bring. The last link of this formidable barrier system was completed on June 17, when the Army Corps of Engineers announced that they had finished a $3 billion flood-control ring around the West Bank of Orleans, Jefferson, Plaquemines and St. Charles parishes, on the opposite side of the Mississippi River from New Orleans. The only work remaining on the $14.5 billion Hurricane and Storm Damage Risk Reduction System is a $615 million project to install three permanent pumps to replace temporary pumps installed on canals leading from New Orleans into Lake Pontchartrain. The new flood defense system already has undergone a stern test, thanks to Hurricane Isaac of 2012. Isaac was a large, slow-moving Category 1 storm with 80 mph winds that brought a storm surge characteristic of a Category 2 storm to New Orleans. The new flood defenses performed admirably, giving confidence that the city's new flood defenses can indeed withstand the 15' storm surge that a 1-in-100 year Category 3 hurricane might bring. The Louisiana coastline has experienced 59 hurricane strikes since 1851 (including Isaac), but only one of these hurricanes brought a storm surge to New Orleans capable of overwhelming the 2013 levee system--if it behaves as designed. That storm was the deadliest hurricane in Louisiana history, the 1893 Chenier Caminanda hurricane, which hit the coast south of New Orleans as a Category 4 storm. Over 2,000 people died in the storm, mostly due to storm surge.


Figure 1. The Gulf Intracoastal Waterway West Closure Complex, part of the $14.5 billion upgrade to New Orleans' flood defenses in the wake of Hurricane Katrina.

New Orleans' Achilles Heel: the Mississippi River levee system?
But the New Orleans levee system has an Achilles' heel, one that makes it vulnerable to a mere Category 1 hurricane storm surge. That weakness is the levees that protect the city from the Mississippi River. Although these levees lie more than 100 miles upriver from the Gulf of Mexico, hurricane storm surges from five storms over the past 50 years--Betsy (1965), Katrina (2005), Georges (1998), Isaac (2012), and Gustav (2008)--have pushed storms surges of seven feet or higher upriver to New Orleans. These large surges can occur because strong sustained easterly winds push water into shallow Breton Sound, overtopping the river?~@~Ys east bank south of Pointe ?| la Hache, Louisiana. The surge then penetrates into the Mississippi River, and is confined by levees on the west bank. The main channel?~@~Ys width and depth allow the surge to propagate rapidly and efficiently upriver. Normally, these storm surges moving up the Mississippi River are not a concern for New Orleans, since hurricanes typically arrive in August, September, and October, when the river is at its lowest flow levels, more than 15' below the tops of the levees. But if any of these five hurricanes had occurred when the Mississippi River was in flood--when the river is just 3' below the tops of the levees in New Orleans--the storm surge coming up the river would have easily pushed water over the tops of the levees, filling the below-sea level bowl that much of the city lies in. For example, Hurricane Katrina pushed the highest storm surge on record up the Mississippi River, reaching 13' in New Orleans. But since the river was only at a 3' water level prior to the hurricane, the surge stayed 4' below the tops of the levees. But it wouldn't take a Category 3 hurricane to flood New Orleans if the Mississippi River were at flood stage. A large, slow-moving storm like Hurricane Isaac of 2012 would be able to overwhelm New Orleans' flood defenses. During Hurricane Isaac, a storm surge estimated at 12' moved up the Mississippi in Plaquemines Parish, south of New Orleans. Since salt water is more dense than fresh water, the surge traveled along the bottom of the river, with the fresh water flow of the river lying on top. The surge continued upriver, and before reaching New Orleans, encountered an underwater barrier in Plaquemines Parish. This barrier was constructed by the Army Corps of Engineers in the summer of 2012, in order to keep salt water from moving upstream and contaminating the drinking water for Plaquemines Parish and New Orleans (salt water had made it 90 miles upriver to the outskirts of New Orleans, due to the river being 7' below average in height due to the drought of 2012.) The barrier was able to completely block the flow of salt water upriver, and no salt water made it as far as New Orleans. However, the massive intrusion of ocean water into the river channel caused the mighty Mississippi's fresh water flow to back up for hundreds of miles. Water levels were elevated by 10' in New Orleans (103 miles upstream from the mouth of the Mississippi), 8' in Baton Rouge (228 miles upstream), and 1.4' at Knox Landing, an amazing 314 miles upstream.


Figure 2. Carrollton gage on the Mississippi River at New Orleans. Flood stage on the gage is at 17', which is 3' below the top of the city's levees. Image credit: USACE.


Figure 3. Water level at the Carrollton gage on the Mississippi River at New Orleans during 2013 (solid black line) and during 2012 (dashed black line.) The river is currently 9' higher than it was in 2012. The passage of Hurricane Isaac August 28 - 30, 2012 is apparent as a sharp spike from two to nearly ten feet (the water level actually hit eleven feet, but the averaging in this plot obscures this fact.) Prior to Isaac's arrival, the river was running just two feet above its record low. Isaac drove a storm surge of ten feet to New Orleans, raising the river level to a stage height of eleven feet. Levees on the Mississippi protect New Orleans to a stage height of twenty feet, so Isaac's storm surge was nine feet below the tops of the levees. Image credit: rivergages.com.


Figure 4. Water level at the Carrollton gage on the Mississippi River at New Orleans during the passage of Hurricane Isaac in August 2012. Prior to Isaac's arrival the river was running just two feet above its record low. Isaac drove a storm surge of ten feet to New Orleans. Levees on the Mississippi protect New Orleans to a stage height of 20 feet, so Isaac's storm surge was nine feet below the tops of the levees. Image credit: NOAA Tides and Currents.

The risk of an early-season hurricane hitting during a Mississippi River flood
A huge pulse of flood waters began heading southwards down the Mississippi River in late May, thanks to runoff from torrential rains associated with the deadly thunderstorms that killed 23 people in Oklahoma. The river crested at major flood stage in St. Louis on June 4, and that crest propagated steadily downstream, reaching New Orleans on June 20. The river crested at 12.9', which is about 7' below the tops of the levees protecting the city from the river. The river is will slowly fall over the next few weeks. However, the Upper Mississippi River will reach major flood stage during the first week of July, due to heavy rains over the past week. This pulse of flood water will arrive in New Orleans in late July, keeping the river level higher than average. A slow-moving Category 1 hurricane like Hurricane Isaac hitting during July or August this year could potentially have a storm surge capable of overwhelming the river's levees and flooding the city, due to the relatively high water in the Mississippi River this summer.

While I expect that the risk of storm surge flooding in New Orleans due to an early season hurricane hitting when the Mississippi River is high is only about a 1-in-250 year event, we should expect an increase in this risk in future years, due to climate change. As I blogged about earlier this June, the Atlantic hurricane season is getting longer in association with increased ocean temperatures, and more early-season named storms are occurring in May and June. Heavy precipitation events--predicted by climate models to increase due to more heat and moisture in the atmosphere from global warming--are also on the increase in the U.S., raising the odds of unusually high water in the Mississippi River. Fortunately, the latest 2-week forecast from the GFS model predicts high wind shear over the Gulf of Mexico well into July, and there are no predictions from our reliable models of a potential tropical storm forming in the Atlantic through at least July 3.

A 20% chance that New Orleans will suffer a catastrophic flood in the next 30 years
According to the Army Corps of Engineers, New Orleans' flood defenses currently protect the city from a 1-in-100 year hurricane storm surge, and from a 1-in-750 year Mississippi River flood. A 1-in-100 year flood has a 26% chance of occurring in a 30-year period, so I rate New Orleans' odds of suffering a catastrophic flood that overwhelms its flood defenses at about 20% over the next 30 years. However, these odds are gradually increasing. Coastal Louisiana is sinking, and sea level is rising. These twin effects have given Southern Louisiana the highest levels of relative sea level rise of anyplace in the U.S.: 3' over the past 100 years. While the state of Louisiana has recently approved an ambitious $50 billion plan to help slow down subsidence by diverting sediment from the Mississippi River into coastal marshlands, sea level rise will not slow down this century unless strong action is taken by the nations of the world to cut down Earth's fever by limiting burning of coal, oil, and natural gas. The strongest Atlantic hurricanes are expected to grow stronger and dump up to 20% more precipitation by century's end, increasing the odds of a catastrophic New Orleans flood. New Orleans will need additional multi-billion dollar flood defenses in coming decades if we hope to keep the city. And the U.S.--and the world--need New Orleans. There has to be a port at the end of the Mississippi River. Between Baton Rouge and New Orleans, the Lower Mississippi River has four of the fifteen largest ports in America, which handle over 60% of all U.S. grain exports to the world, thanks to the barges moving downriver. Going upriver, those barges transport the petrochemicals, fertilizers, and raw materials essential for the functioning of U.S. industry and agriculture. When those ports have been closed due to barge accidents or high water levels, the cost has been $300 million per day to the U.S. economy. If we lose the Port of New Orleans for an extended period of time, there are major impacts to the U.S. economy, global economy, and world food supplies. Though the cost would be huge--in excess of $100 billion-- we should consider building at least 1-in-1,000 year flood defenses for New Orleans. The Netherlands has built 1-in-10,000 year flood defenses for their important cities--why are we building only 1-in-100 year defenses, which will only offer more like 1-in-50 year protection by mid-century?

Recent storms surges on Mississippi River at New Orleans
Below is a look at the the tracks of all of the named storms during the period 2008 - 2012 that affected Louisiana, and the level of storm surge experienced on the Mississippi River at New Orleans.


Hurricane Isaac brought a storm surge of 10' to the Mississippi River at New Orleans. Isaac made landfall in Louisiana on August 29, 2012, as a Category 1 hurricane with top winds of 80 mph.


Hurricane Gustav brought a storm surge of 7' to the Mississippi River at New Orleans. Gustav made landfall in Louisiana on September 1, 2008, as a Category 2 hurricane with top winds of 105 mph.


Tropical Storm Ida brought a storm surge of 3' to the Mississippi River at New Orleans. Ida made landfall on November 10, 2009, in Alabama with top winds of 60 mph.


Tropical Storm Lee brought a storm surge of 2' to the Mississippi River at New Orleans. Lee made landfall on September 3, 2011, on the Central Louisiana coast with top winds of 60 mph.

Other recent named storms that have brought a storm surge of 2 - 3' to the Mississippi River at New Orleans include: Tropical Storm Bill (2003), Tropical Storm Isidore (2002), Hurricane Lili (2002), Tropical Storm Hanna (2002), Hurricane Danny (1997), Hurricane Andrew (1992), Hurricane Florence (1988), and Tropical Storm Beryl (1988).

Thanks go to wunderground member Patrick Pearson for providing some of the links used in this article.

This will be my last "live" post until Tuesday, as I'll be taking a few days off. There's going to be a wicked hot heat wave over the Western U.S. and Western Canada while I'm gone, and wunderground's weather historian, Christopher C. Burt, will be updating his blog over the next few days if some notable all-time extremes are observed.

Jeff Masters

Tropical Hurricane

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Quarterback Obama's New Climate Change Game Plan

By: JeffMasters, 1:29 PM GMT on June 26, 2013

Ever since the dawn of human civilization, we've been playing a high-stakes game against Mother Nature. The game: the survival and advancement of civilization. We've done very well at this game over the past century. Humanity has seen tremendous increases in health, life expectancy, and standard of living. Much of the credit for our successful scores against Mother Nature goes to cheap energy afforded by burning Earth's abundant fossil fuels (coal, oil and natural gas.) But we've grown complacent against our foe. In our enthusiastic push to reduce poverty and advance standards of living, we've ignored the greater game: survival. We've ignored the rules of the game: basic physics. If one increases levels of heat-trapping carbon dioxide by 42%, melts away half of the summertime sea ice in the Arctic, changes the reflectivity of the surface by replacing up to half of Earth's land area with crops and cities, puts massive clouds of sunlight-reflecting and sunlight-absorbing soot and pollution into the air, and opens up a huge ozone hole in the Antarctic--as humans have done since in recent decades--physics demands that the weather and climate must change significantly. Since civilization is adapted to the old climate, any shift to a new one will be expensive, destabilizing, and deadly.

Like a game of football, the battle for civilization's survival has Mother Nature stacking the line against us with beefy linemen. Each year that carbon dioxide increases another part per million (ppm), it's like giving Mother Nature's linemen an injection of steroids. They add another pound of bulk, get another millimeter taller, another split second faster. We blew past the "safe" level of CO2, 350 ppm, back in 1988, when Mother Nature had 350-pound linemen. Now in 2013, with 400 ppm of carbon dioxide in the air, the opposing linemen are 400-pound behemoths. These increasingly fearsome opponents have been blitzing our team with tremendous ferocity of late, causing huge losses. There were eleven billion-dollar disasters in the U.S. in 2012--a number surpassed only by the fourteen such disasters the year before. We had the hottest year on record in 2012, and largest drought since the 1930s Dust Bowl. The previous year, 2011, saw the greatest floods on record on America's three biggest rivers. While some of these losses could have happened if Mother Nature had had her old 280-pound linemen--like in the late 1800s--450 pound linemen are much more likely to tear into the backfield and create huge losses. Heat waves, floods, and droughts are the sort of extreme weather events that climate change can make more intense and frequent.


Figure 1. On a hot day at Georgetown University, President Barack Obama removes his jacket before speaking about climate change on Tuesday, June 25, 2013. AP Photo.

Lined up against Mother Nature's increasingly imposing linemen has been a team afraid to rise to the challenge. Our quarterback, President Obama, has merely been handing off the ball--running "safe" plays into the line that gain little or no yardage. We've had only one first down since Obama took office--a major increase in fuel efficiency for cars--and the game is already getting late into the second half. Mother Nature has been running up the score against us. A lot of the fans in the stadium have tuned out the game, focusing instead on fights in the stands or getting beer at the concession stand. Many of the commentators have not been reporting the score, or claiming that the rules are different than what they really are. But this game is deadly serious. We must limit global warming to 2°C (3.6°F)--the generally accepted threshold for "dangerous" civilization-destabilizing climate change. We're already one-third of the way there. The fact that we are seeing increasingly wild weather extremes at that level of warming is not good. We are experiencing the outer spiral bands of the coming climate change storm, and it is too late to avoid major damage. But it is not too late to avoid catastrophic damage. Our current policies have us on track to warm the planet by 5°C (9°F) by 2100, a level that would cause Category 5-level devastation to human civilization. We must do everything possible to avoid that future. The measures that Obama proposed in his speech are significant steps that will help. The directive to the EPA to move forward to regulate emissions of carbon dioxide from power plants--the source of 40% of our nation's CO2--is particularly significant. It's great to see our quarterback showing the guts to make some riskier plays, and try and make a first down. And it's great to see the team take measures to beef up our linemen against Mother Nature's bigger line, by putting money into climate resiliency and defending our coasts against higher storm surges. But if we hope to score a lot of points, win the game, and keep global warming under 2°C, much stronger action--both in the U.S. and internationally--is needed. Nature does not care about what is politically possible. All it cares about is physics. Fundamentally, what are the levels of heat-trapping gases like carbon dioxide? How much sunlight is arriving at the surface? We badly need all of the major carbon-polluting nations to agree on and implement very aggressive efforts to cut heat-trapping gas levels within the next 5 - 10 years, or I fear we will have to start throwing the equivalent of "Hail Mary" passes to win the game--high-risk efforts to geo-engineer the climate to slow down climate change. The cost of inaction is much higher than the cost of action. The International Energy Agency says that in order to keep global warming below 2°C, "Delaying stronger climate action until 2020 would avoid $1.5 trillion in low-carbon investments up to that point, but an additional $5 trillion would then need to be invested through to 2035 to get back on track."

I am optimistic that we prevail and keep a livable climate. President Obama reminded everyone today of the tremendous power of American business and ingenuity, and I strongly believe those qualities will be instrumental in helping us meet the greatest challenge of our generation--climate change.

Links
Wunderground's climate change blogger Dr. Ricky Rood offers his take on Obama's speech.
The President’s Climate Action Plan
Short Fact Sheet.

Jeff Masters

Climate Change Politics

Updated: 12:29 AM GMT on June 27, 2013

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President Obama Delivering Major Climate Change Speech Today

By: JeffMasters, 1:19 PM GMT on June 25, 2013

At 1:55pm today, Tuesday June 25th, President Obama will speak at Georgetown University on the growing threat of climate change. It's the first formal dedicated speech he's given on the issue since he was elected in 2008, and the President will lay out his vision of where we need to go and what we can to do to address and prepare for the serious implications of a changing climate. President Obama is expected to announce a series of actions to combat climate change that do not require Congressional approval, including the regulation of new and existing power plants by the EPA to reduce carbon dioxide emissions. The speech will not address the status of the proposed Keystone XL oil pipeline between the United States and Canada, though.

The Weather Channel will be presenting the President's speech live at 1:55pm ET, with special live coverage including expert commentary before and after. I'll be one of the guests, and will appear live between 1:30 - 3:00 pm EDT during several of the segments. You can also listen to President Obama's speech live at http://whitehouse.gov/live. Late this afternoon, I plan to make a new blog post on the speech. Will the President lay out a vision for getting us into the end zone, or will he merely hand off the ball for another plunge into the line of Mother Nature's increasingly ferocious tacklers?


Video 1. Preview of President Obama's climate change speech.

Jeff Masters

Climate Change Politics

Updated: 1:52 PM GMT on June 25, 2013

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Calgary Flood May be Canada's Most Expensive Flood in History

By: JeffMasters, 1:53 PM GMT on June 24, 2013

The massive floods that devastated Calgary, Canada late last week have raced downstream, and are now bringing the highest flood waters ever recorded to Medicine Hat, Alberta's 5th largest city (population 67,000.) The flood peaked early Monday morning in Medicine Hat, which had evacuated 10,000 residents in anticipation of the flood. The homes of nearly all of the residents evacuated have received flood damage, according to CBC News.


Figure 1. A historic flood quenches the Flames: The inside of the Calgary Saddledome, in Calgary, Alberta, home to the National Hockey League's Calgary Flames. The Saddledome was flooded up to the 10th row, leaving the dressing rooms submerged on Saturday, June 22, 2013. (AP Photo/Calgary Flames)


Figure 2. The closed Trans-Canada Highway in Canmore, Alberta, Canada, along Cougar Creek on Friday June 21, 2013. Image credit: The Canadian Press.


Video 1. Ground-level video of the same stretch of the Trans-Canada Highway as shown in the aerial photo above. The rampaging Cougar Creek flows with incredible power.

Costliest flood in Canadian history?
The meteorological set-up for the flood began when the jet stream got "blocked" into a high-amplitude pattern that brought record heat to Alaska, but forced heavy rainfall to fall across the Bow River Basin on Wednesday night, with up to 190 mm (7.51”) falling in some areas over just a 24-hour period. Widespread heavy rains of 50.8 mm (2”) blanketed the entire river basin, sending the Bow River to near-record flood levels. At the peak of the flooding, the Bow and Elbow rivers were flowing through Calgary at three times their peak levels from a 2005 flood that caused $275 million in damage. Calgary, Canada's 5th largest city (population 1.2 million), was forced to evacuate 100,000 people, and the downtown area was submerged by the flood waters. Three people died. Over the weekend, 65,000 people were allowed to return to their homes, but the city remains under a state of emergency. The Calgary flood will be one of the most damaging floods in Canadian history. While it is too early to come up with a reliable figure for the damages, insurance industry experts said on Friday that the Calgary floods could cost $500 - $800 million--two to three times the cost of the city's 2005 floods. The June 2013 Alberta flood has the potential become the most expensive flood in Canadian history, exceeding the $800 million price tag of the April 4, 2011 flood in Southern Manitoba, along the Assiniboine River and Lake Manitoba.


Figure 3. The top ten most expensive natural disasters in Canadian history (not adjusted for inflation.) The most expensive flood in Canadian history occurred in April 2011, when flooding on the Assiniboine River and on Lake Manitoba caused $800 million in damage. Water levels rose so high in Lake Manitoba that some beach front homes ended up three km into the lake. Image credit: EM-DAT.

Wunderblogger Christopher C. Burt has a look at the disaster in his Friday post.

Jeff Masters

Flood

Updated: 2:10 PM GMT on June 24, 2013

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Over 500 Killed in India's Monsoon Floods

By: JeffMasters, 4:25 PM GMT on June 21, 2013

Earth's deadliest natural disaster so far in 2013 is the deadly flooding in India's Himalayan Uttarakhand region, where torrential monsoon rains have killed at least 556 people, with hundreds more feared dead. At least 5,000 people are missing. According to the Indian Meteorological Department, Uttarakhand received more than three times (329%) of its normal June rainfall from June 1 - 21, and rainfall was 847% of normal during the week June 13 - 19. Satellite estimates indicate that more than 20" (508 mm) or rain fell in a 7-day period from June 11 - 17 over some regions of Uttarakhand, which lies just to the west of Nepal in the Himalayas. Dehradun, the capital of Uttarakhand, received 14.57" (370 mm) of rain in 24 hours on June 16 - 17. This was the highest 24-hour rainfall in city history, according to an official from the India Meteorological Department. Dr. Dave Petley's Landslide Blog details that the torrential rains triggered a massive landslide that hit Uttarakhand's Hindu shrine in Kedarnath, which lies just a short distance from the snout of two mountain glaciers. The shrine is an important pilgrimage destination this time of year, and was packed with visitors celebrating the char-dham yatra: a pilgrimage to the four holy sites of Gangotri, Kedarnath, Yamnotri and Badrinath. Apparently, heavy rainfall triggered a collapse event on the mountain above Kedarnath, which turned into a debris flow downstream that struck the town. The main temple was heavily damaged, and numerous buildings in the town were demolished. It was Earth's deadliest landslide since the August 2010 Zhouqu landslide in China.

According to Aon Benfield's May Catastrophe Report, Earth's deadliest natural disasters of 2013 so far:

Winter weather, India, Bangladesh, Nepal, 1/1 - 1/20, 329 deaths
Earthquake, China, 4/20, 196 deaths
Flooding, Southern Africa, 1/10 - 2/28, 175 deaths
Flooding, Argentina, 4/2 - 4/4, 70 deaths
Flooding, Kenya, 3/10 - 4/30, 66 deaths


Figure 1. Indo-Tibetan Border Police (ITBP) arrive to rescue stranded Sikh devotees from Hemkunt Sahib Gurudwara, a religious Sikh temple, to a safe place in Chamoli district, in northern Indian state of Uttarakhand, India, Monday, June 17, 2013. AP photo.


Figure 2. Satellite-estimated rainfall for the 7-day period June 11 - 17, 2013, from NASA's TRMM satellite exceeded 20 inches (508 mm) over portions of India's Uttarakhand province, leading to catastrophic floods. Image credit: NASA.

A record early arrival of the monsoon
The June 2013 monsoon rains in Uttarakhand were highly unusual, as the monsoon came to the region two weeks earlier than normal. The monsoon started in South India near the normal June 1 arrival date, but then advanced across India in unusually rapid fashion, arriving in Pakistan along the western border of India on June 16, a full month earlier than normal. This was the fastest progression of the monsoon on record. The previous record for fastest monsoon progression occurred in 1961, when all of India was under monsoon conditions by June 21. Reliable monsoon records go back to 1961, and are patchy before then. Fortunately, no more heavy rain is expected in Uttarakhand over the next few days, as the monsoon will be active only in eastern India. Heavy rains are expected again in the region beginning on June 24. Wunderblogger Lee Grenci's post, Summer Monsoon Advances Rapidly across India: Massive Flooding Ensues, has more detail on the meteorology of this year's monsoon. There is criticism from some that the devastating floods were not entirely a natural disaster--human-caused deforestation, dam building, and mining may have contributed. "Large-scale construction of dams and absence of environmental regulations has led to the floods," said Sunita Narian, director general of Delhi based advocacy group Centre for Science and Environment (CSE).


Figure 3. The summer monsoon arrived in southwest India right on schedule (June 1) in South India, but it spread northward much faster than usual, reaching Pakistan a full month earlier than normal. Solid green contours indicate the progress of the 2013 summer monsoon (each contour is labeled with a date). You can compare this year's rapid advance to a "normal" progression, which is represented by the dashed, red contours (also labeled with dates).

Monsoons in India: a primer
Disastrous monsoon floods are common in India and surrounding nations, and 60,000 people--an average of 500 people per year--died in India due to monsoon floods between 1900 - 2012, according to EM-DAT, the International Disaster Database. EM-DAT lists sixteen flood disasters which killed 1,000 or more people in India since records began in 1950. Here are the number of people killed in these events, along with the month and year of occurrence and locales affected:

4892, Jul 1968, Rajasthan, Gujara
3800, Jul 1978, North, Northeast
2001, May - Oct, 1994, Assam, Arunachal Pradesh
2000, Jul 1961, North
1811, Aug 1998, Assam, Arunachal, Bihar
1600, Aug 1980, Uttar Pradesh, Bihar
1591, Jul 28, 1989, Maharashtra, Andhra Prade
1479, Sep 1995, Bihar, Haryana, Punjab
1442, Aug 1997, Andhra Pradesh, Arunachal
1200, Jul 24 - Aug 5, 2005 Gujarat, Madhya Pradesh
1200, Aug 1987, Assam, Bihar, West Bengal
1103, Jul 3 - Sep 22, 2007, Bihar, Uttar Pradesh
1063, Jun 11 - Jul 21, 2008 West Bengal, Orissa
1023, Jun 1971, North
1000, Sep 22 - Oct 9, 1988, Punjab, Himachal Pradesh
1000, Oct 1961

The monsoon occurs in summer, when the sun warms up land areas more strongly than ocean areas. This happens because wind and ocean turbulence mix the ocean's absorbed heat into a "mixed layer" approximately 50 meters deep, whereas on land, the sun's heat penetrates at a slow rate to a limited depth. Furthermore, due to its molecular properties, water has the ability to absorb more heat than the solid materials that make up land. As a result of this summertime differential heating of land and ocean, a low pressure region featuring rising air develops over land areas. Moisture-laden ocean winds blow towards the low pressure region and are drawn upwards once over land. The rising air expands and cools, condensing its moisture into some of the heaviest rains on Earth--the monsoon. Monsoons operate via the same principle as the familiar summer afternoon sea breeze, but on a grand scale. Each summer, monsoons affect every continent on Earth except Antarctica, and are responsible for life-giving rains that sustain the lives of billions of people. In India, home for over 1.1 billion people, the monsoon provides 80% of the annual rainfall. The most deadly flooding events usually come from monsoon depressions (also known as monsoon lows.) A monsoon depression is similar to (but larger than) a tropical depression. Both are spinning storms hundreds of kilometers in diameter with sustained winds of 50 - 55 kph (30 - 35 mph), nearly calm winds at their center, and generate very heavy rains. Typically, 6 - 7 monsoon depressions form each summer over the Bay of Bengal and track westwards across India.

The future of monsoons in India
A warming climate loads the dice in favor of heavier extreme precipitation events. This occurs because more water vapor can evaporate into a warmer atmosphere, increasing the chances of record heavy downpours. In a study published in Science in 2006, Goswami et al. found that the level of heavy rainfall activity in the monsoon over India had more than doubled in the 50 years since the 1950s, leading to an increased disaster potential from heavy flooding. Moderate and weak rain events decreased during those 50 years, leaving the total amount of rain deposited by the monsoon roughly constant. The authors commented, "These findings are in tune with model projections and some observations that indicate an increase in heavy rain events and a decrease in weak events under global warming scenarios." We should expect to see an increased number of disastrous monsoon floods in coming decades if the climate continues to warm as expected. Since the population continues to increase at a rapid rate in the region, death tolls from monsoon flooding disasters are likely to climb dramatically in coming decades. However, my greater concern for India is drought. The monsoon rains often fail during El Niño years, and more than 4.2 million people died in India due to droughts between 1900 - 2012. Up until the late 1960s, it was common for the failure of the monsoon rains to kill millions of people in India. The drought of 1965 - 1967 killed at least 1.5 million people. However, since the Green Revolution of the late 1960s--a government initiative to improve food self-sufficiency using new technology and high-yield grains--failure of the monsoon rains has not led to mass starvation in India. It is uncertain whether of not the Green Revolution can keep up with India's booming population, and the potential that climate change might bring more severe droughts. Climate models show a wide range of possibilities for the future of the Indian monsoon, and it is unclear at present what the future might hold. However, the fact that one of the worst droughts in India's history occurred in 2009 shows that serious droughts have to be a major concern for the future. The five worst Indian monsoons along with the rainfall deficits for the nation:

1) 1877, -33%
2) 1899, -29%
3) 1918, -25%
4) 1972, -24%
5) 2009, -22%

References
Goswami, et al., 2006, " Increasing Trend of Extreme Rain Events Over India in a Warming Environment", Science, 1 December 2006:Vol. 314. no. 5804, pp. 1442 - 1445 DOI: 10.1126/science.1132027

Wunderground's climate change blogger Dr. Ricky Rood wrote a nice 3-part series about the challenges India faces due to climate change after he completed a 2009 trip there.


Video 1. Flood waters claim a multi-story apartment building in Uttarakhand province, India, on June 17, 2013.

Historic flooding in Calgary, Alberta
Torrential rainfall on Wednesday night and Thursday has resulted in the most extensive flooding in Alberta Province, Canada in at least 8 years, with some 100,000 people facing evacuations in the city of Calgary. Wunderblogger Christopher C. Burt has a look at the disaster in his latest post. The floods are due, in part to the "stuck" jet stream pattern that brought record heat to Alaska this week.

Jeff Masters

Flood Climate Change

Updated: 1:52 PM GMT on July 15, 2013

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May 2013 Earth's 3rd Warmest May; Central European Floods Cost $22 Billion

By: JeffMasters, 5:07 PM GMT on June 20, 2013

May 2013 was the globe's 3rd warmest May since records began in 1880, according to NOAA's National Climatic Data Center (NCDC). NASA rated it the 10th warmest May on record. The year-to-date period of January - May has been the 8th warmest such period on record. May 2013 global land temperatures were the 3rd warmest on record, and global ocean temperatures were the 5th warmest on record. May 2013 was the 339th consecutive month with global temperatures warmer than the 20th century average. Global satellite-measured temperatures in May 2013 for the lowest 8 km of the atmosphere were 12th or 11th warmest in the 35-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH), respectively. The Northern Hemisphere snow cover extent during May 2013 was the 3rd lowest in the 47-year period of record, and the lowest May extent on record over Eurasia. Unusually low May snow cover allows the Arctic to heat up much more rapidly than usual, decreasing the temperature difference between the Equator and the Arctic, potentially leading to extreme jet stream configurations, according to research by Dr. Jennifer Francis of Rutgers. An extreme jet stream configuration was responsible for the record $22 billion floods in Central Europe in late May and early June, and it is possible that the unusually low May Northern Hemisphere snow cover contributed to the unusual jet stream behavior. Wunderground's weather historian, Christopher C. Burt, has a comprehensive post on the notable weather events of May 2013 in his May 2013 Global Weather Extremes Summary. Don't miss his post's impressive photo of a rare strong tornado that hit Italy on May 3.


Figure 1. Departure of temperature from average for May 2013, the 3rd warmest May for the globe since record keeping began in 1880. Several regions around the world had record warmth, including north central Siberia, west central Australia, parts of northern and eastern Europe, parts of Libya and Algeria in northern Africa, part of northeastern China, the Philippines, and part of northern South America. Record cold was observed in western Greenland. Image credit: National Climatic Data Center (NCDC) .

Five billion-dollar weather disasters in May
At least five billion-dollar weather disasters hit Earth during May. The most damaging of these was the historic flood disaster that killed at least 23 people in Central Europe in late May and early June. Record flooding unprecedented since the Middle Ages hit major rivers in Austria, the Czech Republic, Germany, Poland and Slovakia; the Danube River in Passau, Germany hit its highest level since 1501, and the Saale River in Halle, Germany was the highest in its 400-year period of record. Numerous cities recorded their highest flood waters in more than a century, although in some locations the great flood of 2002 was higher. Total damage from the flood is estimated to be $22 billion by Aon Benfield, making the flood the 5th costliest non-U.S. weather disaster in world history. The world-wide tally of billion-dollar weather disasters so far in 2013 is twelve, and the U.S. total is four, according to the May 2013 Catastrophe Report from insurance broker AON Benfield. This is double the number of billion-dollar disasters from their April 2013 report:

1) Floods in Central Europe, May - June, $22 billion
2) Drought, Brazil, 1/1 - 5/31, $8.3 billion
3) Tornado in Moore, OK and associated U.S. severe weather, 5/18 - 5/22, $5 billion
4) Drought in Central and Eastern China, 1/1 - 4/30, $4.2 billion
5) Flooding in Indonesia, 1/20 - 1/27, $3.31 billion
6) Flooding in Australia, 1/21 - 1/30, $2.5 billion
7 Tornadoes and severe weather, U.S., 5/26 - 6/2, $2 billion
8) Winter weather in Europe, 3/12 - 3/31, $1.8 billion
9) Drought, New Zealand, 1/1 - 5/10, $1.6 billion
10) Flooding in Argentina, 4/2 - 4/4, $1.3 billion
11) Winter weather, Plains, Midwest, Northeast U.S., 2/24 - 2/27, $1.1 billion
12) Severe weather in the Midwest U.S., 3/18 - 3/20, $1 billion


Figure 2. The Danube River in Grein, Austria was barely kept in check on June 6, 2013, by a floodwall. Image credit: IBS Engineering.


Figure 3. The preliminary $22 billion price tag of the May - June 2013 Central European floods would put that disaster in 5th place on the list of most expensive non-U.S. weather-related disasters.

Neutral El Niño conditions continue in the equatorial Pacific
For the 14th month in row, neutral El Niño conditions existed in the equatorial Pacific during May 2013. NOAA's Climate Prediction Center (CPC) expects neutral El Niño conditions to last through summer. The large majority of the El Niño models predict neutral conditions will last through the fall of 2013. Temperatures in the equatorial Eastern Pacific need to be 0.5°C below average or cooler for three consecutive for a La Niña episode to be declared; sea surface temperatures were 0.2°C below average as of May 17, and have been +0.1 to -0.4°C from average since April 1, 2013.

Arctic sea ice falls to 10th lowest May extent on record
Arctic sea ice extent during May reached its tenth lowest extent in the 35-year satellite record, according to the National Snow and Ice Data Center (NSIDC).

Jeff Masters

Climate Summaries

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Tropical Storm Barry Hits Mexico With 45 mph Winds

By: JeffMasters, 2:37 PM GMT on June 20, 2013

Tropical Storm Barry made landfall near Veracruz, Mexico at 8 am CDT on Thursday, June 20, as an unremarkable tropical storm with top winds of 45 mph. Heavy rain will be the main threat from Barry, and up to ten inches are expected to fall in some mountainous regions as Barry pushes inland and dissipates over the next day. Satellite loops show that Barry is a small storm, and its heavy rains will affect only a modest area of Mexico. Elsewhere in the tropical Atlantic, none of the reliable computer models is showing tropical cyclone development in the next seven days.


Figure 1. Satellite image of Tropical Storm Barry near the time of landfall.

Barry's place in history
Barry is the second named storm of June 2013, and its formation date of June 19 is a full six weeks earlier than the usual August 1 date of formation of the season's second storm. Only two hurricane seasons since 1851 have had as many as three tropical storms form in June: 1936 and 1968. The formation of two Gulf of Mexico storms so early in the year does not necessarily suggest that we will have an active hurricane season. June storms forming in the Caribbean and Tropical Atlantic are typically a harbinger of an active hurricane season, though.

The formation of Tropical Storm Andrea and now Tropical Storm Barry in June continues a pattern of an unusually large number of early-season Atlantic named storms we've seen in recent years. During the period 1870 - 2012, we averaged one named storm every two years in June, and 0.7 named storms per year during May and June. In the nineteen years since the current active hurricane period began in 1995, there have been sixteen June named storms (if we include 2013's Tropical Storm Andrea and Tropical Storm Barry.) June activity has nearly doubled since 1995, and May activity has more than doubled (there were seventeen May storms in the 75-year period 1870 - 1994, compared to six in the nineteen-year period 1995 - 2013.) Some of this difference can be attributed to observation gaps, due to the lack of satellite data before 1966. However, even during the satellite era, we have seen an increase in both early season (May - June) and late season (November - December) Atlantic tropical storms. Dr. Jim Kossin of the University of Wisconsin looked at the reasons for this in a 2008 paper titled, "Is the North Atlantic hurricane season getting longer?" He concluded that there is a "apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high." He found that hurricane season for both the period 1950-2007 and 1980-2007 got longer by 5 - 10 days per decade (see my blog post on the paper.)

Jeff Masters

Hurricane

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Tropical Storm Barry Forms

By: JeffMasters, 7:49 PM GMT on June 19, 2013

Data from the Air Force Hurricane Hunters this afternoon indicates that Tropical Storm Barry has formed in the extreme southern Gulf of Mexico. The aircraft measured winds at their flight level of 1000 feet as high as 47 mph, which implies winds of at least 40 mph at the surface, using the usual 10% reduction rule for winds measured at 1000 feet. Barry has a small but growing area of heavy thunderstorms, as seen on satellite loops. The thunderstorms are steadily showing more organization this afternoon, and low-level spiral bands have begun to appear. Wind shear was a moderate 15 knots on Wednesday afternoon, but is expected to fall to the light range, 5 - 10 knots, during the 12 hours before landfall. Barry is taking a very similar track Tropical Storm Marco of 2008. That storm spun up quickly in the Bay of Campeche and developed sustained winds of 65 mph before making landfall in Veracruz State of Mexico. Small storms like Barry and Marco (which was the smallest tropical storm ever recorded in the Atlantic) can experience very rapid fluctuations in intensity. The Bay of Campeche is a region where the topography aids the spin-up of tropical cyclones, and I expect Barry will have time to attain sustained winds of 65 mph before making landfall late Thursday morning or early Thursday afternoon near Veracruz, Mexico. However, since the storm is so small, these winds would affect only a very small portion of the coast. Heavy rain will be the main threat from Barry, regardless of whether or not it makes landfall as a weak or strong tropical storm. A ridge of high pressure over the Gulf of Mexico should keep any of Barry's rains from reaching the U.S. Elsewhere in the tropical Atlantic, none of the reliable computer models is showing tropical cyclone development in the next seven days.


Figure 1. MODIS satellite image of Tropical Storm Barry at 12:40 pm EDT June 19, 2013. Image credit: NASA.

Barry's place in history
Barry is the second named storm of June 2013, and its formation date of June 19 is a full six weeks earlier than the usual August 1 date of formation of the season's second storm. Only two hurricane seasons since 1851 have had as many as three tropical storms form in June: 1936 and 1968. The formation of two Gulf of Mexico storms so early in the year does not necessarily suggest that we will have an active hurricane season. June storms forming in the Caribbean and Tropical Atlantic are typically a harbinger of an active hurricane season, though.

The formation of Tropical Storm Andrea and now Tropical Storm Barry in June continues a pattern of an unusually large number of early-season Atlantic named storms we've seen in recent years. Climatologically, June is the second quietest month of the Atlantic hurricane season, behind November. During the period 1870 - 2012, we averaged one named storm every two years in June, and 0.7 named storms per year during May and June. In the nineteen years since the current active hurricane period began in 1995, there have been sixteen June named storms (if we include 2013's Tropical Storm Andrea and Tropical Storm Barry.) June activity has nearly doubled since 1995, and May activity has more than doubled (there were seventeen May storms in the 75-year period 1870 - 1994, compared to six in the nineteen-year period 1995 - 2013.) Some of this difference can be attributed to observation gaps, due to the lack of satellite data before 1966. However, even during the satellite era, we have seen an increase in both early season (May - June) and late season (November - December) Atlantic tropical storms. Dr. Jim Kossin of the University of Wisconsin looked at the reasons for this in a 2008 paper titled, "Is the North Atlantic hurricane season getting longer?" He concluded that there is a "apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high." He found that hurricane season for both the period 1950-2007 and 1980-2007 got longer by 5 - 10 days per decade (see my blog post on the paper.)

Portlight receives $25K grant to help victims of Oklahoma tornadoes
The disaster relief charity founded by members of the wunderground community, Portlight.org, announced this week that they had received a $25,000 grant from Americares.org to replace wheelchairs, scooters, ramps and other equipment lost or damaged in the May and June 2013 storms in Oklahoma. About 200 Oklahomans with mobility issues are expected to benefit over the next 45 days. The program is an extension of a partnership that began earlier this year to install ramps for New Jersey residents affected by Superstorm Sandy. It was also announced earlier this month that Portlight and the American Red Cross have signed a Letter of Agreement to work together in disaster response, in order to improve shelter accessibility and share resources and information.Visit Portlight's wunderground blog to learn more or to donate to this worthy cause.


Figure 2. Portlight volunteers hard at work in Moore, Oklahoma, after the devastating May 20, 2013 tornado.

Jeff Masters

Hurricane

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Baked Alaska: 98° Reading Ties All-Time State Heat Record

By: JeffMasters, 5:21 PM GMT on June 19, 2013

Alaska is a land of extremes, but the weather of the past month has been truly exceptional. An intense ridge of high pressure, part of an extreme jet stream pattern that has become "stuck" in place for many days, is creating the state's hottest heat wave in 44 years this week. Numerous cities in Alaska have recorded their all-time hottest temperatures on record, and according to wunderground's weather historian, Christopher C. Burt, the unofficial 98° measured at Bentalit Lodge on Monday, June 17, ties the record for the hottest reliably measured temperature in state history. The only other time Alaska has been this hot was on June 15, 1969, when the mercury hit 96° in Fairbanks, and a 98° reading was recorded in Richardson (near Fairbanks.) Mr. Burt writes: One thing that is so astonishing about the current heat wave in Alaska is how abnormally cold it was just a month ago. McGrath, which reached its all-time record high of 94° on Monday, recorded a 15° temperature on May 18th, the coldest temperature (by 4°) ever measured so late in the season there (McGrath went on to reach 86° on May 29th, its warmest May temperature on record!).


Figure 1. Another hot day in the Great Land: forecast highs for Wednesday, June 19, call for high temperatures in excess of 90° north of the Arctic Circle in Alaska.


Figure 2 . A rare cloud-free view of Alaska. This June 17, 2013 MODIS shot of Alaska, taken during the state's hottest heat wave in 44 years, is remarkably cloud-free-thanks to the intense ridge of high pressure over the state. The heat helped fuel several wildfires, marked with red squares. Image credit: NASA.

Links
Alaska Bakes with All-time Heat Records by wunderground's weather historian, Christopher C. Burt

All-Time Heat Records Broken in . . . Alaska?! by Andrew Freeman of climatecentral.org

Jeff Masters

Heat

Updated: 5:24 PM GMT on June 19, 2013

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TD 2 Slowly Organizing, Headed Towards Veracruz, Mexico

By: JeffMasters, 1:50 PM GMT on June 19, 2013

Tropical Depression Two is slowly spinning west-northwest across the extreme southern Gulf of Mexico--the Bay of Campeche--at 9 mph. The storm has a small area of heavy thunderstorms, as seen on Mexican radar and satellite loops. The thunderstorms are slowly showing more organization this morning, but the storm has little low-level spiral banding, poor upper-level outflow, and is fighting dry air on its west side. However, the Bay of Campeche is a region where the topography aids the spin-up of tropical cyclones, and I expect TD 2 will have enough time to become Tropical Storm Barry before making landfall late Thursday morning near Veracruz, Mexico. Wind shear was a moderate 15 - 20 knots on Wednesday morning, but is expected to fall to the light range, 5 - 10 knots, during the 12 hours before landfall. TD 2 is taking a very similar track Tropical Storm Marco of 2008. That storm spun up quickly in the Bay of Campeche and developed sustained winds of 65 mph before making landfall in Veracruz State of Mexico. Small storms like TD 2 and Marco (which was the smallest tropical storm ever recorded in the Atlantic) can experience very rapid fluctuations in intensity, and it would not surprise me if TD 2 intensified suddenly into a 60 mph tropical storm before making landfall. However, since the storm is so small, these winds would affect only a very small portion of the coast. Heavy rain will be the main threat from TD 2, regardless of whether or not it makes landfall as a tropical depression or as a strong tropical storm. A ridge of high pressure over the Gulf of Mexico should keep any of TD 2's rains from reaching the U.S. An Air Force hurricane hunter plane is scheduled to arrive in TD 2 near 2 pm EDT today. Elsewhere in the tropical Atlantic, none of the reliable computer models is showing tropical cyclone development in the next seven days.


Figure 1. Morning satellite image of TD 2 at 8:12 am EDT June 19, 2013. Image credit: Navy Research Lab, Monterey.


Figure 2. MODIS satellite image of Tropical Storm Marco on October 6, 2008. Marco was the smallest tropical storm ever recorded in the Atlantic. Image credit: NASA.

Portlight receives $25K grant to help victims of Oklahoma tornadoes
The disaster relief charity founded by members of the wunderground community, Portlight.org, announced this week that they had received a $25,000 grant from Americares.org to replace wheelchairs, scooters, ramps and other equipment lost or damaged in the May and June 2013 storms in Oklahoma. About 200 Oklahomans with mobility issues are expected to benefit over the next 45 days. The program is an extension of a partnership that began earlier this year to install ramps for New Jersey residents affected by Superstorm Sandy. It was also announced earlier this month that Portlight and the American Red Cross have signed a Letter of Agreement to work together in disaster response, in order to improve shelter accessibility and share resources and information.Visit Portlight's wunderground blog to learn more or to donate to this worthy cause.


Figure 3. Portlight volunteers hard at work in Moore, Oklahoma, after the devastating May 20, 2013 tornado.

Jeff Masters

Hurricane

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Tornado Hits Denver International Airport

By: JeffMasters, 12:35 AM GMT on June 19, 2013

Tornadoes are difficult to observe, since they rarely move over instruments that can directly measure their winds. A rare exception occurred on Tuesday, when an EF-1 tornado obligingly ran directly over the weather station at Denver International Airport, which recorded a wind gust of 97 mph. Remarkably, the weather station was not destroyed, and continued to transmit data after the tornado had passed. There was no major damage reported at the airport.


Figure 1. Radar reflectivity image of the Denver International Airport tornado. The tornado was only five miles from the Terminal Doppler Weather Radar at the airport, allowing a unique up-close view of the precipitation-free doughnut hole where the tornado was. The tornado was about 100 - 200 yards wide.


Video 1. Tornado at the Denver International Airport on June 18, 2013. The Weather Channel has many more photos of the tornado.

Jeff Masters

Tornado

Updated: 12:36 AM GMT on June 19, 2013

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TD 2 Crossing the Yucatan, Bringing Heavy Rains

By: JeffMasters, 1:44 PM GMT on June 18, 2013

Tropical Depression Two is slowly spinning west-northwest across Belize after making landfall late Monday afternoon in southern Belize. The storm is bringing heavy rain to Belize, Northern Guatemala, and Mexico's Yucatan Peninsula, as seen on Belize radar and satellite loops. The center of TD 2 will remain over land all day Tuesday, but TD 2's west-northwest track may be able to bring the storm over the Gulf of Mexico's southern Bay of Campeche on Wednesday--if the storm hasn't dissipated by then. The Bay of Campeche is a region where the topography aids the spin-up of tropical cyclones, and TD 2 may have barely enough time to become Tropical Storm Barry with 40 mph winds before making landfall on Thursday between Veracruz and Tampico. However, the track of the storm may also keep it just inland during the remainder of the week, keeping it from ever getting to tropical storm strength. Heavy rains are the storm's main threat, but a ridge of high pressure over the Gulf of Mexico should keep any of TD 2's rains from reaching the U.S. Observations from an AMSU instrument on a polar orbiting satellite on Monday afternoon found that TD 2 had developed a modest warm core characteristic of a weak tropical storm, and it is possible that NHC will upgrade TD 2 to a tropical storm in post-analysis after the hurricane season is over. Elsewhere in the tropical Atlantic, none of the reliable computer models is showing tropical cyclone development in the next seven days.


Figure 1. MODIS satellite image of TD 2 taken on Monday afternoon, June 17, 2013. image credit: NASA.

Participate in Tuesday's live radio call-in show to talk climate change in Tea Party country
I spent last week in Granby, Colorado at the American Geophysical Union's conference on climate change communication. Approximately 100 of the world's top climate scientists and specialists in communication gathered to discuss how to effectively communicate climate change. Four of the speakers at that conference will be part of a radio call-in radio show on KCNR 1460AM from downtown Redding, the politically conservative heart of deep red Northern California. The show is today, Tuesday, June 17, from 10 am - noon EDT. The show will be live-streamed at http://www.kcnr1460.com/, and will be preserved in the archives as a podcast. KCNR is a Fox News radio station with all-conservative talk radio programming, featuring such guests as Laura Ingraham, Dennis Miller, and Mike Huckabee. Call in with questions today at 530-605-4565. The four guests will be:

1) Gavin Schmidt (NASA GISS and RealClimate)
2) Simon Donner  (http://www.geog.ubc.ca/~sdonner/)
3) Bob Henson (Rough Guide to Climate Change)
4) Melanie Fitzpatrick (Union of Concerned Scientists)

Jeff Masters

Hurricane

Updated: 3:03 PM GMT on June 18, 2013

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Tropical Depression Two Forms Near Belize

By: JeffMasters, 3:21 PM GMT on June 17, 2013

Tropical Depression Two has formed in the extreme Southwest Caribbean, about 60 miles east of the coast of Belize. The storm is bringing heavy rain to Belize, as seen on Belize radar, and has produced up to 6 - 8" inches of rain over eastern Nicaragua and Honduras, according to satellite estimates. The center of circulation will be over water for about 4 - 6 hours today, before moving ashore over Belize. This may be enough time for the storm to become Tropical Storm Barry with 40 mph winds. Satellite loops show that the system is well-organized, has plenty of spin, has good upper-level outflow to the north, and has a large of amount of heavy thunderstorm activity that is increasing in intensity and areal converge. Wind shear is a moderate 15 - 20 knots, and ocean temperatures are warm, 28 - 29°C. The Hurricane Hunter mission for Monday has been canceled, as the storm will be ashore by the time they reach it.


Figure 1. Morning satellite image of TD 2.

Forecast for TD 2
TD 2 will cross over the Yucatan Peninsula on Monday night and Tuesday, and may emerge into the extreme southern Gulf of Mexico--the Bay of Campeche--on Tuesday night or Wednesday. At that point, the models continue to predict a slow west-northwest motion, bringing the center of TD 2 ashore into Mexico between Veracruz and Tampico on Thursday. Wind shear is expected to remain moderate through Wednesday. The Bay of Campeche is a region where the topography aids the spin-up of tropical cyclones, so I expect this storm will become a tropical storm if its center moves over water in the Bay of Campeche. The center may remain just inland, though, keeping the storm from developing. There is no indication from the models that this system will affect the U.S., as a strong ridge of high pressure over the U.S. during the coming week should keep the tropical wave trapped in the southern Gulf of Mexico, keeping all the storm's rainfall confined to Mexico.

Jeff Masters

Hurricane

Updated: 3:24 PM GMT on June 17, 2013

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93L drenching Belize, May Have Time to Develop

By: JeffMasters, 2:41 PM GMT on June 17, 2013

A well-organized tropical disturbance (93L) is centered over the northwest coast of Honduras, in association with a tropical wave that is moving west-northwest at 12 mph. The storm is bringing heavy rain to Belize, as seen on Belize radar, and has produced up to 6 - 8" inches of rain over eastern Nicaragua and Honduras, according to satellite estimates. The wave's center of circulation will move over water for about 4 - 6 hours this afternoon, before moving ashore over Belize. This may be long enough for 93L to become a tropical depression or tropical storm, as satellite loops show that the system is well-organized, has plenty of spin, has good upper-level outflow to the north, and has a large of amount of heavy thunderstorm activity that is increasing in intensity and areal converge. Wind shear is a moderate 15 - 20 knots, and ocean temperatures are warm, 28 - 29°C. NHC is giving the disturbance a 40% chance of developing into a tropical depression or tropical storm by Wednesday. I put these odds higher, at 60%. The Air Force Hurricane Hunters are on call to investigate 93L Monday afternoon.


Figure 1. Latest satellite image of 93L.

The wave will cross over the Yucatan Peninsula on Monday night and Tuesday, and may emerge into the extreme southern Gulf of Mexico--the Bay of Campeche--on Tuesday night or Wednesday. At that point, the models continue to predict a slow west-northwest motion, bringing the center of 93L ashore into Mexico between Veracruz and Tampico late in the week. Wind shear is expected to remain moderate through Wednesday. The Bay of Campeche is a region where the topography aids the spin-up of tropical cyclones, so I expect this storm will become a tropical depression or tropical storm if its center moves over water in the Bay of Campeche. The center may remain just inland, though, keeping the storm from developing. There is no indication from the models that this system will affect the U.S., as a strong ridge of high pressure over the U.S. during the coming week should keep the tropical wave trapped in the southern Gulf of Mexico, keeping all the storm's rainfall confined to Mexico.

Jeff Masters

Hurricane

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Caribbean Disturbance Little Threat to Develop

By: JeffMasters, 2:20 AM GMT on June 16, 2013

A concentrated area of heavy thunderstorms has developed over the Southwest Caribbean near the coast of Nicaragua in association with a tropical wave that is moving slowly west northwest towards Nicaragua and Honduras. Wind shear is a high 20 - 30 knots, which will keep any development slow. The high shear is due to the presence of the subtropical jet stream, which is expected to push northwards over the next few days. This may allow wind shear to fall to the moderate range on Monday, when the wave will be in the Northwest Caribbean, between Honduras and Belize. NHC is giving the disturbance only a 10% chance of developing into a tropical depression or tropical storm by Monday, but these odds may increase on Monday when the wave has crossed into the Northwest Caribbean--if the wind shear drops. The wave will cross over the Yucatan Peninsula on Tuesday and may emerge into the Southern Gulf of Mexico's Bay of Campeche as early as Wednesday. At that point, the models continue to predict a slow west-northwest motion, bringing the wave ashore into Mexico between Veracruz and Tampico late in the week. Wind shear is expected to remain high during the entire period, keeping any development slow. The Bay of Campeche is a region where the topography aids the spin-up of tropical cyclones, so the disturbance's odds of formation are the greatest on Wednesday through Friday, after it crosses the Yucatan. None of the models develop the disturbance, and there is no indication that this system will affect the U.S., as a strong ridge of high pressure over the U.S. during the coming week should keep the tropical wave trapped in the southern Gulf of Mexico.


Figure 1. MODIS satellite image of the tropical disturbance in the Southwest Caribbean on Saturday, June 15, 2013. Image credit: NASA.

Have a great weekend, everyone, and I'll be back Monday with a new post.

Jeff Masters

Hurricane

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Colorado's Costliest Fire in History Kills 2; Severe Thunderstorms Pound Mid-Atlantic

By: JeffMasters, 3:51 AM GMT on June 14, 2013

Two people are dead in the Colorado Springs area due to the Black Forest fire, which continues to rage virtually unchecked about five miles northeast of Colorado's second largest city (population 400,000.) The fire' had burned through 15,700 acres by late Thursday afternoon, and was 5% contained. Over 38,000 people in 13,000 homes had been evacuated. The weather was no help on Thursday, as afternoon temperatures spiked to 90°, winds were sustained at 33 mph, gusting to 40 mph, and the humidity dropped as low as 14%. The fire began on Tuesday, June 11, during a record heat wave. Colorado Springs hit 98° on June 10--the city's hottest temperature ever recorded so early in the year. The temperature topped out at 97° on June 11. The extreme heat, combined with the extreme drought gripping the region, made for ideal fire conditions. Fire conditions will not be as dangerous in the Colorado Springs area on Friday, as a weak cold front is expected to pass through the region during the afternoon, bringing cooler temperatures and increased humidity. Strong winds may still be a problem, though.


Figure 1. The Black Forest Fire burns behind a stand of trees on June 12, 2013, near Colorado Springs, Colo. (Chris Schneider/Getty Images)


Figure 2. Aerial view of a Colorado Springs neighborhood burned in the Black Forest Fire on June 13, 2013. (Image: AP Photo/John Wark)

The three most expensive fires in Colorado history have all occurred in the past year
The 360 homes burned by this week's Black Canyon fire are the most ever destroyed in Colorado by a fire, and will likely make it the most expensive fire in Colorado history. The previous record was the $353 million Waldo Canyon fire of June 23 - July 10, 2012. That fire killed two people, destroyed 347 homes, forced the evacuation of over 32,000 people, and burned 18,247 acres of land. The High Park fire of June, 2012, which destroyed 259 buildings near Fort Collins, now ranks as the third most expensive Colorado fire (it was the most expensive one at the time.) The Black Forest fire has a long ways to go if it wants to challenge the 2002 Hayman Fire as the largest fire in Colorado history. The Hayman fire burned 138,000 acres, an area about nine times as large as this week's Black Forest fire.

According to a federal report released by the U.S. Department of Agriculture in 2012, Colorado can expect to see a sharp increase in wildfires during the coming decades, if the climate warms as expected. The report cited research predicting that a 1.8°F increase in Colorado's average temperature--the level of warming expected by 2050 under a moderate global warming scenario--would cause a factor of 2.8 - 6.6 increase in fire area burned in the state.


Video 1. Aerial view of the Colorado Springs Black Forest fire on June 11, 2013.

Severe thunderstorms pound the Mid-Atlantic
It was another intense day of severe thunderstorm activity for the Mid-Atlantic region on Thursday. A child was killed in Virginia by a falling tree, and at least three people were injured in Albemarle, North Carolina when a violent thunderstorm blew trees onto homes. NOAA's Storm Prediction Center (SPC) logged 376 reports of damaging thunderstorm wind gusts in the 15 hours ending at 11:25 pm EDT Thursday night, and three of these gusts were 74 mph or greater. SPC is now acknowledging that Wednesday's bow echo that traveled 600 miles from Indiana to New Jersey was a low-end derecho, with over 150 damaging wind reports. The most impressive thunderstorm winds from the derecho occurred in Wabash County, Indiana, where a "macroburst" produced winds of 90 - 100 mph across an area seven miles long and three miles wide, destroying three buildings and causing extensive tree damage. Total damage from the two-day severe weather outbreak over the Midwest and Mid-Atlantic will likely run into the hundreds of millions of dollars.


Figure 3. Severe weather reports for the 15 hours ending at 11:25 pm EDT June 14, 2013, from SPC.


Figure 4. Radar composite of the June 12 - 13 bow echo that traveled from Indiana to new Jersey. Image credit: NOAA/SPC.

Jeff Masters

Fire Severe Weather

Updated: 5:51 PM GMT on June 15, 2013

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Severe Thunderstorms Rip From Chicago to Baltimore

By: JeffMasters, 2:55 PM GMT on June 13, 2013

It was a wild weather night over much of the Midwest, Great Lakes, and Mid-Atlantic on Wednesday, as tornadoes and an organized complex of severe thunderstorms known as a bow echo brought damaging winds to a large swath of the country. NOAA's Storm Prediction Center (SPC) logged twelve preliminary reports of tornadoes in Iowa, Illinois, and Ohio, but no injuries or major damage were reported with the twisters. A large area of severe thunderstorms organized into a curved band known as a "bow echo" over Indiana during the evening. The bow echo raced east-southeastwards at 50 mph overnight, spawning severe thunderstorm warnings along its entire track, and arrived in Washington D.C. and Baltimore, Maryland near 9 am EDT Thursday morning. SPC logged 159 reports of high thunderstorm wind gusts of 58 mph or greater in the 26 hours ending at 10 am EDT Thursday morning, and three of these gusts were 74 mph or greater. SPC did not classify this event as a "derecho", since the winds were not strong enough to qualify. Last year's June 29, 2012 derecho had 675 reports of wind gusts of 58 mph or greater, with 35 of these gusts 74 mph or greater. Thirteen people died in the winds, mostly from falling trees; 34 more people died from heat-related causes in the areas where 4 million people lost power in the wake of the great storm.

Another round of severe weather is expected over the Mid-Atlantic states Thursday afternoon and evening, and SPC has placed portions of this region in their "Moderate Risk" area for severe weather.


Figure 1. Lightning strikes the Willis Tower (formerly Sears Tower) in downtown on June 12, 2013 in Chicago, Illinois. (Photo by Scott Olson/Getty Images)


Figure 2. An organized line of severe thunderstorms took the shape of a "bow echo" over Indiana last night, triggering severe thunderstorm warnings along the entire front of the bow.


Figure 3. Severe weather reports for the 24 hours ending at 8 am EDT June 13, 2013, from SPC.

Big wind in the Windy City
I watched with some trepidation Wednesday evening as a large tornado vortex signature on radar developed west of Chicago, heading right for one of the most densely populated areas in the country. Fortunately, the storm pulled its punch, and Chicago was spared a direct hit by a violent tornado. But what would happen if a violent, long-track EF4 or EF5 tornado ripped through a densely populated urban area like Chicago? That was the question posed by tornado researcher Josh Wurman of the Center for Severe Weather Research in Boulder and three co-authors in a paper published in the January 2007 issue of the Bulletin of the American Meteorological Society. Their astonishing answer: damage of $40 billion and 13,000-45,000 people killed--the deadliest natural disaster in American history, eclipsing the Galveston Hurricane (8,000 fatalities.)


Figure 4. Tornadoes to affect the Chicago area, 1950-2005. Background image credit: Google Earth. Tornado paths: Dr. Perry Samson.

Huge tornado death tolls are very rare
A tornado death toll in the ten of thousands seems outlandish when one considers past history. After all, the deadliest tornado in U.S. history--the great Tri-state Tornado of March 18, 1925--killed 695 people in its deadly rampage across rural Missouri, Illinois, and Indiana. That was before the advent of Doppler radar and the National Weather Service's excellent tornado warning system. In fact, there has only been one tornado death toll over 100 (the 158 killed in the Joplin, Missouri tornado in 2011) since 1953, the year the NWS began issuing tornado warnings. Chicago has been hit by one violent tornado. On April 21, 1967 a 200-yard wide F4 tornado formed in Palos Hills in Cook County, and tore a 16-miles long trail of destruction through Oak Lawn and the south side of Chicago. Thirty-three people died, 500 more were injured, and damage was estimated at $50 million.


Figure 5. Wind speed swaths for the 1999 F5 Mulhall, Oklahoma tornado if it were to traverse a densely populated area of Chicago. Units are in meters/sec (120 m/s = 269 mph, 102 m/s = 228 mph, and 76 m/s = 170 mph). Winds above 170 mph usually completely destroy an average house, with a crudely estimated fatality rate of 10%, according to Wurman et al.. Insets x, y, and z refer to satellite photo insets in Figure 2. Image credit: Bulletin of the American Meteorological Society.


Figure 6. Aerial photographs from Google Earth of densely populated area of Chicago (insets x, y, and z from Figure 5) These areas contain mainly single-family homes, with housing units densely packed on small lots. A mixture of three-story apartments and single-family homes is typical across the Chicago metropolitan area and many older cities such as New York City and Detroit. At lower right is a photo of Moore, OK, showing lower density housing like the 1999 Bridgecreek-Moore tornado passed through.

The paper by Wurman et al., "Low-level winds in tornadoes and the potential catastrophic tornado impacts in urban areas" opens with an analysis of the wind structure of two F5 tornadoes captured on mobile "Doppler on Wheels" radar systems--the May 3, 1999 Bridgecreek-Moore tornado, which hit the southern suburbs of Oklahoma City, and the Mulhall, Oklahoma tornado of the same day, which moved over sparsely populated rural regions. The Bridgecreek-Moore tornado had the highest winds ever measured in a tornado, 302 mph. Winds of EF4 to EF5 strength (greater than 170 mph) are capable of completely destroying a typical home, and occurred over a 350 meter (1150 foot) wide swath along this tornado's path. The Mulhall tornado had weaker winds topping out at 245-255 mph, but had EF4 to EF5 winds over a much wider swath--1600 meters (one mile).

The F4 to F5 winds of the Bridgecreek-Moore tornado killed 36 people. Given the population of the area hit, between 1% and 3% of the people exposed to these winds died. The authors thought that this number was unusually low, given the excellent warnings and high degree of tornado awareness in Oklahoma's population. They cited the death rate in the 1998 Spencer, South Dakota F4 tornado that destroyed 30 structures and caused six deaths, resulting in a death rate of 6% (assuming 3.3 people lived in each structure). There are no studies that relate the probability of death to the amount of damage a structure receives, and the authors estimated crudely that the death rate per totally destroyed structure is 10%. This number will go down sharply if there is a long warning time, as there was in the Oklahoma tornadoes. If one takes the Mulhall tornado's track and superimposes it on a densely populated region of Chicago (Figure 5), one sees that a much higher number of buildings are impacted due to the density of houses. Many of these are high-rise apartment buildings that would not be totally destroyed, and the authors assume a 1% death rate in these structures. Assuming a 1% death rate in the partially destroyed high-rise apartment buildings and a 10% death rate in the homes totally destroyed along the simulated tornado's path, one arrives at a figure of 13,000-45,000 killed in Chicago by a violent, long-track tornado. The math can applied to other cities, as well, resulting in deaths tolls as high as 14,000 in St. Louis, 22,000 in Dallas, 17,000 in Houston, 15,000 in Atlanta, and 8,000 in Oklahoma City. Indeed, the May 31, 2013 EF5 tornado that swept through El Reno, Oklahoma, killing four storm chasers, could have easily killed 1,000 people had it held together and plowed into Oklahoma City, hitting freeways jammed with people who unwisely decided to flee the storm in their cars. The authors emphasize that even if their death rate estimates are off by a factor ten, a violent tornado in Chicago could still kill 1,300-4,500 people. The authors don't give an expected frequency for such an event, but I speculate that a violent tornado capable of killing thousands will probably occur in a major U.S. city once every few hundred years.

Jeff Masters

Severe Weather Tornado

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Record heat fuels destructive fires in drought-baked Colorado

By: JeffMasters, 1:42 PM GMT on June 12, 2013

Destructive wildfires erupted in three locations in drought-baked Colorado on Tuesday, fanned by strong winds and the hottest temperatures ever recorded in the state so early in the year. The mercury soared to 100°F in Denver on Tuesday, their earliest 100° day on record (previous earliest 100° day: June 14, 2006, 102°.) It was the second consecutive day Denver recorded its hottest temperature for so early in the year. At Lamar in Southeast Colorado, the mercury soared to 111°, just one degree below their hottest temperature ever measured, and 3° shy of the all-time hottest temperature ever measured in Colorado, the 114° reading in Sedgwick on July 11, 1954. The most destructive fire in Colorado Tuesday was the Black Forest fire burning near Colorado Springs. The fire destroyed over 60 buildings and forced the evacuation of several thousand people. The fire was aided by nearly ideal conditions on Tuesday afternoon--Colorado Springs hit 97° (only the 2nd time the city has been that hot this early in the year), with sustained winds of 29 mph gusting to 36 mph, and a humidity of 4%. Colorado Springs is under extreme drought.


Figure 1. A garage is fully engulfed in flames as the Black Forest Fire continues to burn out of control northeast of Colorado Springs, Colo. on June 11, 2013. (Helen H. Richardson/The Denver Post/Getty Images)


Figure 2. Wild fires burn near Rocky Mountain National Park, Colorado Springs, and Royal Gorge in Colorado, and in two locations in New Mexico, at 4:40 pm EDT June 11, 2013. Record heat and strong winds hit the region on Tuesday, causing critical fire conditions. The Image credit: NASA.

The forecast: better, but still dangerous
Fire conditions will not be as dangerous in Colorado today, as winds will be lower, and temperatures will be a few degrees cooler due to a weak cold front that moved through the state overnight. Nevertheless, the air is still extremely dry and temperatures will be very hot, making it difficult for firefighters to gain the upper hand on the blazes. A red flag warning for dangerous fire conditions is posted for Colorado Springs, where winds of 10 - 20 mph, gusting to 30 mph, are expected in combination with relative humidities as low as 9% and temperatures in the low 90s. Colorado and New Mexico can expect a destructive fire season the remainder of June and into July, due to severe to exceptional drought conditions and hot temperatures. Relief will likely come in July with the arrival of wetter conditions thanks to the annual Southwest U.S. monsoon. Colorado Springs experienced the most expensive wildfire in Colorado history in 2012, the $353 million Waldo Canyon fire. The burn started on June 23rd and burned through July 10th, burning a total of 18,247 acres. Approximately 347 homes were burned, 2 people were killed, and over 32,000 residents were evacuated.


Video 1. A close escape from the Colorado Springs Black Forest fire. "I could hear the roar and the explosions of residential propane tanks heading toward Black Forest and Shoup Roads. Then came a wave of intense heat followed by a burst of fast-moving, oncoming flames. Firefighters and cops panicked, ordering me to leave: "Take pictures somewhere else," yelled one officer. I'm certain within moments of my escape the fire gobbled up a gas station and Firehouse BBQ restaurant at the corner I was standing on."

Related: Wildfires in the U.S. will be at least twice as destructive by 2050, burning around 20 million acres nationwide each year, according to a federal report released by the U.S. Department of Agriculture in 2012. The report cited research predicting that a 1.8°F increase in temperature in Colorado would cause a factor of 2.8 - 6.6 increase in fire area burned.

Wunderground member mfrazzz has a webcam pointed at the Colorado Springs Black Forest fire.


Figure 3. Severe weather outlook for Wednesday.

Severe weather outbreak Wednesday and Thursday
Tens of millions of Americans will be subject to a large outbreak of severe thunderstorms on Wednesday and Thursday, as a powerful low pressure system moves from the Great Lakes area to the East Coast. The greatest danger on Wednesday is for an organized complex of thunderstorms, possibly becoming a "derecho" event that brings widespread damaging straight-line winds to multiple states. A few strong tornadoes are also possible, and the Storm Prediction Center has issued their highest level of alert "High Risk" for Chicago and northern Indiana. This is the first "High Risk" forecast SPC has put out in 2013. Today marks the first "High Risk" forecast for Chicago since May 30, 2004, and the 16th since 1980. You can follow the outbreak on our severe weather page.


Jeff Masters

Fire

Updated: 7:23 PM GMT on June 12, 2013

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Extreme Jet Stream Pattern Triggers Historic European Floods

By: JeffMasters, 2:48 PM GMT on June 09, 2013

A historic multi-billion dollar flood disaster has killed at least eighteen people in Central Europe after record flooding unprecedented since the Middle Ages hit major rivers in Austria, the Czech Republic, Germany, Poland and Slovakia over the past two weeks. The Danube River in Passau, Germany hit the highest level since 1501, and the Saale River in Halle, Germany was the highest in its 400-year period of record. Numerous cities recorded their highest flood waters in more than a century, although in some locations the great flood of 2002 was higher. The Danube is expected to crest in Hungary's capital city of Budapest on June 10 at the highest flood level on record, 35 cm higher than the record set in 2006. The flooding was caused by torrential rains that fell on already wet soils. In a 2-day period from May 30 - June 1, portions of Austria received the amount of rain that normally falls in two-and-half months: 150 to 200 mm (5.9 to 7.9"), with isolated regions experiencing 250 mm (9.8"). This two-day rain event had a greater than 1-in-100 year recurrence interval, according to the Austrian Meteorological Agency, ZAMG. Prior to the late May rains, Austria had its seventh wettest spring in 150 years, which had resulted in the ground in the region becoming saturated, leading to greater runoff when the rains began.


Figure 1. Aerial view of the flooded Danube River in Deggendorf, Germany on Friday, June 7, 2013. (AP Photo/Armin Wegel)


Figure 2. The Danube River in Grein, Austria was barely kept in check by a floodwall built by IBS Engineering. Image credit: IBS Engineering.

Floods caused by a blocking high pressure system
The primary cause of the torrential rains over Central Europe during late May and early June was large loop in the jet stream that developed over Europe and got stuck in place. A "blocking high" set up over Northern Europe, forcing two low pressure systems, "Frederik" and "Günther", to avoid Northern Europe and instead track over Central Europe. The extreme kink in the jet stream ushered in a strong southerly flow of moisture-laden air from the Mediterranean Sea over Central Europe, which met up with colder air flowing from the north due to the stuck jet stream pattern, allowing "Frederik" and "Günther" to dump 1-in-100 year rains. The stuck jet stream pattern also caused record May heat in northern Finland and surrounding regions of Russia and Sweden, where temperatures averaged an astonishing 12°C (21°F) above average for a week at the end of May. All-time May heat records--as high as 87°F--were set at stations north of the Arctic Circle in Finland.


Figure 3. Nine-day rainfall amounts in portions of Southern Germany and Western Austria exceeded 12" (305 mm.) Image credit: ZAMG.

If it seems like getting two 1-in-100 to 1-in-500 year floods in eleven years is a bit suspicious--well, it is. Those recurrence intervals are based on weather statistics from Earth's former climate. We are now in a new climate regime with more heat and moisture in the atmosphere, combined with altered jet stream patterns, which makes major flooding disasters more likely in certain parts of the world, like Central Europe. As I discussed in a March 2013 post, "Are atmospheric flow patterns favorable for summer extreme weather increasing?", research published this year by scientists at the Potsdam Institute for Climate Impact Research (PIK) in German found that extreme summertime jet stream patterns had become twice as common during 2001 - 2012 compared to the previous 22 years. One of these extreme patterns occurred in August 2002, during Central Europe's last 1-in-100 to 1-in-500 year flood. When the jet stream goes into one of these extreme configurations, it freezes in its tracks for weeks, resulting in an extended period of extreme heat or flooding, depending upon where the high-amplitude part of the jet stream lies. The scientists found that because human-caused global warming is causing the Arctic to heat up more than twice as rapidly as the rest of the planet, a unique resonance pattern capable of causing this behavior was resulting. According to German climate scientist Stefan Rahmstorf, "Planetary wave [jet stream] amplitudes have been very high in the last few weeks; we think this plays a role in the current German flooding event." More rains are in store for the flood area through Monday, then the blocking pattern responsible for the great 2013 Central European flood is expected to disintegrate, resulting in a return to more typical June weather for the next two weeks.


Figure 4. The northward wind speed (negative values, blue on the map, indicate southward flow) at an altitude of 300 mb in the mid-latitudes of the Northern Hemisphere during July 1980, July 2011, and the last twelve days of May 2013. July of 2011 featured an unusually intense and long-lasting heat wave in the U.S. (the 4th warmest month in U.S. history), and the normally weak and irregular waves (like observed during the relatively normal July of 1980) were replaced by a strong and regular wave pattern. Late May 2013 was also very extreme, resulting the great Central European floods of 2013. Image credit: Vladimir Petoukhov and Stefan Rahmstorf.

Links
Stefan Rahmstorf's blog (translated from German) on the unusual jet stream patterns that caused the Central European floods of 2013.

NASA has high-resolution MODIS satellite images showing the flooding of the Elbe River in Germany.

My April 2013 post, "Unusually cold spring in Europe and the Southeast U.S. due to the Arctic Oscillation", has a good summary of recent unusual jet stream patterns and the science behind them.


Video 1. Climate, Ice, and Weather Whiplash: In this June 3, 2013 video by the Yale Climate Forum's Peter Sinclair, Rutgers' Jennifer Francis and Weather Underground's Jeff Masters explore the 'Why?' of two years of mirror images of weather across North America.

I'm in Granby, Colorado this week for the American Geophysical Union's Chapman Conference on Climate Change Communication. Many of the talks will be webcast live; you can see a list of the talks (times in MDT) here. My talk, "The Weather Underground Experience," is scheduled for Monday at 4:30 pm MDT. I'll give a 15-minute overview of the history of wunderground, and what I've learned about communicating weather and climate change information along the way. There is live tweeting going on from the conference, #climatechapman. My blog updates this week may be somewhat random as a result of the conference, but I'm not seeing anything in the tropics worthy of discussion at this point.

Jeff Masters

Flood Climate Change

Updated: 7:17 PM GMT on June 10, 2013

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Tropical Storm Andrea Spreading Heavy Rains to U.S. East Coast

By: JeffMasters, 1:39 PM GMT on June 07, 2013

Tropical Storm Andrea is rapidly losing its tropical characteristics as it barrels northeastwards at 27 mph up the U.S. East Coast, but it still has plenty of tropical moisture that is feeding very heavy rains. Rains of 2 - 4" are expected along a swath from South Carolina to New England from Andrea over the next two days. Pine Ridge, NC has received 6.5" of rain from Andrea, and New River MCAS, North Carolina picked up 2" of rain as of 9 am EDT this morning, along with a wind gust of 47 mph at 3:18 am. The same band of heavy thunderstorms spawned a possible tornado near Hubert, North Carolina at 4:45 am EDT. Andrea has spawned a preliminary count of eleven tornadoes, which is a respectable number for a landfalling June tropical storm, but not a record. According to TWC's severe weather expert Dr. Greg Forbes, there have been two other June tropical storms since the year 2000 that spawned far more tornadoes--Tropical Storm Bill during June 29 - July 3, 2003 (32 tornadoes in FL, GA, LA, AL, MS, SC, NC, NJ), and Tropical Storm Allison of June 7 - 17 2001 (28 tornadoes in FL, AL, GA, LA, MS, SC, VA, MA, ME.) Only one of Andrea's tornadoes caused an injury, a tornado that hit The Acreage in Palm Beach County at 6:45 am EDT. The highest storm surge from Andrea was 4.55' at Cedar Key, Florida.


Figure 1. Yummy’s cafe in Gulfport, Florida was hit Thursday morning by a waterspout that moved ashore and became a tornado.(LAUREN CARROLL/Tampa Bay Times)


Figure 2. Predicted rainfall for the 48-hour period from 8 am EDT Friday, June 7, to 8 am EDT Sunday, June 8, 2013. Image credit: NOAA.


Video 1. NASA animation of Andrea satellite images. More cool NASA images of Andrea are here.

The Atlantic hurricane season is getting longer
Andrea's formation in June continues a pattern of an unusually large number of early-season Atlantic named storms we've seen in recent years. Climatologically, June is the second quietest month of the Atlantic hurricane season, behind November. During the period 1870 - 2012, we averaged one named storm every two years in June, and 0.7 named storms per year during May and June. In the nineteen years since the current active hurricane period began in 1995, there have been fifteen June named storms (if we include 2013's Tropical Storm Andrea.) June activity has nearly doubled since 1995, and May activity has more than doubled (there were seventeen May storms in the 75-year period 1870 - 1994, compared to 6 in the 19-year period 1995 - 2013.) Some of this difference can be attributed to observation gaps, due to the lack of satellite data before 1966. However, even during the satellite era, we have seen an increase in both early season (May - June) and late season (November - December) Atlantic tropical storms. Dr. Jim Kossin of the University of Wisconsin looked at the reasons for this in a 2008 paper titled, "Is the North Atlantic hurricane season getting longer?" He concluded that there is a "apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high." He found that hurricane season for both the period 1950-2007 and 1980-2007 got longer by 5 to 10 days per decade (see my blog post on the paper.)

Invest 92L in the Central Atlantic no threat to develop
Satellite images show that disorganized tropical wave is in the Central Atlantic, about a two-day journey from the Lesser Antilles Islands. NHC designated this system 92L Thursday afternoon. High wind shear of 30 - 40 knots is ripping up the thunderstorms in 92L as they form, and wind shear is predicted to remain 30 - 40 knots for the next five days, making development unlikely. The wave will likely bring heavy rain showers and gusty winds to the northern Lesser Antilles Islands beginning on Sunday night. None of the reliable computer models is showing development of a tropical cyclone in the Atlantic over the next seven days.

Jeff Masters

Hurricane

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Tropical Storm Andrea hits Florida

By: JeffMasters, 11:19 PM GMT on June 06, 2013

Tropical Storm Andrea made landfall near 5:40 pm EDT in the Big Bend region of Florida as a tropical storm with 65 mph winds. Andrea had a busy day Thursday in Florida, dumping heavy rains, spawning ten tornadoes, and bringing a storm surge of up to 4.5' to the coast. While the Hurricane Hunters did measure sustained winds of 65 mph over the ocean shortly before landfall, very few land stations recorded sustained winds in excess of tropical storm force, 39 mph. Here are some of the higher winds measured at coastal stations:

A personal weather station at Bald Point State Park near Apalachicola had sustained winds of 46 mph at 10 am EDT.
Cedar Key had sustained winds of 40 mph, gusting to 50 mph, at 3:43 pm EDT.
Punta Gorda had sustained winds of 37, gusting to 58, at 1:04 pm EDT.
St. Petersburg topped out at 34 mph, gusting to 48 mph, at 10:23 am EDT.

Two sets of tornadic rain bands moved through West Florida on Thursday, one between 2 am and 5 am, and the other between 10 am and 3 pm, spawning a total of five suspected tornadoes. The first band produced two EF-0 tornadoes: one with 75 mph winds that hit Myakka City, damaging 3 homes and 10 other buildings, and one with 80 mph winds that cut throughout the heart of Sun City, causing minor damage. NWS damage surveys will be occurring Friday in Fort Myers, Venice, Clearwater, and Gulfport to check out the damage swaths of the other three suspected tornadoes.

The Florida East Coast was hit by five suspected tornadoes. Only one caused an injury, a tornado that hit The Acreage in Palm Beach County at 6:45 am EDT. Two other tornadoes were reported in Broward and Palm Beach Counties, and two more were reported in coastal areas near the Georgia border.

Here are the highest storm surge values as of 7:00 pm EDT:

3.2' at Tampa (at McKay Bay Entrance)
2.5' at Clearwater Beach (near St. Petersburg)
4.5' at Cedar Key


Figure 1. MODIS satellite image of Tropical Storm Andrea at 1pm EDT Thursday, June 6, 2013. At the time, Andrea had top winds of 60 mph and was 5.7 hours away from landfall in Florida's Big Bend. Image credit: NASA.


Video 1. NASA animation of Andrea satellite images. More cool NASA images of Andrea are here.

The Atlantic hurricane season is getting longer
Andrea's formation in June continues a pattern of an unusually large number of early-season Atlantic named storms we've seen in recent years. Climatologically, June is the second quietest month of the Atlantic hurricane season, behind November. During the period 1870 - 2012, we averaged one named storm every two years in June, and 0.7 named storms per year during May and June. In the nineteen years since the current active hurricane period began in 1995, there have been fifteen June named storms (if we include 2013's Tropical Storm Andrea.) June activity has nearly doubled since 1995, and May activity has more than doubled (there were seventeen May storms in the 75-year period 1870 - 1994, compared to 6 in the 19-year period 1995 - 2013.) Some of this difference can be attributed to observation gaps, due to the lack of satellite data before 1966. However, even during the satellite era, we have seen an increase in both early season (May - June) and late season (November - December) Atlantic tropical storms. Dr. Jim Kossin of the University of Wisconsin looked at the reasons for this in a 2008 paper titled, "Is the North Atlantic hurricane season getting longer?" He concluded that there is a "apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high." He found that hurricane season for both the period 1950-2007 and 1980-2007 got longer by 5 to 10 days per decade (see my blog post on the paper.)


Figure 2. MODIS satellite image of 92L taken on June 6, 2013. Image credit: NASA.

Invest 92L in the Central Atlantic headed towards the Lesser Antilles
Satellite images show that a large and unusually well-organized tropical wave for so early in the season has developed in the Central Atlantic, midway between Africa and the Lesser Antilles Islands. The wave has a modest degree of spin and heavy thunderstorms. NHC designated this system 92L Thursday afternoon. High wind shear of 20 - 25 knots is ripping up the thunderstorms in 92L as they form, though, and wind shear is predicted to increase to 30 - 40 knots Thursday night through Monday, making development unlikely. The wave will likely bring heavy rain showers and gusty winds to the northern Lesser Antilles Islands beginning on Sunday night.

Jeff Masters

Hurricane

Updated: 11:28 PM GMT on June 06, 2013

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Andrea Intensifies to a 60 mph Tropical Storm, Spawns 5 Tornadoes in Florida

By: JeffMasters, 1:30 PM GMT on June 06, 2013

Tropical Storm Andrea has exceeded expectations. An Air Force hurricane hunter plane flying through Andrea near 3 am EDT found that a strong band of heavy thunderstorms with moderate turbulence and intense lightning had wrapped partway around the center, and Andrea had intensified into a respectable tropical storm with 60 mph sustained winds and a central pressure of 997 mb. The intensification occurred despite the presence of a large area of dry air to the storm's west, and high wind shear of 25 knots. Satellite loops show that Andrea has expanded in size this morning, and its heavy thunderstorms have become more intense. The heaviest thunderstorms were in a band well away from the center, extending from Tampa southwestwards over the Gulf of Mexico. There is a large slot of dry air behind this band, and Andrea may be able to close this intrusion of dry air off early this afternoon, and build additional heavy thunderstorms near its center. However, given the continued presence of dry air and increasing wind shear, and little time before landfall, it will be difficult for Andrea to reach hurricane strength before landfall occurs early this evening--though I won't rule out intensification to a 70 mph tropical storm. Heavy rains of 3 - 6" that have the potential to cause flash flooding will be the storm's main threat. Carrabelle, near Apalachicola, reported 4.5" of rain in a 5-hour period ending at 8 am EDT. Tornadoes in some of the heavier thunderstorms in Andrea's spiral bands are also a concern, and the storm had already spawned five tornadoes as of 9 am EDT. Bands of heavy thunderstorms with embedded rotating thunderstorms capable of generating tornadoes where over both the west and east coasts of Florida between 6 am - 8am, triggering tornado warnings in the counties near Fort Lauderdale and Tampa Bay. A tornado hit The Acreage in Palm Beach County at 6:45 am EDT, injuring one person, damaging homes, and downing trees and power lines. Two other tornadoes were reported on Florida's east coast, one in Broward County, and one in Palm Beach County. Andrea also spawned two tornadoes southeast of Tampa Bay between 2:30 am and 4 am EDT Thursday, but damage was minor. Most of South and Central Florida are under a tornado watch today. A storm surge of 2 - 5 feet is predicted for Tampa Bay northward to Apalachicola, and rip currents will be a risk for swimmers who brave the high surf. As of 9 am EDT Thursday, our wundermap with the storm surge layer turned on was showing storm surge levels just over 1 foot near Tampa and Apalachicola on Florida's Gulf Coast.

We won't have any new wind measurements from the Hurricane Hunters until about 3 pm EDT. Buoy 42036, 122 miles west-northwest of Tampa, reported sustained winds of 40 mph, gusting to 51 mph, between 7 am - 8 am EDT, when the center of Andrea was located about 60 miles to the south-southwest. Winds at a personal weather station at Bald Point State Park near Apalachicola hit 39 mph at 9 am EDT. Winds at Cedar Key were sustained at 28 mph, gusting to 34 mph, at 8:33 am EDT.



Figure 1. Composite radar reflectivity image of Tropical Storm Andrea at 9 am EDT Thursday, June 6, 2013.

Andrea's place in history
Andrea formed in a typical location for early-season storms. The Gulf of Mexico, Western Caribbean, and Bahamas are the usual areas for the genesis of June tropical storms. Andrea's formation date of June 5 is over a month earlier than the average July 9 date for formation of the season's first named storm. On average, the Atlantic sees one June named storm every two years. In 2012, we'd already had two named storms by this point in the season--Alberto and Beryl. This year is the second time a storm named Andrea has appeared in the Atlantic. The previous incarnation, Subtropical Storm Andrea of 2007, wandered off the U.S. East Coast in May, and never made landfall. The 2013 version of Andrea is highly unlikely to get its name retired, and we'll be seeing a third coming of the storm in 2019.

Jeff Masters

Hurricane

Updated: 5:26 PM GMT on June 06, 2013

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Tropical Storm Andrea Forms in Gulf of Mexico

By: JeffMasters, 11:15 PM GMT on June 05, 2013

The Atlantic has its first named storm of the 2013 hurricane season: Tropical Storm Andrea. An Air Force hurricane hunter plane was able to locate a closed center of circulation, and found surface winds of 40 mph in the large area of thunderstorms on the east side of the center. Satellite loops show that Andrea is a lopsided storm. It's center of circulation is exposed to view, due to a large region of dry air that covers the entire Central and Western Gulf of Mexico. This dry air is from a trough of low pressure whose upper level winds are also creating moderate wind shear of 15 - 20 knots over Andrea. Wind shear is forecast to rise to the high range, 20 - 40 knots, by Thursday. Andrea is forecast to make landfall along the northern Gulf Coast of Florida by Thursday evening, so the system has a short window of time to intensify. Given the large amount of dry air to Andrea's west, and the forecast for increasing shear up until landfall, I expect that the strongest sustained winds Andrea could have before landfall are 50 mph. Heavy rains will be the storm's main threat, though a few isolated EF-0 tornadoes will also be possible in some of the heavier thunderstorms in Andrea's spiral bands. A storm surge of 2 - 4 feet is predicted for Tampa Bay northward to Apalachicola, and rip currents will be a risk for swimmers who brave the high surf. Fort Pickens, located in Gulf Islands National Seashore on a barrier island offshore from Pensacola, Florida, has been closed to visitors due to the approaching storm. A single 2-lane road vulnerable to storm surges runs to Fort Pickens. Officials want to prevent a repeat of the situation that occurred in September 2011, when Tropical Storm Lee pushed a storm surge over the road that blocked it with sand and debris, trapping numerous campers and visitors in Fort Pickens. As of 7 pm EDT, our wundermap with the storm surge layer turned on was showing storm surge levels were less than 1 foot along the Florida coast.


Figure 1. MODIS image of Tropical Storm Andrea in its formative stages, taken at 12:20 pm EDT Wednesday, June 5, 2013, five hours before it was named. Image credit: NASA.

Andrea's place in history
Andrea formed in a typical location for early-season storms. The Gulf of Mexico, Western Caribbean, and Bahamas are the usual areas for the genesis of June tropical storms. Andrea's formation date of June 5 is over a month earlier than the average July 9 date for formation of the season's first named storm. On average, the Atlantic sees one June named storm every two years. In 2012, we'd already had two named storms by this point in the season--Alberto and Beryl. This year is the second time a storm named Andrea has appeared in the Atlantic. The previous incarnation, Subtropical Storm Andrea of 2007, wandered off the U.S. East Coast in May, and never made landfall. The 2013 version of Andrea is highly unlikely to get its name retired, and we'll be seeing a third coming of the storm in 2019.

Jeff Masters

Hurricane

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Gulf Distubance 91L More Organized, Headed Towards Florida

By: JeffMasters, 5:21 PM GMT on June 05, 2013

Tropical disturbance 91L in the Southeast Gulf of Mexico has gotten more organized over the past day, and the Hurricane Hunters are scheduled to fly their first mission of 2013 this afternoon to see if the storm is becoming a tropical depression. Buoy 42003 near the heaviest thunderstorms of 91L measured sustained winds of 33 mph, gusting to 41 mph this morning at 2 am EDT. Satellite loops show a lopsided storm, with a large area of heavy thunderstorms on the east side of a center of circulation that is trying to develop at the edge of a region of dry air that covers the entire Central and Western Gulf of Mexico. This dry air is due to a trough of low pressure whose upper level winds are also creating moderate wind shear of 15 - 20 knots. Wind shear is forecast to rise to the high range, by Thursday, and 91L is forecast to make landfall along the northern Gulf Coast of Florida on Thursday evening, so the system has a short window of time to intensify. NHC is giving the disturbance a 50% chance of developing into a tropical cyclone. I put these odds higher, at 60%. If it does develop, it will be difficult for 91L to get any stronger than a 45 mph tropical storm in the Gulf of Mexico. Regardless of whether or not 91L develops into a tropical depression, heavy rains will be the storm's main threat. A swath from Florida to New England can expect 2 - 4" of rain. A few isolated EF-0 tornadoes will also be possible along the northern Florida Gulf Coast. A storm surge of 1 - 3 feet is predicted for Cedar Key, Florida, and rip currents will be a risk for swimmers who brave the high surf. Fort Pickens, located in Gulf Islands National Seashore on a barrier island offshore from Pensacola, Florida, has been closed to visitors due to the approaching storm. A single 2-lane road vulnerable to storm surges runs to Fort Pickens. Officials want to prevent a repeat of the situation that occurred in September 2011, when Tropical Storm Lee pushed a storm surge over the road that blocked it with sand and debris, trapping numerous campers and visitors in Fort Pickens.

The storm is getting caught up in a trough of low pressure that will pull it quickly to the north-northeast beginning on Thursday, with the center expected to move over coastal North Carolina on Friday afternoon, and over Massachusetts on Friday night. If 91L does manage to become a tropical storm before making landfall on Thursday, it will quickly degenerate into a regular extratropical low pressure system before moving up the East Coast.


Figure 1. Latest satellite image of Invest 91L.


Figure 2. Predicted precipitation for the 7-day period ending June 12, 2013 from the NWS/NCEP. A swath of 2 - 4" of rain is expected from Florida to New England from 91L.

Jeff Masters

Hurricane

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Largest Tornado on Record: the May 31 El Reno, OK EF-5 Tornado

By: JeffMasters, 9:54 PM GMT on June 04, 2013

The largest tornado in recorded history was Friday's May 31, 2013 EF-5 tornado in El Reno, Oklahoma, the National Weather Service in Norman, Oklahoma announced on Tuesday. The EF-5 re-classification was based upon Doppler radar data taken by Oklahoma University's mobile RaXPol radar. According to comments made by tornado researcher Rick Smith at a press conference today, the mobile radar was positioned on top of an overpass, and recorded winds close to the surface of up to 295 mph in satellite suction vorticies that orbited the large, main vortex. The large, main vortex had EF-4 winds of 185 mph, and the satellite suction vortices moved across the fields at that speed, and rotated on their own at speeds of up to 110 mph, giving a combined wind speed of up to 295 mph in some of the satellite vortices. It's no wonder that so many storm chasers got in trouble with this tornado, since these suction vortices moved as speeds of up to 185 mph towards them as the tornado rapidly expanded into the largest on record. The tornado killed tornado scientist Tim Samaras and his two chase partners, Paul Samaras and Carl Young, and also killed an amateur storm chaser, Richard Charles Henderson. The 295 mph winds of the El Reno tornado rank second only to the world-record 302 mph (135 m/s) winds recorded in the Moore, Oklahoma tornado of May 3, 1999. However, the Moore tornado's winds were measured at an altitude of 105 feet (32 meters), so the winds near the surface may have been higher in the El Reno tornado.


Figure 1. Path of the May 31, 2013 El Reno, Oklahoma tornado from the National Weather Service in Norman, Oklahoma. Note how the tornado began moving directly down I-40 as it headed towards Oklahoma City; had the tornado maintained its EF-5 strength and moved down I-40 into Oklahoma City, where traffic was bumper-to-bumper due to people trying to flee, the greatest tornado disaster in U.S. history would have resulted.


Video 1. The May 31, 2013 El Reno, Oklahoma EF-5 tornado as filmed by storm chasers Justin Hoyt and Stephen Barabas, another team of chasers that were in extreme danger from the tornado. Their description: "The LONGER, INCREDIBLE WAY TOO CLOSE video of the multivortex tornado near El Reno, Oklahoma on May 31st. This beast quickly turned onto us and grew into an over 2.6 mile wedge, the largest on record. After the easy escape from the multivortex, we ended up dropping south right into the damage path of the monster, getting caught up in its outer circulation. The dangerous aspect was that chasers were positioned all over the road and backed up in a panic instead of immediately turning around." Warning: foul language, including one F-bomb. A more detailed account of the chase is here.

Previous record largest tornado: 2.5 miles in diameter
The previous official record for the widest tornado belonged to the EF-4 Wilber - Hallam, Nebraska tornado on May 22, 2004, which had a damage path up to 2.5 miles wide. However, NOAA's Storm Data publication documents that the EF-3 Edmonson, Texas tornado of May 31, 1968 had a damage path width between 2 and 3 miles (3.2 and 4.8 km) wide. In addition, Doppler radar measurements indicate that the May 4, 1999 Mulhall, Oklahoma EF-4 tornado--which thankfully passed mostly over farmland--would have caused damage over a path 4 miles wide at its peak size, had it encountered a built-up area.


Figure 2. Damage swath of the Wilber - Hallam, Nebraska F-4 tornado of May 22, 2004 was up to 2.5 miles wide, making it one of the largest tornadoes on record.

Wunderground has large 2 Mb animations of the high-resolution radar reflectivity and Doppler velocity Level II radar data, with the damage path of the May 31, 2013 El Reno tornado overlaid.

Jeff Masters

Tornado

Updated: 4:33 PM GMT on June 05, 2013

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Little Change to 91L; Amateur Storm Chaser Killed in May 31 El Reno, OK Tornado

By: JeffMasters, 2:59 PM GMT on June 04, 2013

There has been little change to tropical disturbance 91L in the Southeast Gulf of Mexico and Western Caribbean. Satellite loops show a large area of heavy thunderstorms with poor organization, and there is no evidence of an organized surface circulation trying to form. Wind shear is a high 30 knots, and is forecast to remain high, 20 - 30 knots, today, so any development should be slow to occur. However, wind shear is predicted to drop to the moderate range, 10 - 20 knots, on Wednesday, which should give 91L a better chance to organize. NHC is giving the disturbance a 30% chance of developing into a tropical cyclone by Thursday. I put these odds higher, at 40%. The Hurricane Hunters are on call to fly into 91L on Tuesday afternoon, but this flight will likely be cancelled. Regardless of whether or not 91L develops into a tropical depression, heavy rains will be the storm's main threat. Mexico's Yucatan Peninsula, Western Cuba, and South Florida can expect 5 - 8" of rain from the disturbance over the next four days. Heavy rains from 91L may spread up the U.S. East Cost late this week. The computer models predict that 91L should stay large and poorly organized, and if it does develop, it will be difficult for it to get any stronger than a 45 mph tropical storm in the Gulf of Mexico.


Figure 1. Latest satellite image of Invest 91L.


Video 1. The May 31, 2013 El Reno, Oklahoma EF-3 tornado as filmed from a commercial tornado tour led by Tempest Tours. This is one of the most impressive videos I've ever seen, from a meteorological standpoint, of a developing tornado. It appears that the chasers got closer to the tornado than they liked, as evidenced by the honking horns you hear, telling people to leave, a few minutes into the video.

Amateur storm chaser killed in Friday's El Reno tornado
Tornado scientist Tim Samaras and his two chase partners, Paul Samaras and Carl Young, were killed Friday by an EF-3 tornado that hit El Reno, Oklahoma. It has now been revealed that the storm killed an amateur storm chaser, Richard Charles Henderson. According to an article in The Oklahoman,

From his pickup, amateur storm chaser Richard Charles Henderson took a cellphone photo of the first tornado Friday and excitedly sent it to a friend. Minutes later, that tornado would kill him.

“That was the end of his life right there,” said the friend, George “Sonny” Slay. “He said, ‘I'm having fun,'” Slay recalled Monday. “He told me he was riding around … chasing the storms …. I said, ‘You better quit that!'
“And, then, I guess he was en route to the position that he got in because he said, ‘There goes Channel 9!' He said, ‘You might even see me on TV.' And, then a few seconds later, he said, ‘Oop, there's Channel 5!'”

Slay said the picture came in at 6:05 p.m. About 10 minutes later, Slay heard a loud popping noise over the phone. Henderson cursed, and then asked Slay if he had heard the sound.

“I said, ‘Yeah, I heard it. What was it?' And he said, ‘It's debris hitting my pickup.' I said, ‘You better get your ass out of there.' Then the phone went dead.

Henderson, of Hinton, was one of at least 18 people who died because of Friday's tornadoes and storms. His body was found near El Reno.


Henderson's death underscores the dangers of storm chasing by people who don't know what they are doing, and is also likely the unfortunate consequence of the huge amount of dramatic media attention that storm chasing has received in recent years.


Video 2. The view from my veteran storm chaser Chris Novy's D-TEG dashcam as he accidentally drove his storm chasing vehicle into a swollen creek, nearly killing him.


Figure 2. Chris Novy posted on his Facebook page this image of the bridge he drove off. Note the guard rail that stops short of the plunge he took. I hope the road commission extends this guard rail to prevent a future accident!

Veteran storm chaser almost killed in Friday's El Reno flash flood
There is also news that another veteran storm chaser, Chris Novy, nearly died in Friday's storm--but from a flash flood. As Novy recounted in Mike Smith Enterprises Blog,

"I approached a flooded road and made a quick U-turn rather than driving [all the way] into the water. This was a naturally smart move. Unfortunately my turn resulted in me plunging off a hidden embankment and splashing nose-first right into a swollen creek where I sunk straight to the bottom, I traveled several hundred feet underwater with the car quickly filling up. At one point I was completely surrounded by water and just holding my breath in the darkness. Somehow the driver-side and passenger-side windows broke and I was flushed from the vehicle. I surfaced after a bit and found myself racing down the creek. A cop called out to me and I was able to swim to him and his life-saving grab.

Analysis:
It probably would have been best for the police car (seen right before my turn) to have completely blocked the road the emergency lights on. As it was, the scene seemed like just a water hazard but probably should have been clearly marked as a no-go zone.

I should have come to a complete stop and taken more time to evaluate the situation. Ideally I should have just put it into reverse and slowly backed out. I took a dangerous situation and made it even worse leaping before I looked.

Lessons learned:
Turn around, don't drown!"



Figure 3. Portlight volunteers hard at work in Moore, Oklahoma, after the devastating May 20, 2013 tornado.

Portlight helping victims of Oklahoma tornadoes, and hosting the Getting It Right Conference
I had the pleasure last night of giving the welcoming speech to the attendees of the "Getting It Right Conference" in Atlanta, hosted by my favorite disaster relief charity, Portlight.org.The conference has brought together over 125 disaster response professionals to discuss shelter and transportation accessibility for people with disabilities. There will be live blogging from the conference on Portlight's wunderground blog, 8am to 5pm Tuesday, and 8am to 11am on Wednesday. Check it out! It's remarkable how far Portlight has come since its humble beginnings in September 2008, when wunderground members Patrick Pearson and Paul Timmons put together a grass-roots effort to help out victims of Hurricane Ike. Portlight has now dispensed over $2 million in aid to the needy, and hundreds of volunteers have worked on various Portlight projects since 2008. Indeed, Portlight volunteers are now hard at work helping victims of Oklahoma's devastating May tornadoes. Keep up the great work!

Jeff Masters

Hurricane Tornado

Updated: 3:00 PM GMT on June 04, 2013

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Invest 91L Bringing Heavy Rains to Florida, Cuba, and Mexico

By: JeffMasters, 3:44 PM GMT on June 03, 2013

The Atlantic hurricane season began on June 1, and we already have a threat to discuss. A trough of low pressure has developed over the Western Caribbean, Mexico's Yucatan Peninsula, and Southeast Gulf of Mexico, and is dumping heavy rains over the area. Hurricane Barbara, which died on Thursday as it attempted to cross Mexico's Isthmus of Tehuantepec into the southernmost Gulf of Mexico, has contributed moisture to this disturbance, which has been designated 91L by NHC. Satellite loops show a large area of heavy thunderstorms with poor organization, and there is no evidence of an organized surface circulation trying to form. Wind shear is a high 30 knots, and is forecast to remain high, 20 - 30 knots, over the next five days, so any development should be slow to occur. NHC is giving the disturbance a 20% chance of developing into a tropical cyclone by Wednesday. The Hurricane Hunters are on call to fly into 91L on Tuesday afternoon, if necessary. Regardless of whether or not 91L develops into a tropical depression, heavy rains will be the storm's main threat. Mexico's Yucatan Peninsula, Western Cuba, and South Florida can expect 5 - 8" of rain from the disturbance over the next four days. Heavy rains from 91L may spread up the U.S. East Cost late this week. The computer models predict that 91L should stay large and poorly organized, and if it does develop, it will be difficult for it to get any stronger than a 45 mph tropical storm in the Gulf of Mexico.


Figure 1. Latest satellite image of Invest 91L.

Jeff Masters

Hurricane

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Tornado Scientist Tim Samaras and Team Killed in Friday's El Reno, OK Tornado

By: JeffMasters, 5:43 PM GMT on June 02, 2013

Veteran tornado scientist Tim Samaras, his son, environmental photographer Paul Samaras, 24, and meteorologist Carl Young, 45, died while chasing Friday's EF-3 tornado in El Reno, Oklahoma. The tornado killed at least nine people, in total. "Thank you to everyone for the condolences. It truly is sad that we lost my great brother Tim and his great son, Paul," said the brother of Tim Samaras, Jim Samaras, on Tim's Facebook page. "They all unfortunately passed away but doing what they LOVED." Tim, his son Paul, and Carl Young were all featured chasers on the Discovery Channel’s series, Storm Chasers, and Tim was known throughout the chase community as a conscientious and safety-minded chaser. Carl Young, who holds a Masters degree in meteorology from the University of Nevada, joined Samaras in the field in 2003. According to his Discovery Channel biography, Young and Samaras chased over 125 tornadoes together: "Carl's finest moment came on June 11, 2004 near Storm Lake, Iowa. Working with Tim, they defied the odds and deployed their probes right in the path of a tornado. The six-camera video probe captured amazing footage from multiple angles while the sensor probe recorded data that revealed just how fast wind speeds are close to the ground."


Figure 1. TWC's Mike ‪Bettes‬ crew caught this image of the El Reno, Oklahoma tornado of May 31, 2013 before the tornado caught them and rolled their vehicle. The tornado killed tornado scientists/storm chasers Tim Samaras, Paul Samaras, and Carl Young.


Figure 2. Storm chasers in North Dakota aligned themselves to spell out "T S" in honor of Tim Samaras today. Image credit: spotternetwork.org.

Tornado science loses a pioneer
Tim Samaras had been a tornado scientist for over 25 years. He was the founder of TWISTEX, the Tactical Weather Instrumented Sampling in Tornadoes Experiment, a 2011 field experiment designed to help learn more about tornadoes and increase lead time for warnings, which resulted in many peer-reviewed publications and conference presentations. One of Tim Samaras' most widely recognized contributions to tornado science is his placement of an aerodynamically-designed probe in the path of an EF-4 tornado near Manchester, South Dakota on June 24, 2003. The probe measured a world-record pressure fall of 100 mb over a 40 second period.

One of the publications from the TWISTEX program, "Near-Ground Pressure and Wind Measurements in Tornadoes" recounts this close call Tim had in a tornado in 2011: "As the storm approached, the crew noted that the supercell was moving more sharply to the right of its former course, placing them near the projected path of the low-level mesocyclone. The crew drove south on Highway 259, attempting to position south of the low-level mesocyclone before it crossed the highway. With considerable tree cover in this region hampering the visual observation of the storm's features, TWISTEX crews could not position south of the mesocyclone on Highway 259 before the mesocyclone reached this road. Thus, the two mobile mesonet stations, M2 and M3, had an unplanned tornado encounter with a developing tornadic circulation while the mesonet was traveling south on Highway 259."


Figure 3. One of Tim Samaras' most widely recognized contributions to tornado science is his placement of an aerodynamically-designed probe in the path of an EF-4 tornado near Manchester, South Dakota on June 24, 2003. The probe measured a world-record pressure fall of 100 mb over a 40 second period. See the NWS article and conference paper on the event. Thanks to wunderground member Scott Lincoln for this link.

A storm chasers' nightmare
Cars and tornadoes can prove a dangerous mix even for the world's most experienced storm chasers. Driving at high speeds though heavy rain, large hail, and high winds is hazardous. If one is lucky enough to chase down a tornado, even the most experienced chasers can find themselves in a serious life-threatening situation when unexpected events occur. The exact circumstances of the deaths of Tim Samaras and his team are not clear, but the El Reno tornado was an extremely dangerous one to chase. Tornadoes by their nature are unpredictable, and can change course unexpectedly, or pop up suddenly. It's particularly dangerous when a tornado is wrapped in rain, making it hard to see, or if a chaser is operating in a heavily populated area, where roads may suddenly become congested. All four of these conditions occurred Friday during the El Reno tornado. The El Reno tornado was wrapped in rain and difficult to see as it headed west towards Oklahoma City, and suddenly made a jog to the southeast as a Weather Channel team led by Mike Bettes was attempting to get in front of the storm, and the tornado lifted their vehicle off the ground, rolled it multiple times, and hurled it 200 yards into a nearby field. Austin Anderson was driving the Tornado Hunt vehicle, and suffered several broken bones and was hospitalized. Although Austin will have to undergo surgery in the next few days, doctors say he is expected to make a full recovery. StormChasingVideo.com storm chaser Brandon Sullivan and his chase partner Brett Wright got caught in the tornado northwest of Union City, OK and slammed with debris as the tornado hit a barn that exploded in front of them. Meteorologist Emily Sutton and storm chaser Kevin Josefy of local Oklahoma City TV station KFOR also had a very close call with the El Reno tornado Friday afternoon. They got too close to the tornado, and were forced to floor the car in reverse to escape flying debris. With branches of trees crashing around them, Sutton began feeling debris hitting her back, and realized that the rear windshield of the car must have gotten destroyed. Both were uninjured. Reed Timmer's armor-plated "Dominator" chase vehicle had its hood torn off by the tornado. Wunderground member Levi32 was out storm chasing during the El Reno Tornado, and got stuck in traffic on Highway 4 and couldn't move. "We looked up above the car and saw the wall cloud over top of us, with very quick rotation and rising scud indicating the updraft. We were definitely too close."


Video 1. Severe storm researcher and engineer Tim Samaras talks about his view on tornadoes and what remains to be understood in this interview posted on May 21, 2013.


Video 2. A tornado passes over one of Tim Samaras' specially designed six-camera video probes on June 11, 2004 near Storm Lake, Iowa.

Tornadoes and cars: a dangerous mix
A vehicle is about the worst place you can be in a tornado, as the tornado's winds can easily roll a car. (The only place less safe is probably a mobile home, as a tornado's winds can roll mobile homes almost as readily, and mobile homes don't come with seat belts and air bags.) At least five of the deaths in Friday's El Reno tornado occurred in vehicles. There was one local TV station that urged residents without underground shelters to get in their cars and "get south" in advance of the tornado that was approaching Oklahoma City, since chasers were reporting that the El Reno tornado may have been so strong that only an underground shelter would have provided adequate protection. This terrible piece of advice likely contributed to the incredible traffic jams that we saw on I-35, I-40, I-44, and other local roads Friday night. Thousands of cars were bumper-to-bumper on the roads as a dangerous tornado approached them. Had the El Reno tornado plowed directly down one of these car-choked interstates, the death toll could have easily exceeded 500. If you are located in a metro area and don't have an underground shelter, the best thing to do it to take shelter in an interior windowless room or hallway, with protective furniture over your body. Getting in a car and attempting to flee the tornado is the worst thing you can do in an urban area. You may not be able to see the tornado if it is dark or the tornado is wrapped in rain. You are likely to encounter hazardous winds, rain, and hail, run into unexpected traffic, or flooded or debris-blocked roads that will put you directly in the path of the tornado. Even without an underground shelter, most people will be able to survive a dangerous EF-4 tornado. Case in point: during the Mannsford, Oklahoma EF- 4 tornado of 1984, a packed church received a direct hit, and everyone in the church survived. The only fatality was a man who drove to the church to get his wife. It is often better to abandon your vehicle and take shelter in a ditch, if you are caught in a car during a tornado. However, if there is already flying debris in the air, leaving your car and exposing yourself to the debris in order to get to a ditch may be more hazardous than staying in your car. Furthermore, ditches are prone to flash floods. Four deaths during the El Reno tornado were from a family of seven that sheltered in a drainage ditch, and were washed into the Deep Fork River by a flash flood. Searchers are still looking for the other three bodies. A 2002 research paper, "UNSAFE AT ANY (WIND) SPEED? Testing the Stability of Motor Vehicles in Severe Winds" found that: "The stability and superior safety of being in a vehicle in severe winds, relative to occupying a mobile home or being outdoors, should be considered." Also, TWC's severe weather expert, Dr. Greg Forbes, commented on the pros and cons of abandoning one's vehicle for a ditch in a 2009 blog post, "Tornado Safety - Cars Versus Ditches: A Controversy." His personal take on what he would do if his car was being overtaken by a tornado, and no sturdy buildings were nearby to take shelter in: "I can't see myself getting out of the vehicle. I'd try first to drive away from the tornado. Both the NWS and the American Red Cross actually also advocate this. If you can determine which way the tornado is moving toward, face your body toward that direction and then go to the right, as shown in the diagram below. That is usually toward the south or southeast. The reason that it's best to head this way is that if you went to the left you would normally get into the region where largest hail and blinding rain occur in the kind of supercell, rotating thunderstorms that often spawn tornadoes. If I had no such driving option and I did feel the urge to get out of my car, I'd try to get into a building, and into a ditch well away from the car as the last resort."

My condolences and prayers go to all of the family and friends of Tim Samaras, Paul Samaras, and Carl Young. Their deaths are a terrible shock to the meteorological community, and a great loss for tornado science. I hope that their deaths will lead towards safer tornado chasing, and help spur efforts to use emerging drone technology to take measurements in dangerous storms such as tornadoes and hurricanes.

Jeff Masters

Tornado

Updated: 1:19 PM GMT on June 03, 2013

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A Night of Tornado Chaos in Oklahoma City: 9 Killed, 71 Injured

By: JeffMasters, 7:21 PM GMT on June 01, 2013

It was a terrifying evening of tornado chaos and extreme atmospheric violence in the Oklahoma City area on Friday. Three tornadoes touched down near the city, killing nine, injuring at least 71, and causing widespread destruction. Huge hail up to baseball-sized battered portions the the metro area, accompanied by torrential flooding rains, widespread damaging straight-line winds, and lightning that flashed nearly continuously. The strongest tornado, which touched down west of Oklahoma City in El Reno, has been preliminarily rated an EF-3 with 136 - 165 mph winds. The tornado warning for the storm was issued 19 minutes before it touched down. Two other EF-3 tornadoes touched down near St. Louis, Missouri, and NOAA's Storm Prediction Center (SPC) logged 20 preliminary tornado reports on Friday. Tinker Air Force Base on the east side of Oklahoma City reported sustained winds of 68 mph, gusting to 88 mph, at 8:09 pm CDT. The Oklahoma City airport had sustained winds of 53 mph, gusting to 71 mph at 7:26 pm. These winds were generated by the massive and powerful downdrafts from the supercell thunderstorm that spawned the El Reno tornado. Thankfully, Friday was likely the peak day for this week's severe weather outbreak, as SPC is calling for only a "Slight Risk" of severe weather Saturday and Sunday.


Figure 1. TWC's Mike ‪Bettes‬ crew caught this image of the El Reno, Oklahoma tornado of May 31, 2013 before the tornado caught them and rolled their vehicle.



Figure 2 and 3. Radar reflectivity (top) and Doppler velocity (bottom) images of the May 31, 2013 El Reno, Oklahoma tornado.


Figure 4. Preliminary tracks of the three tornadoes that touched done near Oklahoma City on May 31, 2013. Image credit: NWS Norman, OK.

Tornadoes and cars: a dangerous mix
A vehicle is about the worst place you can be in a tornado, as the tornado's winds can easily roll a car. (The only place less safe is probably a mobile home, as a tornado's winds can roll mobile homes almost as readily, and mobile homes don't come with seat belts and air bags.) At least five of the deaths in Friday's El Reno tornado occurred in vehicles attempting to flee. There was one local TV station that urged residents without underground shelters to get in their cars and "get south" in advance of the tornado that was approaching Oklahoma City, since chasers were reporting that the El Reno tornado may have been so strong that only an underground shelter would have provided adequate protection. This terrible piece of advice likely contributed to the incredible traffic jams that we saw on I-35, I-40, I-44, and other local roads Friday night. Thousands of cars were bumper-to-bumper on the roads as a dangerous tornado approached them. Had the El Reno tornado plowed directly down one of these car-choked interstates, the death toll could have easily exceeded 500. If you are located in a metro area and don't have an underground shelter, the best thing to do it to take shelter in an interior windowless room or hallway, with protective furniture over your body. Getting in a car and attempting to flee the tornado is the worst thing you can do in an urban area. You may not be able to see the tornado if it is dark or the tornado is wrapped in rain. You are likely to encounter hazardous winds, rain, and hail, run into unexpected traffic, or flooded or debris-blocked roads that will put you directly in the path of the tornado. Even without an underground shelter, most people will be able to survive a dangerous EF-4 tornado. Case in point: during the Mannford, Oklahoma EF-4 tornado of 1984, a packed church received a direct hit, and everyone in the church survived. The only fatality was a man who drove to the church to get his wife. (Thanks to wunderground member AGWcreationists for this link.) It's better to abandon your vehicle and take shelter in a ditch, if you are caught in a car during a tornado.


Video 1. The Weather Channel storm chasers weren't the only ones who got themselves in an extremely dangerous situation on May 31. StormChasingVideo.com storm chaser Brandon Sullivan and his chase partner Brett Wright got caught in the tornado northwest of Union City, OK and slammed with debris as the tornado hit a barn that exploded in front of them.


Video 2. When the hunters became the hunted: Weather Channel storm chasers ‪Mike Bettes and two photographers were in their Tornado Hunt vehicle when they were hit by a tornado in El Reno, Oklahoma on May 31,‬ ‪2013. ‬The tornado picked their car up off the ground and rolled it 6 - 8 times before depositing it in a field 200 yards away. All the occupants were wearing seat belts and the air bags deployed, likely saving their lives. Bettes sustained minor injuries, including stitches in his hand. It was the first injury sustained by a Weather Channel personality covering violent weather, according to company spokesperson Shirley Powell.

A storm chasers' nightmare
Cars and tornadoes can prove a dangerous mix even for the world's most experienced storm chasers. Driving at high speeds though heavy rain, large hail, and high winds is hazardous. If one is lucky enough to chase down a tornado, even the most experienced chasers can find themselves in a serious life-threatening situation when unpredictable events occur. Tornadoes by their nature are unpredictable, and can change course unexpectedly, or pop up suddenly. It's particularly dangerous when a tornado is wrapped in rain, making it hard to see, or if a chaser is operating in a heavily populated area, where roads may suddenly become congested. All four of these conditions occurred Friday during the El Reno tornado, and it is very fortunate that multiple chasers were not killed. The El Reno tornado was wrapped in rain and difficult to see as it headed west towards Oklahoma City. The twister suddenly made a jog to the southeast as a Weather Channel team led by Mike Bettes was attempting to get in front of the storm, and the tornado lifted their vehicle off the ground, rolled it multiple times, and hurled it 200 yards into a nearby field. StormChasingVideo.com storm chaser Brandon Sullivan and his chase partner Brett Wright got caught in the tornado northwest of Union City, OK and slammed with debris as the tornado hit a barn that exploded in front of them. Meteorologist Emily Sutton and storm chaser Kevin Josefy of local Oklahoma City TV station KFOR also had a very close call with the El Reno tornado Friday afternoon. They got too close to the tornado, and were forced to floor the car in reverse to escape flying debris. With branches of trees crashing around them, Sutton began feeling debris hitting her back, and realized that the rear windshield of the car must have gotten destroyed. Both were uninjured. Reed Timmer's armor-plated "Dominator" chase vehicle had its hood torn off by the tornado. Wunderground member Levi32 was out storm chasing during the El Reno Tornado, and got stuck in traffic on Highway 4 and couldn't move. "We looked up above the car and saw the wall cloud over top of us, with very quick rotation and rising scud indicating the updraft. We were definitely too close. We made it home safely last night, but not until after an insanely wild day. One hour of chasing turned into six more of being chased by at least 2 tornadoes and a 3rd wall cloud, one of which was the one that went right through downtown Oklahoma City. At one point we were stuck in traffic underneath the El Rino wall cloud watching rotating, rising scud directly above the car. I am hoping and praying that the daylight does not reveal more fatalities.

Would I go again? Yes, but not today, or tomorrow, and I would take even greater care. We had no clue we would get caught the way we did. I thought we had done everything right. We were kind of freaking out for a while. That velocity signature you guys saw with radar folding and multiple vortices - we were under the southern edge of it. We never got a clear view of the tornado, but we could tell just how close it was to our north. It was unreal. The inflow got pretty strong.

We were almost ready to jump out and take cover right before we found a route south, which ended up being slow. It became a six-lane highway south as everyone panicked and drove on the wrong side of the road. Even we did so. We thought we were clear until we saw the training of tornadic supercells on radar, all connected somehow. I've never seen anything like that. My best pictures of the day were of the wall cloud that followed behind the El Reno storm. We didn't see a funnel from that one either, but it chased us south for a long time, and we heard from radio that it spawned a confirmed tornado in Tuttle, when we realized that we were in Tuttle.

A third mesocyclone showed up behind that one as we continued slowly south, eventually reaching Blanchard. It looked weaker than the others but we weren't going to escape it, so we took shelter in a storm room in the local grocery store for about an hour. It then took a long time to find a way around the huge hail cores to get back home. Lightning flashes were occurring 10 times per second as we drove home in the dark. It was almost calming to watch as we got over the semi-shock that we were all in. None of us in the car had seen a tornado before. We didn't see one yesterday, but we were chased by two."



Video 3. Birth of the El Reno wedge tornado. As the tornado touched down, it produced a rare display of suction vortices.

Video 4. Storm chasers Jeff Piotrowski and Kathryn Piotrowski captured impressive footage of a double vortex tornado near El Reno, Oklahoma on May 31, 2013.

Severe storms causing major flooding
The 5.64" of rain that fell at the Oklahoma City Will Rogers Airport on Friday was their 6th wettest day in city history, and brought the total rainfall for the month of May to 14.52", the wettest May in Oklahoma City's history (Thanks to BaltimoreBrian for this link.) The North Canadian River in Oklahoma City rose sixteen feet in twelve hours, cresting at its 2nd highest flood on record this Saturday morning. The heavy rains have spread eastwards on Saturday, causing more flooding problems. Paducah, KY had its wettest June day and 3rd wettest day on record on June 1, with 5.73" of rain (all-time record: 7.49" on 9/5/1985.) Major flooding is occurring along a substantial stretch of the Mississippi River in Iowa, Illinois, and Missouri.


Figure 5. The North Canadian River in Oklahoma City rose sixteen feet in twelve hours, reaching its 2nd highest flood on record this Saturday morning.


Figure 6. Radar-estimated rainfall in the Oklahoma City area reached 8+" over some areas from Friday's storm.

Remains of Hurricane Barbara may bring heavy rains to Mexico, Florida, and Cuba
Today, June 1, is the official first day of the Atlantic Hurricane season, and we already have our first Atlantic tropical disturbance to talk about. Hurricane Barbara, which died on Thursday as it attempted to cross Mexico's Isthmus of Tehuantepec into the southernmost Gulf of Mexico, has left behind an area of disturbed weather over the southernmost Gulf of Mexico. There is very little heavy thunderstorm activity associated with Barbara's remnants apparent on satellite loops this Saturday afternoon. Wind shear is a high 20 knots in the region, and the area of disturbed weather is quite small, so I don't expect any development to occur over the next few days. NHC is giving the disturbance a 10% chance of developing into a tropical cyclone by Monday. Moisture from the remnants of Barbara may combine with moisture from an area of heavy thunderstorms expected to build over the Western Caribbean this weekend, and begin bringing heavy rains to Mexico's Yucatan Peninsula and Western Cuba on Sunday and Monday. These heavy rains may spread to Southwest Florida as early as Monday night. The computer models predict that this disturbance should be large and poorly organized, making development into a Gulf of Mexico tropical cyclone unlikely.

My next post will be Monday at the latest.

Jeff Masters

Tornado

Updated: 8:56 PM GMT on August 01, 2013

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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