Dr. Jeff Masters' WunderBlog

Extreme Flooding in Alabama and Florida; 1 EF-4 and 5 EF-3 Tornadoes Rated

By: JeffMasters, 2:31 PM GMT on April 30, 2014

After two wild days of tornado devastation across the U.S. on Sunday and Monday, an unexpected break occurred on Tuesday, when only nine tornadoes touched down. NOAA’s Storm Prediction Center (SPC) had issued a forecast for a “Moderate Risk” of severe weather over much of Alabama and Mississippi, but none of Tuesday’s tornadoes hit those states. Instead, North Carolina saw the bulk of the activity, with eight preliminary reports of tornadoes. The welcome forecast bust was caused by a very difficult to predict scenario—a cluster of intense thunderstorms called a Mesoscale Convective System (MCS) remained strong Monday night over a large portion of the Southeast coast, creating a large pool of cool, stable air. This cool air formed its own high pressure system that reduced instability and cut off the flow of moist, unstable air into the Southeast from the Gulf of Mexico on Tuesday afternoon. However, the moisture that was cut off from flowing northwards instead fell to the ground over coastal Alabama and the Florida Panhandle in the form of torrential rains on Tuesday. A flash flood emergency has been declared this morning in Pensacola, Florida and Mobile, Alabama. Record daily rainfall amounts were set on Tuesday in both cities, with 11.13” and 11.24”, respectively. Pensacola Airport recorded a remarkable 5.68 inches of rain in just one hour ending at 10 pm Tuesday night. Flood waters closed a 30-mile stretch of I-10 near the Alabama/Florida border Tuesday night, and a 5-mile stretch remained closed this morning. Numerous high-water rescues have been performed Tuesday night and Wednesday morning, and one drowning has occurred, in a vehicle that tried to cross flooded Highway 29. Two deaths were also reported this morning in Athens, Georgia , where severe thunderstorm winds toppled a tree onto a car.


Figure 1. Storm chaser Jim Edds is trapped in the Florida Panhandle by extreme flooding, but was able to tweet out this photo this morning. The Pensacola News Journal has also been tweeting some remarkable photos of the flooding.


Figure 2. Radar-estimated rainfall for the Florida Panhandle for April 29 and 30, 2014. Precipitation amounts in excess of 12” were indicated just west of Pensacola. The spectacular rains were reminiscent of what happened June 7 - 11 2012. Torrential rains in excess of 20” flooded portions of southern Alabama and the Florida Panhandle when a large plume of moisture from the Gulf of Mexico interacted with an upper-level disturbance over the region. Flooding was particularly severe in Pensacola, FL, where 13.13 inches of rain fell on June 9.

Tornado outbreak death toll rises to 35
Sunday and Monday’s tornado rampage across the Midwest and Southeast U.S. brought at least five EF-3 tornadoes and one EF-4 tornado, and has claimed 35 lives. For the 24-hour period beginning at 8 am Monday, SPC logged 72 preliminary tornado reports from five states. An additional 35 preliminary tornado reports came on Sunday, bringing the two-day preliminary tornado total to 107. The deadliest tornado was an EF-3 that killed 14 people in Arkansas, ravaging the towns of Mayflower and Vilonia. Damage surveys are not yet complete, but the strongest tornado rated so far was an EF-4 with 185 mph winds that hit Louisville, Mississippi on April 28. The tornado killed nine people, carved a damage path 35 miles long and up to 3/4 mile wide, and stayed on the ground for 56 minutes. The NWS survey noted:

“THIS TORNADO PRODUCED A LARGE AREA OF EF2 TO EF4 DAMAGE ALONG ITS PATH. HUNDREDS OF STRUCTURES WERE HEAVILY DAMAGED AND THOUSANDS OF TREES WERE SNAPPED AND UPROOTED. THE EF4 DAMAGE CONSISTED OF SEVERAL HOMES AND APARTMENTS THAT WERE REDUCED TO SLABS...INDUSTRIAL BUILDINGS THAT WERE COLLAPSED...CHICKEN HOUSES THAT WERE COMPLETELY DESTROYED WITH LITTLE TRACE LEFT OF THEM...DEBARKED AND DENUDED TREES AND A COLLAPSED CELL TOWER.”


Figure 3. Severe weather outlook for Wednesday, April 30, 2014, as issued on Wednesday by NOAA's Storm Prediction Center. For the first time this week, the severe threat is below the “Moderate Risk” level.

Wednesday the final day of this week’s severe weather outbreak
The strong, slow-moving low pressure system that brought this week’s deadly tornadoes will continue to spawn a few more supercell thunderstorms capable of generating large hail, damaging winds, and tornadoes on Wednesday. NOAA's Storm Prediction Center (SPC) has issued their “Slight Risk" forecast of severe weather over a region stretching from Maryland southwest to north Florida. Rainfall amounts of 1 - 3 inches can be expected in much of the severe weather risk area, with some 3+ inch totals in Florida and Eastern Pennsylvania.

Disaster Relief Donations Needed
The devastation from this week’s tornadoes have brought a need for donations for disaster relief. The Portlight.org disaster relief charity, founded by members of the wunderground community, is supporting the efforts of a group of local volunteers in Arkansas doing search and rescue, and needs donations. Portlight volunteers are working in tornado-hit towns to clear debris and help with other clean-up efforts. This team will also be visiting shelters and reaching out to survivors with disabilities to determine their immediate needs, whether for replacement of durable medical equipment and ramps, or for assistance with shelter and transportation issues. The Red Cross is also a great place to send your donation dollars.

Jeff Masters

Tornado Flood Severe Weather

Updated: 2:37 PM GMT on April 30, 2014

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Two-day U.S. Tornado Outbreak Kills at Least 29 People; More Tornadoes Expected Today

By: JeffMasters, 2:13 PM GMT on April 29, 2014

A swarm of deadly and devastating tornadoes ripped through the Southeast U.S. on Monday, killing at least 13 people, bringing the two-day death toll from this week’s tornado outbreak to at least 29. Hardest hit were Mississippi and Alabama, which lay in the bullseye of the High Risk” area for severe weather issued by NOAA’s Storm Prediction Center early that afternoon. It was the second consecutive day a “High Risk” outlook had been issued by SPC, and the threat of strong and deadly tornadoes continues again on Tuesday, with a “Moderate Risk” of severe weather expected over Alabama and Mississippi. The tornado activity in Mississippi and Alabama on Monday was remarkably violent and long-lasting; Alabama’s first tornado warning was issued at 12:37 pm CDT, and the last was nearly sixteen hours later, at 4:20 am (thanks to wunderground member sar2401 in Alabama for this info.) Mississippi suffered the highest death toll on Monday, with eight killed. Three people died in Alabama, including a University of Alabama swimmer who died saving his girlfriend from a collapsing building. Two other people died in Lincoln County, Tennessee, near the border with Alabama. In all, for the 24-hour period beginning at 8 am Monday, SPC logged 64 preliminary tornado reports from five states, along with 135 reports of damaging winds and 49 reports of hail. An additional 33 preliminary tornado reports came on Sunday, bringing the two-day preliminary tornado total to 97. Hardest hit on Sunday was Arkansas, where fifteen people died in tornadoes. Mayflower and Vilonia, Arkansas, located about fifteen miles northwest and north of Little Rock, had ten people killed by a tornado that has been preliminarily rated as at least an EF-3 by the National Weather Service. Sunday tornadoes also killed one person in Iowa and one in Oklahoma.


Figure 1. Tornado damage in Tupelo, Mississippi, pictured Monday evening. (J. Robert Senseman)


Figure 2. Radar reflectivity image of the supercell thunderstorm that hit Tupelo, Mississippi at 19:39 UTC (3:39 pm EDT) on April 28, 2014. Tupelo’s position is denoted by the circle with a “+“ in it, and lies next to a hook-shaped echo commonly seen in strong tornadoes. The Tupelo tornado killed one person in a car, and was preliminarily rated an EF-2 with winds of 111 - 135 mph. Radar data showed that this tornado lofted debris 35,000 feet into the air.


Figure 3. Doppler velocity image of the supercell thunderstorm that hit Tupelo, Mississippi. Note the clump of green colors lying right next to orange and red colors near Tupelo, showing that winds moving both towards the radar and away from the radar were located in close proximity to each other—the signature of a rotating mesocyclone in a severe thunderstorm capable of spawning a strong tornado.


Figure 4. Severe weather outlook for Tuesday, April 29, 2014, as issued on Tueday by NOAA's Storm Prediction Center.

Tornado and severe weather outbreak continues on Tuesday and Wednesday
The strong, slow-moving low pressure system that brought this weekend’s deadly tornadoes will spawn spawn more supercell thunderstorms capable of generating large hail, damaging winds, and a few strong tornadoes on Tuesday. NOAA's Storm Prediction Center (SPC) has issued their "Moderate Risk" forecast of severe weather over much of Mississippi and Alabama for Tuesday, with a wide swath of the Eastern half of the U.S. under a “Slight Risk” of severe weather. The set-up for getting strong tornadoes does not appear to be as dangerous today as it was on Monday, and I don’t think we will see as many tornadoes. The upper-level winds over the Southeast U.S. will not be as strong, leading to less wind shear available to get tornadoes spinning. Still, instability will be very high, and I do expect we will see a few strong EF-3 tornadoes in Mississippi and Alabama. The risk of severe weather will diminish considerably on Wednesday, but most of the Southeast U.S. will be still be in SPC’s “Slight Risk” region for severe weather. The severe threat will finally end Thursday morning as the cold front responsible moves off the coast.


Video 1. This animation of NOAA's GOES-East satellite data shows the development and movement of the weather system that spawned tornadoes affecting seven central and southern U.S. states on April 27-28, 2014. Credit: NASA/NOAA GOES Project


Video 2. Scott Peake's close-up intercept of the strong-violent Louisville, MS tornado on April 28, 2014.

New Wunderground Tornado Infographics
Weather Underground has just released two new tornado infographics. Share these with your friends living in at-risk areas for tornadoes:

Tornadoes Cities and Interstates: http://www.wunderground.com/weather-infographics/tornadoes/

Tornado Safety: http://www.wunderground.com/weather-infographics/tornado-safety/



In the tornado safety infographic, we recommend driving away from a tornado rather than parking your vehicle beneath a freeway overpass. Keep in mind that a vehicle is one of the worst places 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.) 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. Sometimes it is 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. 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. 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."

Disaster Relief Donations Needed
The devastation from this week’s tornadoes have brought a need for donations for disaster relief. The Portlight.org disaster relief charity, founded by members of the wunderground community, is supporting the efforts of a group of local volunteers in Arkansas doing search and rescue, and needs donations. Portlight volunteers are working in tornado-hit towns to clear debris and help with other clean-up efforts. This team will also be visiting shelters and reaching out to survivors with disabilities to determine their immediate needs, whether for replacement of durable medical equipment and ramps, or for assistance with shelter and transportation issues. The Red Cross is also a great place to send your donation dollars.

Jeff Masters

Tornado

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Tornadoes Kill 16 in Arkansas, Oklahoma, and Iowa

By: JeffMasters, 1:07 PM GMT on April 28, 2014

The quiet 2014 severe weather season turned grimly violent over the weekend, as multiple deadly tornadoes ended our record-long start to a year without a tornado fatality. Media reports put Sunday's death toll at 16, with 164of deaths in Arkansas, one in Iowa, and one in Oklahoma. Hardest-hit were Mayflower and Vilonia, Arkansas, located about fifteen miles north of Little Rock. A large and powerful tornado that had been on the ground nearly an hour carved through the region near sunset, killing at least ten people. Damage photos appeared to show at least EF-3 type damage, and there was a report from relayed from amateur radio to the NWS that two homes in Vilonia had been “wiped clean to the foundation”, which would imply higher than EF-3 damage. There has been only one known F5 tornado in Arkansas history, on April 10, 1929. Vilonia was hit just three years ago, on April 25, 2011, by an EF-2 tornado that killed four people.


Figure 1. Travel trailers and motor homes are piled on top of each other at Mayflower RV in Mayflower, Ark., Sunday, April 27, 2014. (AP Photo/Danny Johnston)


Figure 2. Radar reflectivity image of the supercell thunderstorm that hit Vilonia, Arkansas at 00:52 UTC (7:52 pm CDT) on April 27, 2014. Vilonia’s position is denoted by the circle with a “+“ in it, and lies underneath a classic hook-shaped echo commonly seen from strong tornadoes.


Figure 3. Doppler velocity image of the supercell thunderstorm that hit Vilonia, Arkansas tornado. Note the clump of green colors lying right next to orange and red colors over Vilonia, showing that winds moving both towards the radar and away from the radar were located in close proximity to each other, the signature of a rotating mesocyclone in a severe thunderstorm capable of spawning a strong tornado.

The Arkansas Department of Emergency Management said three people also died in Arkansas’ Pulaski County and one in White County from tornadoes on Sunday. NOAA's Storm Prediction Center (SPC) had put much of Arkansas in their “High Risk” area for potential severe weather yesterday. It was the first “High Risk” outlook issued by SPC in 2014. According to The Encyclopedia of Arkansas History and Culture, the deadliest outbreak in Arkansas history occurred on March 21, 1952, when 112 people lost their lives. The most deadly recent outbreak was on March 1, 1997, which resulted in 25 Arkansas fatalities.

Outside of Arkansas, a tornado hit Quapaw, OK on Sunday, killing one person and destroying the fire station. In Kansas, the governor declared a state of emergency for Baxter Springs, where a tornado destroyed 70 homes and 20 businesses. In all, SPC logged 31 preliminary tornado reports from five states on Sunday, 107 reports of damaging winds, and 118 reports of hail. Also on Sunday, an 11-month old died from injuries suffered during a tornado on Friday in Chowan County, North Carolina. It was the first U.S. tornado death of 2014.


Figure 4. Severe weather outlook for Monday, April 28, 2014, as issued on Monday by NOAA's Storm Prediction Center.

Tornado and severe weather outbreak continues on Monday and Tuesday
The strong, slow-moving low pressure system that brought this weekend’s deadly tornadoes will spawn spawn more supercell thunderstorms capable of generating large hail, damaging winds, and a few strong tornadoes on Monday. NOAA's Storm Prediction Center (SPC) has issued their "Moderate Risk" forecast of severe weather over much of Mississippi, central and northern Alabama and west and central Tennessee. The risk of severe weather will diminish on Tuesday, but most of the Southeast U.S. will be in SPC’s “Slight Risk” region for severe weather. Wednesday will see additional severe thunderstorms along the Southeast U.S. coast, and the severe threat will finally end Wednesday night as the storm responsible moves off the coast.


Video 1. Damage from the Mayflower/Vilonia, Arkansas tornado taken from a drone operated by storm chaser Brian Emfinger of KATV.

Jeff Masters

Tornado

Updated: 5:26 PM GMT on April 28, 2014

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More Tornado Strikes May Occur in Mobile Home Parks; Weekend Plains Tornado Outbreak?

By: JeffMasters, 3:47 PM GMT on April 25, 2014

It's well-known that one should avoid mobile homes during a tornado, as their relatively flimsy construction and tendency to roll when exposed to high winds leads to numerous deaths each tornado season. The majority of tornado deaths occur in mobile homes for this reason, but tornado experts have long wondered why mobile home parks seem to get disproportionately more tornado strikes than other residential areas. New research by Purdue University researchers Olivia Kellner and Dev Niyogi suggests that "transitions zones"--areas where dramatically different landscapes meet, like where a city fades into farmland, or a forest meets a plain--are more prone to tornado touch downs. Since mobile home parks are often located at the edge of built-up areas, they may actually get hit more often.


Figure 1. Damage to 2-year-old C.J. Martin's mobile home park near Evansville, Indiana due to a November 6, 2005 tornado. Twenty people. including C.J., died in the F3 tornado that devastated his Eastbrook Mobile Home Park in Evansville. The storm hit at 2am, when many residents were asleep and didn't hear the tornado sirens. C.J.'s mother, Kathryn Martin, pushed lawmakers to adopt a bill requiring all mobile homes in Indiana to have a weather radio with a tone alert system, which could have saved many lives in the mobile home park that night. C.J.'s Law was signed into law by Indiana governor Mitch Daniels later that year. Image credit: Paducah, KY NWS.

The researchers studied where tornadoes touched down in Indiana between 1950 and 2012, and found that 61% of tornado touchdowns occurred within 1 kilometer (about 0.62 mile) of urban areas, and 43% fell within 1 kilometer of forest. Kellner said the percentages suggest that certain locations may increase the likelihood of tornado touchdowns due to increased "surface roughness"--an abrupt change in the height of land surface features, which can stretch or squash a column of air, increasing its rate of spin, which could contribute to the formation of tornadoes. Forecasters and city planners may need to pay closer attention to these "transition zones" to better understand tornado risks, said Olivia Kellner, doctoral student in the Department of Earth, Atmospheric and Planetary Sciences in a press release. "There are still many unanswered questions about tornado climatology, but what we're finding is that there may be a relationship between the Earth's surface and the atmosphere that contributes to where tornadoes tend to touch down." The study also found that tornado touchdowns in urban areas tend to occur at about 1 and 10 miles from the city center. Kellner said these "rings" of increased tornado activity could be related to how cities are developed. "Cities impact the surrounding climate in terms of regional airflow and temperature," she said. "The size of cities, what they're made of and the heat they produce are factors that could affect the microclimate."

Original study: Kellner, O., and D. Niyogi, 2014, Land-surface Heterogeneity Signature in Tornado Climatology? An Illustrative Analysis over Indiana 1950-2012, Earth Interactions, doi: http://dx.doi.org/10.1175/2013EI000548.1


Figure 2. Severe weather outlook for Sunday, April 27, 2014, as issued on Friday, April 25, by NOAA's Storm Prediction Center.

Weekend tornado and severe weather outbreak coming for the Plains
A multi-day severe weather event is expected Saturday, Sunday, and Monday across the Central U.S., as a strong low pressure system will spawn supercell thunderstorms capable of generating large hail, damaging winds, and a few strong tornadoes. The most dangerous day appears to be Sunday, and NOAA's Storm Prediction Center (SPC) has issued their "Moderate Risk" forecast of severe weather over portions of Arkansas , Oklahoma, Texas, and Louisiana that day. The action will begin Saturday afternoon along a swath from Central Texas northwards into Oklahoma and Kansas, but at present, Saturday's threat warrants only a "Slight Risk" classification from SPC. This weekend's severe weather outbreak has the potential to be the most dangerous one of this relatively quiet 2014, which has yet to spawn a killer tornado. The relatively cool and dry weather across Tornado Alley so far this year has led to no EF-3 or stronger tornadoes as of April 24, which is a record-long wait since modern tornado records began in 1950. According to tornado historian Tom Grazulis' book, Significant Tornadoes 1680-1991, "serious efforts" to document all tornadoes began in 1953, which was the first full year of tornado watches issued by the U.S. Weather Bureau, now the National Weather Service.

I'll have a new post on Monday. Have a great weekend, everyone!

Jeff Masters

Tornado

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Earth Has Its 4th Warmest March on Record; Weekend Severe Weather Outbreak Coming

By: JeffMasters, 1:21 PM GMT on April 23, 2014

March 2014 was the globe's 4th warmest March since records began in 1880, according to NOAA's National Climatic Data Center (NCDC) and NASA. March 2014 global land temperatures were the 5th warmest on record, and global ocean temperatures were also the 5th warmest on record. The year-to-date January - March period has been the 7th warmest on record for the globe. Global satellite-measured temperatures in March 2013 for the lowest 8 km of the atmosphere were 11th or 9th warmest in the 36-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH), respectively. Northern Hemisphere snow cover during March was the 6th lowest in the 48-year record. Wunderground's weather historian, Christopher C. Burt, has a comprehensive post on the notable weather events of March 2014 in his March 2014 Global Weather Extremes Summary.


Figure 1. Departure of temperature from average for March 2014, the 4th warmest March for the globe since record keeping began in 1880. Much of Europe had a top-five warmest March, including Austria (2nd), Norway (3rd), Denmark (4th), Germany (3rd), Latvia (3rd), the Netherlands (3rd), and Slovakia (1st.) In the U.S., Vermont had its coldest March on record, and Michigan, New York, Maine, and New Hampshire all had top-five coldest Marches on record. Image credit: National Climatic Data Center (NCDC) .



One billion-dollar weather disaster in March 2014: Drought in Brazil
One billion-dollar weather-related disaster hit the Earth during March 2014: Southeastern Brazil's worst drought in 50 years, which has cost at least $4.3 billion so far this year, according to the March 2014 Catastrophe Report from insurance broker Aon Benfield. This is the third most expensive natural disaster in Brazil's history, and the second consecutive year of disastrous drought in the country. Drought in Northeast Brazil during the first five months of 2013 caused an estimated $8 billion in damage--Brazil's second most expensive natural disaster in recorded history. According to the international disaster database EM-DAT, Brazil's costliest natural disaster was the drought of 1978 ($2.3 billion in 1978 dollars, or $8.3 billion 2014 dollars.)


Disaster 1. Cattle in a drought-parched filed in Quixada, Ceara state, Brazil on January 2, 2014. Small farmers in Ceara state have not able to harvest corn to feed cattle, and have been selling them at a loss. Aurelien Francisco Barros/AFP/Getty Images.


Figure 2. The deadliest U.S. weather disaster of March 2014 was the tragic landslide at Oso, Washington that killed 41 people and did $10 million in damage. The landslide was triggered by record March rains that saturated the soils. The nearby Seattle airport measured 9.44” (240 mm) of precipitation in March, a new record for the month. Photo by Washington State Patrol.

An El Niño Watch continues
March 2014 featured neutral El Niño conditions in the equatorial Eastern Pacific, but NOAA has issued an El Niño Watch for the summer and fall of 2014, giving a greater than 50% chance that an El Niño event will occur by the summer. The April 10 El Niño discussion from NOAA's Climate Prediction Center noted that "there remains considerable uncertainty as to when El Niño will develop and how strong it may become. This uncertainty is amplified by the inherently lower forecast skill of the models for forecasts made in the spring." None of the El Niño models (updated in mid-April 2014) predict La Niña conditions for peak hurricane season, August-September-October 2014, and 16 of 20 predict El Niño conditions. Temperatures in the equatorial Eastern Pacific need to be 0.5°C above average or warmer for three consecutive months for an El Niño episode to be declared; sea surface temperatures were +0.2°C from average as of April 21. El Niño conditions tend to make quieter than average Atlantic hurricane seasons, due to an increase in upper-level winds that create strong wind shear over the Tropical Atlantic. There is currently a Westerly Wind Burst (WWB) over the equatorial Pacific Ocean that is helping push warm water eastwards towards South America. If this Westerly Wind Burst persists and expands eastwards through early May, the odds of an El Niño event will increase.

Arctic sea ice falls to 5th lowest March extent on record
Arctic sea ice extent during March was 5th lowest in the 36-year satellite record, according to the National Snow and Ice Data Center (NSIDC). The winter maximum extent of Arctic sea ice came on March 21, and was the 5th lowest such peak on record. Temperatures in the Arctic were 2 - 6°C (4 -11°F) above average during the last half of the month, but a late-season surge in ice extent came as the Arctic Oscillation turned strongly positive the second week of March, with unusually low sea level pressure in the eastern Arctic and the northern North Atlantic. The associated pattern of surface winds helped to spread out the ice pack, keeping ice extent greater than it would have been. There was a modest increase in thick, multi-year ice over the winter, and the Arctic is in better shape to resist a record summer melt season this year than it was in 2013.


Figure 2. Regions most at risk of severe weather for the period Saturday, April 26 - Monday, April 28, 2014, as predicted by NOAA's Storm Prediction Center at 4:15 am EDT Wednesday, April 23, 2014.

Weekend tornado and severe weather outbreak coming for the Plains
A significant multi-day severe weather event is expected Saturday, Sunday, and Monday across the Central U.S. A strong low pressure system will trundle slowly across the region, spawning supercell thunderstorms capable of generating large hail, damaging winds, and a few strong tornadoes. The action will begin Saturday afternoon along a swath from Central Texas northwards into Oklahoma and Kansas, then gradually shift eastwards on Sunday and Monday. Recent runs of the GFS and European model have been very consistent in showing moderate to extreme instability in the warm air ahead of the storm's cold front Saturday through Monday, and this weekend's severe weather outbreak has the potential to be the most dangerous one of this relatively quiet 2014. This year has yet to spawn a killer tornado, setting a new record for latest date of the year's first killer tornado. The previous record belonged to 2002, when the year's first killer tornado struck April 21 (an F-3 that killed a man in a mobile home in a rural area of Wayne County, Illinois.) The relatively cool and dry weather across Tornado Alley so far this year has led to no EF-3 or stronger tornadoes as of April 23, and that's also a record-long wait since modern tornado records began in 1950. According to tornado historian Tom Grazulis' book, Significant Tornadoes 1680-1991, "serious efforts" to document all tornadoes began in 1953, which was the first full year of tornado watches issued by the U.S. Weather Bureau, now the National Weather Service.

I'll have a new post on Friday.

Jeff Masters

Climate Summaries

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Earth Day 2014 Wunderphoto Selections

By: JeffMasters, 11:50 AM GMT on April 22, 2014

Today is Earth Day, a day to celebrate the beauty of the atmosphere, oceans, and biosphere of the planet that sustains us. As is my tradition on Earth Day, I present my favorite wunderphotos uploaded to our web site over the past year. I want to thank everyone who has participated in making this the largest (1.7 million!) and best weather photo gallery on the Internet--your photos are truly an inspiration! Many of my choices were taken from our Worldview Gallery, updated weekly with the top wunderphotos of the week.


Figure 1. My favorite wunderphoto of the past year, "The Green Heaven", was taken on October 31, 2013 in Senja, northern Norway, by wunderphotographer Altred. It's the background image on my laptop.

Wunderground's new Billion-Dollar Weather Disasters of 2013 Infographic
Earth set a new record for billion-dollar weather disasters in 2013 with 41, as I detailed in a January blog post. For Earth Day this year, Weather Underground's superb graphic artist Jerimiah Brown has created a new Billion-Dollar Weather Disasters of 2013 Infographic that helps put last year's extraordinary weather events in perspective.


Figure 2. My favorite lightning of the past year, "Bahama Blast!", was taken on July 11, 2013 in Freeport, Bahama, by wunderphotographer AsylumRat.

Wunderground's Awesome Lightning Infographic
If you want to learn more about lightning, Jerimiah has also created an awesome new interactive lightning infographic.

I'll be part of a live Earth Day Google+ hangout at 1:15 pm EDT Tuesday with Huffington Post. The topic is, "Where Will The Next Natural Disaster Hit?"

Jeff Masters

Atmospheric Phenomena

Updated: 3:42 PM GMT on April 22, 2014

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UFOs, Human Frequencies in Radar Data, and Other Emails From Responsible Persons

By: JeffMasters, 3:34 PM GMT on April 21, 2014

It's a bit of a slow weather day, so I thought I'd share with you today a few of the more interesting inquiries I've gotten during my 20 years working with Weather Underground. I responded to all of the emails, but not the phone calls. Enjoy!

Jeff Masters


Notes from a phone message taken by my business partner, Jeff Ferguson on May 3, 2002:
It turns out that there is a person in Texas who uses our Nexrad radar imagery to locate people. He can pick up their frequencies from the Nexrad imagery. It turns out that human frequencies are embedded in each image. He would not explain to me how he picks up these frequencies, since it is a proprietary process, invented by him.

Notes from two phone messages received by my business partner, Jeff Ferguson, on June 8, 2001:
D.H. called. He has information on a technology which controls the weather. He is only interested in talking to people he can trust. I assured him that you were trustworthy, and you are the most qualified person in our company to discuss his ideas. He has gone broke developing his ideas, so he hopes you can call him quickly, since he does not pay his phone bill and they will be shutting it off soon. No, he doesn't trust e-mail. He has contacted other companies, but they do not seem to have people he can trust with this information.

Email from March 6, 1998:
"I am writting, because my mother was talking to my grandmother who lives in the Torch Lake vacinity, and she was looking outside, and she noticed that there was a object in the sky, that kept moving around, and changing color, I am not kidding, I was just wondering if you happened to see this odd object.......I live in Northport Michigan, and I can see this object, it keeps fading in and out, and when it fades back into a visible focas, it is always in a different spot, then before, and it also has 3 colors, white, then red, then blue, I am not going to assume, that it is a UFO, but who knows. I hope that you take this seriously, and would like to hear from you as soon as possible........I am looking at it from the east, and I live near the lake."

Email from February 16, 1998:
"I,M A VERY RESPONSIBLE PERSON. SINCE I WAS A LITTER BOY I BEEN LOOKING AND STUDYNG THE SUN. ON FEB,1996 ONE MORNING I WAS LOOKING AT THE SKY AND WHAT I SAW THE SUN ACTING UP. I SAW BIG EXPLOSION AND SOMETHING LIKE LAVA RUNNING DOWN....I SAW LOT OF FIRE YELLOW,ORANGE AND A PURPLE RING AROUND THE SUN. THE EXPLOSIONS STILL GOING TODAY.ON OCTOBER 10,1997 I SEND A LETTER TO THE PRESIDENT BILL CLINTON? WHY TO BILL? BECAUSE RUN ALL GOVERMENT DEPARMENT. IN THE LETTER WAS A WARNING OF WHAT I SAW AND WAS COMING. IN LETTER I EXLPAIN TO BILL THAT THE GOVERMENT SHOULD ORDER THE CLEANING OF ALL RIVER AND TO PLACE LEVIS ON ALL RIVERBANKS IN U.S. I ALSO IN THE LETTER I EXPLAIN TO BILL ABOUT THE BAD WEATHER COMING TO CALIFORNIA. A LOT OF RAIN AND HIGH WIND,COLORADO LOT OF SNOW. TEXAS LOT OF RAIN AND SNOW FOR THE EAST THE BEST WEATHER IN YEARS,I EXPLAIN TO BILL THAT HE HAS TO ORDER THE ALL LUMBER COMPANYS TO STOP CUTTING ALL TREE. EL NINO IS NOTHING MORE THAN A HEAT WAVE OF EXTRA HEAT COMING OUT THE SUN DO TO THE EXPLOSIONS INSIDE THE SUN THE BAD WEATHER WE ARE HAVING IS HERE TO STAY FOR A LONG TIME THINGS ARE GIONG TO GET WORSE AND WE CAN DO ANYTHING ABOUT......I SEND A LETTER TO NASA AND I STYLL WAYTING FOR A RESPONSE…"

Email from April 20, 1999:
"Say, I've got a question. I read in the Weekly World News that the winter of 1999 would be an "Icy Hell," including sustained temperatures below 0 degrees for the great lakes region lasting weeks and weeks, most likely a result of God's warning of Jesus' Second Coming. Clearly this was not the weather pattern we experienced in January, February, and not even in March. However, it is still wholly conceivable that we may be seeing an Icy Hell in what remains in April, or even early May. Is this something I should worry about? Should I be stockpiling the crops that are going to be damaged in sums in the billions? Should I seek higher ground lest a second Ice Age cover me in thousands of feet of glacier? Clearly you can see how this is a grave concern of mine."

Email received October 17, 2002:

"Hello! I don't know if this is the right place to turn to, but it is worth a try! On the night of October 14th, I was driving from California, to Utah. I don't remember exactly where I was, but I think it was 40 or so miles outside of Barstow. In the sky, we saw a bright light, with a green tint in the middle of it. Coming out of the light was a bright red wavy line, that looked almost like the trail of an airplane. It didn't move anywhere. In fact, we left before it did. (Whatever it was...) If you have ANY information as to what that strange light was, I would really appreciate it! I'm just glad that there were others with me, otherwise I would think I was going insane! Thank you! "

Email received April 22, 2006:

"Perhaps a planetary catastrophe originating from the Atlantic Ocean due to a medium size impact event. On this assumption, a series of giant waves, including one tsunami almost two hundred meters in height, will be born from a succession of underwater eruptions. These watery giants, decreasing with distance, will touch the majority of the Atlantic coasts; in particular, those most at risk lie between the equator and the tropic of Cancer. The victims of May 25 2006 will be tens of millions. The devastated survivors will be more numerous still. The economic losses will be enormous, well beyond the scales of destruction hitherto tested by our civilization. North America and Europe will not be saved, but will be affected in less dramatic proportions. By extension, other remote countries will be also affected. Please think twice before doing something else. You could save the life of thousands of people by warning them! Great respect to you!"

Humor

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More Water For California: New Enormous Water Works Programs Are Expensive

By: JeffMasters, 9:18 PM GMT on April 18, 2014

The end of the rainy season is nearly here, and California faces a long, dry summer with a Sierra snowpack that is only 33% of normal. There is no significant precipitation in the forecast for California through April 25, but the state still has another shot at a decent round of heavy precipitation the last few days of April, according the latest long-range forecasts from the GFS model. If this storm does materialize, March and April precipitation would be near average for California, helping offset the November - February period, which was the driest such 3-month period in California's recorded history. The winter rainy season of 2013 - 2014 is going to end up well below average for precipitation, though, and comes on the heels of two other poor rainy seasons, which leaves California in a dire drought situation. The April 15, 2014 Drought Monitor is showing that 99.8% of California is in drought, with 95% of the state in Severe, Extreme, or Exceptional drought.


Figure 1. Predicted precipitation for the 7-day period ending Friday, April 25, 2014. No significant rain capable of easing the drought is expected to fall in California in the coming week. Image credit: NOAA/HPC.


Figure 2. The latest NOAA seasonal drought forecast calls for drought to persist or intensify until the end of July across much of the Southwestern and Western U.S., including all of California and Nevada. Image credit: NOAA/CPC.

Ways to Ease California's Drought
There is only one major river in the Southwest, the Colorado River, and in most years the flow in the river is far less than the amount of water allocated to stockholders drawing water from the great river. Over 30 million people depend on the Colorado River for their water, including much of Southern California, and the river irrigates farmland that produces 15% of the nation's food. Two major studies, one by the U.S. Bureau of Reclamation in 2012, and one by the non-profit Pacific Institute in 2013, laid out five major ways that the Colorado River basin can get more water. As I outlined in Part 1, 2, and 3 of this series over the past month, three ways to get more water for the thirsty Southwest are through:

1) Conservation measures
2) Cloud seeding
3) Desalinization plants

Another option is to build more enormous water works programs. California already has a number of massive multi-billion dollar water works programs that shuttle water from water-rich areas to water-poor areas. For example:

The $1.75 billion California State Water Project and the federal Central Valley Project, which collect water from rivers in Northern California and redistribute it to Southern California through a network of aqueducts, pumping stations, and power plants.

The All-American Canal, which takes water from the Colorado River and supplies California's Imperial Valley. It is the Imperial Valley's only water source.

The Colorado River Aqueduct, completed in 1939, which takes water from the Colorado River on the California/Arizona border and pipes it 242 miles to the west into Southern California.


Figure 3. Landsat-8 image of the region just west of Yuma, Arizona, showing several of the major Colorado River canals that have been built to divert the river's water: the All-American Canal, which takes water from the Colorado River and supplies California's Imperial Valley, and the Central Feeder Canal, which supplies Mexico. Image credit: NASA Earth Observatory.

However, there really isn't much excess water to be had in the Western U.S. anymore. So, another option might be to pipe water over the Rockies from the Missouri River watershed. A "Missouri River Reuse Project" has been proposed by officials in Colorado and in the U.S. Department of Reclamation. This 30-year, multi-billion dollar project would divert water from the Missouri River across Kansas to the Front Range of the Colorado Rockies, where the water could then be pumped into the headwaters of the Colorado River. The cost of the water delivered would be similar to desalinization, about $2000 per acre-foot. This very high cost has made the project unattractive, and it has also met with opposition from environmental groups. "Huge pipelines aren't solutions to the fundamental problem that we are using more water than we can sustain. You can't build more water," said Drew Beckwith, a water policy manager for Western Resource Advocates, in a 2012 interview with the Denver Post. "We need to work together on conservation and reuse strategies that can have an immediate positive impact."

Other massive engineering projects, including building aqueducts to bring water from Washington's Snake and Columbia rivers, a tunnel under the Pacific Ocean to import water from Alaska, towing icebergs to California, or using water bags or tanker vessels to transport water, were deemed much too expensive to be considered practical in the U.S. Bureau of Reclamation study. Their cost was at least 50% more than using desalinized water.

Have a great weekend, everyone!

Jeff Masters

Drought

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California Drought/Polar Vortex Jet Stream Pattern Linked to Global Warming

By: JeffMasters, 6:56 PM GMT on April 16, 2014

From November 2013 - January 2014, a remarkably extreme jet stream pattern set up over North America, bringing the infamous "Polar Vortex" of cold air to the Midwest and Eastern U.S., and a "Ridiculously Resilient Ridge" of high pressure over California, which brought the worst winter drought conditions ever recorded to that state. A new study published this week in Geophysical Research Letters, led by Utah State scientist S.-Y. Simon Wang, found that this jet stream pattern was the most extreme on record, and likely could not have grown so extreme without the influence of human-caused global warming. The study concluded, “there is a traceable anthropogenic warming footprint in the enormous intensity of the anomalous ridge during winter 2013-14, the associated drought and its intensity."


Figure 1. An extreme jet stream patten observed at 00 UTC on January 16, 2014. Color-coded wind speeds at a pressure of 300 mb (roughly 9,000 meters or 30,000 feet) show the axis of the jet stream over North America, with a large upside-down "U"-shaped ridge of high pressure over the West Coast. California is outlined in orange. The strongest winds of the jet stream (orange colors, 160 mph) were observed over the Northeast United States, where a strong "U"-shaped trough of low pressure was anchored. Image generated from the 00 UTC January 16, 2014 run of the GFS model, and plotted using our wundermap.

Using observations and a climate model to diagnose the human contribution to the jet stream pattern

The researchers studied the historical pressure patterns for November - January over North America during the period 1960 - 2014, and found that a strong "dipole" pattern of high pressure over Western North America and low pressure over Eastern North America, such as occurred during the winter of 2013 - 2014, tended to occur naturally during the winter immediately preceding an El Niño event. Since NOAA is giving a greater than 50% of an El Niño event occurring later in 2014, this past winter's dipole pattern may have been a natural expression of the evolving progression towards El Niño. The study also found that the dipole pattern could be intensified by two other natural resonances in the climate system: the Arctic Oscillation, and a variation of ocean temperatures and winds in the Western North Pacific called the Western North Pacific (WNP) pattern. But the dipole of high pressure over California combined with the "Polar Vortex" low pressure trough over Eastern North America during November 2013 - January 2014 was of unprecedented intensity, and extremes in this dipole pattern--both in the positive and negative sense--have been increasing since 2000 (the peak negative value occurred during the winter of 2009 - 2010.) The researchers used a climate model to look at whether human-caused climate change might be interfering with the natural pattern to cause this unusual behavior. They ran their climate model both with and without the human-caused change to the base state of the climate included, and found that they could not reproduce the increase in amplitude of the dipole pattern unless human-caused global warming was included. They concluded, "It is important to note that the dipole is projected to intensify, which implies that the periodic and inevitable droughts California will experience will exhibit more severity. The inference from this study is that the abnormal intensity of the winter ridge is traceable to human-induced warming but, more importantly, its development is potentially predicable." In an email to me, the lead author of the study, Simon Wang, emphasized that the opposite sign of the dipole--an extreme trough of low pressure over Western North American, combined with an extreme ridge of high pressure over Eastern North America--is also expected to be more intense when it occurs, leading to an increase in extremely wet winters in California.

Dr. Joe Romm's post on the study, "Bombshell: Study Ties Epic California Drought, ‘Frigid East’ To Manmade Climate Change", has this quote by climate scientist Michael Mann on the new research:

We know that human-caused climate change has played a hand in the increases in many types of extreme weather impacting the U.S., including the more pronounced heat waves and droughts of recent summers, more devastating hurricanes and superstorms, and more widespread and intense wildfires.

This latest paper adds to the weight of evidence that climate change may be impacting weather in the U.S. in a more subtle way, altering the configuration of the jet stream in a way that disrupts patterns of rainfall and drought, in this case creating an unusually strong atmospheric “ridge” that pushed the jet stream to the north this winter along the west coast, yielding record drought in California, flooding in Washington State, and abnormal warmth in Alaska. The recent IPCC assessment downplays these sorts of connections, making it very conservative in its assessment of risk, and reminding us that uncertainty in the science seems to be cutting against us, not for us. It is a reason for action rather than inaction.



Figure 2. One of the key water supply reservoirs for Central California, Lake Oroville, as seen on January 20, 2014. Thanks to an unusually intense ridge of high pressure over Western North America, California endured its driest November - January period on record this past winter, resulting in the worst winter drought on record. Image credit: California Department of Water Resources.

Other research connecting extreme circulation patterns to human causes
This week's paper by Dr. Wang is the second he has authored which has found a human fingerprint on extreme atmospheric circulation patterns. His 2013 paper, "Identification of extreme precipitation threat across midlatitude regions based on short-wave circulations," discussed how there's been a trend during the period 1979 - 2010 towards a pronounced circulation shift involving the low-level jet stream (LLJ), which is capable of bringing more extreme precipitation events (and droughts) to the mid-latitudes. Using four different climate models, the study found that the circulation shift only occurs when one runs climate models with the effects of human-caused emissions of greenhouse gases like carbon dioxide included; "control" runs of these models using only natural changes to the climate could not reproduce the observed increase in this more extreme circulation pattern. The paper concluded that several recent extreme precipitation events, including those leading to the 2008 Midwest flood in U.S., the 2011 tornado outbreaks in southeastern U.S., the 2010 Queensland flood in northeastern Australia, and to the opposite sense, the 2012 central U.S. drought, could have been influenced by human-caused changes to the atmospheric circulation. The fact that his research helps us understand how human-caused climate change is contributing to higher amplitude jet stream patterns should make them more predictable, potentially saving lives and money.

References
Wang, S, Davies, R.E., and R.R. Gillies, 2013, "Identification of extreme precipitation threat across midlatitude regions based on short-wave circulations," J. Geophys. Res. Atmos., 118, 11,059–11,074, doi:10.1002/jgrd.50841.

Wang, S., Hipps, L., Gillies, R.R., and J.-H. Yoon, 2014, "Probable causes of the abnormal ridge accompanying the 2013-14 California drought: ENSO precursor and anthropogenic warming footprint", Geophysical Research Letters, DOI: 10.1002/2014GL059748. News Release.

Related information
There is an growing body of research exploring connections between human-caused climate change and the increase in unusual jet stream patterns we've seen in recent years. Most of this research focuses on potential linkages between Arctic warming and atmospheric circulation patterns. Below are links to wunderground blog posts on the subject, and to the original research studies and associated press releases.

"The Changing Face of Mother Nature", wunderground guest post by Dr. Jennifer Francis of Rutgers, April 22, 2013.

Extreme jet stream causing record warmth in the east, record cold in the west (January 2013)

Arctic sea ice loss tied to unusual jet stream patterns (April 2012)

Our extreme weather: Arctic changes to blame? (December 2011)

Florida shivers; Hot Arctic-Cold Continents pattern is back (December 2010)

Jet stream moved northwards 270 miles in 22 years; climate change to blame? (June 2008)

Dr. Ricky Rood has done a whole series of posts on climate change and the Arctic Oscillation, including:

Cold Weather in Denver: Climate Change and Arctic Oscillation (8)

Are the changes in the Arctic messing with our weather? The Future of Blocking

Papers linking Arctic warming to an increase in negative AO/NAO conditions
Deser, C., R. Tomas, M. Alexander, and D. Lawrence, 2010, "The seasonal atmospheric response to projected Arctic sea ice loss in the late 21st century," J. Clim., 23, 333–351, doi:10.1175/2009JCLI3053.1.

Francis, J.A., and S.J. Vavrus (2012), "Evidence linking Arctic amplification to extreme weather in mid-latitudes," Geophysical Research Letters, 21 February, 2012. Accompanying article at the Yale Forum on Climate Change, Linking Weird Weather to Rapid Warming of the Arctic.

Francis, J. A., W. Chan, D. J. Leathers, J. R. Miller, and D. E. Veron, 2009, "Winter northern hemisphere weather patterns remember summer Arctic sea-ice extent," Geophys. Res. Lett., 36, L07503, doi:10.1029/2009GL037274.

Honda, M., J. Inoue, and S. Yamane, 2009, "Influence of low Arctic sea-ice minima on anomalously cold Eurasian winters," Geophys. Res. Lett., 36, L08707, doi:10.1029/2008GL037079.

Jaiser, R., K. Dethloff, D. Handorf, A. Rinke, J. Cohen (2012), "Impact of sea ice cover changes on the Northern Hemisphere atmospheric winter circulation", Tellus A 2012, 64, 11595, DOI: 10.3402/tellusa.v64i0.11595

Liu et al. (2012), "Impact of declining Arctic sea ice on winter snowfall", Proc. Natl. Academy of Sciences, Published online before print February 27, 2012, doi: 10.1073/pnas.1114910109. Accompanying press release. My blog post.

Mori et al. 2014, Robust Arctic sea-ice influence on the frequent Eurasian cold winters in past decades, Nature Geoscience, doi:10.1038/ngeo2277.

Overland, J. E., and M. Wang, 2010, "Large-scale atmospheric circulation changes associated with the recent loss of Arctic sea ice," Tellus, 62A, 1.9.

Petoukhov, V., and V. Semenov, 2010, "A link between reduced Barents-Kara sea ice and cold winter extremes over northern continents," J. Geophys. Res.-Atmos., ISSN 0148-0227.

Seager, R., Y. Kushnir, J. Nakamura, M. Ting, and N. Naik (2010), "Northern Hemisphere winter snow anomalies: ENSO, NAO and the winter of 2009/10," Geophys. Res. Lett., 37, L14703, doi:10.1029/2010GL043830.

Seierstad, I. A., and J. Bader (2009), "Impact of a projected future Arctic Sea Ice reduction on extratropical storminess and the NAO," Clim. Dyn., 33, 937-943, doi:10.1007/s00382-008-0463-x.

Tang et al., "Cold winter extremes in northern continents linked to Arctic sea ice loss," Environ. Res. Lett. 8 014036 doi:10.1088/1748-9326/8/1/014036. My April 2013 blog post.

Papers linking Arctic warming to Western U.S. drought
Sewall, Jacob O., 2005, Precipitation Shifts over Western North America as a Result of Declining Arctic Sea Ice Cover: The Coupled System Response, Earth Interact., 9, 1–23. doi: http://dx.doi.org/10.1175/EI171.1

Sewall, J.O., and L.C. Sloan, 2004, Disappearing Arctic sea ice reduces available water in the American west, Geophys. Res. Lett., 31, L06209, doi:10.1029/2003GL019133. Accompanying news release.

Papers linking Arctic sea ice loss to changes in summer rainfall
Li Y, LR Leung, Z Xiao, M Wei, and Q Li. 2013, Interdecadal Connection between Arctic Temperature and Summer Precipitation over the Yangtze River Valley in the CMIP5 Historical Simulations, Journal of Climate 26(19):7464-7488. DOI: 10.1175/JCLI-D-12-00776.1 Accompanying press release.

Li, Y, and L.R. Leung, 2013, "Potential Impacts of the Arctic on Interannual and Interdecadal Summer Precipitation in China", Journal of Climate 26(3):899-917. DOI: 101175/JCLI-D-12-00075.1

Screen, J.A., 2013, "Influence of Arctic sea ice on European summer precipitation", Environ. Res. Lett. 8 044015 doi:10.1088/1748-9326/8/4/044015. Accompanying press release.

Wu, B., Zhang R, D’Arrigo. R., and J. Su, 2013, "On the relationship between winter sea ice and summer atmospheric circulation over Eurasia," J. Clim. 26 5523–36

Papers exploring the link between Arctic warming to changes in large-scale atmospheric circulation
Cassano, E.N., Cassano, J.J, Higgins, M.E., and M.C. Serreze, 2013, "Atmospheric impacts of an Arctic sea ice minimum as seen in the Community Atmosphere Model", Int. J. Climatol., in press. (doi:10.1002/joc.3723)

Jaiser, R. et al., 2012, Impact of sea ice cover changes on the Northern Hemisphere atmospheric winter circulation, Tellus A 64, 11595.

Overland, J.E., Francis, J.A., Hanna, E., and M. Wang, 2012, "The recent shift in early summer Arctic atmospheric circulation," Geophys. Res. Lett. 39 L19804, DOI: 10.1029/2012GL053268

Petoukhov, V., Rahmstorf, S., Petri, S., Schellnhuber, H. J. (2013), "Quasi-resonant amplification of planetary waves and recent Northern Hemisphere weather extremes" Proceedings of the National Academy of Sciences, (Early Edition) [doi:10.1073/pnas.1222000110]. Easy-to-read description of the paper by the authors, published at http://theconversation.edu.au. Accompanying press release. My March 2013 blog post.

Screen, J.A., and I. Simmonds, 2013, "Exploring links between Arctic amplification and mid-latitude weather", Geophys. Res. Lett. 40 959–64.

Tang, Q.T. at al., 2014, Extreme summer weather in northern mid-latitudes linked to a vanishing cryosphere, Nature Climate Change 4, 45–50, doi:10.1038/nclimate2065


Jeff Masters

Climate Change Extreme Weather Drought

Updated: 7:59 PM GMT on November 19, 2014

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Wunderground Launches Major Site Redesign and New Logo

By: JeffMasters, 12:13 PM GMT on April 15, 2014

Back when I helped found the world's first commercial on-line weather service--The Weather Underground--back in 1995, we adopted a simple and colorful rainbow logo that expressed our mission well: a website dedicated to unlocking and sharing vast amounts of weather data with as many people as possible using the latest digital technologies, in a way that is visually appealing and engaging. Nineteen years later, we are transitioning to a completely new logo, as part of a site-wide redesign aimed at furthering that mission. We kept the colors and vibrancy of the rainbow but replaced the rainbow shape with the letters "WU"; a raindrop over the "U" represents rain falling into a rain gauge, a nod to our incredible Personal Weather Station (PWS) community (34,000 strong!) As our users have moved from desktop computers to mobile devices, we've had to adapt our user interface designs to cope with the increasing levels of data we've collected being presented on decreasing screen sizes. The layout and features of our site are now available and usable across all devices. We've worked with our users to organize our site in a more intuitive way, so you can access the information you want quicker and easier. We've updated our type to a more legible typeface, and changed our core color palette with the user in mind. Not only does the new color palette better convey information consistently across our products, it also works better for the color blind. We've added a new PWS dashboard, which lets you see rapid fire data from any personal weather station. 


Figure 1. As we slowly rolled out the features of the new web site over the past two weeks, our logo has gone through the transformations seen here.

If you have specific criticism, praise, or bug reports to pass on about the new site, go to our New Site Design Feedback page, fill out the form at the bottom of any city forecast page, or submit an email to support@wunderground.com. To learn more about the site re-design, and to see a timeline of the history of Weather Underground, see our new site redesign page. For those of you are are still fans of our original design, we will continue to support our original "classic" web site at http://classic .wunderground.com. Thanks for participating in the wunderground community!

Jeff Masters

Recent News

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IPCC: Cost of Avoiding Dangerous Climate Change Super-Affordable if We Act Now

By: JeffMasters, 7:10 PM GMT on April 13, 2014

Climate change is a huge threat to civilization if we do nothing more to reduce it, but the costs are very affordable if we start now, said the Nobel-prize winning Intergovernmental Panel on Climate Change (IPCC) today, in the third installment of their once-every-seven-years report on the climate. Today's report on mitigation--how we can slow down climate change--was the most hopeful of the reports, since it found that the cost of keeping global warming under the "dangerous" level of 2°C will only reduce "consumption growth" of the global economy by 0.06% per year if we start immediately and act strongly. Since consumption growth is expected to increase between 1.6% and 3% per year in the coming decades, we’re talking about annual growth that is, for example, 2% rather than 2.06%. This is a small price to pay to greatly decrease the risks of increased hunger, thirst, disease, refugees, and war outlined in the IPCC's frightening Working Group 2 report on risks and adaptation released two weeks ago. Today's report was authored by 235 scientists from 58 countries, and was approved by the governments of every nation of the world who cared to send a representative to the week-long approval meeting in Berlin, Germany. There is one more portion of the 2013 - 2014 IPCC report coming, a grand summary of Parts 1, 2, and 3 that will be released around November 1, 2014. Some key themes from today's report on mitigation:

Emissions of greenhouse gases are rising at a near-record pace. Greenhouse gas emissions grew 2.2% per year between 2000 - 2010, compared to a rate of 1.3% per year between 1979 - 2000. The increase was 3% per year between 2010 - 2011, and 1 - 2% from 2011 - 2012. About 76% of the greenhouse gases emitted were in the form of CO2, with 16% from methane. In 2010, ten countries accounted for about 70% of the world's CO2 emissions from fossil fuels and industrial processes. About half of the cumulative human-caused CO2 emissions between 1750 and 2010 have occurred in the last 40 years.

If we are going to avoid a dangerous 2°C (3.6°F) warming, we must make large and rapid cuts in greenhouse gas emissions. At the 2010 climate talks in Cancun, the governments of the world agreed that global warming should be kept under 2°C (3.6°F) above pre-industrial levels in order to avoid a "dangerous" threshold of climate change. The new IPCC report says that in order to do this, the share of zero and low carbon energy sources like solar, wind, nuclear, and unproven technologies like fossil fuel with Carbon Capture and Storage (CCS) must at least triple by 2050, and greenhouse gas emissions will have to fall 40 - 70%, compared to 2010 levels. By 2100, emissions of CO2 need to be near zero. This would require about $30 billion per year less to be spent on fossil fuels from 2010 - 2029, $147 billion per year more to be spent on zero and low carbon energy sources, and several hundred billion per year more per year to be spent on energy efficiency. (For comparison, the annual global total investment in the energy system is $1.2 trillion.) The report emphasizes that the greenhouse gas reduction promises made at the 2010 Cancun summit for the year 2020 are not enough to keep warming of the planet below 2°C at the lowest cost, though will likely keep a 3°C temperature rise from occurring.

If the world delays mitigation through 2030, it will be much more expensive and perhaps impossible to keep warming below 2° C. Models that delayed doing significant emission cuts until 2030 showed that the economic costs during the transition to renewable energy and in the long-term would be higher. Also, if some key (and unproven) technologies such as Carbon Capture and Storage (CCS) and Bio-Energy with Carbon Capture and Storage (BECCS) turn out not to be feasible at large scales, it will be difficult to keep warming below 2° C.

Keeping Earth's temperature rise below 2°C will have additional co-benefits. For example:
1) Reducing air pollution. The World Health Organization reported that in 2012 about 7 million people died--one in eight of total global deaths--as a result of air pollution exposure.
2) Improving energy security, leading to less price volatility and fewer supply disruptions.
3) Environmental protection.

There is a huge opportunity in the next few decades to build low-emission cities. Urban land cover is projected to expand by 56 - 310% between 2000 and 2030. Most of this urban infrastructure has yet to be built, presenting a tremendous opportunity to build the new urban areas so they emit fewer greenhouse gases. However, this will require strong policy, technical, financial and institutional measures.

Economic and population growth are the main drivers of greenhouse gas emissions. We've grown far more efficient at producing goods using less energy, meaning that the "energy intensity" of the global economy steadily declined from 2000 - 2010. However, increasing economic growth and population growth have outpaced the decline in energy intensity, resulting in higher greenhouse gas emissions. "Without additional efforts to reduce GHG emissions beyond those in place today, emissions growth is expected to persist driven by growth in global population and economic activities." If we take no additional measures to slow down human-caused climate change, the planet is expected to warm by about 4°C by 2100 compared to per-industrial levels. That's the same difference in temperature as between today's climate and the Ice Age.

Greenhouse gas emissions from deforestation are decreasing. Some good news is that the global rate of deforestation has been going down, which has made greenhouse gas emissions due to land use changes decline (greenhouse gas emissions due from agriculture, forestry, and other land use are 24% of the human total.) These type of emissions are projected to continue to fall, and possibly go to zero by 2100.

Renewable energy is growing fast, but needs help to increase its market share. In order to help renewable energy grow more rapidly, direct or indirect subsidies are needed. Indirect subsidies could occur by taxing fossil fuels or adopting a cap and trade system. The report doesn't recommend any particular policy actions, but does note that "to help reduce possible adverse effects on lower income groups who often spend a large fraction of their income on energy services, many governments have utilized lump‐sum cash transfers or other mechanisms targeted on the poor."

Links
New Blockbuster IPCC Climate Report: Comprehensive, Authoritative, Conservative, my September 2013 post on who the IPCC is, and how they write their reports.

Landmark 2013 IPCC Report: 95% Chance Most of Global Warming is Human-Caused, my September 2013 post on Part I of the 2013 - 2014 IPCC report.

IPCC: Climate Change Increasing Risk of Hunger, Thirst, Disease, Refugees, and War, my March 31, 2014 post on Part II of the 2013 - 2014 IPCC report.

Available: professionals willing to speak about climate change to local groups
If your school, chamber of commerce, church, library, or community club needs a local expert on climate science to come speak, the University Corporation for Atmospheric Research (UCAR) and the United Nations Foundation can help out, thanks to a new effort called climatevoices.org. The organization has more than 160 volunteer experts from al 50 states in a database that is searchable by geographic location, expertise, and languages spoken. If you are have expertise in climate science and are interested in volunteering for this network, please go to climatevoices.org and create a profile. I have my own set of slides I use for such talks that anyone is welcome to borrow from, available at http://www.wunderground.com/hurricane/2013/climatetalk.ppt.

Jeff Masters

Climate Change

Updated: 9:47 PM GMT on April 13, 2014

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Category 4 Tropical Cyclone Ita Hits Queensland, Australia

By: JeffMasters, 3:36 PM GMT on April 11, 2014

Category 4 Tropical Cyclone Ita powered ashore along Australia’s Queensland coast near 9 pm local time (10 UTC) on Friday with sustained winds rated at 145 mph by the Joint Typhoon Warning Center. Satellite loops show that Ita has weakened considerably since landfall, with the cloud tops in the eyewall clouds warming. Radar loops from Cairns, Australia show torrential rains from Ita are affecting a large stretch of Queensland as the storm track parallel to the coast, just inland. Cape Flattery caught the eyewall, and had sustained winds of 70 mph (10-minute average), gusting to 99 mph. Cooktown recorded sustained winds of 48 mph, gusting to 71 mph. Fortunately, Ita appeared to be undergoing an eyewall replacement cycle at landfall, and was probably weaker than a Category 4 storm when it came ashore. Ita hit a portion of the coast that is relatively lightly populated, and damage should be nowhere near the $3.6 billion price tag of the last Category 4 cyclone to hit Queensland, Tropical Cyclone Yasi of February 2, 2011.


Figure 1. Visible satellite image of Tropical Cyclone Ita taken at 04 UTC April 11, 2014. At the time, Ita was a Category 4 storm with 145 mph sustained winds. Image credit: NASA.

Jeff Masters

Hurricane

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Category 4 Ita Nearing Australia

By: JeffMasters, 10:32 PM GMT on April 10, 2014

Dangerous Category 4 Tropical Cyclone Ita is nearing landfall in Australia’s Queensland state. Maximum sustained winds estimated by the Joint Typhoon Warning Center were 155 mph at 18 UTC on Thursday, just 1 mph below the threshold of Category 5 strength. The Australia’s Bureau of Meteorology estimated that Ita had a central pressure of 930 mb at 18 UTC. Satellite loops show a moderate-sized tropical cyclone surrounded by an intense eyewall with very cold cloud tops. Radar loops from Cairns, Australia show spiral bands from Ita are already bringing heavy rains to the coast. With moderate wind shear of 10 - 15 knots and ocean temperatures near 28°C, Ita should be able to maintain Category 4 strength until landfall occurs Friday evening local time in Australia. The center of Ita is likely to pass very close to Cooktown (population 2,400) as a major hurricane, and near Cairns (population 143,000) as a weakening Category 1 storm. Ita will likely be the strongest tropical cyclone to hit Queensland since Category 4 Tropical Cyclone Yasi hit on February 2, 2011. Yasi killed one person and did $3.6 billion in damage.


Figure 1. Visible satellite image of Ita taken at 21:32 UTC (5:32pm EDT) April 10, 2014. Image credit: NOAA/SSD.

Ita passing close to location of world-record tropical cyclone high water mark
Storm surge is a huge concern from Ita, and the cyclone is passing just east of the location of the world record high water mark from a tropical cyclone: the 13 - 14.6 meters (43 - 48 feet) from Australia's March 5, 1899 Bathurst Bay Cyclone. That Category 5 storm was a monster, with sustained winds in excess of 175 mph, and a central pressure between 880 and 914 mb. Mahina killed at least 307 people, mostly on pearling ships, and was the deadliest cyclone in Australian history. The eyewitness account of Mahina's record storm surge was provided by Constable J. M. Kenny, who journeyed to Barrow Point on Bathurst Bay to investigate a crime on the day of the storm. While camped on a ridge 40 feet above sea level and 1/2 mile inland, Kenny's camp was inundated by a storm wave, reaching waist-deep. On nearby Flinders Island, fish and dolphins were found on top of 15 meter (49 foot) cliffs. However, an analysis by Nott and Hayne (2000) found no evidence of storm-deposited debris higher than 3 - 5 meters above mean sea level in the region. They also cited two computer storm surge simulations of the cyclone that were unable to generate a surge higher than three meters. Indeed, Bathurst Bay is not ideally situated to receive high storm surges. The Great Barrier Reef lies just 20 - 40 km offshore, and the ocean bottom near the bay is not shallow, but steeply sloped. Both of these factors should conspire to keep storm surges well below the record 13 - 14.6 meters reported. The authors concluded that the actual surge from the Bathurst Bay Cyclone may have been 3 - 5 meters. The observed inundation at 13 meters elevation, plus the observation of dolphins deposited at 15 meters above sea level could have been caused by high waves on top of the surge, they argue. Waves on top of the surge (called "wave run-up") can reach five times the wave height at the shore for steeply fronted coasts like at Bathurst Bay. Since waves in the Bathurst Bay Cyclone could easily have been 3 meters, 15 meters of wave run-up on top of the surge is quite feasible. Since wave run-up doesn't count as surge, the status of the 1899 Bathurst Bay Hurricane as the world record holder for storm surge is questionable. However, the event is certainly the world record holder for the high water mark set by a tropical cyclone's storm surge, an important category in its own right.


Figure 2. Satellite image of Bathurst Bay, Queensland Province, Australia. The record 43 - 48 foot storm surge wave occurred on Barrow Point, marked by an "x" on the map above. Image credit: NASA.


Figure 3. Track of the 1899 Bathurst Bay cyclone. Bathurst Bay is located at the point where the 914 mb pressure is listed. Image credit: Whittingham, 1958.

References:
Nott, J, N. Hayne, 2000: How high was the storm surge from Tropical Cyclone Mahina?", Australian Journal of Emergency Management, Autumn 2000.

Anonymous, 1899, The Outridge Report--The Pearling Disaster 1899: A Memorial", The Outridge Company, 1899

Whittingham, 1958, "The Bathurst Bay hurricane and associated storm surge", Australian Meteorological Magazine, No. 27, pp. 40-41. Scanned and put on-line courtesy of John McBride.

Jeff Masters

Hurricane

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James Cameron's 'Years of Living Dangerously' Rocks

By: JeffMasters, 12:55 AM GMT on April 09, 2014

The biggest story of our time is climate change. The stunningly severe and unprecedented extreme weather events of the past few years are just a early harbinger of the civilization-shaking events our increasingly hostile and violent atmosphere will throw at us, as Earth's climate responds as it must to the huge changes humans have wrought. Unfortunately, the greatest story of our time has thus far primarily been told by scientists, who are not natural story tellers. Effective story telling is essential to communicating important truths, since it acts on a gut level. That's why I'm excited about the latest effort to tell the story of climate change by one of Hollywood's master story tellers--James Cameron, creator of Titanic and Avatar.


Video 1. The first episode of Showtime’s ”Years of Living Dangerously” has been posted in its entirely to YouTube.

Years of Living Dangerously
Beginning on Sunday, April 13, at 10pm EDT, an 8-part documentary series on climate change called Years of Living Dangerously airs on Showtime, the premium cable service. The previews I've seen show a top-notch production effort with stunning visuals. Starring are Jessica Alba, Harrison Ford, Arnold Schwarzenegger, Lesley Stahl, and Thomas L. Friedman. The science is excellent, provided by climate science experts like Heidi Cullen, Michael Mann, Katharine Hayhoe, James Hansen, and Joe Romm. Dr. Romm promises: "This will blow you away. Nothing like this has ever been on TV. Indeed, this isn't just landmark climate TV. It is landmark TV, in terms of its storytelling and cinematography and the way it uses experts and celebrities. This is not a talking heads show. This is like 60 Minutes meets Homeland or Game of Thrones." After viewing the first episode, I have to agree—this is the most compelling documentary ever done on climate change. I like how the show focuses on the greatest threat climate change poses to civilization—drought. The causes of the 2012 Texas drought are explored by Texas Tech climate scientist Katherine Hayhoe. Harrison Ford studies how intensifying drought conditions in recent years in the regions surrounding the Mediterranean Sea, including Syria, have been linked to human-caused climate change. Could climate change have contributed to the outbreak of the brutal civil war there? The issue is explored in detail in this first episode of "Years of Living Dangerously."

Dangerous climate change is already upon us, and I look forward to seeing this greatest story of our time being told on Showtime's “Years of Living Dangerously” on Sunday evenings over the coming weeks.

Jeff Masters

Book and Movie Reviews

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An Expensive Way to Ease California's Drought: Desalinization Plants

By: JeffMasters, 2:53 AM GMT on April 07, 2014

With the middle of April approaching, there is no significant precipitation in the forecast for California in the coming ten days, and there is a good chance that the California rainy season is at least 95% over. As wunderground's weather historian, Christopher C. Burt, documents in his April 3 California Drought Update, the California rainy season lasts from October to mid-April, and typically only 10 - 15% of the rainy season precipitation falls after April 1. While enough precipitation fell over the past two months to prevent the current rainy season from hitting record low precipitation levels, the 2013 - 2014 rainy season was the third consecutive poor rainy season, leaving California in a dire drought situation. The winter of 2013 - 2014 had the most severe winter drought conditions since record keeping began in 1895, and California faces a long, dry summer with a Sierra snowpack that is only 33% of normal. The April 3, 2014 Drought Monitor is showing that 99.8% of California is in drought, with 95% of the state in Severe, Extreme, or Exceptional drought.


Figure 1. Predicted precipitation for the 7-day period ending at 8pm EDT Sunday, April 13, 2014. No significant rain is expected to fall in California in the coming week. Image credit: NOAA/HPC.

Ways to Ease California's Drought
There is only one major river in the Southwest, the Colorado River, and in most years the flow in the river is far less than the amount of water allocated to stockholders drawing water from the great river. Over 30 million people depend on the Colorado River for their water, including much of Southern California, and the river irrigates farmland that produces 15% of the nation's food. Two major studies, one by the U.S. Bureau of Reclamation in 2012, and one by the non-profit Pacific Institute in 2013, laid out five major ways that the Colorado River basin can get more water. As I outlined in Part 1 and 2 of this series last month, two ways to get more water for the thirsty Southwest are through conservation measures and cloud seeding. A much more expensive way--typically costing 2 to 20 times more than conservation techniques--is to make fresh water out of salt water using a desalinization plant.


Figure 2. Arizona's Yuma Desalting Plant, used to treat saline agricultural runoff and create fresh water. Image credit: U.S. Bureau of Reclamation.

Desalinization Plants
Fresh water can be wrung out of the ocean by forcing it through filtration membranes used in the reverse osmosis process. The high pressures needed consume a lot of energy--even more energy than it takes to pump water from Northern California rivers to Los Angeles over a 2000'-high mountain obstacle. Desalinized water provides less than 1% of California's fresh water, and costs nearly double what water imported from Northern California rivers and the Colorado River costs. However, given that desalinized water is "drought-proof", there are efforts to greatly expand the creation of fresh water from the sea. The $734 million Carlsbad Desalination Project in San Diego County, California, scheduled to be completed in 2016, will generate about 56,000 acre-feet annually, at a projected cost of $2135 per acre-foot. This largest desalinization plant in the U.S. is projected to meet 7 percent of San Diego County’s demand in 2020, and will push up the typical home's water bill by $5 to $7 a month, according to the San Diego Water Authority. A sister plant has been proposed near Los Angeles. California currently has six operational desalinization plants, with three others that are partially or fully idled due to their high cost of operation. remains unused and has been partially dismantled, because the city found cheaper sources of water.

I’ll discuss several other ways California can get more water in future blogs posts in the coming weeks.

Jeff Masters

Drought

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Record-Warm Subsurface Pacific Waters May Bring Moderate to Strong El Niño Event

By: Michael Ventrice , 3:19 PM GMT on April 04, 2014

Today's guest blog post is by Dr. Michael Ventrice, an operational scientist for the Energy team at Weather Services International (WSI). This is a follow-up post to the one he did on February 21 on the progress of El Niño. Today's post is very technical! - Jeff Masters

There have been tremendous changes in the Pacific Ocean over the past two months which continue to favor a moderate to strong El Niño event later this spring and summer. Since my previous post on February 21, NOAA's Climate Prediction Center (CPC) has issued an El Niño watch.

To begin, we are currently observing what looks to be the strongest downwelling oceanic Kelvin wave event since satellite records began in the 1970s. This still needs to be verified in reanalysis, but a large swath of 6°C (11°F) ocean temperature anomalies at a depth of 100 - 200 meters (Figure 1) clearly illustrates the significance of this event. To review, oceanic Kelvin waves travel only from west to east at extremely slow speeds (2-3 m/s). These waves have been alluded to as the facilitators of El Niño. There are two phases of an oceanic Kelvin wave, the “Upwelling” phase and the “Downwelling” phase. The Upwelling phase of an oceanic Kelvin wave pushes colder water from the sub-surface towards the surface, resulting in cooling at the surface. The Downwelling phase is the opposite, where warmer waters at the surface of the West Pacific warm pool are forced to sink, resulting a deepening of the thermocline and net warming in the sub-surface.


Figure 1. Departure of ocean temperature from average along the Equator in the Pacific Ocean on March 29, 2014 (top), shows a large area of 6°C (11°F) ocean temperature anomalies at a depth of 100 - 200 meters. A time lapse is available here. Image credit: NOAA/CPC.

In the West Pacific, the thermocline is rising in response to strong upwelling (cold ocean temperature anomalies near the surface). In the central and eastern Pacific, the thermocline is deepening as the warm pool has begun to rapidly shift towards the Date Line. An enlightening time lapse can be found on the NOAA/CPC webpage. Note the lens of colder than average ocean temperature anomalies at the surface in the far eastern Pacific. This can be attributed to a surge in the Easterly trade winds over the eastern equatorial Pacific, which pushes water away from the coast, resulting in some upwelling off the west coast of South America. The surge in the trade winds is just an expression of atmospheric processes occurring in the tropics at intra-seasonal (weekly) timescales. Nevertheless, it is evident that the entire West Pacific Warm Pool has begun to shift eastward, and there is a large adjustment in the Pacific Ocean currently underway.

That being said, we still need to see some favorable atmospheric forcing this month to continue the forward advancement of a full-basin El Niño. In particular, west-to-east blowing winds along the Equator are needed to keep pushing warm water eastwards towards South America. Keeping this in mind, there are some signs of an upcoming period of westerly wind bursts along the equatorial Central Pacific in the next few weeks.



Figure 2. Rainfalls rates over the Indian Ocean (shaded colors), departure of the winds at 200 mb from average (arrows), and Kelvin filtered velocity potential at 200 mb (VP200, contours.) Image credit: Michael Ventrice.

An exceptionally strong atmospheric convectively coupled Kelvin wave (CCKW) is currently propagating across the equatorial Indian Ocean. IMPORTANT: An atmospheric CCKW is DIFFERENT than an oceanic Kelvin wave since atmospheric CCKWs are stratospheric waves in the *atmosphere* that are confined to just the equatorial band. Thus we cannot experience a CCKW passage in North America. CCKWs often couple with thunderstorm activity within the troposphere in the tropics. In addition, CCKWs in the atmosphere are non-dispersive in theory, so they can make many circuits around the globe before attenuating from external forcing such as friction; oceanic Kelvin waves can only travel the distance of whatever basin they are in (in this case, the Pacific). However, *both* atmospheric CCKWs and oceanic Kelvin waves propagate from west to east only.



Figure 3. A time-longitude plot of unfiltered VP200 anomalies (shaded) with Kelvin filtered VP200 anomalies (contours; dashed contours represent the upper-level divergent phase of the CCKW or its convectively active phase) illustrates the non-dispersive nature of this CCKW, as it makes a complete circuit around the globe. Image credit: Michael Ventrice.



Figure 4. GFS model forecast for April 6, 2014. Six-hour precipitation rates are shaded. Often during and up to a few days after the passage of a strong CCKW, tropical cyclones can develop on either side of the Equator, depending on the season. An example can be seen over the Southern Indian Ocean this week, where the GFS model is forecasting the development of a tropical “gyre” that could become a tropical depression. Note the equatorial westerlies are a component of the anatomy of the CCKW circulation itself.

The forecast calls for this Indian Ocean CCKW to push across the Date Line during mid-April. This would be a time when we might see another period of westerly winds develop across the equatorial Central Pacific--favorable atmospheric conditions for a full-basin El Niño to emerge. The anticipated westerly wind burst in mid-April may be composed of individual tropical cyclones, or extra-tropical waves intruding the tropics.

In addition to the CCKW itself, there are higher than average probabilities of another developing Madden Julian Oscillation (MJO) to emerge over the West Pacific following the passage of this strong CCKW, in mid-to-late April. A great deal of my graduate study work focused on CCKW-MJO interactions and the plot below is from Ventrice et al. (2012), which is of a time-longitude composite plot of unfiltered VP200 anomalies (shaded), Kelvin filtered outgoing long wave radiation (OLR) anomalies (black contours), and MJO filtered OLR anomalies (orange contours). From selecting only dates where a strong CCKW passed the eastern tropical Atlantic, a lagged composite approach from these dates reveal a remarkable picture. Once the CCKW passes across Africa to over the Indian Ocean, we often observe a developing MJO event over the Indian Ocean that then propagates eastward across the Pacific region thereafter. There are increased chances of a similar scenario to play out over the next few weeks.



Why does this matter for El Niño? Well, within and following the passage the convectively active phase of the MJO, we often observe an increased number of West Pacific typhoons and low-level westerly wind flow. This is what is likely needed to continue the eastward advancement of the West Pacific Warm Pool this spring, and provides more evidence for a full-basin El Niño event to emerge later this spring in through summer. Furthermore, it is important to note that the latest climate model forecasts are now more aggressive with the amplitude of the potential emerging El Niño. This can be seen in both the ECMWF and CFSv2 Niño3.4 forecasts. For the purpose of illustration, below is the CFSv2 model forecast from mid-February 2014:



And here is the CFSv2 model forecast from Early April 2014:


Nearly a +0.5°C adjustment has been made in just one month for the June-July-August period and beyond, indicating that the model is even more bullish on the El Niño this spring in through summer.

Bottom Line: The Pacific Ocean continues to show signs of a developing moderate to strong El Niño event. During strong full-basin El Niño’s, we often observe cooler than average temperatures in summer across the eastern two thirds of the U.S., and lower than average Atlantic hurricane activity.

Michael Ventrice

Dr. Michael Ventrice is an operational scientist for the Energy team at Weather Services International (WSI), who provide market-moving weather forecasts and cutting-edge meteorological analysis to hundreds of energy-trading clients worldwide. Follow the WSI Energy Team on Twitter at @WSI_Energy and @WSI_EuroEnergy.

Atmospheric Phenomena

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Camille of 1969 Downgraded to Second Strongest Landfalling U.S. Hurricane

By: JeffMasters, 2:48 PM GMT on April 02, 2014

On the night of August 17, 1969, mighty Category 5 Hurricane Camille smashed into the Mississippi coast with incredible fury, bringing the largest U.S. storm surge on record--an astonishing 24.6 feet in Pass Christian, Mississippi (a record since beaten by 2005's Hurricane Katrina.) Camille barreled up the East Coast and dumped prodigious rains of 12 - 20 inches with isolated amounts up to 31" over Virginia and West Virginia, with most of the rain falling in just 3 - 5 hours. The catastrophic flash flooding that resulted killed 113 people, and the 143 people the storm killed on the Gulf Coast brought Camille's death toll to 256, making it the 15th deadliest hurricane in U.S. history. Up until now, Camille's landfall intensity had been rated at 190 mph--the highest on record for an Atlantic hurricane, and second highest on record globally, behind Super Typhoon Haiyan's 195 mph winds at landfall in the Philippines in November 2013. However, Camille's landfall intensity has now been officially downgraded to 175 mph, thanks to a reanalysis effort by Margie Kieper and Hugh Willoughby of Florida International University and Chris Landsea and Jack Beven of NHC. Camille's central pressure at landfall was lowered from the previous 909 mb to 900 mb, though. The re-analysis results, presented Tuesday at the American Meteorological Society's 31st Conference on Hurricanes and Tropical Meteorology , puts Camille in second place for the strongest landfalling hurricane in U.S. history. The top spot is now held by the Great 1935 Labor Day Hurricane that hit the Florida Keys, which reanalysis showed had 185 mph winds and a central pressure of 892 mb at landfall. The only other Category 5 hurricanes on record to hit the U.S. were 1992's Hurricane Andrew (165 mph winds and a 922 mb central pressure) and the 1928 “San Felipe” Hurricane in Puerto Rico (160 mph winds, 931 mb central pressure.) Category 5 hurricanes have maximum sustained winds of 156 mph or greater. Revisions to Camille were accomplished by obtaining the original observations from ships, weather stations, coastal radars, Navy/Air Force/Environmental Science Services Administration (ESSA) Hurricane Hunter aircraft reconnaissance planes, ESSA/NASA satellite imagery, and by analyzing Camille based upon our understanding of hurricanes today. (ESSA is now the National Oceanic and Atmospheric Administration--NOAA.)


Figure 1. Hurricane Camille as seen on Sunday, August 17, 1969, about eight hours before making landfall on the Mississippi coast. At the time, Camille was a peak-strength Category 5 storm with 175 mph winds. Image credit: NOAA/NCDC.


Figure 2. Ships beached by Hurricane Camille's record storm surge in Mississippi. Image credit: NOAA photo library.

Hurricane Audrey of 1957 Downgraded to a Category 3
A reanalysis effort on the 1955 - 1964 Atlantic hurricane seasons is also underway, and Sandy Delgado of the Cooperative Institute for Marine and Atmospheric Studies (CIMAS) in Miami, FL reported on Tuesday that Hurricane Audrey, which had previously been rated as the only June Category 4 Atlantic hurricane, has now lost that distinction. Audrey's top winds at landfall were downgraded to Category 3 status, from 145 mph to 120 mph, which still makes it the strongest landfalling June Atlantic hurricane on record (though Hurricane Alma passed just west of Key West on June 8, 1966 as a Category 3 storm with 125 mph winds.) Audrey killed 416 people in Texas and Louisiana, making it the 7th deadliest hurricane in U.S. history. Delgado's analysis also found twelve previously unrecognized tropical storms from the 1955 - 1964 period.


Figure 3. Hurricane Audrey near landfall on June 27, 1957. At the time, Audrey was a Category 3 storm with 120 mph winds. Image credit: NOAA.

Reanalysis of 1946 - 1950 hurricanes completed
HURDAT, the official Atlantic hurricane database, has now been updated with a reanalysis of the 1946 to 1950 hurricane seasons. This was an active period for hurricanes, with 13 striking the continental United States (an average five year span would have about nine U.S. hurricane impacts.) Five of the 13 were major hurricanes at U.S. landfall, and all five struck Florida. These are a Category 4 hurricane in Fort Lauderdale in 1947, a Category 4 hurricane in Everglades City in 1948, a Category 4 hurricane in Lake Worth in 1949, Category 3 Hurricane Easy in Cedar Key in 1950, and Category 4 Hurricane King in Miami in 1950. Of these, King and the 1948 and 1949 hurricanes were upgraded from a Category 3 to a Category 4 based upon the reanalysis. Having five major hurricanes making landfall in Florida is a record for a five year period, equaled only by the early 2000s. In addition, nine new tropical storms were discovered and added into the database for this five year period. The number of major hurricanes for 1950 was reduced from eight to six, putting that year in second place for the most major hurricanes in one year. The record is now held by 2005, with seven major hurricanes (Dennis, Emily, Katrina, Maria, Rita, Wilma, Beta; thanks go to Mark Cole for bringing this stat to my attention.) Andrew Hagen, Donna Sakoskie, Daniel Gladstein, Sandy Delgado, Astryd Rodriguez, Chris Landsea and the NHC Best Track Change Committee all made substantial contributions toward the reanalysis of the 1946 - 1950 hurricane seasons.

Jeff Masters

Hurricane

Updated: 4:14 PM GMT on April 02, 2014

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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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