A look at weather extremes and the big-picture climate connections.

Tropical Storm Andrea To Drench Florida, East Coast

Just five days into the 2013 Atlantic Hurricane Season, and the first named storm system of the season has formed in the Gulf of Mexico. Tropical Storm Andrea is a weak tropical storm with maximum sustained winds of 40 mph as of early Wednesday evening. It is not expected to intensify significantly before making landfall near Tallahasee, Fla., on Thursday evening, but may ride up the East Coast as a wind-blown, soaking rainstorm through the weekend. 

The National Hurricane Center has issued a tropical storm warning for the west coast of Florida from Boca Granda to Ochlockneee River, with tropical storm watches going up from Flagler Beach, Fla., to Surf City, N.C. 

5-day track forecast for Tropical Storm Andrea.
Click image to enlarge. 
Credit: National Hurricane Center.

The biggest threat from the storm will be the plume of heavy rain it will spread from Florida to the Northeast during the next several days, potentially leading to flooding in some areas. Already, it is spreading heavy rain into water-logged Florida, where flooding is a growing concern. Depending on the strength of the storm, some coastal flooding is also possible along portions of the Florida Gulf Coast.

Florida has had above-average rainfall recently, with West Palm Beach receiving nearly 16 inches during the month of May — nearly a foot above average. Miami had 11 inches during May, which was also well above average.

The National Weather Service is forecasting several inches of rain across the Florida peninsula through Thursday night, along with the possibility of isolated tornadoes....


Killer El Reno Tornado Was Widest Ever Recorded: NWS

The tornado that struck El Reno, Okla., on May 31 was an EF-5 twister, the strongest on the Enhanced Fujita Scale, the National Weather Service reported on Tuesday. The tornado had a stunning width of 2.6 miles, which makes it the widest tornado on record worldwide. The twister killed 13, four of whom were storm chasers, including pioneering tornado researcher Tim Samaras.

The width of the tornado was equivalent to the entire north-south length of New York City's Central Park, which extends 2.5 miles from 59th street in Manhattan to 110th street.

View of the El Reno tornado from KFOR-TV in Oklahoma City.
Credit: KFOR.com

The massive size, and the tornado's rapid expansion, plus damaging winds that rotating around the edges of the tornado all likely played a role in catching so many tornado chasers and motorists offguard.

The NWS had initially rated the tornado an EF-3 after viewing damage on the ground, but the upgrade was made after examining radar data from mobile Doppler radars that were in the field observing the tornado.

The NWS statement said:

"The tornado has been upgraded to an EF-5 tornado based on velocity data from the research mobile radar from the University of Oklahoma RAX-POL Radar. In addition... the width of [the] tornado was measured by the mobile radar data to be 2.6 miles after the tornado passed east of U.S. Highway 81 south of El Reno."

The path and width of the El Reno tornado.
Click on the image to enlarge. 
Credit: NWS

"This width is the width of the tornado itself and does not include the damaging straight-line winds near the tornado as determined by the high-resolut...


Oklahoma Facing Another Possible Tornado Outbreak

A multiday severe weather outbreak continues to hammer the Midwest and Plains States, and the National Weather Service is warning that the Oklahoma City area, which was devastated by the Moore tornado earlier this month, may see more significant tornadoes on Friday. The severe thunderstorms are likely to form along a frontal zone that is draped from the Midwest down to the Plains, with a disturbance at the upper levels of the atmosphere adding a necessary spark to the already unstable situation.

Computer projection showing the Convective Available Potential Energy (CAPE) on Friday afternoon, with a maximum centered in Oklahoma. CAPE is one measure of how unstable the atmosphere is. 
Click image to enlarge. Credit: Weatherbell.com

Temperatures have exceeded 100°F in parts of the Sooner State, and the Storm Prediction Center in Norman has issued a tornado watch with a "Particularly Dangerous Situation" designation, meaning that there is a likelihood of significant tornadoes in the watch area. That so-called "PDS watch" includes the Oklahoma City metro area and is in effect until midnight Friday, central time. Another tornado watch was in effect for eastern Kansas and much of central Missouri as of 4 p.m., with more to come as storms fire up toward early evening.

The NWS Office, which was widely praised for the advanced notice it provided to Moore residents during that EF-5 tornado event, issued a steady stream of specific tornado outlook and safety information via its social media accounts on Friday. For example, on its Twitter account, the NWS warned: "Times may change, but I would not want to be driving anywhere in the OKC metro after 4 p.m. today. Tornadoes not certain, but be ready!"...


Tornadoes Rake Okla., Kansas as Storm Threat Continues

A tornado outbreak on Sunday left at least two people dead in Oklahoma and nearly two dozen injured after the busiest day in what had been an unusually tame 2013 tornado season.

The Shawnee, Okla., tornado that caused major damage southeast of Oklahoma City on May 19. 
Credit: TornadoTitans.com/Brett Wright via Facebook.

Severe thunderstorms struck from Oklahoma all the way to Minnesota as a strong cold front edged eastward, plowing into warm and humid air. Strong upper-level winds provided support for supercell thunderstorms, which are thunderstorms that have persistent rotation associated with them, and can cause tornadoes and damaging large hail.

Video footage of the Shawnee, Okla., tornado from Brandon Sullivan/Wicked Wind Media

Several cities narrowly missed direct hits, including Oklahoma City and Wichita, Kan. In Wichita, a tornado touched down near the Mid-Continent Airport, and a “tornado emergency” was declared for the city. On the livefeed of KSN-TV’s storm coverage, the sound of large hail striking the studio’s rooftop was audible, and the TV meteorologists hastily retreated to the station’s storm shelter, leaving an eerily silent radar image on the screen.

A total of 24 tornado reports were received by the Storm Prediction Center in Norman, Okla. The Weather Channel broadcast at least two large tornadoes live as they formed and strengthened, including one of the most damaging twisters, which struck near Shawnee, Okla. The National Weather Service gave the Shawnee tornado a preliminary rating of EF-4 on the Enhanced Fujita Scale, with winds of up to 200 mph.



Deadly Texas Outbreak May Mark End of Tornado Drought

After months with record-low activity, the 2013 tornado season roared back with a vengeance on Wednesday as at least 10 twisters touched down across portions of north-central Texas, killing at least 6 and injuring dozens more. An even broader outbreak of severe weather, including the threat of more tornadoes, is forecast this weekend from North Texas to Missouri, gradually shifting eastward with time.


Eyewitness video of one of the Texas tornadoes on Wednesday.


The hardest-hit community on Wednesday evening was Granbury, about 40 miles southwest of Fort Worth. Hood County Sheriff Roger Deeds told the media that an entire neighborhood, consisting of 100-plus homes, was “heavily damaged to destroyed.”

There were reports that the Granbury tornado was as large as 1-mile wide, and aerial footage on Thursday morning revealed a broad swath of destruction. The town received a tornado warning 20 minutes in advance, according to Reuters. Preliminary reports from the National Weather Service show the tornado was at least an EF-4 on the Enhanced Fujita Scale, with winds of between 166 to 200 mph. Damage surveys have found homes that were completely swiped aside, and reduced to mere concrete slabs.

The Texas tornado fatalities were the second in the Lone Star State since 2007 — an unusually long stretch for a state that typically sees 8 deaths per year, based on statistics from 1961-1990. 

For the U.S., the deadly outbreak shatters the relative calm of t...