WeatherFanatics: First Week of June Yields Multiple Derechos

Saturday, June 7, 2014

First Week of June Yields Multiple Derechos

By Alex Sosnowski, Expert Senior Meteorologist

June 7,2014; 11:15AM,EDT

The first week of June has delivered round after round of severe weather and long-running thunderstorms with high winds from the Plains to the South.
Clusters of thunderstorms are born and can maintain themselves when a north to south temperature contrast exists, significant wind energy is available and there is ample moisture present.
When these severe thunderstorm complexes cause significant wind damage over hundreds of miles, a derecho may have been born.
The definition of a derecho is rather open-ended as explained by the Storm Prediction Center (SPC) but is defined as a thunderstorm complex producing wind gusts of 58 mph or greater at most points along a path of 240 miles or longer.

A man talks on a cell phone on a blocked street in Jonesboro, Arkansas, Thursday, June 5, 2014. (AP Photo/Danny Johnston)
Not all derechos are created equal. The event from late June of 2012 was on the extreme end.
As of Friday morning, the first week of June appears to have yielded two derechos.
The first derecho candidate occurred on Tuesday and traveled from southeastern Nebraska to central Illinois before diminishing. Tuesday's system covered approximately 300 miles, downed trees and power lines, flipped over semis and caused damage to homes and businesses along the way. Prior to the formation of the complex, hail up to the size of baseballs and softballs fell on parts of Nebraska and Iowa.
The second and much longer of the two derechos occurred on Thursday. The Thursday system began over central Kansas and extended for more than a 700-mile path before weakening over northwest Georgia. The storms caused fatalities, knocked down scores of trees and cut the power to thousands of utility customers.

Peak wind gusts were estimated to be between 70 and 80 mph in parts of Kansas, Arkansas, Tennessee, and Alabama, on Thursday, June 5, 2014. Wind Damage (downed trees) Map from NWS San Diego Forecast Office
Determining whether or not a derecho event is about to occur is quite challenging. Changing conditions can result in storms forming in a different location than originally thought, quick termination of the storms or only scattered thunderstorm activity.
The life expectancy of most thunderstorm complexes is a couple of hundred miles or less.
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According to Severe Weather Expert Henry Margusity, "The complex of thunderstorms with high winds has to first cover a significant distance and then damage reports have to be officially verified," Margusity said.
Sometimes the verification process can take days.

This photo of a shelf cloud was taken in Purcell, Oklahoma, as a thunderstorm complex moved across the state on Friday morning, June 6, 2014. (Instagram/kandicarebearzilla)
According to Senior Meteorologist Bernie Rayno, "It looks like there is the potential for two more additional significant thunderstorm complexes before the weekend comes to a close."
There is the potential for one or both of these to take on derecho status.
"While there is a risk to lives and property with the derecho potential, the complexes of thunderstorms will continue to bring needed rainfall to drought areas of the Plains which saw very few of these last year," Rayno said.
The public pays much attention to the severe weather potential when the derecho term is used. However, there is the risk of major damage at the neighborhood level even if a derecho has not be called out ahead of time.
People should continue to pay attention to the weather and be on the lookout for rapidly changing conditions when thunderstorms are in the forecast, especially if they will be outdoors and the alert has been given for severe weather.
AccuWeather.com MinuteCast™ has the minute-by-minute forecast for your exact location in this potentially dangerous situation. Type your city name, select MinuteCast™, and input your street address. On mobile, you can also use your GPS location.

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