A dangerous weather situation is developing in the High Plains on Thursday, as severe thunderstorms capable of producing widespread damaging winds and a few strong tornadoes erupt across the region.
The Storm Prediction Center, which is the branch of the National Weather Service that forecasts severe thunderstorms, has upgraded the region to a “High Risk” of severe weather. This is their most significant category of alert, and signals the high probability of damaging winds, large hail, and tornadoes.
The storm outbreak is occurring because of a combination of weather factors at the surface and in the upper levels of the atmosphere, and forecasters say conditions are ripe for both long-lasting rotating thunderstorms, known as supercells, and a potential “derecho” event, which would produce widespread damaging winds across hundreds of miles of real estate.
The storms were just getting started in Nebraska as of 5:30 p.m. ET, with tornado and severe thunderstorm watches already issued for that state as well as parts of Iowa and Missouri. Storm Prediction Center meteorologists have described the atmosphere in parts of the region as “unstable and increasingly volatile,” as temperatures warm at the surface but remain relatively cold aloft, encouraging the warm air to rise. The winds are changing direction and speed with height, known as wind shear, which is a crucial ingredient for tornado formation.
RT @TWCBreaking: Norfolk, Nebraska. That's some big hail. RT @Jcow: pic.twitter.com/uvbbdzZSxu— The Weather Channel (@weatherchannel) June 3, 2014
Wow... RT @spann Omaha shelf cloud... via WOWT-TV #newx pic.twitter.com/XXPn4qxoqP— Andrea Thompson (@AndreaTWeather) June 3, 2014
A disturbance in the mid-to-upper levels of the atmosphere, at altitudes where commercial aircraft fly, is making the situation especially risky by helping to act as a trigger for the storms. The Storm Prediction Center says that as time goes on throughout Tuesday evening, the thunderstorms may organize into a larger, multistate complex, featuring large hail, isolated tornadoes, and widespread damaging winds of up to 100 miles per hour. If this complex travels far enough, about 250 miles, it would be classified as a derecho (pronounced "deh-REY-cho").
A derecho event made headlines in 2012 after a cluster of storms knocked out power to millions from Ohio to the Atlantic coast of Virginia, plunging the Washington region into darkness, and silencing air conditioners during a heat wave.
Forecasting derecho events involves a high amount of uncertainty, so it’s possible the storms will fall just shy of the official definition, or form into a different type of system than a derecho. According to the Storm Prediction Center, the storms can only be classified as a derecho “if the swath of wind damage extends for more than 240 miles, includes wind gusts of at least 58 mph along most of its length, and several, well-separated 75 mph or greater gusts.”
In Nebraska. about 12 mi South of the town of O'Neill RT @Joel_Muiller: Located 852 rd. and Hwy 281 pic.twitter.com/p7qN8Y0UVc— The Weather Channel (@weatherchannel) June 3, 2014
Outside Atkinson #NEwx MT @Dernesti: Flipped truck from the wind! pic.twitter.com/LaBhaLNJXm— NWS North Platte (@NWSNorthPlatte) June 3, 2014
Nearly 70kt 0-6km shear and 3000j/kg CAPE. Wow. “@WxMstr: 18z Observed sounding for North Platte, NE #newx pic.twitter.com/jD3LpDWDvE”— Ed Vallee Weather (@EdValleeWx) June 3, 2014
Overall, though, the 2014 tornado season has been running well below average in the number of tornadoes, as was the case in 2013.
Global extremes
The storms in Nebraska aren’t the only extreme weather event worldwide of late. A massive heat wave struck parts of northeast Asia during the last week in May into the first week of June, breaking Beijing's all-time high temperature record for the month, at 106 degrees Fahrenheit. All-time monthly record high temperatures have also been set in Japan and South Korea, according to Chris Burt of Weather Underground.