![]() This photo of a rotating storm structure over Roanoke on July 14 appeared in a previous Cardinal Weather column. But, of course, the storms are more likely to form, and more likely to be stronger, if there is abundant moisture, strong lift and a high level of instability. So can having moisture and enough lift – thunderstorms in cooler seasons often form that way, with little instability but a strong cold front or similar feature lifting air. Just having enough moisture and a reasonable amount of instability can sometimes do the trick – these are summer “pulse” thunderstorms that go up with afternoon heating and come down quickly over one spot. (Or, if the updrafts are strong enough to blast through the cap, that may be a sign of a higher risk of strong to severe storms.) If there is a layer of warm and/or dry air aloft, upward motion of warm, moist air can often be stymied – this is called a “cap” and can slow or block thunderstorm development. Instability refers to the property of warmer air rising into cooler air above. Winds blowing upward over mountainous terrain is another potential source of lift. Thunderstorm development requires, at the least, sufficient moisture and enough lift and/or instability for updrafts to elevate that moisture high in the atmosphere as billowing cumulonimbus clouds.Ītmospheric lift can occur with various kinds of weather systems – cold or warm fronts or outflow boundaries plowing air upward ahead of them like a bulldozer, for instance. This developed into a pulse storm that dumped 3+ inches of rain in an hour on parts of eastern Roanoke city and Vinton, while locations only a few miles away got no significant rainfall. Strong updrafts lift crisp, bubbly towering cumulus clouds over the Roanoke Valley, as seen from the Daleville area of Botetourt County, looking south. So, as our August weather generally enters a period of fairly normal temperatures after last week’s brief heat spike (discussed later in this column), with intermittent thunderstorms the remainder of this week and beyond, here is a primer on thunderstorm development and organization with many interesting photographs from Cardinal News readers and staffers. Southwest and Southside Virginia have had several rounds of thunderstorms this summer, varying from localized downpours to Friday’s windy squall line (possibly borderline derecho), over the past few weeks. Courtesy of Storm Prediction Center, NOAA. It’s a close call whether severe winds (58+ mph) continued 240 miles or farther, the minimum qualification for a derecho. ![]() Most of the wind damage reports marked by blue dots were caused by a single line of thunderstorms late Friday, July 28. We can often take it almost for granted without thinking much about the mechanics of how a sunny, sticky day with no hint of clouds can turn into one with menacing dark clouds, electrical currents dancing through the air, booming rumbles, tree-bending winds and huge drops of rain. Seeing cauliflower cumulus clouds bubble skyward and hearing distant rumbles of thunder are as much a part of summer in Virginia (and many other parts of the U.S.) as suntans, swimming pools and vacations. The shelf clouds could cause downed trees, fallen tree limbs and power outages.Want to be the first to see weather news? Sign up for our weekly email weather newsletter, featuring weather journalist Kevin Myatt. The shelf cloud will cause “an abrupt shift in wind direction and increased wind speed, followed within minutes by heavy rain or hail,” according to The Weather Channel. “What you're seeing in a shelf cloud is the boundary between a downdraft and updraft of a thunderstorm or line of thunderstorms,” according to The Weather Channel. The shelf clouds aren’t tornadoes or wall clouds. ![]() Shelf clouds are often seen at the beginning of thunderstorms. ![]() Sometimes these storm clouds can build from the ground and rise up toward the sky in what weather experts call shelf clouds. (For licensing or usage, contact By: Maranda Benefield /hRgi9RLqJ1- Live Storm Chasers August 9, 2018įOX-2 meteorologist Glenn Zimmerman said the footage captured the beginning of a thunderstorm cloud. ![]() Monster apocalyptic shelf cloud structure passing through Anna, IL on Aug 7, 2018! #ILwx #StormHour #Breakingweather ![]()
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