Derecho Controversy in Meteorological Community; Latest on Ansted Microburst

WOAY-TV (Oak Hill, WV): The term derecho is undergoing “reconstruction” and what mechanisms were in place for the Ansted microburst in late May?

The uptick in severe weather this spring brings to mind the damage from the late June 2012 derecho. As Chief Meteorologist Chad Merrill explains, that term is a hot topic of controversy in the meteorological community. He talked about it with DJ Bill Wise on the Lake Country morning show:

Chief Meteorologist Chad Merrill has more information on the Ansted microburst from Sunday, May 26:

The storm system started in western Kentucky with a line of storms and embedded lightning. The feature produced a bowing like feature in the cloud cover as it pushed through West Virginia Sunday afternoon, a sign of strong winds along the system’s leading edge.

The estimated winds were 110 mph or over a quarter mile on Rich Creek Road in Ansted. Both the Reflectivity radar product and even more evident on the Velocity product is the notch or bowing feature where the microburst produced the damage in Ansted. The Velocity radar product also shows winds moving away from the radar.

So how does a microburst form? Well, first of all, lots of dry air aloft is gets funneled into the thunderstorm. That creates evaporative cooling, cooling yields sinking air. That sinking air is accelerated by gravity. As soon as that downdraft and the evaporative cooling force the air down to the ground, it spreads out in a fan-like feature.

Winds can reach 150 mph over a span of up to two miles in a microburst. We saw the damage over a quarter of a mile in length in Anstead. So, this is just a friendly reminder that you can get the same magnitude of wind damage in a microburst along the line of thunderstorms as you do in an EF-2 tornado two like we saw in Hico on April 2nd. Keep that in mind going forward through the severe weather season.

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