Arkansas Storm Team Blog: What's a microburst?
Wind damage, whether from straight-line winds, a microburst, or a tornado, is impactful. But the damage from straight-line winds and microbursts is often mistaken for a tornado. When a storm does damage, like taking down trees or damaging property, the first thought is usually that a tornado hit. But meteorologists have ways to tell what type of wind damage was the culprit in each instance.
A microburst occurs when a strong thunderstorm is healthy enough to sustain rain and hail in its updraft (an updraft is rising, warm, moist air that allows the storm to rise into the atmosphere). At some point, the updraft weakens a bit and can no longer hold the rain and hail within its updraft, so air comes crashing toward the ground and spreads out. This air rushes toward the ground so fast that it can even reach wind speeds up to 100 miles per hour. Their speed means microbursts can cause serious damage, similar to that of a low-end tornado.
To tell whether a microburst or a tornado occurred, there are two different methods meteorologists use. When the event is occurring, meteorologists look at wind speed and direction on radar. A microburst signature on radar is an area of high winds moving away from each other within the storm. Since microbursts occur very quickly, it can be hard to notice them on radar. This radar signature is in stark contrast to a tornado signature on radar, which is a tight area of converging winds within a storm.
The other way meteorologists know if a microburst occurred is by the way the damage falls. A microburst will push damage, like downed trees and other debris, generally in the same direction. When compared to a tornado, tornado damage is scattered in a variety of directions.
On Monday evening (September 15) near Greers Ferry and Heber Springs, a microburst occurred within a severe thunderstorm. In fact, radar shows there may have been a few microbursts within the severe storm that rolled through parts of Cleburne and Van Buren Counties. The above radar image shows diverging winds southwest of Heber Springs at 5:42 p.m. C.D.T. on Monday, shown by the red (wind moving away from the radar in North Little Rock, KLZK) and the bright green (wind moving towards the radar in North Little Rock, KLZK). Monday also didn't have the right atmospheric ingredients in place to support tornadoes, adding another way that meteorologists can confirm a microburst occurred.
from KARK https://ift.tt/If2YOzk
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