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Damaging Winds: Introduction
Damaging winds occur relatively frequently across Kentucky, usually in
association with severe thunderstorms. While many people immediately associate
wind damage with tornadoes, straight-line winds can occur that cause extensive
damage as well.
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Photo Credit: NOAA Photo
Library, NOAA Central
Library |
Severe thunderstorms develop powerful updrafts and downdrafts. An updraft of
warm, moist air helps to fuel a towering cumulonimbus cloud reaching tens of
thousands of feet into the atmosphere. A downdraft of relatively cool, dense
air develops as precipitation begins to fall through the cloud. Winds in the
downdraft can reach in excess of 100 miles per hour. When the downdraft reaches
the ground it spreads out forming a gust front: the strong, often refreshing
wind that kicks up just before the storm hits. As the thunderstorm moves
through the area, the full force of the downdraft in a severe thunderstorm can
be felt as horizontal, straight-line winds with speeds well over 50 miles per
hour (Caracena, et al., 2001)
Damaging straight-line winds occur over a range of scales. At one extreme, a
severe single-cell thunderstorm may cause localized damage from a microburst, a
severe downdraft extending not more than about two miles across, or from a
larger macroburst. In contrast, a powerful meso-scale thunderstorm complex that
develops as a squall line can produce a derecho with damaging winds that carve a
path as much as 100 miles wide and 500 miles long.
A severe thunderstorm poses many threats. While the threat of tornadoes is
well recognized, people often miscalculate the threat of damaging straight-line
winds. Because the gust front of a thunderstorm may arrive well ahead of the
heavy rainfall and intense lightning, people are sometimes caught outdoors or in
locations that do not provide adequate shelter. An awareness of the threat of
damaging winds is the first step in mitigation.
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