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Current Convective Watches
Storm Prediction Center,
National Weather Service (NWS),
National Oceanic and Atmospheric
Administration (NOAA),
U.S. Department of Commerce
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The majesty of a looming thunderhead (colloquial for a thunderstorm
cloud, technically identified as cumulonimbus), highlighted in
bright white and tinged with shades of red and orange by a setting sun,
belies the truly violent and potentially deadly nature of the beast.
Viewed more closely, from beneath its base, the same storm takes on a truly
frightening aspect, cutting off sunlight to appear dirty grey or black,
with roiling, petulent fragments of cloud at its edges being ripped apart
by strong wind shear. Seen at night, this monster puts on a dazzling light
show, with high energy bolts of lightning crackling through the air to
shake the very earth with reverberation caused by the nearly instantaneous
heating of air molecules to temperatures hotter than the surface of the
sun.
Very strong and well-developed thunderstorms (referred to by
meteorologists as cells or, in the case of certain severe
thunderstorms, supercells) can achieve heights in excess
of 60,000 feet (18,000 meters). This pushes their tops well above the
maximum altitudes attainable by today’s commercial airliners. It is
fortunate that, except under the most extreme conditions, very few cells
in an advancing line of thunderstorms (known as a squall line) can
achieve such heights, leaving aircraft a means of navigating, albeit with
an often bumpy ride for passengers, through the breach.
Thunderstorms are capable of producing a variety of intense and severe
weather, including heavy rain, lightning, high straight-line winds,
hail, and tornadoes. Of special concern to aircraft, particularly
during takeoff and landing, are microbursts — strong
downrush winds which often radiate outward from intense thunderstorms.
Major airports have been outfitted with special instruments to warn of
such winds. The difference in air density between cold air plunging
earthward behind a gust front and the warmer, lighter (less dense) surface
air may become visible to weather radar as a thin arc advancing ahead of a
thunderstorm cell.
Thunderstorms can sometimes cause death, injury and destruction far from
their boundaries. Flash flooding, particularly in narrow river
canyons and arroyos such as are plentiful in the Western U.S., has claimed
many lives. Often the parent cloud has long since dissipated; unwary
hikers and travelers may be caught totally off guard under a cloudless sky
by a sudden mad rush of water. Gust fronts formed by strong downburst
winds can fan out miles ahead and to the sides of a strong storm or squall
line. Hail can be ejected from the top of a thunderstorm cloud,
striking aircraft in clear air miles away from the storm. Finally,
lightning can strike as far as ten miles beyond the perimeter of a
thunderstorm; people have actually been struck by lightning that
seemingly appeared out of nowhere, with no thunderstorm
cloud visible.
Thunderstorms are truly awe-inspiring creations of Nature. They are enjoyed
and photographed by many as a consequence of their beauty, their
constantly-changing appearance, and the raw power they unleash. While
they should not be feared, they should be granted a healthy respect due
to the potential destruction and death they are capable of producing.
Since thunderstorms can strike anywhere in the U.S. and throughout most
areas of the world, everyone should know how to recognize an approaching
storm and what to do when thunderstorms are present or expected.
The National Weather Service is tasked with the responsibility for
determining thunderstorm and severe weather threat within the U.S.
Severe weather information is typically disseminated by local and national
broadcast media. Special weather bulletins and severe weather warnings
may be dispatched through civil defense avenues such as the Emergency
Broadcast System. Many communities, particularly in the Midwest, have
siren warning systems that can be activated by civil defense authorities
in the event of a tornado warning. When the potential for severe
weather exists, being aware of weather safeguards and how to respond to
them will help you keep yourself and your family safe.
Authored by Kenneth L. Anderson.
Original article published 4 June 2003, updated 22 June
2005.
Follow links to the right to learn more about severe weather watches and severe weather forecasting.
At the left margin, Related Links address topics of interest
pertaining to weather warnings and other topics
relating to severe weather and meteorology. View the
Weather & Meteorology SiteMap
for a complete list of meteorology and weather-related topics.
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