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SEVERE
THUNDERSTORMS AND TORNADO SAFETY |
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LISTEN
to your NOAA Weather Radio to stay informed about the
latest watches, warnings, and advisories.
At Home:
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Go immediately to the
basement, storm cellar, or lowest level of the
building.
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If there is no basement,
go to an inner hallway or small inner room, such as
a bathroom or closet.
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Get away from windows.
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Go to the center of the
room; corners tend to attract debris.
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Get under a piece of
sturdy furniture, such as a workbench or heavy
table, and hold on to it.
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Use arms to protect head
and neck.
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If in a mobile home, get
out and find shelter elsewhere.
At Work or School:
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Go to the basement or to
an inner hallway in the lowest level of the
building.
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Avoid places with
wide-span roofs, such as auditoriums, cafeterias,
large hallways, and shopping malls.
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Get under a piece of
sturdy furniture, such as a workbench or heavy
table, and hold on to it.
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Use arms to protect head
and neck.
Outdoors:
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If possible, get inside a
building.
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If shelter is not
available, or there is no time to get indoors, lie
down in ditch or low-lying area, or crouch near a
strong building. Beware of a potential for
flooding.
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Use arms to protect head
and neck.
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SEVERE
THUNDERSTORMS AND TORNADO INFORMATION |
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Tornados
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Most tornadoes are found
in, or very near a rotating "wall cloud", on the
south or southwest side of a thunderstorm. The wall
cloud is a distinct lowering of the rain-free (or
almost rain-free) base of a thunderstorm. The
rain-free base is found in the updraft. If you can
locate the inflow region of a thunderstorm, you've
located the potential "hotspot", should a tornado
develop.
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Not all rotating wall
clouds produce a tornado. It is also possible to
have a tornado with no wall cloud present. Research
and video tape evidence strongly suggest that many
tornadoes spin up at the ground level and grow
upwards to the wall cloud or thunderstorm base, and
in doing so, are nearly invisible. It may take
several minutes for the "funnel cloud" to form
inside the tornado. Look for dirt and debris
violently rotating at ground level for confirmation.
In other words, the funnel cloud is not the tornado.
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You may see the funnel
cloud developing downward while at the same time the
nearly invisible tornado winds are causing havoc at
ground level. Consequently, the phrase "tornado
touchdown" is not entirely correct all the time.
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Some tornados can become
rain-wrapped and hard to see as rain in the
rear-flank downdraft wraps around the tornado. It is
important for a severe weather spotter to monitor
what is happening at ground level as well as at the
cloud base. In just about every thunderstorm over
Wisconsin, one can usually find some cloud features
(scud clouds) that briefly resemble a tornado or
funnel cloud. If the cloud feature you are watching
isn't persistent or rotating upon a vertical axis,
it is probably not a funnel cloud or tornado.
Straight-Line Winds
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Straight-line winds can
reach 100 to 150 mph, or briefly equivalent
hurricane force winds.
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One type of straight-line
wind, the downburst, can cause damage equivalent to
a strong tornado and can be extremely dangerous to
aviation.
Lightning
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Each and every flash of
cloud-to-ground lighting is a potential killer.
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Lightning can strike as
far as 10 miles away from the rain area. In a
thunderstorm that is about the distance that you are
able to hear the thunder from the storm. If you can
hear thunder, it is safe to say that you are within
striking distance of lightning.
Air near a lightning bolt
can be heated to 50,000 degrees Fahrenheit, which is
hotter than the surface of the sun.
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If a thunderstorm is
approaching and you feel your hair stand on end,
lightning may be about to strike. Immediately drop
to your knees and bend forward, resting your hands
on your knees – DO NOT LIE FLAT ON THE GROUND.
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When the rain with a
thunderstorm ends, it is still not safe to go out.
Remember the 30-minute rule and wait for 30 minutes
past the last roll of thunder before venturing
outside again.
An average of 21 tornadoes occur each
year in Wisconsin, but some counties can have many
tornado-free years in a row.
An average of 1.86 people die each year from
tornado-related injuries.
Peak tornado season is May through
August, but tornadoes have occurred in every month but
February. Most tornadoes occur between noon and 9 pm,
with 5 pm a favored time. Most Wisconsin tornadoes
travel southwest to northeast or west to east, travel at
speeds of 20 to 40 mph, and persist for less than 10
minutes with a path length of less than 5 miles.
Wisconsin averages over 30 days each year with
thunderstorms. |
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