Tornadoes and Thunderstorms Severe Weather Awareness 2014

Tornadoes and thunderstorms safety awareness and precautions

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Hi, my name is Rodney from the Tampa Bay National
Weather Service office.
Today we will cover tornadoes and thunderstorms,
the next topic for severe weather awareness
week 2014. Let’s get started.
Tornadoes are one of the most destructive
weather forces across the country and can
occur anytime during the year, day or night.
An average of 1,200 tornadoes occur each year
and cause 86 fatalities and 1,500 injuries
nationwide. In 2013 there were 36 tornadoes
reported statewide with 14 of those occurring
here in west central and southwest Florida.
Tornadoes are classified using the Enhanced
Fujita scale which ranks storms from EF0 to
EF5. EF0 and EF1 are very typical here in
Florida. Last year, all 14 tornadoes that
were reported in west central and southwest
Florida were either EF0 or EF1. EF2 and 3
are rare in West central Florida. Most can’t
forget the EF-3 that went through parts of
Sumter and Lake Counties in 2007. EF4 are
very rare in west central Florida and haven’t
been recorded in the last few decades. EF5
is extremely rare in west central Florida
and haven't been reported in recent history.
No one was injured or killed in Florida during
last year’s tornadoes.
There are 3 different scenarios where tornadoes
form in Florida. Frontal System Tornadoes
occur mostly in the late winter and spring...forming
along a preceding squall line. Sea Breeze
or Boundary Collisions Tornadoes are the most
common and happen mainly in the late spring
and summer. Tropical Cyclone Band Tornadoes
form on outer bands of land falling tropical
cyclones.
In general, tornadoes form when rapidly rising
air in a thunderstorm updraft combines with
an increase in wind speed or a change in wind
direction known as shear. The larger the shear,
the greater the rotation and thus the better
chance a tornado will form.
Here are some safety rules. If a tornado warning
has been issued for your area, seek shelter
immediately. If you are inside, seek shelter
in an underground shelter, basement or the
innermost room on the lowest level away from
windows. If you do not have time to get to
the lowest level, get under a bed. At school,
get under your desk. In Open Country - Seek
a nearby shelter, if time permits. If not,
lie flat in the nearest depression, ditch
or culvert. Cover your head with your arms.
Abandon mobile homes and go to a firmly built
shelter. Vehicles are extremely dangerous
in a tornado. If the tornado is visible, far
away, and the traffic is light, you may be
able to drive out of its path by moving at
right angles to the tornado. Otherwise, park
the car as quickly and safely as possible
-- out of the traffic lanes. Get out and seek
shelter in a sturdy building. Avoid seeking
shelter under bridges, which may cause deadly
traffic hazards while offering little protection
against flying debris.
For the second half of today’s topic we’ll
focus on Thunderstorms. Thunderstorms are
almost a daily occurrence in Florida between
June and September mainly because of the sea
breeze. This figure shows the average number
of thunderstorm days each year throughout
the U.S. So we can see that areas from near
Tampa Bay south to Lee county have to deal
with thunderstorms 100 days a year. All thunderstorms
are dangerous with lightning, heavy rainfall
and gusty winds, but today we’re going to
focus on the most dangerous type, the severe
thunderstorm.
One definition of a severe thunderstorm is
a thunderstorm that has wind gusts exceeding
58 mph. These winds can be classified as either
straight line winds or downburst winds. The
damage created by these winds can be equivalent
to that seen from a tornado and can level
large areas of forest and housing developments.
The other criteria to be classified as a severe
thunderstorm is hail of 1 inch or greater
in diameter. Hail is more common in late spring
/ early summer, but can occur any time of
year. Hail is very destructive for property
and crops causing over 1 billion dollar in
damage each year. If you are caught outside
in a hail storm, seek shelter immediately
as hail can cause serious injuries.
Remember to always plan ahead and check the
forecast at weather.gov/tampa.
For more tips on tornado and thunderstorm
safety, check these websites.
This concludes the topic for today. The next
training topic will be temperature extremes
and wild fires.