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Severe Weather Awareness Week
Be Prepared and Stay Safe during Severe Weather |
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Monday
(March 4th) |
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Tuesday
(March 5th) |
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Wednesday
(March 6th) |
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Thursday
(March 7th) |
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Friday
(March 8th) |
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Today's Topic: Tornadoes!
Monday's Activities:
Click any Topic to Expand or Contract
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1. Learn about Tornadoes. |
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Tornado - A violently rotating column of air touching the ground, usually attached to the base of a thunderstorm.
Tornadoes are nature"s most violent storms. Spawned from powerful thunderstorms, tornadoes can cause fatalities and devastate a neighborhood in seconds. Winds of a tornado may reach 300 miles per hour. Damage paths can be in excess of one mile wide and 50 miles long. Strong downburst (straight-line) winds may also occur due to the same thunderstom. Hail is very commonly found very close to the tornadoes, as the strongest thunderstorms that spawn tornadoes are formed under the atmospheric conditions that are also highly likely to make hail. Every state is at some risk from this hazard.
Some tornadoes are clearly visible, while rain or nearby low-hanging clouds obscure others. Tornadoes develop extremely rapidly, and may dissipate just a quickly. Most tornadoes are on the ground for less than 15 minutes.
Before a tornado hits, the wind may die down and the air may become very still. A cloud of debris can mark the location of a tornado even if a funnel is not visible. Tornadoes generally occur near the trailing edge of a thunderstorm. It is not uncommon to see clear, sunlit skies behind a tornado. (Preceding paragraphs are edited from FEMA source: http://www.fema.gov/hazard/tornado/index.shtm)
See this excellent reference on Tornadoes
Nature's Most Violent Storms
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2. How common are Tornadoes in Pennsylvania? |
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Local Tornado Historical Climatology
PA Map of Tornadoes (by County through 2009)
PA Tornado Magnitude and Frequency (by Month)
Map of PA Tornado Occurrance Times (by Hour of Day)
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3. What is the EF-Scale? |
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The Enhanced Fujita Scale or EF-Scale
The EF-Scale is a rating of how strong a tornado was. It is calculated by surveying the damage and comparing it with damage to similar objects at certain wind speeds. The EF-Scale is not meant to be used as a measure of how strong a tornado currently on the ground is.
Link to the SPC Page on the EF-Scale
The EF Scale was implemented across the country in February of 2007. The EF-Scale is meant to further refine
the tornado wind-force classifications begun using the F-Scale. The use of the EF-Scale should lead to more
accurate and uniform tornado strength estimates by investigators.
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4. Have a Safety Plan! |
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It is important to have a plan of action in the event a tornado threatens your family,
and to rehearse that plan frequently. Such a plan should include what you and your family
should do when at home, work, school, or outdoors. The time spent planning now could determine
whether or not you survive a tornado.
Plan Ahead
First, know the county in which you live. Severe weather warnings are issued for counties, or
for portions of counties. By keeping a highway roadmap nearby, you can follow storm movements, and
better determine if you are threatened.
Have a NOAA Weather Radio handy at all times. Make sure your model has an tone-alarm feature, which
will activate the radio when warnings or watches are issued for your area. If you are planning to be
outdoors for an extended period of time, keep up with the latest weather information from your local
National Weather Service office.
If you see a tornado, or hear that the National Weather Service has issued a Tornado Warning for your location...
Know Where to Go
In a home or a building, move to a pre-designated shelter, preferably the basement or the lowest
floor of your home. Don't worry about opening your windows first - that would be a mistake, just get
to the basement, and get under a sturdy piece of furniture or workbench. Grab blankets to cover yourself
with, which will protect you from flying debris.
If an underground shelter (basement) is not available, move to an interior room or hallway on the
lowest floor, and crouch down close to the floor. Again, grab extra blankets to protect yourself from
flying debris. Stay away from windows - as they can shatter due to flying debris and the force of the wind.
If you are in a mobile home: Immediately move to a substantial shelter.
If you are caught outdoors and cannot get to a safe building. As a last resort, you should:
- Immediately get into a vehicle, buckle your seat belt and try to drive to
the closest sturdy shelter.
- If your vehicle is hit by flying debris while you are driving, pull over and
park.
- Stay in the car with the seat belt on. Put your head down below the
windows; cover your head with your hands and a blanket, coat or other
cushion if possible.
- If you can safely get noticeably lower than the level of the roadway,
leave your car and lie in that area, covering your head with your hands.
Your choice of whether to stay in your car should be driven by your specific
circumstances. Your best choice remains getting to a secure building with a
basement or saferoom.
- If you find yourself outside or in a car with a tornado approaching and you
are unable to get to a safe shelter, you remain at risk whether you stay in your car or
seek shelter in a depression or ditch, both of which are last resort options
that provide little protection. The safest place to be is in an underground
shelter, basement or safe room.
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Daily Safety Message:
...PENNSYLVANIA SEVERE WEATHER AWARENESS WEEK...
THIS WEEK...MARCH 4TH THROUGH MARCH 8TH...IS SEVERE WEATHER
AWARENESS WEEK IN PENNSYLVANIA.
WE WILL COVER VARIOUS TOPICS RELATING TO SEVERE WEATHER AND WEATHER
SAFETY THROUGHOUT THE WEEK.
OUR TOPIC FOR TODAY...TORNADOES AND TORNADO SAFETY.
WE WILL COVER THE DIFFERENCE BETWEEN A TORNADO WATCH AND A
TORNADO WARNING...AND GIVE YOU TIPS ON WHAT TO DO WHEN A WATCH
OR WARNING IS ISSUED FOR YOUR LOCATION.
WHAT IS A TORNADO?
A TORNADO IS A VIOLENTLY ROTATING COLUMN OF AIR IN CONTACT WITH THE
GROUND. THE WIND SPEEDS INSIDE A TORNADO RANGE FROM UNDER 100 MILES
AN HOUR UP TO 300 MILES AN HOUR. THEY CAN TRAVEL WITH A FORWARD
SPEED AS FAST AS 70 MPH...AND CAN DESTROY VIRTUALLY EVERYTHING IN
THEIR PATH.
WHILE MOST TORNADOES THAT OCCUR IN PENNSYLVANIA ARE NOT AS STRONG AS
THEIR COUNTERPARTS IN THE PLAINS...STRONG AND DAMAGING TORNADOES CAN
AND DO OCCUR HERE. IN FACT...PENNSYLVANIA RANKS IN THE TOP 25 FOR
TORNADO OCCURRENCE IN THE UNITED STATES...AVERAGING TWENTY TORNADOES
PER YEAR. BETWEEN MAY 31ST AND JUNE 2ND OF 1998...PENNSYLVANIA WAS
HIT BY 40 TORNADOES...SOME OF WHICH HAD WIND SPEEDS OVER 200 MPH.
WHAT DOES A TORNADO WATCH MEAN?
A TORNADO WATCH IS ISSUED BY THE NATIONAL WEATHER SERVICE IN ORDER
TO ALERT YOU THAT SEVERE THUNDERSTORMS ARE EXPECTED TO DEVELOP...
AND TO HIGHLIGHT THAT THOSE STORMS HAVE THE POTENTIAL TO PRODUCE
TORNADOES. A TORNADO WATCH COVERS A VERY WIDE AREA...GENERALLY ABOUT
THE SIZE OF A STATE. A TORNADO WATCH WILL LAST FOR SEVERAL
HOURS...EXPIRING ONLY WHEN THE THREAT OF THUNDERSTORMS IS EXPECTED
TO END.
WHAT SHOULD YOU DO WHEN A TORNADO WATCH IS ISSUED?
GO ABOUT YOUR NORMAL ACTIVITIES...BUT WATCH THE SKY AROUND YOU FOR
DEVELOPING STORMS. PERIODICALLY LISTEN TO NOAA WEATHER RADIO OR
MEDIA OUTLETS FOR UPDATES AND POSSIBLE WARNINGS.
KNOW WHICH COUNTY YOU LIVE IN...AND WHICH ONES BORDER YOUR
COMMUNITY. THINK OF A SAFE PLACE TO MOVE TO QUICKLY IF A TORNADO
WARNING IS ISSUED FOR YOUR LOCATION...OR IF THUNDERSTORMS APPROACH.
WHAT DOES A TORNADO WARNING MEAN?
A TORNADO WARNING IS ISSUED WHEN METEOROLOGISTS SPOT A DEVELOPING
TORNADO USING DOPPLER RADAR...OR WHEN A TORNADO HAS BEEN SIGHTED
BY TRAINED SKYWARN SPOTTERS. THE WARNING MEANS A TORNADO IS GOING
TO MOVE THROUGH YOUR AREA SOON...SO YOU NEED TO TAKE IMMEDIATE
ACTION TO PROTECT YOUR LIFE AND PROPERTY.
TORNADO WARNINGS ISSUED BY NATIONAL WEATHER SERVICE METEOROLOGISTS
TYPICALLY COVER AREAS SMALLER THAN ONE COUNTY...AND FOR A DURATION
OF GENERALLY LESS THAN ONE HOUR. IN THE TEXT OF THE WARNING
STATEMENT...WE TRY TO MAKE A SPECIFIC LIST OF TOWNS THAT ARE LIKELY
TO BE IN THE PATH OF THE TORNADO. YOU SHOULD LISTEN TO HEAR IF
COMMUNITIES OR LANDMARKS NEAR YOU ARE MENTIONED IN THE WARNING.
WHAT YOU SHOULD DO WHEN A TORNADO WARNING IS ISSUED FOR YOUR AREA...
TAKE IMMEDIATE ACTION...BUT REMAIN CALM. IF YOU ARE AT HOME OR IN
A SMALL BUILDING...GO TO THE BASEMENT OR TO AN INTERIOR ROOM ON
THE LOWEST FLOOR. CLOSETS...BATHROOMS...AND OTHER INTERIOR ROOMS
WITHOUT WINDOWS OFFER THE BEST PROTECTION. AVOID WINDOWS AND GET
UNDER SOMETHING STURDY OR COVER YOURSELF WITH A MATTRESS.
IF YOU ARE IN A SCHOOL...HOSPITAL...OR SHOPPING CENTER...GO TO A
PRE-DESIGNATED SHELTER AREA. STAY AWAY FROM LARGE OPEN AREAS SUCH
AS GYMS OR AUDITORIUMS...HALLWAYS AND SMALL INTERIOR ROOMS OFFER
THE BEST PROTECTION. DO NOT GO OUTSIDE TO YOUR CAR. IF YOU ARE IN
A HIGH-RISE BUILDING...GO TO AN SMALL INTERIOR ROOM OR HALLWAY ON
THE LOWEST FLOOR POSSIBLE. DO NOT USE THE ELEVATOR.
MOBILE HOMES ARE EASILY TOSSED ABOUT BY THE STRONG WINDS OF A
TORNADO. IMMEDIATELY TAKE SHELTER IN A SUBSTANTIAL STRUCTURE.
IF YOU ARE CAUGHT OUTDOORS AND CANNOT GET TO A SAFE
BUILDING...AS A LAST RESORT...YOU SHOULD:
IF YOU HAVE ACCESS TO A VEHICLE...GET IN AND BUCKLE YOUR SEAT BELT
AND TRY TO DRIVE TO THE CLOSEST STURDY SHELTER. IF YOUR VEHICLE IS
HIT BY FLYING DEBRIS WHILE YOU ARE DRIVING...PULL OVER AND PARK.
STAY IN THE CAR WITH THE SEAT BELT ON. PUT YOUR HEAD DOWN BELOW THE
WINDOWS...COVER YOUR HEAD WITH YOUR HANDS AND A BLANKET...COAT OR
OTHER CUSHION IF POSSIBLE.
IF YOU CAN SAFELY GET NOTICEABLY LOWER THAN THE LEVEL OF THE
ROADWAY...LEAVE YOUR CAR AND LIE IN THAT LOW AREA...COVERING YOUR
HEAD WITH YOUR HANDS.
YOUR CHOICE OF WHETHER TO STAY IN YOUR CAR SHOULD BE DRIVEN BY YOUR
SPECIFIC CIRCUMSTANCES. IF YOU ARE IN A CAR OR IF YOU SEEK SHELTER
IN A DEPRESSION OR DITCH WITH A TORNADO APPROACHING...YOU REMAIN AT
RISK. THE SAFEST PLACE TO BE IS IN AN UNDERGROUND SHELTER...BASEMENT
OR SAFE INTERIOR ROOM.
FOR ADDITIONAL INFORMATION ON TORNADOES AND SEVERE WEATHER CHECK OUT
OUR WEB SITE AT:
weather.gov
OUR WEATHER SAFETY TOPICS FOR THE REST OF THE WEEK WILL BE...
TUESDAY...THUNDERSTORM SAFETY.
WEDNESDAY...FLASH FLOOD SAFETY.
THURSDAY...RIVER FLOOD SAFETY.
FRIDAY...SKYWARN SEVERE WEATHER SPOTTERS.
NOW IS THE TIME TO PREPARE FOR THIS YEAR'S SEVERE WEATHER SEASON.
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Local Climate, Water & Weather Topics:
Forecasts, Current Hazards, Current Conditions, Water Resources, Radar, Satellite, Climate,
Weather Safety, Wireless/PDAs, Feature Articles,
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weather.gov 
