National Weather Service United States Department of Commerce

Tornado Safety

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 feture, 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.

General Tornado Info

Frequently Asked Tornado Questions (link to the NWS Storm Prediction Center).

Local Tornado Historical Climatology

 


Central PA Tornadoes by County through 2010
 


 

 

PA Tornado Magnitude and Frequency (by Month)
 

 
  The Enhanced Fujita Scale
(EF Scale)

The EF Scale, which became operational on February 1, 2007, is used to assign a tornado a 'rating' based on estimated wind speeds and related damage. When tornado-related damage is surveyed, it is compared to a list of Damage Indicators (DIs) and Degrees of Damage (DoD) which help estimate better the range of wind speeds the tornado likely produced. From that, a rating (from EF0 to EF5) is assigned.

The EF Scale was revised from the original Fujita Scale to reflect better examinations of tornado damage surveys so as to align wind speeds more closely with associated storm damage. The new scale has to do with how most structures are designed.


EF SCALE
EF Rating 3 Second Gust (mph)
0 65-85
1 86-110
2 111-135
3 136-165
4 166-200
5 Over 200

*** IMPORTANT NOTE ABOUT EF SCALE WINDS: The EF scale still is a set of wind estimates (not measurements) based on damage. Its uses three-second gusts estimated at the point of damage based on a judgment of 8 levels of damage to the 28 indicators listed below. These estimates vary with height and exposure. Important: The 3 second gust is not the same wind as in standard surface observations. Standard measurements are taken by weather stations in open exposures, using a directly measured, "one minute mile" speed.


Assigning a Tornado Rating Using the EF Scale

The NWS is the only federal agency with authority to provide 'official' tornado EF Scale ratings. The goal is assign an EF Scale category based on the highest wind speed that occurred within the damage path. First, trained NWS personnel will identify the appropriate damage indicator (DI) [see list below] from more than one of the 28 used in rating the damage. The construction or description of a building should match the DI being considered, and the observed damage should match one of the 8 degrees of damage (DOD) used by the scale. The tornado evaluator will then make a judgment within the range of upper and lower bound wind speeds, as to whether the wind speed to cause the damage is higher or lower than the expected value for the particular DOD. This is done for several structures not just one, before a final EF rating is determined.


Enhanced F Scale Damage Indicators

NUMBER
(Details Linked)
DAMAGE INDICATOR ABBREVIATION
1 Small barns, farm outbuildings SBO
2 One- or two-family residences FR12
3 Single-wide mobile home (MHSW) MHSW
4 Double-wide mobile home MHDW
5 Apt, condo, townhouse (3 stories or less) ACT
6 Motel M
7 Masonry apt. or motel MAM
8 Small retail bldg. (fast food) SRB
9 Small professional (doctor office, branch bank) SPB
10 Strip mall SM
11 Large shopping mall LSM
12 Large, isolated ("big box") retail bldg. LIRB
13 Automobile showroom ASR
14 Automotive service building ASB
15 School - 1-story elementary (interior or exterior halls) ES
16 School - jr. or sr. high school JHSH
17 Low-rise (1-4 story) bldg. LRB
18 Mid-rise (5-20 story) bldg. MRB
19 High-rise (over 20 stories) HRB
20 Institutional bldg. (hospital, govt. or university) IB
21 Metal building system MBS
22 Service station canopy SSC
23 Warehouse (tilt-up walls or heavy timber) WHB
24 Transmission line tower TLT
25 Free-standing tower FST
26 Free standing pole (light, flag, luminary) FSP
27 Tree - hardwood TH
28 Tree - softwood TS
Other background information: