Tornado Safety


Tornado Season

Tornadoes can occur at any time of the year. In the southern states, peak tornado occurrence is in March through May, while peak months in the northern states are during the summer. Tornadoes are most likely to occur between 3 p.m. and 9 p.m. but have been known to occur at all hours of the day or night.

Watches Versus Warnings

Many people confuse the meaning of a tornado watch and tornado warning issued by the National Weather Service. Here's the difference:

  • Watch: Tornadoes are possible in your area; remain alert for approaching storms.
  • Warning: A tornado has been sighted or indicated by weather radar. If a tornado warning is issued for your area and the sky becomes threatening, move to your predesignated place of safety.

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Fujita Tornado Intensity Scale

A common misnomer regarding the Fujita scale is that many people confuse it to be a measurement of size of a tornado when in actuality it is the amount of destruction caused by the tornado.

Category F0

  • Gale tornado (40 to 72 miles per hour)
  • Light damage
    • Some damage to chimneys
    • Break branches off trees
    • Push over shallow-rooted trees
    • Damage to sign boards

Category F1

  • Moderate tornado (73 to 112 miles per hour)
    • The lower limit is the beginning of hurricane wind speed
  • Moderate damage
    • Peel surface off roofs
    • Mobile homes pushed off foundations or overturned
    • Moving autos pushed off the roads

Category F2

  • Significant tornado (113 to 157 miles per hour)
  • Considerable damage
    • Roofs torn off frame houses
    • Mobile homes demolished
    • Boxcars pushed over
    • Large trees snapped or uprooted
    • Light-object missiles generated

Category F3

  • Severe tornado (158 to 206 miles per hour)
  • Severe damage
    • Roofs and some walls torn off well-constructed houses
    • Trains overturned
    • Most trees in forest uprooted
    • Heavy cars lifted off ground and thrown

Category F4

  • Devastating tornado (207 to 260 miles per hour)
  • Devastating damage
    • Well- constructed houses leveled
    • Structure with weak foundation blown off some distance
    • Cars thrown
    • Large missiles generated

Category F5

  • Incredible tornado (261 to 318 miles per hour)
  • Incredible damage
    • Strong frame houses lifted off foundations and carried considerable distance to disintegrate
    • Automobile sized missiles fly through the air in excess of 100 yards
    • Trees debarked
    • Incredible phenomena will occur

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Safety & Preparedness

It is important to remain alert to signs of an approaching tornado and seek shelter if threatening conditions exist. Look for environmental clues including a dark sky, large hail, or a loud roar.

You can stay warned by listening to NOAA weather radio. Remember sirens are only designed for outdoor warning you may not hear them in your home. By having a NOAA weather radio with the S.A.M.E technology you can set the radio to only alert to weather events in Harper County and would not have to listen to all weather events in other counties.

The NOAA weather frequency is 162.400; this is channel one on most radios. The S.A.M.E. code for Harper County is 020077. If you need any assistance please call Harper County Emergency Management at 620-842-3506 and someone will assist you in programming your radio.

If a warning is issued, move to a pre-designated shelter such as a basement; stay away from windows.

Storm Prediction

The Storm Prediction Center is now using Categorical Convective Outlooks to help predict severe thunderstorms and tornado outbreaks. These outlooks are available online.

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