|
What's the wait for a tornado warning?
Tornadoes come and go so quickly and are so small that predicting where
and when one will hit more than 15 to 30 minutes ahead of time is not
possible. The average warning time for a tornado with winds of 158 miles an hour or faster - the type that accounts for most deaths - is 18 minutes.
Here's how the ability to warn of tornadoes compares with other natural disasters:
- Effects of a strong El Nino: Predictable six months or more in advance, but only the general picture over several-month periods. No details such as when storms will occur or how much rain or snow they'll bring.
- Volcanic eruption: Possibly weeks in advance if scientists are monitoring the volcano. Exact time and size of an eruption can't be predicted, only that one seems likely.
- Major flood on a large river: A week or more for downstream locations, but only approximate times and heights of the flood at different locations.
- A blizzard: Maybe three or four days, but only for the general, large area likely to be affected.
- Severe thunderstorms: A day or two warning to say there's a possibility of dangerous thunderstorms, flash floods and tornadoes in a large area, but not exactly where or when.
- Hurricane: Twelve to 24 hours' warning that somewhere along a 200-mile coastline will be hit.
- Flash flood: Maybe an hour if data are available such as from automated rain and stream-height gauges.
- Earthquake: No warning. Most seismologists don't expect warnings to be possible in the near future, if ever.
By Jack Williams, USA TODAY
Inside the tornado information index
|
