Here is an excerpt from the following URL:
http://webserv.chatsystems.com/~dosw...ado_essay.html


"On the other hand, only about 25% of tornado warnings actually experience a
tornado somewhere within the warned area. That is, the false alarm ratio
[FAR] is about 75% [These numbers vary somewhat from year to year and from
place to place]. If you hear a tornado warning, then the area within the NWS
warning will actually experience a tornado about 1 time out of 4. That is
roughly 250 times the likelihood when the climatology is as high as 1 in
1000! In most places around the country, being in a tornado warning makes
you around 1000 times more likely than your local climatological frequency.
Sure, the warnings aren't perfect and everyone wants to lower the false
alarm rate.
Unfortunately, if we lower the FAR, we also will surely lower the odds that
a warning will be issued when a tornado does occur (the POD). As it now
stands, individual forecasters who don't have a warning out when a
disastrous tornado hits are in a lot more personal trouble than forecasters
who issue false alarms. The NWS as a whole gets blamed for the FAR problem,
not individual forecasters. Just how would you react if you were a
forecaster under these circumstances? It seems obvious to most individual
forecasters that you'd best "cover your a**" with a warning if there is even
a low probability of a tornado. Disaster survey teams don't investigate
false alarms, looking for someone to blame; they only go out after
disastrous events. Given the politics, I certainly can't fault forecasters
for their choices."

As with most scientific matters, this can get quite complicated.

Regards,

Declan

"COACHSTING" wrote in message
...
About what percent of doppler indicated tornadoes are ever verified as
having
been twisters which reached the ground?


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