[BC] Tornado warnings

[Bailey, Scott]

Kirk,
   During the storms around here, do you think that the local TV
stations here, especially 2 & 5, overreact of to some things they notice
on the radar?

Scott

-----Original Message-----
From: broadcast-bounces at radiolists.net
[mailto:broadcast-bounces at radiolists.net] On Behalf Of Kirk Harnack
Sent: Friday, September 01, 2006 8:34 AM
To: 'Broadcasters' Mailing List'
Subject: RE: [BC] Tornado warnings

"Calling" a tornado is often a touchy subject.  Before there was Doppler
radar, the NWS would sometimes call a tornado based solely on a
hook-echo
return, but they'd say "confirmed" or "unconfirmed" to clarify their
call.

Even with Doppler radar (WSR-88D) used by the NWS, calling a tornado
isn't
an exact science.  Here's a fairly recent study...
http://cstar.cestm.albany.edu:7773/Research/Comet99/Paper20aa.htm

Figure 1 of this paper shows increasing level of certainty when
gate-to-gate
shear (that's velocity toward the Doppler radar in one cell, adjacent to
velocity away from the Doppler radar in the next cell) vs. the
large-scale
rotational velocity of the mesocyclone.

Another, very recent, paper - scheduled to be presented in November at
an
AMS Conference on Severe Local Storms, describes uncertainties posed
even
when 4 Doppler radars are observing the same storm...
http://ams.confex.com/ams/23SLS/techprogram/paper_115287.htm


Probably the paper that best answers the question before our group is
this
one, written by Mark Rose in Nashville's Weather Forecast Office...
http://www.srh.noaa.gov/ssd/techmemo/sr215.htm

Mark describes the call-to-action prerequisites.  Indeed, the 4th one
for a
Tornado Warning seems a bit weak...

a. Tornado indicated by radar:

    * A tornado may form at any time. Take cover now! Abandon mobile
homes
and vehicles for more substantial shelter. Avoid windows.
    * Radar shows strong signs that a tornado is developing. Take cover
now!
    * This storm shows strong rotation and may produce a tornado at any
time. Do not wait. Go to a safe place now! Put as many walls between you
and
the outside as possible.
    * Doppler radar indicates a tornado may form at any time. Take cover
now! Abandon mobile homes and vehicles. Move to an interior room or
hallway
on the lowest floor away from windows.



... And leaves much interpretation up to the forecaster.  

It's certainly inappropriate for NWS Watch or Warning criteria to be
abused
in either direction.  What we don't know is just what indications were
seen
on Doppler in NC.  I drove through western NC yesterday; lots of rain
and
mean, mean skies.  I saw enough sheared clouds to make me think that the
weather *could* have produced a tornado.


Best,

Kirk Harnack


Kevin Webb wrote:

> 
> Kent,
> 
> You are correct for being confused and this is a problem I 
> see that's gotten worse.  Potential does not equal tornado.  
> When I used to do weather on TV we did *not* report a tornado 
> warning until one was sighted by a reliable contact (police, 
> known weather spotter, etc.).  But that was in the 80's.
> We were a bit advanced because we actually -had- weather 
> radar.  That's showing my age. 
> 
> Now they run a tornado warning if they see the conditions are 
> correct on Doppler radar and *not* necessarily an actual 
> tornado.  Yes you can see the classic "hook" or comma 
> signature of wind shear that's *likely* to turn into a 
> tornado but that doesn't mean it IS a tornado.  
> 
> I'd like to see someone do a study of when they run tornado 
> warnings based solely on the radar signature vs. one that's 
> actually touched down.  I'll bet they'll see that it is less 
> than 1 out of 10 times that signature turns into anything at 
> all.  This is way too close to crying wolf and the result is 
> the public turns a blind eye and doesn't take the warning seriously.
> Plus how many more injuries and deaths have occurred because 
> of the "cry wolf" syndrome of late??
> 
> 
> Kevin Webb
> ------------------------------------


Ken Winrich posed:

> 
> During the Ernesto thingy here in North Carolina, the NWS 
> kept sending out tornado WARNINGS, but then said that the 
> potential was there for a tornado.
> Correct me if I am wrong but that sounds like a tornado 
> WATCH.  Not once did they say there was one on the ground.  
> In the Midwest when we got a tornado warning, we knew we had 
> one on the ground.  Paint me confused.  Do the different NWS 
> office have different standards?
> 
> Signed,
> 
> Your soggy engineer....

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