[BC] Re: Tornado warnings

[Mike McCarthy]

I happen to disagree with the latter two products you suggest. Most of the 
F-3 or greater tornadoes in the past 5 years have been detected long before 
they touched down. Often times the radar will see circulation forming 
several minutes to maybe a 1/2 hour before the column of air touches the 
ground.  In the case of larger tornadoes which exhibit F-3 thru F-5 wind 
speeds, the circulation is detected 10-20 minutes before touchdown on a 
fairly reliable basis.  Especially if the circulation is seen at all 
elevations.  By splitting the call to action messages, you add confusion.

The only locations a tornado will form and potentially not be seen by radar 
are:

At the very fringe of the Dopplar coverage (75 miles and beyond) where the 
beam at base elevation is already several miles up and the pixel area 
equals more than a square mile; and
where the terrain might shadow the radar, like a mountain valley shielded 
by a ridge.

Tornadoes are also hard to detect within even Dopplar if they are what are 
known as "heavy precipitation tornadoes".  This is where the twister is 
surrounded by extremely heavy rain.  The 1990 Plainfield, IL. F5 twister 
was one such tornado.  The twister was completely wrapped in a heavy rain 
column masking it's rotation.  There is no known tape or film of the 
twister except at it's very beginning as a funnel before it touched down. 
It's that element of surprise which was the cause of all the deaths in the 
area.

What makes them very hard to see on radar is the rotational speed data is 
masked by the extremely heavy precipitation returns.  If there is a hail 
column mixed in, the density of the precipitation return is even more 
intense.  At anything more than 50 or so miles, it's extremely difficult to 
see a heavy precipitation tornado by Dopplar.

In recent years, there have been 5 different wind events which have been 
defined often mistaken as tornadoes, but are clearly not.  While the damage 
those events create is the same, the supporting atmospheric dynamics are 
all very different from tornadoes.

I'm a trained spotter of some 25 years, a member of the local AMS chapter, 
and a long time net control operator for spotter nets.

MM

At 05:44 PM 9/1/2006 -0400, Kevin Webb wrote
>It is agreed there needs to be an advance warning if conditions are
>favorable, that we should take advantage of the latest technology and sound
>a warning of some kind as soon as possible.  However the current system
>issues warnings too quickly and too often so that people tend to ignore
>them.  What I forgot to mention is perhaps it is time to consider a slightly
>different system where there are 3 levels, maybe Tornado Watch (obvious),
>Tornado Warning (tornado signature spotted on radar), and Tornado On the
>Ground (or Tornado Touched Down) so that the threat is made much clearer to
>the public in a meaningful way.
>
>Kevin
>-------------------------------------
>
>Date: Fri, 1 Sep 2006 09:05:36 -0400
>From: "Ernie Belanger" <armtx at mhcable.com>
>Subject: Re: [BC] Tornado warnings
>
>There has long been confusion between Warnings and Watches.
>
>If you read the definition and understand it then you know that WARNINGS are
>
>issued when a tornado is imminent.  That would mean that when the infamous
>hook is spotted and most likely a tornado will spawn the WARN.
>
>
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