Partner's Meeting2) Too many counties in Storm Based Warnings
3) Watches and Warnings on Feb. 11, 2009
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Since 1999 – 6 per year (30% without confirmation)
New directive will require confirmation (visual report or radar observation of debris)
Reduces to an average of 4 events per year
In exceedingly rare situations, when a severe threat to human life and catastrophic damage from a tornado is imminent or ongoing, the forecaster may insert the headline "...TORNADO EMERGENCY FOR [GEOGRAPHIC AREA]...". Additionally, in such a situation, this headline should only be used when reliable sources confirm a tornado, or there is clear radar evidence of the existence of a damaging tornado such as the observation of debris.
--NWSI 10-511 (final draft)
Severe Thunderstorm Warnings
Approximately 1% of Severe Thunderstorm Warnings include more than 12 counties
Change to NWSI 10-511: “Warnings should contain no more than 12 counties”
Next Generation Warning Tool Sub-team looking at improved warning formats (text and graphics)
- To include both our full text messages and options for parsing to cell phone text messages
- Will involve partners
Weak Instability
Damaging Winds &
Isolated Tornadoes
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F4 Franklin TN 12/24/88
- First three – TOR
- Second three – SVR
DESPITE VERY WEAK INSTABILITY...THE THREAT OF LOCALLY DAMAGING WINDS WILL INCREASE WITH TIME DUE TO DRYING ALOFT AND ENHANCED POTENTIAL FOR DOWNWARD TRANSFER OF MOMENTUM. LOW AND MID LEVEL VERTICAL SHEAR PROFILES WILL ALSO BE FAVORABLE FOR BOW/LEWP STRUCTURES ALONG THE LINE AND AN ATTENDANT RISK OF ISOLATED TORNADOES. _ -- From Tornado Watch 16
Tornado Watch #16 – Issued 11:40AM
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16 TOR
2 Tornadoes
Summary
High Shear / Low Instability Events are challenging from a watch and warning standpoint
NWS increasing effort on addressing very large severe thunderstorm warnings
Too many tornado warnings - - Ideas?