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Polygon Warnings

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					 Polygon Warnings
The Sharp Focus on
      Service

 NWS Partners’ Workshop
   Silver Spring, MD
       June, 2006
         Goal – Improving Warning Service




                                 Polygon Eliminates
                                 False Alarm for this
                                        Area




Polygon Watch and Warning Team
           Review - WFO Case Study
     During two convective seasons, one CR WFO issued 46
     tornado warnings covering:
      – 38,280 square miles
      – Included 595 towns
     Utilizing the polygon approach, the polygons covered:
      – 10,374 square miles
      – Included 169 towns
     If the polygon approach were in place, when compared
     with the county approach:
      – Reduction in total area warned - 27,906 square miles
      – Reduction in total number of towns warned - 426...a
         reduction of 72%!



Polygon Watch and Warning Team
           Review – 2005 Case Study
      April through mid June 2005: an SR WFO issued 52 convective
      warnings covering:
        – 41,733 square miles
        – Included 636 towns
      Utilizing the polygon approach, the polygons covered:
        – 11,291 square miles
        – Included 198 towns
      Number of events which occurred outside the polygon but within
      the county: 2
      If the polygon approach were in place, when compared with the
      county approach:
        – Reduction in total area warned - 73%
        – Reduction in total number of towns warned - 70%




Polygon Watch and Warning Team
          Polygon Evaluation WFOs
               Polygon Warning Evaluation WFOs
                 March 1 – September 30 2005




Polygon Watch and Warning Team
                   Falsely Alarmed Area
      Polygon Evaluation test sites, 1 March – 30
      September 2005, all warnings:

     Reduction of area warned, by polygon
     when compared to the area of the county,
     or the reduction of “Falsely Alarmed Area”
                                    72.07%
          (Is this the same as a similar reduction in false alarms? Yes, it means
        a person in a given location, on average, would be falsely alarmed 72% less.
                    Note: This should not be confused with FAR as used in GPRA metrics )




Polygon Watch and Warning Team
                Value of reduced area warned
    Dr. Daniel S. Sutter*, Associate Professor of Economics, University of Oklahoma
        estimates that…

           If the typical polygon tornado warning was about 1/4 the size of the typical warned
           county, the value of reduced time under tornado warnings would be almost $100
           million per year; %
           Reducing the area of the typical tornado warning to 1/4 of the current county size
           would produce about the same increase in value of the warning as reducing the false
           alarm rate to zero.

           Reducing the area of the typical tornado warning to 1/4 of the current county size
           increases warning credibility and, thereby, the value of the warning.
    %http://www.crh.noaa.gov/sharedoc/crh/taking%20cover.doc
    http://www.crh.noaa.gov/sharedoc/crh/polygon%20tornado%20warnings.doc

    *Author of “eco-weather” articles in Weather and Forecasting 2002 and 2005: (http://ams.allenpress.com/pdfserv/10.1175%2FWAF857.1
    http://ams.allenpress.com/pdfserv/10.1175%2F1520-0434(2002)017%3C0619:TSETSB%3E2.0.CO%3B2 ).




Polygon Watch and Warning Team
         Today - Partner Acceptance

   Media
   New Industry (StormCall & Emergency
   Communications Network)
   Emergency Managers (selective siren
   activation)
   FAA (terminal warnings)
   Private Sector Opportunities (StormHawk)


Polygon Watch and Warning Team
         Today – Partner Acceptance




Polygon Watch and Warning Team
       Douglas County, CO. Flash Flood
       Warning




Polygon Watch and Warning Team
              Implementation – When?



     Test Sites – continue as in 2005
     “Unofficial” Sites – Participation this season
     and/or 2007 is encouraged
     National Implementation – 2008




Polygon Watch and Warning Team
             Where were we in 2003?
  All Polygon Warnings Issued in 2003
  (SVR, blue and TOR, red)




Polygon Watch and Warning Team

				
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