Polygon Warnings The Sharp Focus on Service The Sharp Focus on Service NWS Partners’ Workshop Silver Spring, MD June, 2006

Polygon WarningsPolygon Warnings The Sharp Focus on The Sharp Focus on

ServiceService

NWS Partners’ Workshop NWS Partners’ Workshop Silver Spring, MDSilver Spring, MD

June, 2006June, 2006

Polygon Watch and Warning TeamPolygon Watch and Warning Team

Polygon Polygon Eliminates False Eliminates False

Alarm for this Alarm for this AreaArea

Goal – Improving Warning Goal – Improving Warning ServiceService


Review - WFO Case Review - WFO Case StudyStudy

During two convective seasons, one CR WFO issued During two convective seasons, one CR WFO issued 46 tornado warnings covering:46 tornado warnings covering:– 38,280 square miles38,280 square miles– Included 595 townsIncluded 595 townsUtilizing the polygon approach, the polygons Utilizing the polygon approach, the polygons covered:covered:– 10,374 square miles10,374 square miles– Included 169 townsIncluded 169 townsIf the polygon approach were in place, when If the polygon approach were in place, when compared with the county approach:compared with the county approach: – Reduction in total area warned - Reduction in total area warned - 27,906 square 27,906 square

milesmiles– Reduction in total number of towns warned - Reduction in total number of towns warned -

426...a 426...a reduction of 72%!reduction of 72%!


Review – 2005 Case Review – 2005 Case StudyStudy

April through mid June 2005: an SR WFO issued 52 April through mid June 2005: an SR WFO issued 52 convective warnings covering:convective warnings covering:– 41,733 square miles41,733 square miles– Included 636 townsIncluded 636 towns

Utilizing the polygon approach, the polygons covered:Utilizing the polygon approach, the polygons covered:– 11,291 square miles11,291 square miles– Included 198 townsIncluded 198 towns

Number of events which occurred outside the polygon Number of events which occurred outside the polygon but within the county: 2but within the county: 2If the polygon approach were in place, when compared If the polygon approach were in place, when compared with the county approach:with the county approach: – Reduction in total area warned - Reduction in total area warned - 73% 73% – Reduction in total number of towns warned - Reduction in total number of towns warned - 70%70%


Polygon Warning Evaluation WFOsMarch 1 – September 30 2005

Polygon Evaluation WFOs


Falsely Alarmed Area Falsely Alarmed Area

Polygon Evaluation test sites, 1 March Polygon Evaluation test sites, 1 March – 30 September 2005, all warnings:– 30 September 2005, all warnings:

Reduction of area warned, by polygon Reduction of area warned, by polygon when compared to the area of the when compared to the area of the county, or the reduction of “Falsely county, or the reduction of “Falsely Alarmed Area” Alarmed Area”

72.07%72.07% (Is this the same as a similar reduction in false alarms? Yes, it means(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. 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 metricsNote: This should not be confused with FAR as used in GPRA metrics ) )


Value of reduced area Value of reduced area warnedwarned

Dr. Daniel S. Sutter*, Associate Professor of Economics, University of Dr. Daniel S. Sutter*, Associate Professor of Economics, University of Oklahoma estimates that…Oklahoma estimates that…

If the typical polygon tornado warning was about 1/4 the size of the typical 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 warned county, the value of reduced time under tornado warnings would be almost be almost $100 million per year$100 million per year; ; %%

Reducing the area of the typical tornado warning to Reducing the area of the typical tornado warning to 1/41/4 of the current of the current county size would produce about the same increase in value of the county size would produce about the same increase in value of the warning as reducing the false alarm rate to warning as reducing the false alarm rate to zerozero. .

Reducing the area of the typical tornado warning to Reducing the area of the typical tornado warning to 1/41/4 of the current of the current county size increases warning credibility and, thereby, the value of the county size increases warning credibility and, thereby, the value of the warning.warning.

%%http://www.crh.noaa.gov/sharedoc/crh/taking%20cover.dochttp://www.crh.noaa.gov/sharedoc/crh/taking%20cover.doc http://www.crh.noaa.gov/sharedoc/crh/polygon%20tornado%20warnings.dochttp://www.crh.noaa.gov/sharedoc/crh/polygon%20tornado%20warnings.doc

*Author of “eco-weather” articles in *Author of “eco-weather” articles in Weather and ForecastingWeather and Forecasting 2002 and 2005: 2002 and 2005: ((http://ams.allenpress.com/pdfserv/10.1175%2FWAF857.1http://ams.allenpress.com/pdfserv/10.1175%2FWAF857.1http://http://ams.allenpress.com/pdfserv/10.1175%2F1520-0434(2002)017%3C0619:TSETSB%3E2.0.CO%3B2ams.allenpress.com/pdfserv/10.1175%2F1520-0434(2002)017%3C0619:TSETSB%3E2.0.CO%3B2 ). ).


Today - Partner Today - Partner AcceptanceAcceptance

MediaMedia

New Industry New Industry (StormCall & (StormCall & Emergency Communications Network)Emergency Communications Network)

Emergency ManagersEmergency Managers (selective (selective siren activation)siren activation)

FAAFAA (terminal warnings) (terminal warnings)

Private Sector Opportunities Private Sector Opportunities (StormHawk)(StormHawk)


Today – Partner Today – Partner AcceptanceAcceptance


Douglas County, CO. Flash Flood Douglas County, CO. Flash Flood WarningWarning


Implementation – When?Implementation – When?

Test Sites – continue as in 2005Test Sites – continue as in 2005

““Unofficial” Sites – Participation this Unofficial” Sites – Participation this season and/or 2007 is encouragedseason and/or 2007 is encouraged

National Implementation – 2008National Implementation – 2008


Where were we in 2003? Where were we in 2003?

All Polygon Warnings Issued in 2003 (SVR, blue and TOR, red)

Documents

Polygon Warnings The Sharp Focus on Service The Sharp Focus on Service NWS Partners’ Workshop Silver Spring, MD June, 2006