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Probabilistic MOS Guidance for Hazards. Meteorological Development Lab September 2008. Background. MDL is producing probabilistic guidance (EKDMOS) for T, Td, MaxT, MinT, QPF from NCEP's GEFS. Output is grids that define probability distribution of weather element. Technique
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Probabilistic MOS Guidance for Hazards Meteorological Development Lab September 2008
Background • MDL is producing probabilistic guidance (EKDMOS) for T, Td, MaxT, MinT, QPF from NCEP's GEFS. • Output is grids that define probability distribution of weather element. • Technique • Regression applied to NCEP ensemble means. • KDE, normal kernel, mean and standard deviation from regression. • Spread Adjustment. • Can these techniques be applied to high impact weather? • If so, we could generate probability distributions of impact variables. • Customers/partners could set their own thresholds.
Strategy • Choose predictands that • Relate closely to NWS W/W/A • Have a quasi-normal distribution • Combination of gridded guidance and appropriate WFO tools could help W/W/A generation. • Including Graphical Hazardous Weather Outlook • Candidates • Wind Chill Temperature (WCH) • Heat Index (HDX)
Wind Chill Temperature • Directly relates to • Extreme Cold Watch • Extreme Cold Warning • Wind Chill Watch • Wind Chill Warning • Wind Chill is defined as a function of Temperature and Wind Speed in NWSI 10-513. • Range of values • Will limit development sample to a range of useful values. • Chart in NWSI 10-513 suggests T<= 40F and WindSpd >= 5 mph. SR SOOs suggest T<=50F.
Heat Index • Directly relates to • Excessive Heat Watch • Excessive Heat Warning • Heat Advisory. • Heat Index is defined as a function of Temperature and RH in NWSI 10-515. Two adjustments are provided as well. • Range of values • Will limit development sample to a range of useful values. • Chart in NWSI 10-515 suggests T>= 85F.