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Special SevereWeather & Heavy Rain Weather Briefing 03/19/2012 srh.noaa/shv/briefing

Special SevereWeather & Heavy Rain Weather Briefing 03/19/2012 www.srh.noaa.gov/shv/briefing. Keith Stellman Warning Coordination Meteorologist. National Weather Service Shreveport, Louisiana. Overview. ** Significant Severe Weather and Rainfall Event Setting up across the region **

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Special SevereWeather & Heavy Rain Weather Briefing 03/19/2012 srh.noaa/shv/briefing

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  1. Special SevereWeather& Heavy Rain Weather Briefing03/19/2012www.srh.noaa.gov/shv/briefing Keith Stellman Warning Coordination Meteorologist National Weather Service Shreveport, Louisiana

  2. Overview **Significant Severe Weather and Rainfall Event Setting up across the region** Setup: Cutoff – slow moving upper low Stalled Front High Precipitable Water (99th percentile) Soils prepped from the recent rains Impacts Serious Flooding/Flash Flooding!! Tues AM->Thu AM Severe Weather Threat Late Monday/Early Tues Damaging Winds – Strong! Tornadoes (primarily East TX/SE OK/SW AR) National Weather Service Shreveport, Louisiana

  3. Current Satellite/Water Vapor Strong Polar Jet diving Down the backside of this low L Strong ridge holding strong East of the area H Note the plume of moisture from the Pacific National Weather Service Shreveport, Louisiana

  4. Radar @ 1045 AM Monday • Strong Storms developing • Expect this line to shift east slowly with stronger storms

  5. Monday PM • Upper level low beginning to cut off. • Waves of storms moving across west/NW areas L

  6. 10 PM 7 PM Monday PM Thru Tuesday AM Model Radar Simulation 4 AM 1 AM

  7. Precip through Tues 7 AM • High Risk of excessive rainfall i.e. Flash Flooding Excessive Rainfall Outlook

  8. Severe Weather Threat – Monday PM/Tuesday AM SPC Moderate risk area Primary Threats: Damaging Winds Tornadoes

  9. Tuesday PM • Front aligns along Sabine River from north->south • Storms train over the same areas • Low cuts off over west TX

  10. 10 AM Note kinks in line 7 AM Tuesday AM Thru Tuesday PM Model Radar Simulation 1 PM 4 PM

  11. Rainfall Forecast Tuesday AM – WednesdayAM • Axis of heavy rains along LA/TX border and SW AR • 3”- 6” ..isolated 8”

  12. Severe Weather Threat – Tuesday Primary Threats: Damaging Winds Tornadoes SPC Slight risk area Increased Risk in Orange outlined areas

  13. Wednesday PM • Heavy Band shifts into Eastern LA • Low still cutoff over TX • Rainfall over in TX. Ongoing in LA, S AR.

  14. Rainfall Forecast Wednesday AM – Thursday AM • Heaviest axis expected across Eastern LA.. US 165 Corridor • 2”- 3” …isolated 4”

  15. Computer Model Total Rainfall Forecast (ECMWF) Note the heavy axis in East TX SW AR/ SE OK

  16. Computer Model Total Rainfall Forecast (GFS) • 2 Swaths of 5”-8” • This model has shown the highest amounts through the forecast

  17. Computer Model Total Rainfall Forecast (NAM) • 1 large Swath of 5”-8” with a max of 9”-10” • This model has been the Western most

  18. Computer Model Total Rainfall Forecast (NAM) • 1 large Swaths of 5”-8” with a max of 9”-10” • This model has been the Western most

  19. Computer Model Total Rainfall Forecast (SREF) • 1 large Swath of 5”-8” • This is a combination of numerous model runs

  20. Some perspective on the amountsTop 10 Wettest March – SHV (1874-2011) Rank Value Ending Date 11.99 3/31/1945 11.67 3/31/1876 9.93 3/31/1912 9.31 3/31/1922 9.30 3/31/1934 9.27 3/31/1874 9.00 3/31/1888 8.72 3/31/1997 8.04 3/31/1894 7.90 3/31/2000 *** We could break the top 10 wettest March Rainfalls this week!! Month to date: 3.41” – SHV 6.68” – LFK 6.42” – MLU 3.03” – TYR 3.03” – TXK 2.43” - DEQ

  21. Precipitable Water (inches)A measure of the amount of moisture in the atmosphere 7 AM Tues Wed AM GFS model Indicating 85 kt low level jet Believability? Max 1.77” Max 1.80” Forecasts from the GFS computer model

  22. Climatology of Precipitable Water This event falls above the 99th percentile and approaches the maximum value observed in March….based on the forecast PW values X

  23. Impacts • River Impacts • Sabine, Neches, Sulphur, Red system..including parts of the Red, Upper Ouachita • Moderate flooding most areas…Some Major (Sulphur) • Depends on location of heaviest rainfall & duration at which the rain falls • Other Impacts • Significant Flash Flooding • Tues AM->Thu AM • Severe Weather Threat • Late Mon/Early Tues • Damaging Winds - Strong • Tornadoes National Weather Service Shreveport, Louisiana

  24. NEXT CONFERENCE CALL: Possibly Friday 3/20 Time TBD www.srh.noaa.gov/shv/briefing National Weather Service Shreveport, Louisiana

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