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SPC Severe Weather Forecasting Overview

SPC Severe Weather Forecasting Overview. David Imy david.imy@noaa.gov. SPC Organization. Storm Prediction Center Evolution. Congress recognized the need for a severe weather center in late 1940s (after two tornadoes at Tinker AFB) 1950 in Washington, D.C.

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SPC Severe Weather Forecasting Overview

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  1. SPC Severe Weather ForecastingOverview David Imy david.imy@noaa.gov

  2. SPC Organization

  3. Storm Prediction Center Evolution • Congress recognized the need for a severe weather center in late 1940s (after two tornadoes at Tinker AFB) • 1950 in Washington, D.C. • 1953 in Kansas City, MO as National Severe Storms Forecast Center • 1996 in Norman, OK as the NOAA Storm Prediction Center

  4. National Weather Center

  5. National Weather Center Occupants • Storm Prediction Center • National Severe Storms Laboratory • WFO Norman • Warning Decision Training Branch • University of Oklahoma Meteorological Dept. • Oklahoma Climate Survey

  6. SPC Mission Statement SPC exists to protect life and property of the American people through the issuance of timely, accurate watch and forecast products dealing with tornadoes and other mesoscale hazardous weather.

  7. Severe Criteria • ** Tornadoes • ** Hail ¾” diameter or larger • ** Thunderstorm winds > 57 mph

  8. How Do We Accomplish Mission? • Issue Severe Thunderstorm and Tornado Watches for the CONUS • Issue Convective Outlooks for Days 1-8 and Fire Outlooks Days 1-8 • Issue needed Mesoscale Discussions for short term hazardous weather (severe, winter and heavy rain)

  9. SPC Products • Convective Outlooks • Day 1 (today) • Day 2 (tomorrow) • Day 3 (day after tomorrow) • Day 4-8 • Severe Weather Watches • Tornado • Severe Thunderstorm

  10. Other SPC Products • Mesoscale Discussions • Watch Status Messages • Severe Weather Stats • Fire Weather Outlooks • Day 1 (today) • Day 2 (tomorrow) • Experimental Day 3-8

  11. I. Pattern Recognition/Forecaster Experience • Classical synoptic-dynamic setting for some severe weather outbreaks (but other patterns are regionally / event dependent) • Southwest monsoon, northeast U.S., pulse severe, hurricane-tornado, etc.

  12. II. Climatology Knowledge of climatology is a good first step to provide information about when/where events more likely to occur

  13. Probability of F2 or greater tornado within 25 miles of a point EXAMPLES: Week of Feb 19th Week of May 6th

  14. III. Parameter Evaluation This changes more rapidly than pattern recognition and climatology OLD: Lifted Index, Showalters, Total-Totals, etc. NEW: CAPE, SRH, LCL Height, 0-1km shear, etc. • Also, technology and research allows more meaningful parameters that link observable scales to storm-scale (cloud-scale models).

  15. Analysis of Surface and Upper Air Parameters

  16. Deep Layer Shear (0-6 km)

  17. Instability (MLCAPE)

  18. Low Level Shear (0-1km)

  19. Supercell Composite Parameter

  20. Significant Tornado Parameter

  21. Severe Weather Outlooks • Categorical • Slight • Moderate • High • Probabilistic • Tornadoes • Hail • Convective Winds

  22. Categorical Outlooks • Slight (SLGT) • 5-20 Severe Hail Events • 5-20 Severe Wind Events • 2-5 Tornadoes • Moderate (MDT) • 20-50 Severe Hail Events • 20-50 Severe Wind Events • 6-19 Tornadoes • High • > 19 Tornadoes with 2+ potentially producing F3-F5 damage • Derecho - producing extreme wind damage (> 50 reports)

  23. Probability Outlooks • Provides the threat of severe weather occurring within 25 miles of any point within the area • Tornadoes • Large hail • Severe convective winds • Also threat for extreme severe

  24. Feb 16, 2006 Categorical Outlook

  25. Feb 16, 2006 Hail Probabilities

  26. Feb 16, 2006 Wind Probabilities

  27. Feb 16, 2006 Tornado Probabilities

  28. Probability Outlook Intervals • Tornadoes • 2%, 5%, 10%,15%, 30%, 45%, 60% • Hail • 5%, 15%, 25%, 35%, 45%, 60% • Convective Wind • 5%, 15%, 25%, 35%, 45%,60% • Extreme (> 10%) • Tornadoes F2+ damage • Hail 2.0+ inches diameter • Winds 65+ kt

  29. Severe Weather Watches

  30. Tornado Watches Issued when: strong/violent tornado (F2 – F5) damage is possible 2 or more tornadoes are expected Not all tornadoes will occur in a watch!

  31. “Particularly Dangerous Situation” (PDS) Watches • Tornado watches • Multiple strong or violent (F2 – F5 damage) events • Severe Thunderstorm Watches • Long lived wind events (derechoes)

  32. Severe Thunderstorm Watch • OrganizedSevereStorms • Supercells • Squall lines • Multicell complexes • Extreme severe storms • Wind gusts > 64 kt (73 mph) • Damage to permanent structures • Hail > 2.0 inches diameter

  33. Tornado Watch 33

  34. Watch #33 Severe Weather Probabilities

  35. Watch-By-County Tornado Watch

  36. Coming Soon- New Watch Web Presentation

  37. Watch Outline Update (WOU) ** All counties in watch included in initial issuance ** As local NWS offices clear counties from watch (WCN), the WOU will be updated with those counties removed ** The SPC does not remove counties from a watch; the local offices control the watch after issuance

  38. Mesoscale Convective Discussions (MD) • Goal is to issue pre-watch MDs 1 to 3 hours prior to a Severe Thunderstorm or Tornado watch issuance. - Define area(s) of concern - State expected watch type - Provide meteorological reasoning – most important Also issued to address following hazards: - Outlook Upgrade - Heavy Rainfall - Winter Weather

  39. Mesoscale Discussions ZCZC MKCSWOMCD ALL;334,0996 373,0979 353,0979 314,0996; ACUS3 KMKC 032023 >MKC MCD 032023 TXZ000_OKZ000_032300_ SPC MESOSCALE DISCUSSION #0345 FOR...SW OK/NW TX... CONCERNING...SEVERE THUNDERSTORM POTENTIAL... WATER VAPOR IMAGERY SHOWS A LEAD MID LEVEL SHORT WAVE TROUGH MOVING ENEWD OVER E/NE NM THIS AFTERNOON...AND THIS IS CONFIRMED BY PROFILER TIME SERIES FROM AZC/GDA/TCC/JTN. MID/UPPER 60 DEWPOINTS AND TEMPERATURES NEAR 80 ARE CONTRIBUTING TO SURFACE_BASED CAPE VALUES OF 3500_5000 J/KG OVER WRN OK AND NW TX TO THE E OF THE DRYLINE. CONVERGENCE ON THE DRYLINE IS NOT STRONG AND A CIRRUS SHIELD OVER THE TX PANHANDLE/ NW TX/ WRN OK SHOULD LIMIT ADDITIONAL SURFACE HEATING... BUT VISIBLE /RADAR IMAGERY HAS SHOWN THE FIRST ATTEMPTS AT TCU OVER FAR NW TX AS OF 20Z WITHIN A BREAK IN THE CIRRUS. MID LEVEL FLOW AND VERTICAL SHEAR WILL INCREASE OVER NW TX AND WRN OK THROUGH LATE AFTERNOON... WITH AN INCREASING THREAT OF SUPERCELLS NEAR THE DRYLINE FROM 00 to 03Z. THIS AREA IS BEING MONITORED FOR A POSSIBLE TORNADO WATCH. ..THOMPSON.. 05/03/99 ...PLEASE SEE WWW.SPC.NOAA.GOV/ FOR GRAPHIC PRODUCT... NNNN

  40. Fire Weather Outlook • Three Types of Areas • Critical • Extremely Critical • Dry Thunderstorm

  41. Day One Fire Weather Outlook

  42. Day Two Fire Weather Outlook

  43. SPC Web Page www.spc.noaa.gov

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