SPC Severe Weather Forecasting Overview David Imy david

SPC Severe Weather Forecasting Overview David Imy david. imy@noaa. gov

SPC Organization Director Admin Officer WCM Admin Coord. Operations Branch Chief Science Branch Chief 5 Lead Forecasters Science Operations Officer 10 Mesoscale/Outlook Forecasters 3 Technologists 5 Assistant Mesoscale Forecasters 2 System Analysts Software Analyst Contract Computer Tech Contract Programmer

Storm Prediction Center Evolution • Congress recognized the need for a severe weather center in late 1940 s (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

National Weather Center

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

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.

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

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)

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

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

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.

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

Probability of F 2 or greater tornado within 25 miles of a point EXAMPLES: Week of Feb 19 th Week of May 6 th

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 -1 km shear, etc. • Also, technology and research allows more meaningful parameters that link observable scales to storm-scale (cloud-scale models).

Analysis of Surface and Upper Air Parameters

Deep Layer Shear (0 -6 km)

Instability (MLCAPE)

Low Level Shear (0 -1 km)

Supercell Composite Parameter

Significant Tornado Parameter

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

Categorical Outlooks Ý Slight (SLGT) Ý Ý Moderate (MDT) Ý Ý 5 -20 Severe Hail Events 5 -20 Severe Wind Events 2 -5 Tornadoes 20 -50 Severe Hail Events 20 -50 Severe Wind Events 6 -19 Tornadoes High Ý Ý > 19 Tornadoes with 2+ potentially producing F 3 -F 5 damage Derecho - producing extreme wind damage (> 50 reports)

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

Feb 16, 2006 Categorical Outlook

Feb 16, 2006 Hail Probabilities

Feb 16, 2006 Wind Probabilities

Feb 16, 2006 Tornado Probabilities

Probability Outlook ~ Tornadoes Intervals ~ ~ Hail ~ ~ 5%, 15%, 25%, 35%, 45%, 60% Convective Wind ~ ~ 2%, 5%, 10%, 15%, 30%, 45%, 60% 5%, 15%, 25%, 35%, 45%, 60% Extreme (> 10%) Tornadoes F 2+ damage ~ Hail 2. 0+ inches diameter ~ Winds 65+ kt ~

Severe Weather Watches

Tornado Watches Issued when: Ý strong/violent tornado (F 2 – F 5) damage is possible Ý 2 or more tornadoes are expected Not all tornadoes will occur in a watch!

“Particularly Dangerous Situation” (PDS) Watches • Tornado watches – Multiple strong or violent (F 2 – F 5 damage) events • Severe Thunderstorm Watches – Long lived wind events (derechoes)

Severe Thunderstorm Watch ÝOrganized Severe Storms ÝSupercells ÝSquall lines ÝMulticell complexes ÝExtreme severe storms ÝWind gusts > 64 kt (73 mph) ÝDamage to permanent structures ÝHail > 2. 0 inches diameter

Tornado Watch 33

Watch #33 Severe Weather Probabilities

Watch-By-County Tornado Watch

Coming Soon- New Watch Web Presentation

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

Mesoscale Convective Discussions (MD) Ú 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

Mesoscale Discussions ZCZC MKCSWOMCD ALL; 334, 0996 373, 0979 353, 0979 314, 0996; ACUS 3 KMKC 032023 >MKC MCD 032023 TXZ 000_OKZ 000_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 20 Z 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 03 Z. THIS AREA IS BEING MONITORED FOR A POSSIBLE TORNADO WATCH. . . THOMPSON. . 05/03/99. . . PLEASE SEE WWW. SPC. NOAA. GOV/ FOR GRAPHIC PRODUCT. . . NNNN

Fire Weather Outlook Ø Three Types of Areas Ø Ø Ø Critical Extremely Critical Dry Thunderstorm

Day One Fire Weather Outlook

Day Two Fire Weather Outlook

SPC Web Page www. spc. noaa. gov