SPC Mission Statement. Tornado in Miami, FL Photo: Miami Herald. What is SPC s Responsibility? More SPC Products. SPC Products

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1 The NOAA/NWS Storm Prediction Center Adapted from a presentation to UNCA atmospheric science students by David Imy 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. Salt Lake City, Utah Photo: KTVX News 4 Tornado in Miami, FL Photo: Miami Herald What is SPC s Responsibility? Forecast severe storms across the 48 contiguous states Hail ¾ diameter or larger Thunderstorm winds > 57.5 mph Also monitor for: Heavy rain Winter Weather Conditions favorable for wildfire initiation SPC Products Severe Weather Outlooks Day 1 (today) Day 2 (tomorrow) Day 3 (day after tomorrow) Day 4 8 Severe Weather Watches Tornado Severe Thunderstorm More SPC Products Mesoscale Discussions Watch Status Messages Severe Weather Statistics Fire Weather Outlooks Day 1 (today) Day 2 (tomorrow) Day 3 8 1

2 Severe Weather Outlooks Categorical Slight Moderate High Probabilistic Hail Convective Winds Categorical Outlooks Slight (SLGT) 5-20 Severe Hail Events 5-20 Severe Wind Events 2-5 Tornadoes Moderate (MDT) Severe Hail Events Severe Wind Events 6-19 Tornadoes High > 19 Tornadoes with 2+ potentially producing EF3 EF5 damage Derecho - producing extreme wind damage (> 50 reports) Probability Outlooks Feb 16, 2006 Categorical Outlook Provide the threat of severe weather occurring within 25 miles of any point within the area Large hail Severe convective winds Also provide threat for extreme severe Feb 16, 2006 Hail Probabilities Feb 16, 2006 Wind Probabilities 2

3 Feb 16, 2006 Tornado Probabilities Probability Outlook Intervals 2%, 5%, 10%,15%, 30%, 45%, 60% Hail 5%, 15%, 30%, 45%, 60% Convective Wind 5%, 15%, 30%, 45%,60% Extreme - at least a 10% chance of: F2+ damage Hail 2.0+ inches diameter Winds 65+ kt Day 4 8 Severe Outlook A severe weather area depicted in the Day 4 8 period indicates a 30% or higher probability for severe thunderstorms within 25 miles of any point. 3

4 Storm Reports on Feb 5, 2008 Tornado Watches Issued when strong/violent tornado (EF2 EF5) damage is possible Multiple weak tornadoes are possible Not all tornadoes will occur within a watch! Particularly Dangerous Situation Watches PDS Tornado watches Multiple strong or violent (EF2 EF5 damage) events PDS Severe Thunderstorm Watches Long-lived wind systems with possible widespread damage (derechoes) ZCZC MKCSEL9 ALL ;365, , , ,1004; WWUS9 KMKC MKC WW OKZ000-TXZ URGENT - IMMEDIATE BROADCAST REQUESTED TORNADO WATCH NUMBER 49 STORM PREDICTION CENTER NORMAN OK 344 PM CST THU FEB THE STORM PREDICTION CENTER HAS ISSUED A TORNADO WATCH FOR PORTIONS OF WESTERN OKLAHOMA NORTHWESTERN TEXAS EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 430 PM UNTIL 1100 PM CST....THIS IS A PARTICULARLY DANGEROUS SITUATION... DESTRUCTIVE TORNADOES...LARGE HAIL TO 2 INCHES IN DIAMETER... THUNDERSTORM WIND GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS. Severe Thunderstorm Watch Organized severe storms Supercells Squall lines Multicell complexes Extreme severe storms Wind gusts > 64 kt (73 mph) Damage to permanent structures Hail > 2.0 inches diameter Watch By County Recently moved from parallelogram-based to county-based watches 4

5 Watch Probabilities Severe Thunderstorm Watch 688 Probability Table Mesoscale Discussions ZCZC MKCSWOMCD ALL;334, , , ,0996; ACUS3 KMKC MKC MCD TXZ000_OKZ000_032300_ SPC MESOSCALE DISCUSSION #0345 FOR...SW OK/NW TX... CONCERNING...SEVERE THUNDERSTORM POTENTIAL... Tornadoes Probability of 2 or more tornadoes Probability of 1 or more strong (F2-F4) tornadoes Wind Probability of 10 or more severe wind events Probability of 1 or more wind event > 65 knots Hail Probability of 10 or more severe hail events Probability of 1 or more hailstones >2 inches Combined Severe Hail/Wind Probability of 6 or more combined severe wind/hail events Low (10%) Low (<5%) Mod (60%) Low (10%) Low (10%) Low (<5%) Mod (60%) 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 FOR GRAPHIC PRODUCT... NNNN Mesoscale Discussions: Technical discussions of developing mesoscale features and their impact on hazardous weather What, when, where, why Emphasis on the short term outlook Written in plain language Geared for professional meteorologists Winter weather Freezing rain, rapidly accumulating snow, blizzards Heavy rainfall Severe thunderstorm potential/outlook upgrade 1-2 hours prior to a watch 2-3 hour cycle during watch Change in convective outlook category Thunderstorms not expected to become severe MESOSCALE DISCUSSION 1902 NWS STORM PREDICTION CENTER NORMAN OK 0212 PM CDT SAT JUL AREAS AFFECTED...INTERIOR SRN CA AND FAR SRN NV CONCERNING...SEVERE THUNDERSTORM POTENTIAL...HEAVY RAINFALL VALID Z Z ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON INTO THIS EVENING ACROSS THE IMPERIAL VALLEY OF CA AND THE ADJACENT MTNS. LOCALLY HEAVY RAINFALL WILL ALSO OCCUR WITH ANTICIPATED SLOW MOTION OF INDIVIDUAL CELLS. SURFACE MOISTURE AXIS...WITH DEWPOINTS IN THE LOW TO MID 70S...EXTENDS NNNWD FROM GULF OF CA INTO THE IMPERIAL VALLEY OF CA AND ERN SLOPES OF THE COASTAL RANGES. LOW- LEVEL MOISTURE CONTINUES TO INCREASE NWD INTO THE Greensburg, KS EF5 Tornado May 4, 2007 Photo: Melanie Metz Greensburg, KS EF5 Tornado Damage May 4, 2007 Greensburg, KS EF5 Tornado Damage May 4,

6 Fire Weather Outlook Day 1 Fire Weather Outlook Three Types of Areas Critical Extremely Critical Dry Thunderstorm The Watch/Warning Funnel Concept D a y s Check plan of action Make sure shelter is ready Monitor weather conditions Stay tuned to TV/radio Take shelter! Thunderstorm, Fire Weather, Severe Weather OUTLOOKS H o u r s Detailed Mesoscale DISCUSSIONS M i n SVR/TOR WATCHES u t e WARN s SPC Products Local NWS Products (WFO) SPC Strengths SPECIALIZED FOCUS Forecasters deal ONLY with Mesoscale Hazardous Weather 24 Hours a Day, 365 Days a Year, Entire Continental U.S. COMMITMENT Maintain Continuous Weather Watch Training, Proficiency Checks, Certification EXPERTISE Internationally recognized as Experts Actively Pursue Improvements in Forecasting Visit K. Dewey, High Plains Regional Climate Center 02/02/04 6