SPC Mission Statement SPC exists to protect life and property of the The NOAA/NWS American people through the issuance of timely, accurate watch and forecast products dealing with Storm Prediction Center tornadoes and other mesoscale hazardous weather. Adapted from a presentation to UNCA atmospheric science students by David Imy
Salt Lake City, Utah Photo: KTVX News 4
ATMS 179 – Fall 2008
Tornado in Miami, FL What is SPC’s Responsibility? Photo: Miami Herald ¿Forecast severe storms across the 48 contiguous states ¿ Tornadoes ¿ Hail ¾” diameter or larger ¿ Thunderstorm winds > 57.5 mph ¿Also monitor for: ¿ Heavy rain ¿ Winter Weather ¿ Conditions favorable for wildfire initiation
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
SPC Products More SPC Products ¿Mesoscale Discussions ¿Severe Weather Outlooks ¿Watch Status Messages ¿ Day 1 (today) ¿Severe Weather Statistics ¿ Day 2 (tomorrow) ¿ ¿ Day 3 (day after tomorrow) Fire Weather Outlooks ¿ Day 4–8 ¿ Day 1 (today) ¿ Day 2 (tomorrow) ¿Severe Weather Watches ¿ Day 3–8 ¿ Tornado ¿ Severe Thunderstorm
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
1 Severe Weather Outlooks Categorical Outlooks ¿ Slight (SLGT) ¿Categorical ¿ 5-20 Severe Hail Events ¿ Slight ¿ 5-20 Severe Wind Events ¿ Moderate ¿ 2-5 Tornadoes ¿ High ¿ Moderate (MDT) ¿ 20-50 Severe Hail Events ¿ 20-50 Severe Wind Events ¿Probabilistic ¿ 6-19 Tornadoes ¿ Tornadoes ¿ High ¿ Hail ¿ > 19 Tornadoes with 2+ potentially producing EF3–EF5 ¿ Convective damage Winds ¿ Derecho - producing extreme wind damage (> 50 reports)
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
Probability Outlooks Feb 16, 2006 Categorical Outlook ¿Provide the threat of severe weather occurring within 25 miles of any point within the area ¿ Tornadoes ¿ Large hail ¿ Severe convective winds ¿Also provide threat for extreme severe
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
Feb 16, 2006 Hail Probabilities Feb 16, 2006 Wind Probabilities
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
2 Feb 16, 2006 Tornado Probabilities Probability Outlook Intervals a Tornadoes a 2%, 5%, 10%,15%, 30%, 45%, 60% a Hail a 5%, 15%, 30%, 45%, 60% a Convective Wind a 5%, 15%, 30%, 45%,60% a Extreme - at least a 10% chance of: a Tornadoes F2+ damage a Hail 2.0+ inches diameter a Winds 65+ kt
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
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.
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
3 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!
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
ZCZC MKCSEL9 ALL 250500;365,0980 321,0985 321,1013 365,1004; “Particularly Dangerous Situation” WWUS9 KMKC 242144 MKC WW 242144 Watches OKZ000-TXZ000-250500- URGENT - IMMEDIATE BROADCAST REQUESTED ¿ PDS Tornado watches TORNADO WATCH NUMBER 49 STORM PREDICTION CENTER NORMAN OK ¿ Multiple strong or violent 344 PM CST THU FEB 24 2000 (EF2–EF5 damage) events THE STORM PREDICTION CENTER HAS ISSUED A ¿ PDS Severe TORNADO WATCH FOR PORTIONS OF Thunderstorm Watches WESTERN OKLAHOMA ¿ Long-lived wind systems NORTHWESTERN TEXAS with possible widespread EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 430 PM UNTIL damage (derechoes) 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.
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
Severe Thunderstorm Watch Watch By County
¿Recently moved from “parallelogram-based” ¿ Organized severe storms ¿ Supercells to “county-based” watches ¿ Squall lines ¿ Multicell complexes ¿ Extreme severe storms ¿ Wind gusts > 64 kt (73 mph) ¿ Damage to permanent structures ¿ Hail > 2.0 inches diameter
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
4 Watch Probabilities Mesoscale Discussions Severe Thunderstorm Watch 688 Probability Table
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 Tornadoes STRONG AND A CIRRUS SHIELD OVER THE TX PANHANDLE/ NW TX/ Probability of 2 or more tornadoes Low (10%) WRN OK SHOULD LIMIT ADDITIONAL SURFACE HEATING... BUT VISIBLE /RADAR IMAGERY HAS SHOWN THE FIRST ATTEMPTS AT Probability of 1 or more strong (F2-F4) tornadoes Low (<5%) TCU OVER FAR NW TX AS OF 20Z WITHIN A BREAK IN THE CIRRUS. Wind MID LEVEL FLOW AND VERTICAL SHEAR WILL INCREASE OVER NW Probability of 10 or more severe wind events Mod (60%) TX AND WRN OK THROUGH LATE AFTERNOON... WITH AN INCREASING THREAT OF SUPERCELLS NEAR THE DRYLINE FROM Probability of 1 or more wind event > 65 knots Low (10%) 00 to 03Z. THIS AREA IS BEING MONITORED FOR A POSSIBLE Hail TORNADO WATCH. Probability of 10 or more severe hail events Low (10%) ..THOMPSON.. 05/03/99 Probability of 1 or more hailstones >2 inches Low (<5%) ...PLEASE SEE WWW.SPC.NOAA.GOV/ FOR GRAPHIC PRODUCT... Combined Severe Hail/Wind NNNN Probability of 6 or more combined severe wind/hail events Mod (60%)
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
Mesoscale Discussions: Greensburg, KS EF5 Tornado Technical discussions of developing mesoscale features and May 4, 2007 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 MESOSCALE DISCUSSION 1902 NWS STORM PREDICTION snow, blizzards CENTER NORMAN OK 0212 PM CDT SAT JUL 30 2005 ¿ Heavy rainfall AREAS AFFECTED...INTERIOR SRN CA AND FAR SRN NV CONCERNING...SEVERE THUNDERSTORM ¿ Severe thunderstorm potential/Outlook POTENTIAL...HEAVY RAINFALL upgrade VALID 301912Z - 302145Z ¿ 1-2 hours prior to a watch ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE THIS ¿ 2-3 hour cycle during watch AFTERNOON INTO THIS EVENING ACROSS THE IMPERIAL VALLEY OF CA AND THE ADJACENT MTNS. LOCALLY HEAVY ¿ Change in convective outlook category RAINFALL WILL ALSO OCCUR WITH ANTICIPATED SLOW MOTION OF INDIVIDUAL CELLS. SURFACE MOISTURE ¿ Thunderstorms not expected to AXIS...WITH DEWPOINTS IN THE LOW TO MID 70S...EXTENDS NNNWD FROM GULF OF CA INTO THE IMPERIAL VALLEY OF become severe CA AND ERN SLOPES OF THE COASTAL RANGES. LOW- Photo: Melanie Metz LEVEL MOISTURE CONTINUES TO INCREASE NWD INTO THE
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
Greensburg, KS EF5 Tornado Damage Greensburg, KS EF5 Tornado Damage May 4, 2007 May 4, 2007
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
5 Fire Weather Outlook Day 1 Fire Weather Outlook
¿ Three Types of Areas ¿ Critical ¿ Extremely Critical ¿ Dry Thunderstorm
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
The Watch/Warning Funnel Concept SPC Strengths
D Thunderstorm, Fire Weather, a y Severe Weather OUTLOOKS ¿ SPECIALIZED FOCUS s ¿ Forecasters deal ONLY with Mesoscale Hazardous Weather Check plan of action ¿ 24 Hours a Day, 365 Days a Year, Entire Continental U.S. Make sure shelter is ready Detailed Mesoscale ¿ COMMITMENT H DISCUSSIONS o SPC ¿ Maintain Continuous Weather Watch u ¿ r Products Training, Proficiency Checks, “Certification” s SVR/TOR ¿ EXPERTISE WATCHES ¿ Internationally recognized as Experts Monitor weather conditions M ¿ Stay tuned to TV/radio i Actively Pursue Improvements in Forecasting n u WARN t Local NWS e Products (WFO) Take shelter! s Products (WFO)
ATMS 179 – Fall 2008 ATMS 179 – Fall 2008
Visit www.spc.noaa.gov
© K. Dewey, High Plains Regional Climate Center
02/02/04
ATMS 179 – Fall 2008
6