2 marine thunderstorm wind, as filed by the National Weather Service.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Detroit, MI wrote its last area forecast discussion before the first event at Jul 21, 12:30 PM EST, 5 hours 58 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 130 PM EDT WED JUL 21 2004 .DISCUSSION... GOOD SURFACE DEW POINT POOLING ACROSS FAR NORTHERN CWA NEAR WARM FRONT BOUNDARY WITH CAPES ALREADY IN EXCESS OF 3000J/KG. CONVECTION INITIALLY PULSING IN NATURE...WHICH IS A REFLECTION OF LACK OF DYNAMICS AND WARMING 700 MB TEMPERATURES. DEGREE OF INSTABILITY AND PWAT VALUES STILL CONCERNING THOUGH. MAIN MCS OVER SOUTHERN WISCONSIN ALSO STRUGGLING A LITTLE WITH SUBSTANTIAL CLOUD TOP WARMING THROUGH THE MORNING. MCS IS ALSO TURNING A LITTLE MORE SOUTHEAST AS SUGGESTED BY THE FORWARD PROP CORFIDI VECTORS. THIS MAY PLACE MAIN OUTFLOW BOUNDARY ACROSS THE NORTHERN OHIO VALLEY...RATHER THAN TRACKING EAST ACROSS LOWER MICHIGAN. HOWEVER MCV WORKING ACROSS LAKE MICHIGAN MAY BE STRONG ENOUGH TO PRODUCE SOME ORGANIZATION TO CONVECTION ACROSS THE NORTHERN PORTION OF CWA. MCV TRACKING EAST ACROSS IOWA WILL ALSO ORGANIZE POTENTIAL SEVERE CONVECTION THIS EVENING...WITH 03Z-09Z WINDOW. 10KM TAQ RUC HAS A GOOD HANDLE ON CONVECTION CURRENTLY FIRING OVER THE SAGINAW VALLEY AND TIP OF THUMB...WITH NO REAL ORGANIZATION THROUGH THE AFTERNOON HOURS...THEN BAND OF CONVECTION MOVING THROUGH CWA BETWEEN 03-09Z. GFS/ETA IN GOOD AGREEMENT THROUGH 84 HOURS OVER THE GREAT LAKES...WITH FROPA ACROSS THE NORTH HALF OF CWA BY NOON THURSDAY...THEN SWEEPING SOUTH INTO OHIO VALLEY BY 20Z. FIRST CONCERN THOUGH WILL BE CONVECTION AND HEAVY RAIN OVERNIGHT. BLUE RIVER PROFILER ALREADY SHOWING 45KT 850 MB WINDS...AND TAKING AIM ON SOUTHEAST LOWER THIS EVENING...PWAT INCREASING TO AROUND 2 INCHES...PRE FRONTAL TROF AND MCV BOTH WORKING ACROSS SOUTHERN LOWER BETWEEN 03-09Z. WILL ALSO SEE A GOOD INCREASE IN 0-3KM SHEAR VECTOR AS MID LEVEL WINDS INCREASE. MAIN THREAT WILL BE DAMAGING WINDS...HAIL SHOULD NOT BE MUCH OF A THREAT WITH WET BULB ZERO INCREASING TO GREATER THAN 13K. ONLY THING LACKING WILL BE UPPER JET SUPPORT...WHICH WILL HOLD OFF UNTIL THURSDAY AFTERNOON. WILL CONTINUE WITH CHC POPS THURSDAY AFTERNOON...ESPECIALLY SOUTH. GOOD COLD ADVECTION TO HOLD OFF UNTIL MID AFTERNOON AND RIGHT REAR QUAD OF 300 MB JET SETTING UP OVER SOUTHERN CWA AFTER 18Z. NEGATIVE 850 MB THETA-E ADVECTION BY 18Z SHOULD CUT OF ANY HOPE OF CONVECTION ACROSS THE NORTHERN CWA...THUS WILL MENTION A SLIGHT CHANCE..20 POP...ACROSS THE NORTHERN CWA THROUGH 18Z...THEN 40 POPS SOUTH. MODELS CONSISTENT WITH IMPRESSIVE COLD ADVECTION FOR LATE JULY FOR THURSDAY NIGHT INTO FRIDAY...WITH 850 MB TEMPS DROPPING TO +7C BY FRIDAY AFTERNOON. GUIDANCE TEMPERATURES LOOK TO WARM FOR THURSDAY AFTERNOON AND FRIDAY MORNING...WILL CUT BACK ABOUT 5 DEGREES. && .DTX WATCHES/WARNINGS/ADVISORIES...NONE. && GSS EXPERIMENTAL GRAPHICAL FORECASTS ARE AVAILABLE ONLINE AT HTTP://WWW.CRH.NOAA.GOV/DTX (ALL LOWER CASE)
HAZARDOUS WEATHER OUTLOOK...CORRECTED NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 1245 PM EDT WED JUL 21 2004 MIZ047>049-053>055-060>063-068>070-075-076-082-083-221000- BAY-GENESEE-HURON-LAPEER-LENAWEE-LIVINGSTON-MACOMB-MIDLAND-MONROE- OAKLAND-SAGINAW-SANILAC-SHIAWASSEE-ST. CLAIR-TUSCOLA-WASHTENAW-WAYNE- 1250 PM EDT WED JUL 21 2004 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST LOWER MICHIGAN .DAY ONE...THIS AFTERNOON AND TONIGHT THERE IS A MODERATE RISK FOR SEVERE WEATHER THIS AFTERNOON AND TONIGHT ACROSS ALL OF SOUTHEAST LOWER MICHIGAN. A VERY MOIST AND UNSTABLE AIRMASS IS BUILDING ACROSS THE AREA. SCATTERED THUNDERSTORMS WILL DEVELOP ACROSS THE SAGINAW VALLEY AND THUMB REGION THIS AFTERNOON IN THE VICINITY OF A WEAK FRONTAL ZONE AIDED BY LAKE BREEZES. THESE STORMS WOULD MOVE TO THE NORTHEAST AT 20 MPH. MAIN THREAT WOULD BE WIND GUSTS TO 60 MPH AND HEAVY RAINFALL. THE ATMOSPHERE IS RELATIVELY CAPPED ACROSS THE REST OF SOUTHEASTERN LOWER MICHIGAN WHICH WILL HELP SUPPRESS THUNDERSTORM DEVELOPMENT THROUGH MOST OF THE AFTERNOON BEFORE A FEW STORMS DEVELOP BY LATE AFTERNOON. SOME MAY REACH SEVERE LIMITS WITH WIND GUSTS TO 60 MPH AND HEAVY RAINFALL. SEVERE THUNDERSTORM CHANCES INCREASE THIS EVENING AND EARLY NIGHT ACROSS ALL OF SOUTHEAST LOWER MICHIGAN AS A PREFRONTAL TROF SWINGS EAST ACROSS SOUTHEASTERN LOWER MICHIGAN BETWEEN 8 PM AND 2 AM. THE STORMS WOULD MOVE EAST AT 30 MPH. THE MAIN THREAT WOULD BE WIND GUSTS TO 70 MPH AND VERY HEAVY RAINFALL WHICH MAY CAUSE URBAN AND SMALL STREAM FLOODING. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY THUNDERSTORMS WILL BE POSSIBLE AGAIN THURSDAY AFTERNOON ACROSS THE ENTIRE REGION...WITH THIS ACTIVITY POSSIBLY LINGERING INTO THURSDAY NIGHT ALONG AND SOUTH OF I 69. A STRONG COLD FRONT WILL MOVE THROUGH THE AREA...BRINGING THIS CHANCE OF THUNDERSTORMS. ALTHOUGH THE SETUP IS NOT EXPECTED TO BE QUITE AS FAVORABLE AS TODAY...THE POTENTIAL FOR A FEW SEVERE THUNDERSTORMS WILL STILL EXIST. .SPOTTER INFORMATION STATEMENT... DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGER IMMEDIATELY. SPOTTER ACTIVATION WILL LIKELY BE NEEDED LATE THIS AFTERNOON INTO TONIGHT. COSTELLO HTTP://WWW.CRH.NOAA.GOV/DTX (ALL LOWER CASE)
2 marine thunderstorm wind. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Lake Huron in 2004Every state in 2004This day in weather history
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 5413811, 5414025.