An isolated severe thunderstorm moved north through the Detroit River.
Every event with a place to put it. Tap one for its entry below.
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 episode as NWS DTX wrote it up.
An isolated severe thunderstorm moved north through the Detroit River.
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 Aug 17, 11:45 AM EST, 1 hour 27 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 1245 PM EDT MON AUG 17 2009 .AVIATION... LOW LEVEL MOISTURE AXIS WILL CONTINUE TO GRADUALLY ADVANCE EAST INTO SOUTHEAST MICHIGAN THROUGH TONIGHT...TRANSLATING TO NUMEROUS SHOWERS AND EMBEDDED THUNDERSTORMS TRACKING THROUGH THE REGION. AS THE DEEPER MOISTURE BECOMES FURTHER ENTRENCHED...AT LEAST MVFR CEILINGS/VSBYS ARE EXPECTED TO TAKE HOLD TONIGHT...WITH A CHANCE OF IFR CEILINGS/VSBYS LATE TONIGHT...DEPENDENT ON COVERAGE OF ACTIVITY. MATURE MID LEVEL DRY SLOW WILL WORK INTO LOWER MICHIGAN TOMORROW MORNING...WITH LOW LEVEL WINDS VEERING TO A MORE WESTERLY DIRECTION DRYING THE LOW LEVELS OUT BY AFTERNOON. && .PREV DISCUSSION...ISSUED 448 AM EDT MON AUG 17 2009 SHORT TERM...TODAY DEEP/MOIST SOUTHWEST FLOW NOW ENTRENCHED ACROSS SOUTHEAST LOWER MI EARLY THIS MORNING. THIS IN CONJUNCTION WITH WEAK LOW LEVEL CONVERGENCE ALONG A PRE-FRONTAL TROUGH AND ASCENT WITHIN A WEAK UPPER LEVEL SHORTWAVE SUSTAINING AN AXIS OF ISOLATED/SCATTERED SHOWERS WITH EMBEDDED SLIGHTLY ELEVATED THUNDER ACROSS ROUGHLY THE NORTHWEST PORTION OF THE FORECAST AREA. THIS MOIST AXIS/CONVERGENCE ZONE WILL REMAIN FIRMLY OVERHEAD THROUGH THE DAY...PROVIDING A FOCUS FOR ADDITIONAL DEVELOPMENT BOTH JUST UPSTREAM AND ACROSS THE AREA. WILL CONTINUE TO MONITOR THE EVOLUTION/TRACK OF MCS ACTIVITY NOW STRETCHING FROM NORTHERN MO INTO NORTHWEST IL. ALTHOUGH WANING LOW LEVEL JET SUPPORT WILL LIKELY BRING A DIMINISHING TREND TO THIS ACTIVITY BY MIDDAY...CERTAINLY CANNOT RULE OUT THE REMNANT COLD POOL/MCV SHIFTING INTO THE REGION FOR THE AFTERNOON HOURS. CONSIDERABLE CLOUD DEBRIS WILL CERTAINLY LIMIT THE INSOLATION POTENTIAL...LIKELY LEAVING RATHER MODEST INSTABILITY TO WORK WITH THROUGH PEAK HEATING /1-1.5 J/KG OF SBCAPE/. WINDS NOT OVERLY IMPRESSIVE EITHER...WITH THE STRONGEST MID/UPPER LEVEL WIND FIELD HOLDING TO THE WEST AND KEEPING LOCAL BULK SHEAR VALUES BELOW 25 KNOTS. THIS SETUP FAVORS MORE LOOSELY ORGANIZED STORM STRUCTURES CONTAINING GUSTY WINDS. HEAVY RAINFALL WILL BE MORE OF A CONCERN GIVEN PW VALUES APPROACHING 2.0 INCHES...A STATIONARY MOISTURE FLUX AREA AND WEAK STEERING FLOW. GIVEN MORE LIMITED SOLAR HEATING TODAY...WILL SEE TEMPERATURES HOLD SEVERAL DEGREES BELOW READINGS FROM THIS PAST WEEKEND. THE POSITION OF THE PRIMARY MOISTURE AXIS/THICKER CLOUD FIELD WOULD FAVOR SLIGHTLY BETTER HEATING POTENTIAL ACROSS THE SOUTHEAST COUNTIES. THEREFORE WILL CONTINUE TO DEPICT A TEMPERATURE GRADIENT RANGING FROM MID 80S IN THE SOUTHEAST TO AROUND 80 IN THE NORTHERN SAGINAW VALLEY/THUMB REGION. LONG TERM...TONIGHT THROUGH SUNDAY TONIGHT THROUGH TUESDAY: COMPLEX PATTERN CURRENTLY OVER THE NORTHERN GREAT LAKES WILL CONTINUE TO AFFECT THE WEATHER ACROSS SOUTHEAST MICHIGAN. UPPER LOW SPINNING NEAR THE WESTERN ONTARIO BORDER WILL MOVE SLOWLY EAST ACROSS ONTARIO THROUGH TUESDAY. AREA OF SURFACE LOW PRESSURE AHEAD OF THIS FEATURE (CURRENTLY OVER MANITOBA) HAS ALREADY BEGUN TO MERGE WITH ANOTHER AREA OF SURFACE LOW PRESSURE OVER CENTRAL ONTARIO. MODELS SHOW BOTH OF THESE SURFACE FEATURES WILL CONTINUE TO DRIFT SLOWLY NORTHEAST UNTIL THEY CONSOLIDATE OVER THE ONTARIO/QUEBEC BORDER BY TUESDAY EVENING. ON THE THERMAL SIDE OF THINGS...ACTIVE LOW-LEVEL BAROCLINIC ZONE DRAPED FROM EASTERN ONTARIO TO WESTERN MICHIGAN TO IOWA/MISSOURI (AN OLD BOUNDARY EXTENDING OUT OF THE OCCLUDED SYSTEM OVER CENTRAL ONTARIO) WILL GET KICKED VERY SLOWLY EAST ACROSS EASTERN MICHIGAN TONIGHT THROUGH TUESDAY AS THE SECOND AREA OF LOW PRESSURE AND ASSOCIATED COLD FRONT BEGIN TO PUSH ACROSS THE WESTERN GREAT LAKES. PERIODS OF SHOWERS AND THUNDERSTORMS ARE EXPECTED TO OCCUR BEFORE COLD FRONTAL PASSAGE TUESDAY EVENING. HAVE CARRIED LIKELY POPS THROUGH THIS PERIOD AS WEAK DIFFLUENCE AND LOW-LEVEL JET AXIS AID CONVECTIVE DEVELOPMENT ALONG THE OLD BOUNDARY AND AHEAD OF THE COLD FRONT AND PREFRONTAL TROUGH. CURRENT WATER VAPOR IMAGERY AND 00Z RAOBS SHOW A GOOD PLUME OF MOISTURE LIFTING UP INTO LOWER MICHIGAN...WITH PW VALUES EXPECTED TO APPROACH 1.75 INCHES BY TONIGHT. GIVEN HIGH MOISTURE CONTENT...SLOW STORM MOVEMENT...AND POTENTIAL FOR CONTINUAL REDEVELOPMENT AND TRAVEL ALONG THE REMNANT BOUNDARY IN PLACE...HEAVY RAINFALL WILL CONTINUE TO BE A CONCERN OVERNIGHT AND INTO TUESDAY. LIMITED SURFACE HEATING SHOULD HELP MITIGATE ANY SEVERE THREAT. AREA SHOULD DRY OUT BEHIND THE PASSAGE OF THE COLD FRONT TUESDAY NIGHT...ESPECIALLY AS SURFACE RIDGING EXTENDS INTO LOWER MICHIGAN FROM THE SOUTH. WEDNESDAY THROUGH SUNDAY: STRING OF UPPER SHORTWAVES OVER THE GULF OF ALASKA WILL DIVE ACROSS WESTERN CANADA AND DOWN INTO THE NORTHERN PLAINS BY TUESDAY NIGHT. THIS WILL REINFORCE LONGWAVE TROUGHING FROM THE PLAINS TO NEW ENGLAND THROUGH MIDWEEK. MODELS CONTINUE TO DIFFER WITH HOW LONG THE UPPER TROUGH WILL LINGER OVER THE GREAT LAKES AFTER IT CONSOLIDATES AND SHARPENS...AND WILL CONTINUE TO FAVOR THE SLOWER MODEL SOLUTIONS DUE TO HIGH DEGREE OF AMPLIFICATION OF BOTH UPSTREAM AND DOWNSTREAM RIDGES. THIS WOULD KEEP THE UPPER TROUGH IN THE VICINITY OF MICHIGAN INTO SATURDAY. AT THE SURFACE...RIDGING ON WEDNESDAY WILL GET PUSHED EAST AS RETURN FLOW SETS UP OVER WESTERN AND FAR SOUTHERN MICHIGAN. MODELS HAVE BEEN IN FAIRLY GOOD AGREEMENT WITH THE SLOW PROGRESSION OF A STRONG SURFACE LOW ACROSS THE GREAT LAKES THURSDAY THROUGH FRIDAY NIGHT. THIS WILL BRING ANOTHER POTENTIALLY ACTIVE PERIOD OF WEATHER TO THE REGION BEGINNING WEDNESDAY NIGHT. HAVE OPTED TO KEEP POPS VERY LOW AND LIMITED TO THE FAR SOUTHERN CWA WEDNESDAY AFTERNOON AS RETURN FLOW LOOKS TO INITIALLY PROGRESS VERY SLOWLY AND ISENTROPIC ASCENT LOOKS VERY WEAK AND NOT TOO MOIST EARLY ON. TRANSPORT OF WARMTH AND MOISTURE LOOK TO INCREASE WEDNESDAY NIGHT THROUGH THURSDAY NIGHT AS A STRONG LOW LEVEL JET NOSES UP INTO THE SOUTHERN GREAT LAKES. GIVEN DEGREE OF UPPER DIFFLUENCE SHOWN ON BOTH THE GFS AND EURO AS THE WARM FRONT LIFTS THROUGH SOUTHERN MICHIGAN...FEEL LIKELY POPS ARE WARRANTED. EURO AND GFS CONTINUE TO HINT A SURFACE WAVE MAY RIDE ALONG THE WARM FRONT AS IT LIFTS INTO CENTRAL MICHIGAN...AND WILL HAVE TO KEEP AN EYE ON THIS SCENARIO AS IT COULD ADD EVEN MORE UPRIGHT LIFT. LIKELY POPS CONTINUE INTO FRIDAY AS BEST MODEL CONSENSUS (EURO/GEM) BRINGS THE COLD FRONT ACROSS LOWER MICHIGAN FRIDAY DURING THE LATE AFTERNOON AND INTO THE FIRST HALF OF THE NIGHT. PREVIOUS SOLUTIONS ALL SEEMED TO MOVE THE UPPER TROUGH TO OUR EAST BY SATURDAY EVENING...HOWEVER THE 00Z RUN OF THE EURO NOW LINGERS IT OVERHEAD INTO SUNDAY. WILL CONTINUE TO HOLD ONTO CHANCE POPS ON SATURDAY AND KEEP A DRY SUNDAY...BUT THIS COULD ALL CHANGE AS MODEL SOLUTIONS CONVERGE. MARINE... NUMEROUS SHOWERS AND THUNDERSTORMS WILL DEVELOP THROUGH TONIGHT WITHIN A VERY MOIST PRE-FRONTAL ENVIRONMENT. THIS ACTIVITY WILL CONTINUE INTO TUESDAY AS A FRONTAL BOUNDARY DROPS THROUGH. HEAVY RAINFALL WILL BE POSSIBLE AT TIMES. OUTSIDE OF THUNDERSTORMS... WIND AND WAVE CONDITIONS WILL GENERALLY REMAIN FAVORABLE DURING THIS TIME. WEAK HIGH PRESSURE WILL BRING FAVORABLE BOATING CONDITIONS ON WEDNESDAY. A STRONGER STORM SYSTEM ENTERING THE UPPER MISSISSIPPI VALLEY WILL LEAD TO INCREASING SOUTHERLY WINDS AND THE NEXT CHANCE OF SHOWERS AND THUNDERSTORMS WEDNESDAY NIGHT AND THURSDAY. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MI WATERS OF LAKE ERIE...NONE. && AVIATION.....SF SHORT TERM...MR LONG TERM....HLO MARINE.......MR YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 431 AM EDT MON AUG 17 2009 MIZ047>049-053>055-060>063-068>070-075-076-082-083-180845- MIDLAND-BAY-HURON-SAGINAW-TUSCOLA-SANILAC-SHIAWASSEE-GENESEE-LAPEER- ST. CLAIR-LIVINGSTON-OAKLAND-MACOMB-WASHTENAW-WAYNE-LENAWEE-MONROE- 431 AM EDT MON AUG 17 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST MICHIGAN. .DAY ONE...TODAY AND TONIGHT NUMEROUS SHOWERS AND THUNDERSTORMS WILL DEVELOP THROUGH TONIGHT WITHIN A VERY MOIST ENVIRONMENT. THUNDERSTORMS THAT DEVELOP WILL BE CAPABLE OF PRODUCING LOCALLY HEAVY RAIN...SMALL HAIL TO ONE HALF INCH IN DIAMTER...AND WIND GUSTS TO 45 MPH. AN ISOLATED STORM OR TWO MAY APPROACH SEVERE LIMITS THIS AFTERNOON AND EVENING. STORM MOTION WILL BE TO THE NORTHEAST AT 20 MPH. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY THERE IS A CHANCE OF THUNDERSTORMS TUESDAY AS A WEAK FRONTAL BOUNDARY PUSHES ACROSS LOWER MICHIGAN. HEAVY RAINFALL WILL REMAIN POSSIBLE DURING THIS TIMEFRAME. AFTER A PERIOD OF DRY WEATHER ON TUESDAY NIGHT AND WEDNESDAY...THUNDERSTORMS WILL AGAIN BE POSSIBLE WEDNESDAY NIGHT THROUGH SATURDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT. LCZ422-423-460-LEZ444-LHZ361>363-421-422-441>443-462>464-180845- ST. CLAIR RIVER-DETROIT RIVER-LAKE ST. CLAIR- MICHIGAN WATERS OF LAKE ERIE FROM DETROIT RIVER TO NORTH CAPE MI- LAKE HURON FROM 5NM EAST OF MACKINAC BRIDGE TO PRESQUE ISLE LT BEYOND 5 NM OFF SHORE- LAKE HURON FROM PRESQUE ISLE LIGHT TO STURGEON POINT MI BEYOND 5NM OFF SHORE- LAKE HURON FROM STURGEON POINT TO ALABASTER MI BEYOND 5NM OFF SHORE- OUTER SAGINAW BAY SW OF ALABASTER TO PORT AUSTIN MI TO INNER SAGINAW BAY-INNER SAGINAW BAY SW OF POINT AU GRES TO BAY PORT MI- PORT AUSTIN TO HARBOR BEACH MI-HARBOR BEACH TO PORT SANILAC MI- PORT SANILAC TO PORT HURON MI- LAKE HURON FROM PORT AUSTIN TO HARBOR BEACH BEYOND 5NM OFF SHORE- LAKE HURON FROM HARBOR BEACH TO PORT SANILAC BEYOND 5NM OFF SHORE- LAKE HURON FROM PORT SANILAC TO PORT HURON BEYOND 5NM OFF SHORE- 431 AM EDT MON AUG 17 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF LAKE ERIE...LAKE HURON AND LAKE ST CLAIR. .DAY ONE...TODAY AND TONIGHT NUMEROUS SHOWERS AND THUNDERSTORMS WILL DEVELOP THROUGH TONIGHT WITHIN A VERY MOIST ENVIRONMENT. THUNDERSTORMS THAT DEVELOP WILL BE CAPABLE OF PRODUCING LOCALLY HEAVY RAIN...SMALL HAIL TO ONE HALF INCH IN DIAMTER...AND WIND GUSTS TO 45 MPH. AN ISOLATED STORM OR TWO MAY APPROACH SEVERE LIMITS THIS AFTERNOON AND EVENING. STORM MOTION WILL BE TO THE NORTHEAST AT 20 MPH. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY THERE IS A CHANCE OF THUNDERSTORMS TUESDAY AS A WEAK FRONTAL BOUNDARY PUSHES ACROSS LOWER MICHIGAN. HEAVY RAINFALL WILL REMAIN POSSIBLE DURING THIS TIMEFRAME. AFTER A PERIOD OF DRY WEATHER ON TUESDAY NIGHT AND WEDNESDAY...THUNDERSTORMS WILL AGAIN BE POSSIBLE WEDNESDAY NIGHT THROUGH SATURDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT. MR YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 204 PM EDT MON AUG 17 2009 MIZ076-083-171830- MONROE-WAYNE- 204 PM EDT MON AUG 17 2009 ...SIGNIFICANT WEATHER ADVISORY... AT 200 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM 6 MILES SOUTH OF FLAT ROCK...MOVING NORTH AT 25 MPH. WINDS GREATER THAN 30 MPH...OCCASIONAL CLOUD TO GROUND LIGHTNING...HEAVY DOWNPOURS...ARE EXPECTED WITH THIS STORM. * THE THUNDERSTORM WILL BE NEAR... FLAT ROCK AROUND 215 PM EDT... TRENTON AROUND 220 PM EDT... WYANDOTTE AROUND 230 PM EDT... GUSTY WINDS MAY CAUSE SMALL OBJECTS SUCH AS TRASH BINS TO BLOW AROUND. STAY AWAY FROM HIGH OBJECTS OUTDOORS SUCH AS TREES. SEEK SHELTER IN A STURDY STRUCTURE UNTIL THIS STORM HAS PASSED. SF
The Detroit radar (KDTX), 71 km away, was scanning. The volume nearest the first event began at 18:13 UTC.
1 thunderstorm wind. Local standard time, as filed.
A couple dozen trees were blown down, some of which landed on a few homes.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Michigan in 2009Every state in 2009This day in weather historyWarnings in Michigan, August 2009
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: 187949.