Two localized severe cells developed over the thumb region.
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.
Two localized severe cells developed over the thumb region.
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 16, 9:09 AM EST, 3 hours 21 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 1009 AM EDT SUN AUG 16 2009 .UPDATE... A FEW SHOWERS AND THUNDERSTORMS HAVE ALREADY DEVELOPED THIS MORNING FROM SOUTHWEST LOWER INTO THE SAGINAW VALLEY. THE 12Z DTX SOUNDING IS VERY DRY ABOVE 750MB BUT THIS AIRMASS WILL SOON BE REPLACED BY A MUCH JUICIER ONE. BOTH THE LINCOLN AND WILMINGTON SOUNDINGS HAVE SIGNIFICANTLY MORE MOISTURE WITH PW VALUES RANGING FROM .75 TO 1.00 INCH HIGHER THAN OURS(0.85 INCH). THE DEEPER MOISTURE TO THE SOUTHWEST WAS ANTICIPATED BUT THE MOISTURE THROUGH 650MB ON THE ILN SOUNDING WAS A BIT MORE SURPRISING. ILN IS ALSO 3C COOLER AT 700MB THAN WE WERE WHICH WILL ADVECT NORTH OVER THE CWA THIS AFTERNOON AND HELP TO ERODE THE CAP. GIVEN THE ISOLATED THUNDERSTORMS THAT HAVE ALREADY BEEN ABLE TO MATERIALIZE THIS MORNING AND THE INCREASINGLY MOIST AIRMASS APPROACHING FROM THE SOUTH...HAVE ADDED A CHANCE OF THUNDERSTORMS TO THE FORECAST...MAINLY AFTER 3 PM. THIS IS ALSO SUPPORTED BY THE RUC13...SPC 4KM WRF AND 06Z NAM WHICH SHOW SCATTERED THUNDERSTORMS DEVELOPING. DEWPOINTS ARE STARTING OFF IN THE MID 60S ACROSS EASTERN LOWER MICHIGAN AND NORTHERN OHIO WHILE ALREADY IN THE UPPER 60S/NEAR 70 IN SOUTHWEST LOWER AND INDIANA. MODIFYING THE 12Z DTX SOUNDING WITH DEWPOINTS OF 65-68 DEGREES YIELDS AFTERNOON CAPES OF 1500-2500 J/KG. HIGH FREEZING LEVELS NEAR 15000 FEET AND MODEST SHEAR WILL BE A LIMITING FACTOR FOR STRONG STORMS THIS AFTERNOON. 850-300MB WIND SPEEDS ARE ONLY AROUND 20 KNOTS SO CHANCES OF SEVERE WEATHER WILL BE LIMITED TO AN ISOLATED PULSE TYPE EVENT AS STORMS COLLAPSE. HEAVY RAIN WILL BE POSSIBLE WITH ANY THUNDERSTORM THAT DEVELOPS WITH STORM MOTION TO THE NORTHEAST AT ABOUT 15 MPH. && .PREV DISCUSSION...ISSUED 754 AM EDT SUN AUG 16 2009 AVIATION... PATCHY SHALLOW MVFR FOG EARLY THIS MORNING WILL MIX OVER THE NEXT 1-2 HOURS. OTHERWISE VFR CONDITIONS WILL HOLD THROUGH THE DAY. SCT DIURNAL CU WILL EVOLVE BY MIDDAY WITH CIGS AOA 5K FT WHILE ADDITIONAL HIGHER CLOUD DEBRIS BEGINS TO SPILL EASTWARD DOWNSTREAM OF CONVECTION ACROSS THE MISS VALLEY. A TIGHTER PRESSURE GRADIENT AND GOOD MIXING WILL BRING A FEW SOUTHERLY GUSTS OF 15-20 KNOTS FOR THE AFTERNOON. CANNOT RULE OUT AN ISOLATED SHOWER AT MBS INTO THIS EVENING AS MOISTURE DEEPENS WELL IN ADVANCE OF A COLD FRONT...BUT COVERAGE LOOKS TO REMAIN SPOTTY ENOUGH TO PRECLUDE A MENTION AT THIS TIME. MID/HIGH CLOUD COVER WILL THICKEN TONIGHT AS EARLIER UPSTREAM SHOWERS/THUNDERSTORM DEVELOPMENT BEGINS TO SHIFT EASTWARD. CONFIDENCE REMAINS ON THE LOW SIDE AS TO THE EXACT TRACK OF THIS PRECIPITATION OVERNIGHT. BEST CHANCES WILL BE TOWARD THE NORTH AND WILL INTRODUCE RAIN IN VFR CONDITIONS AT MBS. COVERAGE LOOKS TO BECOME MORE WIDESPREAD INTO MONDAY AS PRECIPITATION FOCUSES ALONG THE COLD FRONT THAT WILL SLOWLY DROP THROUGH THE AREA. PREV DISCUSSION...ISSUED 418 AM EDT SUN AUG 16 2009 SHORT TERM...TODAY LITTLE CHANGE NOTED IN THE OVERALL SETUP FOR TODAY...AS THE REGION REMAINS ON THE NORTHWEST FRINGES OF UPPER RIDGING ELONGATED FROM THE GULF COAST THROUGH THE EASTERN SEABOARD. LOW LEVEL SOUTHERLY FLOW WILL INCREASE THROUGH THE DAY...SUSTAINING WEAK WARM AIR ADVECTION AND MOISTURE TRANSPORT. THIS WILL LEAD TO A 1-2C INCREASE IN THE THERMAL STRUCTURE UP THROUGH 850 MB BY THIS AFTERNOON. THIS WILL RESULT IN HIGHS REACHING THE UPPER 80S/AROUND 90 AREAWIDE. LATEST NAM GUIDANCE CONTINUES TO SHOW A MOIST BIAS WITHIN THE BOUNDARY LAYER BRINGING DEWPOINTS UP INTO THE LOWER 70S ACROSS A PORTION OF THE AREA BY LATE AFTERNOON. THIS LEADS TO A MORE FAVORABLE/UNSTABLE AIRMASS CAPABLE OF OVERCOMING THE MID LEVEL CAP AND GENERATING PRECIPITATION. UPSTREAM OBSERVATIONS STILL DO NOT SUPPORT THIS IDEA...SUGGESTING THE ADVECTION OF DEWPOINTS MORE IN THE MID 60S RANGE. THEREFORE...WILL KEEP DRY CONDITIONS THROUGH 00Z...WITH JUST ANOTHER ROUND OF DIURNAL CU FOR PEAK HEATING. LONG TERM...TONIGHT THROUGH SATURDAY UNSETTLED CONDITIONS LOOK TO DOMINATE THE EXTENDED PERIOD AS WE DEAL WITH THE SLOW PASSAGE OF TWO UPPER LEVEL LOW PRESSURE SYSTEMS ACROSS THE GREAT LAKES. THE FIRST SYSTEM WILL AFFECT US FROM TONIGHT INTO TUESDAY...WHILE THE SECOND SYSTEM WILL MOST LIKELY HAVE AN IMPACT LATE WEDNESDAY THROUGH EARLY SATURDAY. AFTER A PROLONGED STRETCH OF BEAUTIFUL SUMMER CONDITIONS...MORE ACTIVE WEATHER WILL BEGIN TO SPREAD BACK INTO SOUTHEAST MICHIGAN OVERNIGHT. THIS WILL OCCUR AS THE UPPER LEVEL LOW PRESSURE SYSTEM CURRENTLY OVER MONTANA/SASKATCHEWAN TRACKS EAST INTO THE UPPER MIDWEST AND BEGINS TO PUSH A SURFACE TROUGH ACROSS THE WESTERN GREAT LAKES. LATEST RUNS OF THE GFS/NAM/EURO SHOW A SLOW MOVING FRONTAL BOUNDARY PUSHING INTO CENTRAL MICHIGAN TONIGHT. THE PRESENCE OF THIS BAROCLINIC ZONE ALONG WITH FAVORABLE UPPER DIFFLUENCE AND THE LOW-LEVEL JET AXIS SHOULD ALLOW RAIN AND THUNDERSTORMS TO DEVELOP ACROSS THE TRI-CITIES AND THUMB REGIONS BY 8 AM TOMORROW MORNING...AND ACROSS THE REMAINDER OF SOUTHEAST MICHIGAN ON MONDAY. DO NOT ANTICIPATE A WIDESPREAD SEVERE THREAT GIVEN RELATIVELY WEAK UNIDIRECTIONAL WIND FIELDS BY 18Z MONDAY...HOWEVER MODEL CAPE VALUE AROUND 1500 J/KG BY 00Z TUESDAY COULD SUPPORT BRIEF STRONG UPDRAFTS. SURFACE TROUGH AXIS AND COLD FRONT LOOK TO SWEEP ACROSS LOWER MICHIGAN MONDAY NIGHT AND FOR THE FIRST HALF OF TUESDAY...WITH SHOWERS AND THUNDERSTORMS CONTINUING DURING THIS TIMEFRAME IN A VERY MOIST AND MODERATELY UNSTABLE ATMOSPHERE. HEAVY RAIN WILL BE A POSSIBILITY FROM LATE SUNDAY THROUGH FRONTAL PASSAGE ON TUESDAY AS MODEL PW VALUES APPROACH 2 INCHES AND STORM MOTION LOOKS LIMITED TO 25 KNOTS AT BEST. RIDGE OF HIGH PRESSURE WILL THEN BUILD INTO LOWER MICHIGAN LATE TUESDAY AND TUESDAY NIGHT AS THE FIRST UPPER LOW EXITS...HOWEVER THE GREAT LAKES WILL REMAIN ENTRENCHED WITHIN LONGWAVE TROUGHING AS ANOTHER UPPER WAVE DROPS DOWN INTO CENTRAL CANADA AND THE NORTHERN PLAINS. THERE ARE STILL SOME TIMING DIFFERENCES WITHIN THE MODELS SURROUNDING THIS SYSTEM...PARTICULARLY WITH HOW QUICKLY IT EXITS BY THE END OF THE WEEK. WILL CONTINUE TO SHOW A PREFERENCE FOR THE SLOWER EXIT SHOWN IN THE 00Z EURO/UKMET/GEM RUNS GIVEN THE AMPLITUDE OF BOTH THE UPSTREAM AND DOWNSTREAM UPPER RIDGES. THIS WILL ALLOW RETURN FLOW TO SET UP ON WEDNESDAY AS TUESDAYS COLD FRONT LIFTS BACK NORTHWARD AS A WARM FRONT. ALL MODELS REGARDLESS OF TIMING ARE HINTING THAT AT LEAST ONE SURFACE WAVE WILL RIDE ALONG THE WARM FRONT BEFORE THE ARRIVAL OF THE MAIN SURFACE LOW AND COLD FRONT. FOLLOWING THE TIMING OF THE EURO VS THE FASTER GFS...THIS COULD MAKE FOR A VERY WET AND POTENTIALLY ACTIVE THUNDERSTORM PERIOD THURSDAY INTO EARLY FRIDAY BEFORE THE COLD FRONT PUSHES THROUGH. GIVEN THE DEGREE OF HEIGHT FALLS AND LACK OF SURFACE HEATING EXPECTED ACROSS THE GREAT LAKES TOWARDS THE END OF THE WEEK...EXPECT TEMPERATURES TO FALL BACK TO NEAR TO SLIGHTLY BELOW NORMAL. MARINE... WINDS WILL REMAIN PREDOMINATELY OUT OF THE SOUTH THROUGH TUESDAY. DEEPER MIXING WILL BRING SOME INCREASE IN THE WINDS DURING THE DAYTIME HOURS...REACHING 10-15 KNOTS SUSTAINED. SHOWERS AND THUNDERSTORMS WILL DEVELOP ACROSS THE REGION ON MONDAY DOWNSTREAM OF A SLOW MOVING FRONTAL BOUNDARY. THIS BOUNDARY WILL DROP THROUGH THE REGION ON TUESDAY PROVIDING THE FOCUS FOR ADDITIONAL THUNDERSTORM DEVELOPMENT. THIS FRONTAL PASSAGE WILL BRING A BRIEF WIND SHIFT TO THE WEST BY LATE TUESDAY AND TUESDAY NIGHT. WINDS MAY GUST UP TO 25 KNOTS ACROSS FAR NORTHERN LAKE HURON DURING THIS TIME. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MI WATERS OF LAKE ERIE...NONE. && UPDATE...KEC AVIATION.....MR 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 1125 AM EDT SUN AUG 16 2009 MIZ047>049-053>055-060>063-068>070-075-076-082-083-171000- MIDLAND-BAY-HURON-SAGINAW-TUSCOLA-SANILAC-SHIAWASSEE-GENESEE-LAPEER- ST. CLAIR-LIVINGSTON-OAKLAND-MACOMB-WASHTENAW-WAYNE-LENAWEE-MONROE- 1125 AM EDT SUN AUG 16 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR ALL OF SOUTHEAST MICHIGAN. .DAY ONE...THIS AFTERNOON AND TONIGHT THERE IS A CHANCE OF THUNDERSTORMS FOR ALL OF SOUTHEAST MICHIGAN THIS AFTERNOON AS AN INCREASINGLY MOIST AND UNSTABLE AIRMASS ARRIVES OVER THE STATE. THUNDERSTORMS THAT DEVELOP THIS AFTERNOON WILL BE CAPABLE OF PRODUCING LOCALLY HEAVY RAIN...SMALL HAIL TO THREE QUARTERS INCH IN DIAMETER...AND WIND GUSTS TO 45 MPH. AN ISOLATED STORM OR TWO MAY APPROACH SEVERE LIMITS BETWEEN 3 TO 8 PM. STORM MOTION WILL BE TO THE NORTHEAST AT 20 MPH. THE CHANCE OF THUNDERSTORMS CONTINUES INTO TONIGHT...ESPECIALLY TOWARDS THE SAGINAW VALLEY...AS AN AREA OF LOW PRESSURE BEGINS TO MOVE ACROSS THE WESTERN GREAT LAKES. THESE THUNDERSTORMS ARE NOT EXPECTED TO BE SEVERE AS THEY TRACK NORTHEAST AROUND 30 MPH...HOWEVER PERIODS OF HEAVY RAINFALL WILL BE POSSIBLE. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THERE IS CHANCE OF THUNDERSTORMS MONDAY AND TUESDAY AS AN AREA OF LOW PRESSURE PUSHES ACROSS LOWER MICHIGAN. HEAVY RAINFALL IS ALSO POSSIBLE DURING THIS TIMEFRAME. AFTER A PERIOD OF DRY WEATHER ON TUESDAY NIGHT AND WEDNESDAY...CHANCES FOR THUNDERSTORMS WILL RETURN TO THE AREA WEDNESDAY NIGHT THROUGH SATURDAY AS ANOTHER LOW PRESSURE SYSTEM TRACKS ACROSS THE REGION. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED...ALTHOUGH ANY REPORTS OF STRONG WINDS OR HAIL WOULD BE GREATLY APPRECIATED. LCZ422-423-460-LEZ444-LHZ361>363-421-422-441>443-462>464-171000- 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- 1125 AM EDT SUN AUG 16 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF LAKE ERIE...LAKE HURON AND LAKE ST CLAIR. .DAY ONE...THIS AFTERNOON AND TONIGHT THERE IS A CHANCE OF THUNDERSTORMS FOR ALL NEARSHORE WATERS AND SOUTHERN LAKE HURON THIS AFTERNOON AS AN INCREASINGLY MOIST AND UNSTABLE AIRMASS ARRIVES OVER THE STATE. THUNDERSTORMS THAT DEVELOP THIS AFTERNOON WILL BE CAPABLE OF PRODUCING SMALL HAIL TO THREE QUARTERS INCH IN DIAMETER...WIND GUSTS TO 40 KNOTS...AND BRIEF HEAVY DOWNPOURS. THERE IS A SLIGHT CHANCE OF SEVERE WEATHER WITH THUNDERSTORMS TODAY BETWEEN 3 TO 8 PM. STORM MOTION WILL BE TO THE NORTHEAST AT 20 MPH. THERE IS A CHANCE OF THUNDERSTORMS ACROSS ALL OF LAKE HURON TONIGHT. THESE THUNDERSTORMS ARE NOT EXPECTED TO BE SEVERE AS THEY MOVE NORTHEAST AT 25 TO 30 KNOTS. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THERE IS CHANCE OF THUNDERSTORMS MONDAY AND TUESDAY AS AN AREA OF LOW PRESSURE PUSHES ACROSS LOWER MICHIGAN. AFTER A PERIOD OF DRY WEATHER ON TUESDAY NIGHT AND WEDNESDAY...CHANCES FOR THUNDERSTORMS WILL RETURN TO THE AREA WEDNESDAY NIGHT THROUGH SATURDAY AS ANOTHER LOW PRESSURE SYSTEM TRACKS ACROSS THE REGION. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED...ALTHOUGH ANY REPORTS OF STRONG WINDS OR HAIL WOULD BE GREATLY APPRECIATED. KEC YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
The Detroit radar (KDTX), 94 km away, was scanning. The volume nearest the first event began at 17:28 UTC.
2 thunderstorm wind. Local standard time, as filed.
An empty silo was blown down, along with several tree tops blown off.
An old barn was blown over and wires were also reported down.
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: 193209, 193207.