Strong winds associated with a severe thunderstorm downed power poles.
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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 BOU wrote it up.
Strong winds associated with a severe thunderstorm downed power poles.
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 Denver/Boulder, CO wrote its last area forecast discussion before the first event at Aug 4, 2:26 AM MST, 11 hours 9 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DENVER CO 326 AM MDT TUE AUG 4 2009 .SHORT TERM...UPPER LEVEL RIDGE WILL MOVE VERY LITTLE OVER THE NEXT 24 HOURS. HOWEVER...THERE ARE A COUPLE ITEMS OF NOTE THIS MORNING. ONE IS THE UPPER LEVEL SPEED MAX NOW SHOOTING NORTHEAST ACROSS NEVADA...UTAH...AND INTO SOUTHWEST WYOMING. ANOTHER IS THE LOW LEVEL NORTHEASTERLY PUSH OCCURRING BEHIND THE MCS THAT MOVED THROUGH NEBRASKA. THIS WILL BRING INCREASING LOW LEVEL MOISTURE AND INSTABILITY OVER THE NORTHEAST CORNER OF THE STATE WHERE CAPES AROUND 2000 J/KG CAN BE EXPECTED AS DEWPOINTS RISE CLOSE TO 60F. HOWEVER...AT THE SAME TIME THE SLIGHTLY COOLER BOUNDARY LAYER AIR WILL DELAY THE ONSET OF ANY CONVECTION WITH A STRONGER CAP IN PLACE. HOWEVER...THE CAP SHOULD BEGIN TO WEAKEN AS SPEED MAX MENTIONED ABOVE AND ASSOCIATED UPPER LEVEL Q-G LIFT APPROACH THE AREA LATE THIS AFTERNOON AND EVENING. THE MAIN THREAT FROM STORMS TODAY WILL SHIFT FROM GUSTY MICROBURST WINDS NEAR THE FRONT RANGE TO STRONGER STORMS WITH LOCALLY HEAVY RAINFALL...STRONG WET MICROBURST WINDS AND HAIL OVER THE NORTHEAST CORNER WHERE A COUPLE SEVERE STORMS ARE POSSIBLE GIVEN SUFFICIENT WIND SHEAR AND INSTABILITY. CONVECTION SHOULD END FROM WEST TO EAST RATHER EARLY THIS EVENING...BUT NORTHEAST CORNER COULD SEE A FEW STORMS LINGER PAST MIDNIGHT WITH SHORT WAVE GRAZING THAT AREA. .LONG TERM...UPPER RIDGE HOLDING OVER THE SOUTHERN PLAINS WEDNESDAY BEFORE AN UPSTREAM TROUGH WILL MOVE NORTHEASTWARD ACROSS THE GREAT BASIN AND OVER THE NORTHERN ROCKIES...SHIFTING THE RIDGE EASTWARD. THE MOIST EASTERLY SURGE LOOKS TO STILL BE OVER THE NORTHEASTERN PLAINS WEDNESDAY WITH WARMING ALOFT FROM THE RIDGE. THIS WILL CREATE A PRETTY GOOD CAP OVER THE PLAINS. CAPE VALUES WILL BE QUITE LOW OVER THE FRONT RANGE AND MOUNTAINS...HOWEVER NAM IS DEPICTING 3000-4000 J/KG OVER THE NORTHEASTERN PLAINS. THE CAP LOOKS STRONG ENOUGH TO CAP ANYTHING...HOWEVER...A TRIGGER SUCH AS AN OUTFLOW BOUNDARY FROM THE NORTHEAST OR ONE OF SEVERAL IMPULSES IN THE NORTHWEST FLOW ALOFT COULD HELP A STORM OR TWO TAP INTO THAT CAPE AND BECOME QUITE STRONG...OR EVEN SEVERE DUE TO THE GOOD SHEAR VALUES ALSO FOUND OVER THE NORTHEAST CORNER THAT AFTERNOON AND EVENING. MODELS ARE NOT SHOWING MUCH IN THE WAY OF QPF OR POPS...SO HAVE KEPT THE LOW POPS. THE UPPER TROUGH WILL BE APPROACHING ON THURSDAY AS THE RIDGE IS PUSHED EAST. MORE MOISTURE LOOKS TO BE PUMPED UP FROM THE SOUTH...MAINLY MID AND HIGH LEVELS. STILL EXPECTING DRY LOW LEVEL CONDITIONS AND THEREFORE THE SHOWERS AND THUNDERSTORMS THAT DO DEVELOP WILL LIKELY BE ON THE DRIER AND WINDIER SIDE. SOUTHWEST FLOW ALOFT WILL BE INCREASING THURSDAY AND FRIDAY WITH THE HIGHER TERRAIN BEING AFFECTED MORE. MORE MOISTURE LOOKS TO FILTER IN FRIDAY TO KEEP THE SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS. CLOSE PROXIMITY WITH THE JET COULD HELP SOME STORMS TO REALLY GAIN STRENGTH. THE JET WILL STILL BE OVER THE STATE SATURDAY WITH THE UPPER LOW DISSIPATING INTO A TROUGH AND HEAD EAST OVER THE EASTERN US. SOME REMAINING MOISTURE ON THE TAIL END OF THE TROUGH AND THE UPWARD QG VERTICAL VELOCITY MOTION ON THE BOTTOM WILL ALLOW THE SLIGHT CHANCE POPS TO CARRY INTO SATURDAY. WITH THE TROUGH NOW NORTHEAST OF THE STATE...THE UPPER HIGH WILL MAKE ITS WAY BACK WEST SUNDAY AND MONDAY BRINGING DRIER AND WARMER AIR AGAIN. SUBTLE MOISTENING TREND LIKELY AGAIN EARLY NEXT WEEK...BUT AT THIS POINT STILL LOOKING RELATIVELY WARM AND DRY. GRASSES WILL START TO DRY AND WE WILL SEE INCREASING FIRE DANGER...IN THE MOUNTAIN VALLEYS FIRST WHERE THE DRYING PROCESS IS ALREADY UNDER WAY. PLAINS ARE STILL GREEN AT THIS TIME. && .AVIATION...EXPECT ISOLATED HIGH BASED STORMS TO DEVELOP AGAIN THIS AFTERNOON WITH MORE WIDESPREAD GUSTY WINDS UP TO 40 KNOTS. FAVORED TIME PERIOD FOR THIS WOULD BE 21Z-01Z SO WILL CONTINUE FORECAST OF VCTS AND TEMPO GUSTY WINDS IN THE FRONT RANGE TAFS DURING THAT TIME FRAME. VISUAL APPROACHES WILL PREVAIL THROUGH TONIGHT AS ANY CONVECTIVE CLOUD BASES WILL BE AT LEAST 8000 FT AGL. && .BOU WATCHES/WARNINGS/ADVISORIES...NONE. BARJENBRUCH/KRIEDERMAN
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DENVER CO 1041 AM MDT TUE AUG 04 2009 COZ030>051-051200- JACKSON COUNTY BELOW 9000 FEET-WEST JACKSON AND WEST GRAND COUNTIES ABOVE 9000 FEET-GRAND AND SUMMIT COUNTIES BELOW 9000 FEET-SOUTH AND EAST JACKSON/LARIMER/NORTH AND NORTHEAST GRAND/ NORTHWEST BOULDER COUNTIES ABOVE 9000 FEET-SOUTH AND SOUTHEAST GRAND/WEST CENTRAL AND SOUTHWEST BOULDER/GILPIN/CLEAR CREEK/ SUMMIT/NORTH AND WEST PARK COUNTIES ABOVE 9000 FEET-LARIMER AND BOULDER COUNTIES BETWEEN 6000 AND 9000 FEET-JEFFERSON AND WEST DOUGLAS COUNTIES ABOVE 6000 FEET/GILPIN/CLEAR CREEK/NORTHEAST PARK COUNTIES BELOW 9000 FEET-CENTRAL AND SOUTHEAST PARK COUNTY-LARIMER COUNTY BELOW 6000 FEET/NORTHWEST WELD COUNTY-BOULDER AND JEFFERSON COUNTIES BELOW 6000 FEET/WEST BROOMFIELD COUNTY-NORTH DOUGLAS COUNTY BELOW 6000 FEET/DENVER/WEST ADAMS AND ARAPAHOE COUNTIES/ EAST BROOMFIELD COUNTY-ELBERT/CENTRAL AND EAST DOUGLAS COUNTIES ABOVE 6000 FEET-NORTHEAST WELD COUNTY-CENTRAL AND SOUTH WELD COUNTY-MORGAN COUNTY-CENTRAL AND EAST ADAMS AND ARAPAHOE COUNTIES- NORTH AND NORTHEAST ELBERT COUNTY BELOW 6000 FEET/NORTH LINCOLN COUNTY-SOUTHEAST ELBERT COUNTY BELOW 6000 FEET/SOUTH LINCOLN COUNTY-LOGAN COUNTY-WASHINGTON COUNTY-SEDGWICK COUNTY-PHILLIPS COUNTY- 1041 AM MDT TUE AUG 04 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST AND NORTH CENTRAL COLORADO. .DAY ONE...TODAY AND TONIGHT ISOLATED THUNDERSTORMS WILL DEVELOP ACROSS THE MOUNTAINS AND FOOTHILLS...SPREADING EASTWARD ACROSS THE PLAINS DURING THE AFTERNOON AND EVENING. THE AIRMASS WILL REMAIN RELATIVELY DRY...SO THE STORMS WILL BE CAPABLE OF PRODUCING STRONG AND GUSTY WINDS TO 50 MPH BUT ONLY LIGHT RAINFALL. HOWEVER...OVER THE NORTHEAST CORNER OF THE STATE...MOISTURE AND INSTABILITY WILL BE MORE ABUNDANT. AS A RESULT...A FEW STORMS COULD BECOME SEVERE IN AREAS ALONG AND EAST OF A STERLING TO AKRON LINE WITH LARGE HAIL...DAMAGING WINDS AND LOCALLY HEAVY RAINFALL. STRONG DAYTIME HEATING WILL COMBINE WITH A WEAK UPPER LEVEL DISTURBANCE EXPECTED TO MOVE ACROSS THE AREA LATER TODAY TO PRODUCE THE SHOWERS AND STORMS. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY THERE IS A SLIGHT CHANCE OF AFTERNOON AND EVENING THUNDERSTORMS THROUGH THE WEEK. ONE OR TWO THUNDERSTORMS COULD BECOME SEVERE OVER THE FAR NORTHEAST PLAINS ON WEDNESDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED TODAY OR TONIGHT. D-L/COOPER
The Denver radar (KFTG), 63 km away, was scanning. The volume nearest the first event began at 20:32 UTC.
1 thunderstorm wind. Local standard time, as filed.
Intense thunderstorm winds knocked two power poles down at the intersection of County Roads 33 and 98.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2009Every state in 2009This day in weather historyWarnings in Colorado, 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: 182347.