A cold front approaching the area on the 11th ran into a warm and moist air mass. This resulted in some showers and thunderstorms during the afternoon, some of which became strong to locally severe.
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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 PHI wrote it up.
A cold front approaching the area on the 11th ran into a warm and moist air mass. This resulted in some showers and thunderstorms during the afternoon, some of which became strong to locally severe.
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 Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Aug 11, 1:09 PM EST, 1 hour 41 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 209 PM EDT TUE AUG 11 2009 .SYNOPSIS... A WEAK AND DIFFUSE FRONTAL BOUNDARY WILL MOVE THROUGH THE REGION EARLY TONIGHT AND THEN STALL TO THE SOUTH OF THE REGION ON WEDNESDAY. THIS OLD FRONTAL BOUNDARY WILL THEN SEE WAVES OF LOW PRESSURE MOVE ALONG IT THROUGH THE WEEKEND. HIGH PRESSURE SHOULD THEN BUILD OVER THE AREA EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... WITH A WEAK FRONTAL BOUNDARY MOVING THROUGH THE REGION TONIGHT, ALONG WITH AN UPPER AIR DISTURBANCE, SCATTERED TSTMS ARE EXPECTED EARLY TONIGHT. HOWEVER, THE CAPES AS SHOWN ON LAPS ARE NOT EXTREME WITH VALUES GENERALLY BELOW 1200 EXCEPT A BIT HIGHER IN DELMARVA DUE TO HIGHER DEWPOINTS. TSTMS WERE ALREADY FIRING IN WESTERN NY STATE AND NW PA SW INTO OHIO. WITH SOME UNSTABLE AIR OVER THE REGION, I EXPECT SOME OF THESE TSTMS TO MAKE IT TO THE AREA, ESPECIALLY WITH THE MODELS SHOWING A SHORT WAVE ALOFT ASSOCIATED WITH THE CONVECTION. HOWEVER, WINDS ARE GENERALLY WNW AND IT SHOULD BE AFTER SUNSET BEFORE THE ACTIVITY ARRIVES, MEANING A DECREASE IN CAPE AND ACTIVITY EXPECTED TO LESSEN. DUE TO THE UNCERTAINTY, I CARRY CHC POPS ALL AREAS UNTIL 2 AM AND THEN SLIGHT CHANCE AFTER THAT. FCST MINS ARE GENLY A COMPROMISE OF MAV/MET. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... THROUGH THE SHORT TERM...THE PROXIMITY OF THE OLD FRONTAL BOUNDARY TO THE SOUTH MEANS A CHANCE OF SHOWERS AND TSTMS SOUTH, WHILE FARTHER NORTH IT WILL BE A BIT DRIER, SO POPS ARE LOWER. HOWEVER, I STILL KEPT SLIGHT CHC DUE TO WEAK TROUGHING ALOFT. I ALSO TIMED ANY POTENTIAL CONVECTION TO BE MOSTLY DURING THE AFTN/EVENING HOURS. && .LONG TERM /FRIDAY THROUGH TUESDAY/... THROUGH SATURDAY NIGHT...THE PATTERN STAYS WITH HIGH PRESSURE NORTH AND AN OLD FRONTAL BOUNDARY SOUTH WITH AREAS OF LOW PRESSURE MOVING ALONG THE FRONT. THIS PUT THE REGION UNDER ONSHORE FLOW WITH SHOWERS POSSIBLE MAINLY SOUTH. HOWEVER, I ALSO KEPT IN THE TSTM THREAT AS THE OCEAN IS WARM AND ANY DISTURBANCES ALOFT COULD TRIGGER TSTMS WITH WITH MARITIME AIR IN PLACE. SUNDAY, THE LAST WAVE OF LOW PRESSURE SHOULD PULL THE FRONT OUT TO SEA AND ALLOW HIGH PRESSURE TO BUILD IN FROM THE WEST FOR MONDAY. A SOUTHWEST FLOW OF WARM AND HUMID AIR IS FORECAST TO RETURN TUESDAY WITH THE CHANCE OF MORE SHOWERS AND TSTMS. TEMPERATURES LOOKS SEASONABLE, EXCEPT NEAR THE OCEAN WHERE THE ONSHORE FLOW SHOULD ALLOW TEMPS TO BE LOWER THAN FARTHER TO THE WEST. ONCE THE LOW MOVES OFF TO THE EAST, WARMER AIR SHOULD RETURN TO AREAS CLOSER TO THE OCEAN. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR WEATHER ACROSS THE REGION ATTM WITH WESTERLY WINDS AND SOME DOWNSLOPE DRYING AS THE WINDS MOVE ACROSS THE APPALACHIANS. THE NEAREST ACTIVITY IS PARALLEL TO LAKE ERIE AS A LINE OF THUNDERSTORMS PUSHES AWAY FROM THE LAKE TO THE SOUTHEAST. SOME SCATTERED SHOWERS ARE ALSO LOCATED DNORTH OF KIPT AND NORTH OF KJST...AND RECENTLY IN THE POCONOS. THE CELLS ARE MOVING TO 109 DEGREES AT 21 KNOTS. EXPECT TO SEE SOME ISOLATED TSTMS IN OUR REGION BUT NO ORGANIZED CONTECTION EXPECTED. CONDITIONS WILL REMAIN VFR EXCEPT AS A RESULT OF A NEARBY SHOWER. THE SURFACE FRONT WILL SLOWLY DROP DOWN THROUGH PENNSYLVNIA LATE THIS AFTERNOON BRINGING THE SHOWERS CLOSER. IT APPEARS THERE MAY BE A GREATER CONCENTRATION OF TSTMS JUST NORTH OF TTN TO ABE AND ANOTHER OVER SOUTHWEST PA. BY 1 AM WED. THE SURFACE SYSTEM PUSHES SOUTH TONIGHT BUT THE UPPER TROUGH HANGS BACK AND KEEPS UP IN THE CHANCE OF SHOWERS/TSTMS ON THURSDAY. OUTLOOK... MEANWHILE, HIGH PRESSURE WILL BUILD IN BEHIND THE COLD FRONT, BRINGING PREDOMINANTLY VFR CONDITIONS FOR THE REMAINDER OF THE WEEK. && .MARINE... VERY FLAT PRESSURE PATTERN TO REMAIN OVER THE WATERS RESULTING IN SEAONSAL WINDS AND SEAS FOR AUG 11TH. SOME OF OUR MARINE GUIDANCE DOESNT SHOW ANY WAVES ABOVE 3 FEET FOR SEVERAL DAYS, AND EVEN LESS BACK ON DELAWARE BAY. MEANWHILE, THE WINDS SPEEDS LIKELY TO BE HOVERING AROUND 10 KT FOR THE MOST PART FOR THE NEXT SEVERAL DAYS. HOWEVER, IN THE VICINITY OF AN SHOWERS AND THUNDERSTORMS, SOME GUSTY WINDS AND CHOPPY SEAS WILL OCCUR. AND, THE CHANCE OF THUNDERSTORMS IS NOT THE RESULT OF A WIDEPSREAD EVENT, BUT RATHER ISOLATED. WATER TEMPERATURES ARE IN THE 70S TO NEAR 80 IN SOME AREAS AND EVEN AT BUOY 44009 IT HAS REACHED 80 DEGREES A NICE STRETCH OF MARINE WEATHER ON TAP. EVEN THE WEATHER AT THE CANYONS ARE PRETTY GOOD. YOU CAN GET THE LATEST AT WWW.OPC.NCEP.NOAA.GOV THE NATIONAL HURRICANE CENTER IS ISSUING DATA ON THREE SEPERATE SYSTEMS. NOW IS A GOOD TIME TO CHECK AND SEE HOW THE PRODUCTS ARE ISSUED AND KEEP AHEAD OF ANY DEVELOPING SYSTEMS. JUST GO TO WWW.NHC.NOAA.GOV && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && SYNOPSIS...STAUBER NEAR TERM...STAUBER SHORT TERM...STAUBER LONG TERM...STAUBER AVIATION...EBERWINE MARINE...EBERWINE
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 445 AM EDT TUE AUG 11 2009 DEZ001>004-MDZ008-012-015-019-020-NJZ001-007>010-012>027-PAZ054-055- 060>062-067>071-121100- NEW CASTLE-KENT-INLAND SUSSEX-DELAWARE BEACHES-CECIL-KENT MD- QUEEN ANNES-TALBOT-CAROLINE-SUSSEX-WARREN-MORRIS-HUNTERDON-SOMERSET- MIDDLESEX-WESTERN MONMOUTH-EASTERN MONMOUTH-MERCER-SALEM-GLOUCESTER- CAMDEN-NORTHWESTERN BURLINGTON-OCEAN-CUMBERLAND-ATLANTIC-CAPE MAY- ATLANTIC COASTAL CAPE MAY-COASTAL ATLANTIC-COASTAL OCEAN- SOUTHEASTERN BURLINGTON-CARBON-MONROE-BERKS-LEHIGH-NORTHAMPTON- CHESTER-MONTGOMERY-BUCKS-DELAWARE-PHILADELPHIA- 445 AM EDT TUE AUG 11 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PARTS OF EASTERN PENNSYLVANIA AND NEW JERSEY, DELAWARE AND NORTHEASTERN MARYLAND. .DAY ONE...TODAY AND TONIGHT. THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY. THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME. ANZ430-431-450>455-121100- DELAWARE BAY WATERS NORTH OF EAST POINT NJ TO SLAUGHTER BEACH DE- DELAWARE BAY WATERS SOUTH OF EAST POINT NJ TO SLAUGHTER BEACH DE- COASTAL WATERS FROM SANDY HOOK TO MANASQUAN INLET NJ OUT 20 NM- COASTAL WATERS FROM MANASQUAN INLET TO LITTLE EGG INLET NJ OUT 20 NM- COASTAL WATERS FROM LITTLE EGG INLET TO GREAT EGG INLET NJ OUT 20 NM- COASTAL WATERS FROM GREAT EGG INLET TO CAPE MAY NJ OUT 20 NM- COASTAL WATERS FROM CAPE MAY NJ TO CAPE HENLOPEN DE OUT 20 NM- COASTAL WATERS FROM CAPE HENLOPEN TO FENWICK ISLAND DE OUT 20 NM- 445 AM EDT TUE AUG 11 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE COASTAL WATERS OF NEW JERSEY AND DELAWARE AND FOR DELAWARE BAY. .DAY ONE...TODAY AND TONIGHT. THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY. THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 335 PM EDT TUE AUG 11 2009 PAZ054-055-112015- CARBON PA-MONROE PA- 335 PM EDT TUE AUG 11 2009 ...A STRONG THUNDERSTORM WILL AFFECT CARBON AND MONROE COUNTIES... AT 333 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM 14 MILES WEST OF MOUNT POCONO...MOVING SOUTHEAST AT 20 TO 25 MPH. THE THUNDERSTORM WILL BE NEAR LAKE HARMONY...AND ALBRIGHTSVILLE AROUND 340 PM...CHRISTMANS...POCONO PINES...AND TOBYHANNA AROUND 345 PM...MECKESVILLE...POCONO RACEWAY...AND LONG POND AROUND 350 PM...AND JONAS AND PENN FOREST RESERVOIR AROUND 355 PM. WIND GUSTS TO 40 MPH AS WELL AS SMALL HAIL AND FREQUENT...DANGEROUS CLOUD TO GROUND LIGHTNING ARE POSSIBLE FROM THIS STORM.
The Binghamton radar (KBGM), 139 km away, was scanning. The volume nearest the first event began at 19:49 UTC.
1 thunderstorm wind. Local standard time, as filed.
A severe thunderstorm wind gust blew in a garage door of a home in the Indian Mountain Lakes Development.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2009Every state in 2009This day in weather historyWarnings in Pennsylvania, 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: 193639.