An approaching cold front produced strong to severe thunderstorms across southern Delaware during the late afternoon of the 27th.
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 PHI wrote it up.
An approaching cold front produced strong to severe thunderstorms across southern Delaware during the late afternoon of the 27th.
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 Jul 28, 10:25 AM EST, 3 hours 42 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1125 AM EDT TUE JUL 28 2009 .SYNOPSIS... A BERMUDA HIGH PRESSURE AREA WELL TO OUR EAST-SOUTHEAST AND A WEAK TROUGH OF LOW PRESSURE JUST TO OUR WEST WILL BE THE MAIN WEATHER FEATURES THIS AFTERNOON. A FRONT FROM THE NORTHWEST WILL APPROACH TONIGHT INTO WEDNESDAY AND ARRIVE WEDNESDAY NIGHT. THE FRONT SHOULD THEN STALL OVER OUR AREA AND LINGER THROUGH FRIDAY. WEAK HIGH PRESSURE IS EXPECTED SATURDAY INTO SUNDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... DIFFERENTIAL HEATING IN THE NORTHWEST, A SEA/BAY BREEZE IN THE SOUTHEAST, OR MORE GENERALLY A BIT OF ENERGY IN THE MID-LEVEL SOUTHWEST FLOW THAT THE MODELS CANT RESOLVE COULD HELP TRIGGER ISOLATED CONVECTION THIS AFTERNOON. BASICALLY, IN THIS SOUTHWEST UPPER FLOW / BERMUDA HIGH REGIME WE DONT FEEL COMFORTABLE WITHOUT MENTIONING A SLIGHT CHANCE OF THUNDERSTORMS, WHICH MAINTAINS CONTINUITY. ON TEMPERATURES, THE DIFFERENCES BETWEEN THE 850 HPA TEMPERATURES FROM THE 00Z NAM, THE 12Z ECMWF, AND THE 00Z ECMWF ARE RATHER SUBTLE AND ARE SUPPORTIVE OF A COMBINATION OF CONTINUITY AND GUIDANCE. THE 925 HPA WINDS STARTED WEAKLY IN OPPOSITION TO A SEA/BAY BREEZE, BUT HAVE BACKED A BIT DURING THE LATE MORNING TO A DIRECTION THAT IS NEUTRAL TO OR MILDLY IN FAVOR OF ONE. KACY INDICATES A DEVELOPING SEA BREEZE. THEREFORE, A DISCONTINUITY BETWEEN INLAND MAXES AND THOSE CLOSER TO THE WATER IS BEING CARRIED. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...WHATEVER CONVECTION DEVELOPS THIS AFTERNOON MAY LINGER INTO THE EVENING, AND THEN WE THINK THE ADVANCING FRONT WILL BE FAR ENOUGH REMOVED FROM THE AREA TO CARVE OUT A PERIOD OF TIME WITHOUT ANY MENTION OF CONVECTION. WE CONTINUE TO LEAN A BIT ON THE WARM SIDE OF GUIDANCE REGARDING MINS WITH THE ADVANCING FRONT AND THE BERMUDA HIGH TO THE SOUTHEAST. WE ALSO GIVE A NOD TO THE WARM WATER TEMPERATURES NEAR THE ATLANTIC AND BAY SHORES. WEDNESDAY INTO WEDNESDAY EVENING SHOWS SOME DYNAMICS ENTERING THE REGION WITH MID TO UPPER LEVEL Q-VECTOR CONVERGENCE AND A RIGHT REAR QUAD OF AN UPPER JET STREAK FOR ABOUT THE ENTIRE AREA /BETTER NORTHWEST THAN SOUTHEAST/ PER THE 00Z ECMWF AND NAM. LOWER LEVEL FRONTOGENESIS AT 00Z THURSDAY IS ENTERING THE NORTHWESTERN ZONES. THE NAM SHOWS MORE INSTABILITY THAN THE ECMWF, AND INDEED MET TEMPS ARE HIGHER THAN MAV TEMPS, BUT ALL MODELS ARE SHOWING SUFFICIENT INSTABILITY FOR THE DYNAMICS TO WORK WITH. THERE ALSO IS A FAIR AMOUNT OF LOW TO MID LEVEL SPEED AND DIRECTIONAL SHEAR BY 00Z PER THE NAM. THE ECMWF HAS DIRECTIONAL SHEAR UP TO H9, WITH MAINLY ONLY SOME SPEED SHEAR ABOVE THAT. SPC HAS PUT THE ENTIRE AREA UNDER A SLIGHT RISK FOR WEDNESDAY. WE WILL NOT PUT ENHANCED MODIFIERS INTO THE GRIDS AT THIS POINT, BUT WE WILL MENTION OUR CONCERNS /STRONG WINDS, HEAVY DOWNPOURS, LIGHTNING, AND, SINCE SUPERCELLS ARE POSSIBLE, HAIL/ IN THE HWO. IF THE NAM WIND PROFILE IS CORRECT, THEN A CONSIDERABLE AMOUNT OF SPIN MIGHT BE IMPARTED TO THESE STORMS. IF THE ECMWF PROFILE IS CORRECT, THEN TRAINING OF CELLS IS POSSIBLE. NEITHER IS DESIRABLE. THE POPS REFLECT THE OBSERVATION THAT DYNAMICS ARE FORECAST TO BETTER NORTHWEST THAN SOUTHEAST. WE EXPECT ACTIVITY TO LINGER INTO THE EVENING. REGARDING MAX TEMPERATURES ON WEDNESDAY, GUIDANCE HAS COME WAY DOWN IN THE NORTHWEST AND DOWN SOME IN THE SOUTHEAST. THE MODELS ARE BRINGING A LOW ALONG THE FRONT INTO SOUTH CENTRAL PA BY 00Z THURSDAY, AND PERHAPS THIS WOULD KEEP TEMPS DOWN A BIT AS ONE APPROACHES OUR WESTERN ZONES. WE THEREFORE MOVED TOWARD GUIDANCE, ESPECIALLY NORTHWEST, BUT WE HAVE NOT EMBRACED THE COOLER GUIDANCE ANYWHERE. THE PROGGED INSTABILITY, IF IT COMES TO PASS, IS NOT CONSISTENT WITH TOO COOL A BOUNDARY LAYER DESPITE THE ABUNDANT MOISTURE. GIVEN WHERE THE UPPER JET AND THE SURFACE FRONT ARE PROGGED TO BE AT 12Z THURSDAY, WERE CARRYING A FAIR CONTRAST IN WEDNESDAY NIGHT MINS BETWEEN THE NORTHWEST AND SOUTHEAST. PRESENTLY, WE CANT SEE A STRONG DYNAMIC SETUP ON THURSDAY, BUT WE DO HAVE A STALLED FRONT IN THE AREA AND WE ARE MAINTAINING THE CHANCE POPS FROM THE PREVIOUS FORECAST. TEMPERATURES ARE A COMPROMISE BETWEEN CONTINUITY AND GUIDANCE. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... THERE SHOULD NOT BE MUCH CHANGE IN THE PATTERN IN THE LONG TERM PERIOD. WE ARE EXPECTING ANOTHER STALLED BOUNDARY IN THE REGION, WITH A CHANCE OF SHOWERS AND THUNDERSTORMS EACH DAY. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TODAYS FLYING WEATHER WILL NOT BE MUCH DIFFERENT THAN THE PAST FEW DAYS. THE PATCH OF LOW IFR CEILINGS AND VISIBILITIES THAT FORMED AROUND SUNRISE JUST TO THE NORTH AND WEST OF KPHL AND KILG, AND WHICH LINGERED INTO THE POST-DAWN HOURS, WAS MORPHING INTO AN AREA OF CUMULUS. ELSEWHERE, SCATTERED TO BROKEN CUMULUS WAS DEVELOPING AT LATE MORNING. THE MODELS WERE HINTING THAT ISOLATED CONVECTION WILL OCCUR AGAIN THIS AFTERNOON, WITH A FEW CUMULONIMBUS AROUND BY LATE AFTERNOON. LIFTED INDICES WERE FORECAST DOWN TO MINUS 6 OR SO ON THE 12Z NAM FOUS. HOWEVER, COVERAGE SHOULD BE ISOLATED...SO THE CB GROUP ONLY WAS USED IN THE TAFS. AMENDMENTS WILL BE ISSUED IF TIMING CAN BE DETERMINED LATER THIS AFTERNOON. VFR CONDITIONS WILL PREVAIL THIS AFTERNOON, UNLESS A SHOWER OR THUNDERSTORM MOVES OVER A TAF SITE. TONIGHT, MORE VFR CONDITIONS ARE FORECAST WITH SOME CIRRUS OR CIRROSTRATUS. PATCHY FOG IS POSSIBLE AGAIN LATE TONIGHT. OUTLOOK...THE MODELS SUGGEST THAT SHOWERS/THUNDERSTORMS WILL BE MORE WIDESPREAD WEDNESDAY, WITH LONGER PERIODS OF LOWER CONDITIONS AND SOME GUSTY WINDS POSSIBLE. SCATTERED CONVECTIVE ACTIVITY IS AGAIN POSSIBLE THURSDAY AND FRIDAY AS INSTABILITY AND LIFTING MECHANISMS REMAIN IN PLACE. && .MARINE... WINDS OVER THE WATERS FEATURE SOUTH TO SOUTHWEST WINDS AT 5 TO 10 KNOTS...FOR THE MOST PART...WITH 2 TO 4 FT SEAS OVER THE COASTAL WATERS. THESE CONDITIONS SHOULD CONTINUE INTO THIS AFTERNOON, WITH SOME INCREASE IN WIND SPEEDS DURING THIS AFTERNOON AS THE GRADIENT IS SLIGHTLY ENHANCED. WIND SPEEDS AND SEAS ARE EXPECTED TO REMAIN SUB-ADVISORY TONIGHT AND PERHAPS MOST OF OR ALL OF WEDNESDAY. WEATHER WILL BE MAINLY FAIR WITH PERHAPS AN ISOLATED SHOWER OR THUNDERSTORM THIS AFTERNOON AND THIS EVENING. ON WEDNESDAY THE SHOWERS AND THUNDERSTORMS MAY BE MORE NUMEROUS, AND GUSTY WINDS ARE POSSIBLE TOO. THE MODELS INDICATE A GENERAL INCREASE IN WINDS AND WAVES LATE WEDNESDAY, OR WEDNESDAY NIGHT INTO THURSDAY, AT WHICH TIME A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED. THE MODELS SHOW ANOTHER INCREASE IN WINDS AND WAVES FRIDAY NIGHT INTO SATURDAY. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && SYNOPSIS... / DELISI NEAR TERM... / DELISI SHORT TERM...DELISI LONG TERM...IOVINO AVIATION... / OHARA MARINE... / OHARA
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 444 AM EDT TUE JUL 28 2009 DEZ001>004-MDZ008-012-015-019-020-NJZ001-007>010-012>027-PAZ054-055- 060>062-067>071-291000- 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- 444 AM EDT TUE JUL 28 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL DELAWARE...NORTHERN DELAWARE...SOUTHERN DELAWARE...NORTHEAST MARYLAND...CENTRAL NEW JERSEY...NORTHERN NEW JERSEY...NORTHWEST NEW JERSEY...SOUTHERN NEW JERSEY...EAST CENTRAL PENNSYLVANIA...NORTHEAST PENNSYLVANIA AND SOUTHEAST PENNSYLVANIA. .DAY ONE...TODAY AND TONIGHT. HAZARDOUS WEATHER NOT EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY. THE STORM PREDICTION CENTER HAS PLACED THE AREA UNDER A SLIGHT RISK OF SEVERE THUNDERSTORMS ON WEDNESDAY. STRONG WINDS, LARGE HAIL, VERY HEAVY DOWNPOURS RESULTING IN LOCALIZED FLOODING AND FREQUENT, DANGEROUS CLOUD TO GROUND LIGHTNING ARE POSSIBLE. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED ON WEDNESDAY. ANZ430-431-450>455-291000- 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- 444 AM EDT TUE JUL 28 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR ATLANTIC COASTAL WATERS AND DELAWARE BAY WATERS. .DAY ONE...TODAY AND TONIGHT. HAZARDOUS WEATHER NOT EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY. THE STORM PREDICTION CENTER HAS PLACED THE AREA UNDER A SLIGHT RISK OF SEVERE THUNDERSTORMS ON WEDNESDAY. STRONG WINDS, LARGE HAIL, VERY HEAVY DOWNPOURS AND FREQUENT, DANGEROUS CLOUD TO SURFACE LIGHTNING ARE POSSIBLE. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.
The Dover AFB radar (KDOX), 53 km away, was scanning. The volume nearest the first event began at 19:06 UTC.
1 hail, 1 thunderstorm wind. Local standard time, as filed.
A severe thunderstorm dropped quarter size hail in Fenwick Island. The hail was starting to accumulate on the ground before it stopped.
A severe thunderstorm ripped the siding from a building on Grant Avenue in Fenwick Island.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Delaware in 2009Every state in 2009This day in weather historyWarnings in Delaware, July 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: 186335, 186337.