Alert archive / Pennsylvania / Flash Flood Warnings in 2009

Flash Flood Warning 3, NWS Philadelphia/Mount Holly

May 7, 2009Delaware County, Philadelphia County, Pennsylvania; New Castle County, Delaware

NWS Philadelphia/Mount Holly issued this flash flood warning at May 7, 2009, 1:51 AM EDT for Delaware County, Philadelphia County, Pennsylvania; New Castle County, Delaware. It was in force for 5 hr. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
May 7, 2009, 1:51 AM EDT (05:51 UTC)
Expired
May 7, 2009, 6:45 AM EDT
In force
5 hr
Issued by
NWS Philadelphia/Mount Holly
Area
Storm-based polygon
Flood severity
None

Counties New Castle County, DE, Delaware County, PA, Philadelphia County, PA

The radar

The Philadelphia radar (KDIX), 83 km from the middle of the area, began a volume at 05:55 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 00:00Z, 5.9 hours before the alert went out and 203 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Washington/Dulle, VA at 00:00Z on 2009-05-07Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1 joules per kilogram.LCLEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Washington/Dulle, VA at 00:00Z on 2009-05-07The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 257 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
1 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
465 m above ground
0-6 km bulk shear
55 kt
0-1 km storm-relative helicity
257 m²/s²
0-3 km storm-relative helicity
364 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000 
WGUS51 KPHI 070551
FFWPHI
DEC003-PAC045-101-071045-
/O.NEW.KPHI.FF.W.0003.090507T0551Z-090507T1045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
151 AM EDT THU MAY 7 2009

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  NEW CASTLE COUNTY IN NORTHERN DELAWARE...
  THIS INCLUDES THE CITIES OF...WILMINGTON...NEWARK...MIDDLETOWN...
  DELAWARE COUNTY IN SOUTHEAST PENNSYLVANIA...
  PHILADELPHIA COUNTY IN SOUTHEAST PENNSYLVANIA...
  THIS INCLUDES THE CITY OF PHILADELPHIA...

* UNTIL 645 AM EDT

* AT 149 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED   
  FLASH FLOODING FROM HEAVY RAIN AND SCATTERED THUNDERSTORMS OVER 
  THE WARNED AREA WITH MORE HEAVY RAIN EXPECTED AS WELL AS MORE
  THUNDERSTORMS MOVING IN FROM THE SOUTHWEST. RAINFALL RATES OF 
  OVER AN INCH IN LESS THAN AN HOUR IS POSSIBLE.

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
  WISSINOMING...TROUT LAKE...TEMPLE UNIVERSITY...TACONY...SOUTH
  PHILADELPHIA...ROXBOROUGH...PHILADELPHIA INTERNATIONAL AIRPORT...
  NORTHEAST PHILADELPHIA...NEWTOWN SQUARE...MORRIS PARK...
  KENSINGTON...HOLMESBURG...GRADYVILLE...ELAM...CONCORDVILLE...
  CHEYNEY...CHESTNUT HILL...CHELSEA...CENTER CITY...MOUNT PLEASANT...
  SAINT GEORGES...NORTH STAR...HOCKESSIN...GLASGOW...BEAR...
  ASHLAND...GERMANTOWN...YEADON...SWARTHMORE...RADNOR TOWNSHIP...
  NETHER PROVIDENCE TOWNSHIP...LIMA...FOLCROFT...EAST LANSDOWNE...
  DREXEL HILL...CHESTER...BROOMALL...WILMINGTON MANOR...
  TALLEYVILLE...STANTON...PIKE CREEK...NEWPORT...NEW CASTLE...ELSMERE
  AND DELAWARE CITY

PRECAUTIONARY/PREPAREDNESS ACTIONS...

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF FLASH FLOODING IS OBSERVED ACT QUICKLY. MOVE
UP TO HIGHER GROUND TO ESCAPE FLOOD WATERS. DO NOT STAY IN AREAS
SUBJECT TO FLOODING WHEN WATER BEGINS RISING.

DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE
ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS
SAFELY. MOVE TO HIGHER GROUND.

&&

LAT...LON 3979 7573 3984 7560 3987 7562 4006 7538
      3998 7528 4001 7522 4005 7527 4009 7523
      4005 7512 4012 7505 4011 7496 4004 7498
      3995 7514 3988 7518 3984 7537 3962 7560
      3957 7555 3938 7577 3971 7579

$$

RNS/IOVINO

The office that day

Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 6, 9:01 PM EDTFlood WatchPHIDelaware, Philadelphia19 hr
May 7, 1:08 AM EDTFlash Flood WarningPHIChester, Montgomery6 hr
May 7, 1:43 AM EDTFlash Flood WarningPHIBucks5 hr
May 7, 10:15 AM EDTAreal Flood WarningPHIMontgomery3 hr
May 7, 1:42 PM EDTAreal Flood AdvisoryPHIBucks, Montgomery4 hr
May 7, 2:34 PM EDTAreal Flood AdvisoryPHIBucks, Delaware, Montgomery, Philadelphia3 hr
May 7, 2:00 AM EDTRiver Flood WarningPHINew Castle3 hr
May 7, 1:22 PM EDTAreal Flood AdvisoryPHINew Castle4 hr
May 7, 1:33 PM EDTSevere Thunderstorm WarningPHIKent, New Castle66 min

Nearby

Flash Flood Warnings in Pennsylvania, 2009Flash Flood Warnings in Delaware, 2009Every flash flood warning in 2009

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.