Alert archive / Pennsylvania / Flash Flood Warnings in 2009
Flash Flood Warning 45, NWS Philadelphia/Mount Holly
NWS Philadelphia/Mount Holly issued this flash flood warning at Aug 21, 2009, 10:49 PM EDT for Chester County, Pennsylvania. It was in force for 55 min. No storm report in the archive falls inside the area while it was in force.
The area
The outline as issued.
The facts
- Issued
- Aug 21, 2009, 10:49 PM EDT (02:49 UTC)
- Expired
- Aug 21, 2009, 11:44 PM EDT
- In force
- 55 min
- Issued by
- NWS Philadelphia/Mount Holly
- Area
- Storm-based polygon
- Flood severity
- None
County Chester County, PA
The radar
The Dover AFB radar (KDOX), 125 km from the middle of the area, began a volume at 02:50 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, 2.8 hours before the alert went out and 160 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.
- Mixed-layer CAPE
- 669 J/kg
- Mixed-layer CIN
- -46 J/kg
- Mixed-layer LCL
- 480 m above ground
- 0-6 km bulk shear
- 37 kt
- 0-1 km storm-relative helicity
- 62 m²/s²
- 0-3 km storm-relative helicity
- 186 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 5.7
The text
As transmitted, in the capitals the NWS used until 2016.
000
WGUS51 KPHI 220249
FFWPHI
PAC029-220645-
/O.NEW.KPHI.FF.W.0045.090822T0249Z-090822T0645Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1049 PM EDT FRI AUG 21 2009
THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A
* FLASH FLOOD WARNING FOR...
SOUTHERN CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...
THIS INCLUDES THE CITY OF WEST CHESTER...
* UNTIL 245 AM EDT
* AT 1047 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
FLASH FLOODING FROM A THUNDERSTORM OVER THE WARNED AREA.
* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
HOMEVILLE...COCHRANVILLE...PARKESBURG...MARSHALLTON...DOWNINGTOWN
AND COATESVILLE
PRECAUTIONARY/PREPAREDNESS ACTIONS...
ADDITIONAL RAINFALL AMOUNTS OF ANOTHER INCH ARE POSSIBLE IN THE
WARNED AREA.
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 3978 7607 3980 7607 3984 7603 3985 7603
3987 7601 3991 7602 4003 7595 4005 7595
4005 7553 3973 7579 3974 7610
$$
RNS1 follow-up statement
000
WGUS71 KPHI 220344
FFSPHI
FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1144 PM EDT FRI AUG 21 2009
PAC029-220354-
/O.CAN.KPHI.FF.W.0045.000000T0000Z-090822T0645Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
CHESTER PA-
1144 PM EDT FRI AUG 21 2009
...THE FLASH FLOOD WARNING HAS BEEN CANCELLED FOR SOUTHERN CHESTER
COUNTY...
THE HEAVY RAIN HAS ENDED. HOWEVER, A FLASH FLOOD WATCH REMAINS IN
EFFECT AND IF THE HEAVY RAINS RETURN, ANOTHER FLASH FLOOD WARNING
COULD BE NEEDED.
LAT...LON 3978 7607 3980 7607 3984 7603 3985 7603
3987 7601 3991 7602 4003 7595 4005 7595
4005 7553 3973 7579 3974 7610
$$
RNSThe office that day
Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 21, 10:14 PM EDT | Areal Flood Advisory | PHI | Chester | 3 hr |
| Aug 22, 1:40 AM EDT | Areal Flood Advisory | PHI | Bucks, Montgomery, Philadelphia | 3 hr |
| Aug 22, 1:51 AM EDT | Flash Flood Warning | PHI | Montgomery, Philadelphia | 77 min |
| Aug 22, 6:03 AM EDT | Flash Flood Warning | PHI | Montgomery, Philadelphia | 3 hr |
| Aug 22, 6:21 PM EDT | Flash Flood Warning | PHI | Bucks, Northampton | 3 hr |
| Aug 22, 7:00 PM EDT | Flash Flood Warning | PHI | Bucks, Chester, Delaware, Montgomery, Philadelphia | 4 hr |
Nearby
Flash Flood Warnings in Pennsylvania, 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.