Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2008

Severe Thunderstorm Warning 232, NWS Philadelphia/Mount Holly

August 10, 2008Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 10, 2008, 4:45 PM EDT for Chester County, Pennsylvania. It was in force for 75 min. 4 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Aug 10, 2008, 4:45 PM EDT (20:45 UTC)
Expired: Aug 10, 2008, 6:00 PM EDT
In force: 75 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

County Chester County, PA

The radar

The Philadelphia radar (KDIX), 125 km from the middle of the area, began a volume at 20:48 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.

What was reported inside it

Time	Report	Where	Remark
Aug 10, 5:15 PM EDT	HAIL 0.75	10 Ene Quarryville, PA
Aug 10, 5:37 PM EDT	TSTM WND DMG	4 S Chester Springs, PA	8 TO 10 INCH LIMBS DOWN IN EXTON....PEA SIZED HAIL IN WARWICK.
Aug 10, 5:45 PM EDT	HAIL 1	Cochranville, PA	HAIL RANGED FROM PENNY TO QUARTER SIZE AND ACCUMULATED ONE TO TWO INCHES DEEP. MINOR DAMAGE WAS DONE TO VEGETATION WITH SOME LEAVES REMOVED. THE HAIL LASTED BETWEEN 10 AND 12 MINUTES.
Aug 10, 5:50 PM EDT	HAIL 0.75	Oxford, PA

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Aug 10, 10:46 AM EDT	Severe Thunderstorm Watch	SPC	10 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 8.8 hours before the alert went out and 173 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 771 J/kg
Mixed-layer CIN: -66 J/kg
Mixed-layer LCL: 923 m above ground
0-6 km bulk shear: 25 kt
0-1 km storm-relative helicity: 3 m²/s²
0-3 km storm-relative helicity: 85 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.8

Open this sounding in Storm Lab

The text

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

000 
WUUS51 KPHI 102045
SVRPHI
PAC029-102200-
/O.NEW.KPHI.SV.W.0232.080810T2045Z-080810T2200Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
445 PM EDT SUN AUG 10 2008

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 600 PM EDT

* AT 443 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM CAPABLE OF PRODUCING NICKEL SIZE HAIL...AND
  DAMAGING WINDS IN EXCESS OF 60 MPH.  THIS STORM WAS LOCATED 14
  MILES NORTHWEST OF MOUNT VERNON...OR ABOUT 9 MILES SOUTH OF
  LANCASTER...AND MOVING EAST AT 29 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
  PARKESBURG BY 520 PM...
  COATESVILLE BY 530 PM...
  GLENMOORE BY 540 PM...
  DOWNINGTOWN BY 545 PM...
  LIONVILLE BY 550 PM...
  CHESTER SPRINGS BY 555 PM...

THUNDERSTORMS ARE CAPABLE OF PRODUCING HEAVY RAINFALL WHICH MAY
RESULT IN LOCALIZED AREAS OF FLOODING. DO NOT DRIVE IN AREAS WHERE
WATER IS CROSSING THE ROAD.

IN ADDITION TO LARGE HAIL AND DAMAGING WINDS...CONTINUOUS CLOUD TO
GROUND LIGHTNING IS OCCURRING WITH THIS STORM. MOVE INDOORS
IMMEDIATELY LIGHTNING IS ONE OF NATURES NUMBER ONE KILLERS.
REMEMBER...IF YOU CAN HEAR THUNDER...YOU ARE CLOSE ENOUGH TO BE
STRUCK BY LIGHTNING.

THIS STORM HAS A HISTORY OF PRODUCING LARGE DAMAGING HAIL. SEEK 
SHELTER NOW INSIDE A STURDY STRUCTURE AND STAY AWAY FROM WINDOWS

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 700 PM SUNDAY
EVENING FOR DELAWARE AND NORTHEASTERN MARYLAND AND NEW JERSEY AND
EASTERN PENNSYLVANIA.

LAT...LON 3985 7604 3988 7600 3992 7602 4004 7595
      4010 7595 4013 7592 4014 7588 4023 7567
      4006 7541 3999 7547 3977 7578 3975 7606
      3977 7608
TIME...MOT...LOC 2045Z 253DEG 25KT 3992 7623

$$

RNS

2 follow-up statements

000 
WWUS51 KPHI 102107
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
507 PM EDT SUN AUG 10 2008

PAC029-102200-
/O.CON.KPHI.SV.W.0232.000000T0000Z-080810T2200Z/
CHESTER PA-
507 PM EDT SUN AUG 10 2008

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 600 PM EDT
FOR CHESTER COUNTY...

AT 501 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO
INDICATE A SEVERE THUNDERSTORM CAPABLE OF PRODUCING NICKEL SIZE
HAIL...AND DAMAGING WINDS IN EXCESS OF 60 MPH.  THIS STORM WAS
LOCATED NEAR HOMEVILLE...OR 15 MILES SOUTHEAST OF LANCASTER...MOVING
EAST AT 29 MPH.

THE SEVERE THUNDERSTORM WILL BE NEAR...
  ATGLEN BY 515 PM EDT...
  COCHRANVILLE AND PARKESBURG BY 520 PM EDT...
  MODENA...SOUTH COATESVILLE AND COATESVILLE BY 530 PM EDT...
  THORNDALE BY 540 PM EDT...
  MARSHALLTON AND DOWNINGTOWN BY 545 PM EDT...
  WEST CHESTER BY 550 PM EDT...

IN ADDITION TO LARGE HAIL AND DAMAGING WINDS...CONTINUOUS CLOUD TO
GROUND LIGHTNING IS OCCURRING WITH THIS STORM. MOVE INDOORS
IMMEDIATELY LIGHTNING IS ONE OF NATURES NUMBER ONE KILLERS.
REMEMBER...IF YOU CAN HEAR THUNDER...YOU ARE CLOSE ENOUGH TO BE
STRUCK BY LIGHTNING.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 700 PM EDT SUNDAY
EVENING FOR DELAWARE AND NORTHEASTERN MARYLAND AND NEW JERSEY AND
EASTERN PENNSYLVANIA.

LAT...LON 3985 7604 3988 7600 3992 7602 4004 7595
      4010 7595 4013 7592 4014 7588 4023 7567
      4006 7541 3999 7547 3977 7578 3975 7606
      3977 7608
TIME...MOT...LOC 2107Z 262DEG 25KT 3991 7602

$$

RNS

000 
WWUS51 KPHI 102137
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
537 PM EDT SUN AUG 10 2008

PAC029-102200-
/O.CON.KPHI.SV.W.0232.000000T0000Z-080810T2200Z/
CHESTER PA-
537 PM EDT SUN AUG 10 2008

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 600 PM EDT
FOR CHESTER COUNTY...

AT 531 PM EDT...A SEVERE THUNDERSTORM WAS REPORTED CAPABLE OF
PRODUCING QUARTER SIZE HAIL...AND DAMAGING WINDS IN EXCESS OF 60 MPH.
 THIS STORM WAS LOCATED NEAR MODENA...OR 10 MILES WEST OF WEST
CHESTER...MOVING EAST AT 29 MPH.

THE SEVERE THUNDERSTORM WILL BE NEAR...
  MARSHALLTON AND DOWNINGTOWN BY 545 PM EDT...
  WEST CHESTER...EXTON AND 7 MILES SOUTH OF LIONVILLE BY 550 PM
  EDT...
  WEST GOSHEN BY 555 PM EDT...
  MALVERN...6 MILES SOUTHWEST OF PAOLI...8 MILES SOUTHWEST OF
  DEVON-BERWYN AND 9 MILES SOUTHWEST OF CHESTERBROOK BY 600 PM EDT...

IN ADDITION TO LARGE HAIL AND DAMAGING WINDS...CONTINUOUS CLOUD TO
GROUND LIGHTNING IS OCCURRING WITH THIS STORM. MOVE INDOORS
IMMEDIATELY LIGHTNING IS ONE OF NATURES NUMBER ONE KILLERS.
REMEMBER...IF YOU CAN HEAR THUNDER...YOU ARE CLOSE ENOUGH TO BE
STRUCK BY LIGHTNING.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 700 PM EDT SUNDAY
EVENING FOR DELAWARE AND NORTHEASTERN MARYLAND AND NEW JERSEY AND
EASTERN PENNSYLVANIA.

LAT...LON 3986 7603 3988 7600 3992 7602 3994 7600
      3996 7600 4004 7596 4022 7566 4006 7541
      3999 7547 3977 7578 3975 7605
TIME...MOT...LOC 2137Z 262DEG 25KT 3994 7575

$$

RNS

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 10, 10:18 AM EDT	Severe Thunderstorm Warning	PHI	Chester	57 min
Aug 10, 10:44 AM EDT	Severe Thunderstorm Warning	PHI	Delaware	61 min
Aug 10, 11:09 AM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware, Montgomery, Philadelphia	66 min
Aug 10, 11:32 AM EDT	Areal Flood Advisory	PHI	Chester, Delaware	3 hr
Aug 10, 11:46 AM EDT	Severe Thunderstorm Warning	PHI	Delaware	59 min
Aug 10, 12:09 PM EDT	Tornado Warning	PHI	Delaware	36 min
Aug 10, 12:17 PM EDT	Flash Flood Warning	PHI	Chester, Delaware, Montgomery	4 hr
Aug 10, 12:21 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Lehigh, Montgomery	84 min
Aug 10, 12:40 PM EDT	Severe Thunderstorm Warning	PHI	Delaware, Philadelphia	95 min
Aug 10, 1:05 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Carbon, Lehigh, Monroe, Northampton	115 min
Aug 10, 1:10 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester, Montgomery	65 min
Aug 10, 1:47 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Montgomery	58 min
Aug 10, 3:05 PM EDT	Flash Flood Warning	PHI	Chester	3 hr
Aug 10, 3:35 PM EDT	Severe Thunderstorm Warning	PHI	Berks	40 min
Aug 10, 5:25 PM EDT	Areal Flood Advisory	PHI	Berks, Montgomery	110 min
Aug 10, 5:45 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	75 min
Aug 10, 5:59 PM EDT	Areal Flood Advisory	PHI	Chester, Delaware	2 hr
Aug 10, 6:45 PM EDT	Areal Flood Advisory	PHI	Philadelphia	2 hr

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2008 Every severe thunderstorm warning in 2008

Sources

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