Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2009

Severe Thunderstorm Warning 186, NWS Philadelphia/Mount Holly

August 9, 2009Berks County, Chester County, Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 9, 2009, 5:17 PM EDT for Berks County, Chester County, Montgomery County, Pennsylvania. It was in force for 76 min. 1 report 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 9, 2009, 5:17 PM EDT (21:17 UTC)
Expired: Aug 9, 2009, 6:33 PM EDT
In force: 76 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties Berks County, PA, Chester County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 110 km from the middle of the area, began a volume at 21:17 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 9, 5:55 PM EDT	TSTM WND DMG	1 Nnw Honey Brook, PA	TREES AND WIRES DOWN THROUGHOUT THE COUNTY.

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 9, 3:18 PM EDT	Severe Thunderstorm Watch	SPC	5 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 9.3 hours before the alert went out and 197 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: 255 J/kg
Mixed-layer CIN: -88 J/kg
Mixed-layer LCL: 1087 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 243 m²/s²
0-3 km storm-relative helicity: 282 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 6.6

Open this sounding in Storm Lab

The text

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

000 
WUUS51 KPHI 092117
SVRPHI
PAC011-029-091-092245-
/O.NEW.KPHI.SV.W.0186.090809T2117Z-090809T2245Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
517 PM EDT SUN AUG 9 2009

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  SOUTHEASTERN BERKS COUNTY IN EASTERN PENNSYLVANIA...
  CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...
  THIS INCLUDES THE CITY OF WEST CHESTER...
  MONTGOMERY COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 645 PM EDT

* AT 514 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM CAPABLE OF PRODUCING DAMAGING WINDS IN EXCESS
  OF 60 MPH.  THIS STORM WAS LOCATED 26 MILES NORTHWEST OF
  BIRDSBORO...OR 18 MILES NORTHWEST OF READING...AND MOVING SOUTHEAST
  AT 45 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
  BIRDSBORO AND NEW MORGAN AROUND 550 PM EDT...
  ELVERSON AROUND 555 PM EDT...
  PUGHTOWN...CEDARVILLE AND GLENMOORE AROUND 600 PM EDT...
  CHESTER SPRINGS AND LIONVILLE AROUND 610 PM EDT...
  VALLEY FORGE AROUND 615 PM EDT...
  PAOLI AROUND 620 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS STORM HAS A HISTORY OF PRODUCING DESTRUCTIVE WINDS IN THE 
MIDDLE AND UPPER SUSQUEHANNA VALLEY. SEEK SHELTER NOW INSIDE
A STURDY STRUCTURE AND STAY AWAY FROM WINDOWS AND TREES

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

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 1000 PM EDT
SUNDAY EVENING FOR NORTHERN DELAWARE AND NORTHEAST MARYLAND AND NEW
JERSEY AND EASTERN PENNSYLVANIA.

&&

LAT...LON 4047 7558 4020 7515 4006 7537 4005 7542
      4003 7542 3976 7583 3999 7599 4003 7595
      4011 7595 4014 7590 4022 7600
TIME...MOT...LOC 2116Z 310DEG 39KT 4046 7619

$$
 
TFG

2 follow-up statements

000 
WWUS51 KPHI 092203
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
603 PM EDT SUN AUG 9 2009

PAC011-092212-
/O.CAN.KPHI.SV.W.0186.000000T0000Z-090809T2245Z/
BERKS PA-
603 PM EDT SUN AUG 9 2009

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN BERKS COUNTY IS
CANCELLED...

THE LINE OF DAMAGING THUNDERSTORMS HAS MOVED SOUTH OF THE COUNTY.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 1000 PM EDT
SUNDAY EVENING FOR NORTHERN DELAWARE AND NORTHEAST MARYLAND AND NEW
JERSEY AND EASTERN PENNSYLVANIA. A SEVERE THUNDERSTORM WATCH ALSO
REMAINS IN EFFECT UNTIL 1100 PM EDT SUNDAY EVENING FOR SOUTHERN
DELAWARE AND NORTHEASTERN MARYLAND.

LAT...LON 4003 7595 4011 7595 4014 7590 4016 7586
      4023 7574 4036 7542 4020 7515 4006 7537
      4005 7542 3985 7570 3977 7583 3999 7599
TIME...MOT...LOC 2202Z 306DEG 38KT 4024 7553 4004 7591

$$

PAC029-091-092245-
/O.CON.KPHI.SV.W.0186.000000T0000Z-090809T2245Z/
CHESTER PA-MONTGOMERY PA-
603 PM EDT SUN AUG 9 2009

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 645 PM EDT
FOR CENTRAL MONTGOMERY AND CHESTER COUNTIES...

AT 602 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO
INDICATE A LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING
WINDS IN EXCESS OF 60 MPH.  THESE STORMS WERE LOCATED ALONG A LINE
EXTENDING FROM SCHWENKSVILLE TO HONEY BROOK...OR ALONG A LINE
EXTENDING FROM 20 MILES NORTH OF WEST CHESTER TO 17 MILES WEST OF
WEST CHESTER...MOVING SOUTHEAST AT 45 MPH.

SEVERE THUNDERSTORMS WILL BE NEAR...
  SKIPPACK...CHESTER SPRINGS...TRAPPE AND SOUTH COATESVILLE BY 610 PM
  EDT...
  VALLEY FORGE...TROOPER...THORNDALE AND MODENA BY 615 PM EDT...
  EAST NORRITON AND BLUE BELL BY 620 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS STORM HAS A HISTORY OF PRODUCING DAMAGING WINDS IN BERKS
COUNTY. NUMEROUS TREES AND WIRES WERE REPORTED KNOCKED DOWN THROUGHOUT
THE COUNTY. SEEK SHELTER NOW INSIDE A STURDY STRUCTURE AND STAY
AWAY FROM WINDOWS AND TREES

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 1000 PM EDT
SUNDAY EVENING FOR NORTHERN DELAWARE AND NORTHEAST MARYLAND AND NEW
JERSEY AND EASTERN PENNSYLVANIA. A SEVERE THUNDERSTORM WATCH ALSO
REMAINS IN EFFECT UNTIL 1100 PM EDT SUNDAY EVENING FOR SOUTHERN
DELAWARE AND NORTHEASTERN MARYLAND.

&&

LAT...LON 4003 7595 4011 7595 4014 7590 4016 7586
      4023 7574 4036 7542 4020 7515 4006 7537
      4005 7542 3985 7570 3977 7583 3999 7599
TIME...MOT...LOC 2202Z 306DEG 38KT 4024 7553 4004 7591

$$
 
TFG

000 
WWUS51 KPHI 092233
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
633 PM EDT SUN AUG 9 2009

PAC029-091-092243-
/O.CAN.KPHI.SV.W.0186.000000T0000Z-090809T2245Z/
CHESTER PA-MONTGOMERY PA-
633 PM EDT SUN AUG 9 2009

...THE SEVERE THUNDERSTORM WARNING FOR CENTRAL MONTGOMERY AND CHESTER
COUNTIES IS CANCELLED...

THE LINE OF DAMAGING THUNDERSTORMS HAS MOVED SOUTHEAST OF THE AREA.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 1000 PM EDT
SUNDAY EVENING FOR NORTHERN DELAWARE AND NORTHEAST MARYLAND AND NEW
JERSEY AND EASTERN PENNSYLVANIA.

LAT...LON 4003 7595 4011 7595 4014 7590 4016 7586
      4023 7574 4036 7542 4020 7515 4006 7537
      4005 7542 3985 7570 3977 7583 3999 7599
TIME...MOT...LOC 2233Z 306DEG 38KT 4005 7519 3985 7557

$$
 
TFG

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 9, 9:23 AM EDT	Areal Flood Advisory	PHI	Chester, Delaware, Montgomery, Philadelphia	83 min
Aug 9, 9:33 AM EDT	Areal Flood Warning	PHI	Philadelphia	51 min
Aug 9, 11:57 AM EDT	Flash Flood Watch	PHI	Berks, Carbon, Delaware, Lehigh, Monroe, Northampton and 1 more	11 hr
Aug 9, 1:56 PM EDT	Excessive Heat Warning	PHI	Delaware, Philadelphia	30 hr
Aug 9, 1:56 PM EDT	Heat Advisory	PHI	Berks, Lehigh, Northampton	30 hr
Aug 9, 4:30 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Carbon, Lehigh, Monroe, Northampton	90 min
Aug 9, 5:53 PM EDT	Severe Thunderstorm Warning	PHI	Chester	82 min
Aug 9, 6:03 PM EDT	Areal Flood Advisory	PHI	Berks, Chester, Delaware, Montgomery, Philadelphia	117 min
Aug 9, 6:10 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware, Montgomery, Philadelphia	80 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2009 Every severe thunderstorm 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.