Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2011

Severe Thunderstorm Warning 275, NWS Philadelphia/Mount Holly

August 19, 2011Chester County, Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 19, 2011, 5:42 PM EDT for Chester County, Montgomery County, Pennsylvania. It was in force for 48 min. 3 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 19, 2011, 5:42 PM EDT (21:42 UTC)
Expired: Aug 19, 2011, 6:30 PM EDT
In force: 48 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties Chester County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 90 km from the middle of the area, began a volume at 21:44 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 19, 6:00 PM EDT	HAIL 0.88	Chester Springs, PA
Aug 19, 6:09 PM EDT	HAIL 0.5	Chester Springs, PA
Aug 19, 6:20 PM EDT	TSTM WND DMG	Norristown, PA	BRANCHES DOWN

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 19, 1:04 PM EDT	Severe Thunderstorm Watch	SPC	8 hr

The nearest sounding before it

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 9.7 hours before the alert went out and 94 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: 146 J/kg
Mixed-layer CIN: -154 J/kg
Mixed-layer LCL: 1250 m above ground
0-6 km bulk shear: 19 kt
0-1 km storm-relative helicity: 359 m²/s²
0-3 km storm-relative helicity: 370 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

043 
WUUS51 KPHI 192142
SVRPHI
PAC029-091-192230-
/O.NEW.KPHI.SV.W.0275.110819T2142Z-110819T2230Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
542 PM EDT FRI AUG 19 2011

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  NORTHEASTERN CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...
  SOUTHERN MONTGOMERY COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 630 PM EDT

* AT 540 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE HAIL...AND
  DAMAGING WINDS IN EXCESS OF 60 MPH.  THIS STORM WAS LOCATED NEAR
  PUGHTOWN...OR 13 MILES NORTH OF WEST CHESTER...AND MOVING EAST AT
  25 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
  ROYERSFORD AROUND 550 PM EDT...
  PHOENIXVILLE AND TRAPPE AROUND 555 PM EDT...
  VALLEY FORGE AND COLLEGEVILLE AROUND 600 PM EDT...
  KING OF PRUSSIA AROUND 610 PM EDT...
  NORRISTOWN AROUND 615 PM EDT...
  CONSHOHOCKEN AND 9 MILES SOUTH OF LANSDALE AROUND 620 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS IS A DANGEROUS STORM. IF YOU ARE IN ITS PATH...PREPARE
IMMEDIATELY FOR DAMAGING WINDS...DESTRUCTIVE HAIL...AND DEADLY CLOUD
TO GROUND LIGHTNING. PEOPLE OUTSIDE SHOULD MOVE TO A SHELTER...
PREFERABLY INSIDE A STRONG BUILDING BUT AWAY FROM WINDOWS.

PLEASE REPORT HAIL OR STRONG WINDS TO THE NATIONAL WEATHER SERVICE BY
CALLING TOLL FREE...1-877-633-6772...WHEN YOU CAN DO SO SAFELY.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 900 PM EDT FRIDAY
EVENING FOR NORTHERN DELAWARE AND NEW JERSEY AND EASTERN
PENNSYLVANIA.

&&

LAT...LON 4026 7565 4025 7521 4024 7520 4005 7531
      4005 7536 4006 7537 4005 7540 4006 7574
TIME...MOT...LOC 2142Z 278DEG 21KT 4015 7560

$$

TFG

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 18, 8:08 PM EDT	Special Weather Statement	PHI	Berks	67 min
Aug 18, 8:26 PM EDT	Areal Flood Advisory	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	112 min
Aug 18, 8:31 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery	59 min
Aug 18, 8:48 PM EDT	Special Weather Statement	PHI	Monroe	57 min
Aug 18, 8:48 PM EDT	Severe Thunderstorm Warning	PHI	Bucks	57 min
Aug 19, 12:02 AM EDT	Special Weather Statement	PHI	Chester	58 min
Aug 19, 12:50 AM EDT	Special Weather Statement	PHI	Chester, Delaware	40 min
Aug 19, 1:14 AM EDT	Areal Flood Advisory	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	3 hr
Aug 19, 1:31 AM EDT	Special Weather Statement	PHI	Delaware, Philadelphia	59 min
Aug 19, 4:00 AM EDT	Areal Flood Warning	PHI	Delaware	4 hr
Aug 19, 1:46 PM EDT	Severe Thunderstorm Warning	PHI	Monroe	59 min
Aug 19, 2:35 PM EDT	Severe Thunderstorm Warning	PHI	Carbon, Monroe	70 min
Aug 19, 2:38 PM EDT	Areal Flood Advisory	PHI	Carbon, Monroe	3 hr
Aug 19, 2:57 PM EDT	Flash Flood Warning	PHI	Carbon, Monroe	3 hr
Aug 19, 3:47 PM EDT	Severe Thunderstorm Warning	PHI	Carbon, Monroe	58 min
Aug 19, 4:29 PM EDT	Severe Thunderstorm Warning	PHI	Carbon, Lehigh, Monroe, Northampton	61 min
Aug 19, 4:32 PM EDT	Areal Flood Advisory	PHI	Berks, Lehigh, Northampton	2 hr
Aug 19, 4:52 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Lehigh, Montgomery, Northampton	53 min
Aug 19, 5:35 PM EDT	Severe Thunderstorm Warning	PHI	Chester	55 min
Aug 19, 5:39 PM EDT	Areal Flood Advisory	PHI	Chester, Delaware	3 hr
Aug 19, 5:45 PM EDT	Areal Flood Advisory	PHI	Bucks, Montgomery, Philadelphia	3 hr
Aug 19, 5:59 PM EDT	Severe Thunderstorm Warning	PHI	Bucks	80 min
Aug 19, 6:14 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	65 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2011 Every severe thunderstorm warning in 2011

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.