Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2009

Severe Thunderstorm Warning 215, NWS Philadelphia/Mount Holly

August 21, 2009Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 21, 2009, 1:52 PM EDT for Chester County, Pennsylvania. It was in force for 68 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 21, 2009, 1:52 PM EDT (17:52 UTC)
Expired: Aug 21, 2009, 3:00 PM EDT
In force: 68 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

County Chester County, PA

The radar

The Dover AFB radar (KDOX), 129 km from the middle of the area, began a volume at 17:55 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.

What was reported inside it

Time	Report	Where	Remark
Aug 21, 2:45 PM EDT	TSTM WND DMG	5 Nnw Cochranville, PA	TREES AND WIRES DOWN THROUGHOUT THE COUNTY. ALSO, TREE FELL ON AN OCCUPIED VEHICLE IN KENNETT TWP.

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 21, 11:28 AM EDT	Severe Thunderstorm Watch	SPC	7 hr

The nearest sounding before it

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 5.9 hours before the alert went out and 52 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: 96 J/kg
Mixed-layer CIN: -66 J/kg
Mixed-layer LCL: 930 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 43 m²/s²
0-3 km storm-relative helicity: 108 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.6

Open this sounding in Storm Lab

The text

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

000 
WUUS51 KPHI 211752
SVRPHI
PAC029-211900-
/O.NEW.KPHI.SV.W.0215.090821T1752Z-090821T1900Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
152 PM EDT FRI AUG 21 2009

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

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

* UNTIL 300 PM EDT

* AT 149 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM CAPABLE OF PRODUCING PENNY SIZE HAIL...AND
  DAMAGING WINDS IN EXCESS OF 60 MPH.  THIS STORM WAS LOCATED NEAR
  PARKESBURG...OR 16 MILES EAST OF LANCASTER...AND MOVING NORTHEAST
  AT 30 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
  PARKESBURG AROUND 155 PM EDT...
  COATESVILLE AROUND 205 PM EDT...
  HONEY BROOK AROUND 210 PM EDT...
  GLENMOORE AND ELVERSON AROUND 220 PM EDT...
  PUGHTOWN AROUND 235 PM EDT...
  CEDARVILLE AROUND 240 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 800 PM EDT FRIDAY
EVENING FOR NEW JERSEY AND EASTERN PENNSYLVANIA.

&&

LAT...LON 3978 7607 3985 7603 3987 7601 3992 7601
      3993 7600 3996 7600 4003 7595 4011 7593
      4025 7568 4006 7544 3973 7582 3973 7614
TIME...MOT...LOC 1750Z 229DEG 27KT 3997 7600

$$

NIERENBERG

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 21, 12:20 PM EDT	Severe Thunderstorm Warning	PHI	Berks	55 min
Aug 21, 12:55 PM EDT	Severe Thunderstorm Warning	PHI	Carbon, Monroe	35 min
Aug 21, 1:16 PM EDT	Severe Thunderstorm Warning	PHI	Berks	59 min
Aug 21, 1:29 PM EDT	Severe Thunderstorm Warning	PHI	Carbon, Lehigh, Monroe, Northampton	76 min
Aug 21, 1:55 PM EDT	Severe Thunderstorm Warning	PHI	Monroe	65 min
Aug 21, 2:41 PM EDT	Areal Flood Advisory	PHI	Monroe, Northampton	3 hr
Aug 21, 2:47 PM EDT	Flash Flood Watch	PHI	Berks, Carbon, Delaware, Lehigh, Monroe, Northampton and 1 more	35 hr

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.