Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2009

Severe Thunderstorm Warning 162, NWS Philadelphia/Mount Holly

July 31, 2009Chester County, Pennsylvania; Cecil County, Maryland

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Jul 31, 2009, 3:40 PM EDT for Chester County, Pennsylvania; Cecil County, Maryland. It was in force for 65 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: Jul 31, 2009, 3:40 PM EDT (19:40 UTC)
Expired: Jul 31, 2009, 4:45 PM EDT
In force: 65 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties Cecil County, MD, Chester County, PA

The radar

The Dover AFB radar (KDOX), 96 km from the middle of the area, began a volume at 19:40 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
Jul 31, 3:45 PM EDT	TSTM WND DMG	Perryville, MD	TREES REPORTED DOWN IN PERRYVILLE. ALSO, DAMAGE REPORTED TO MULTIPLE CARS AND TRACTOR TRAILERS.

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
Jul 31, 1:18 PM EDT	Severe Thunderstorm Watch	SPC	7 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 7.7 hours before the alert went out and 142 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: 276 J/kg
Mixed-layer CIN: -61 J/kg
Mixed-layer LCL: 888 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: -25 m²/s²
0-3 km storm-relative helicity: 18 m²/s²
Significant tornado parameter: -0.0
Supercell composite: -0.3

Open this sounding in Storm Lab

The text

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

000 
WUUS51 KPHI 311940
SVRPHI
MDC015-PAC029-312045-
/O.NEW.KPHI.SV.W.0162.090731T1940Z-090731T2045Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
340 PM EDT FRI JUL 31 2009

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  CECIL COUNTY IN NORTHEAST MARYLAND...
  THIS INCLUDES THE CITY OF ELKTON...
  SOUTHWESTERN CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 445 PM EDT

* AT 337 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN
  EXCESS OF 60 MPH.  THESE STORMS WERE LOCATED ALONG A LINE 
  EXTENDING FROM 22 MILES WEST OF ELKTON TO 19 MILES EAST OF   
  BALTIMORE...AND MOVING EAST AT 40 MPH.

* SEVERE THUNDERSTORMS WILL BE NEAR...
  ROCK SPRINGS...RICHARDSMERE...OCTORARO AND CONOWINGO AROUND 345 PM
  EDT...
  WEST NOTTINGHAM...WOODLAWN AND RISING SUN AROUND 350 PM EDT...
  FARMINGTON AROUND 355 PM EDT...
  ZION AND LOMBARD AROUND 400 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3980 7579 3953 7578 3948 7595 3949 7594
      3945 7602 3953 7600 3955 7603 3954 7607
      3956 7610 3971 7621
TIME...MOT...LOC 1938Z 252DEG 34KT 3967 7621 3939 7625

$$

AMC

1 follow-up statement

000 
WWUS51 KPHI 312043
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
443 PM EDT FRI JUL 31 2009

MDC015-PAC029-312052-
/O.EXP.KPHI.SV.W.0162.000000T0000Z-090731T2045Z/
CECIL MD-CHESTER PA-
443 PM EDT FRI JUL 31 2009

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHWESTERN CHESTER AND CECIL
COUNTIES WILL EXPIRE AT 445 PM EDT...

THE STORMS WHICH PROMPTED THE WARNING HAVE MOVED EAST OF THE AREA 
AND ARE NO LONGER A THREAT.

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

LAT...LON 3980 7579 3953 7578 3948 7595 3949 7594
      3945 7602 3953 7600 3955 7603 3954 7607
      3956 7610 3971 7621
TIME...MOT...LOC 2042Z 252DEG 34KT 3986 7546 3958 7550

$$

AMC

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 31, 2:13 PM EDT	Flash Flood Warning	PHI	Carbon, Monroe	4 hr
Jul 31, 3:04 PM EDT	Flash Flood Warning	PHI	Bucks, Chester, Montgomery	3 hr
Jul 31, 3:36 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	54 min
Jul 31, 4:03 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	57 min
Jul 31, 4:08 PM EDT	Flash Flood Warning	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	3 hr
Jul 31, 4:31 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Delaware, Montgomery, Philadelphia	59 min
Jul 31, 3:10 PM EDT	Severe Thunderstorm Warning	PHI	Cecil, Kent	65 min
Jul 31, 3:54 PM EDT	Severe Thunderstorm Warning	PHI	Caroline, Kent, Queen Anne's	53 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2009 Severe Thunderstorm Warnings in Maryland, 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.