Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2011

Severe Thunderstorm Warning 30, NWS Philadelphia/Mount Holly

April 28, 20115 counties in Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Apr 28, 2011, 10:00 AM EDT for 5 counties in Pennsylvania. It was in force for 60 min. 2 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: Apr 28, 2011, 10:00 AM EDT (14:00 UTC)
Expired: Apr 28, 2011, 11:00 AM EDT
In force: 60 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties Berks County, PA, Bucks County, PA, Chester County, PA, Lehigh County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 125 km from the middle of the area, began a volume at 14:00 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
Apr 28, 10:05 AM EDT	TSTM WND DMG	Mertztown, PA	LARGE TREE LIMBS DOWN
Apr 28, 11:06 AM EDT	TSTM WND DMG	Flying Hills, PA	TREES AND WIRES DOWN IN CUMRU 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
Apr 28, 4:05 AM EDT	Severe Thunderstorm Watch	SPC	6 hr
Apr 28, 9:45 AM EDT	Severe Thunderstorm Watch	SPC	6 hr

The nearest sounding before it

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 2.0 hours before the alert went out and 97 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: 482 J/kg
Mixed-layer CIN: -47 J/kg
Mixed-layer LCL: 670 m above ground
0-6 km bulk shear: 56 kt
0-1 km storm-relative helicity: 371 m²/s²
0-3 km storm-relative helicity: 401 m²/s²
Significant tornado parameter: 1.3
Supercell composite: 5.5

Open this sounding in Storm Lab

The text

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

488 
WUUS51 KPHI 281400
SVRPHI
PAC011-017-029-077-091-281500-
/O.NEW.KPHI.SV.W.0030.110428T1400Z-110428T1500Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1000 AM EDT THU APR 28 2011

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  BERKS COUNTY IN EASTERN PENNSYLVANIA...
  THIS INCLUDES THE CITY OF READING...
  LEHIGH COUNTY IN EASTERN PENNSYLVANIA...
  WEST CENTRAL BUCKS COUNTY IN SOUTHEAST PENNSYLVANIA...
  NORTH CENTRAL CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...
  NORTHWESTERN MONTGOMERY COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 1100 AM EDT

* AT 956 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED   
  A LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING       
  WINDS TO 60 MPH. THESE STORMS WERE LOCATED ALONG A LINE EXTENDING  
  FROM CLAUSSVILLE TO 7 MILES NORTH OF BIRDSBORO TO NEW MORGAN TO    
  9MILES WEST OF HONEY BROOK...AND MOVING NORTHEAST AT 50 MPH.

* SEVERE THUNDERSTORMS WILL BE NEAR...
  NEW MORGAN AND HONEY BROOK AROUND 1005 AM EDT...
  GLENMOORE...ZIONSVILLE...EMMAUS AND ELVERSON AROUND 1010 AM EDT...
  PUGHTOWN...GILBERTSVILLE AND EAST GREENVILLE AROUND 1015 AM EDT...
  ROYERSFORD AROUND 1020 AM EDT...

  THESE STORMS HAVE HAD A HISTORY OF KNOCKING DOWN SOME TREES IN     
  BERKS COUNTY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THESE SEVERE THUNDERSTORMS MAY CONTAIN LITTLE OR NO LIGHTNING. DO 
NOT WAIT FOR THUNDER BEFORE TAKING COVER. SEEK SHELTER IMMEDIATELY 
INSIDE A STURDY STRUCTURE AND STAY AWAY FROM WINDOWS.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 400 PM EDT
THURSDAY AFTERNOON FOR NORTHERN DELAWARE AND NORTHEASTERN MARYLAND 
AND NEW JERSEY AND EASTERN PENNSYLVANIA. 

&&

LAT...LON 4066 7570 4069 7569 4052 7533 4036 7513
      3998 7598 3999 7599 4003 7595 4011 7595
      4014 7590 4030 7613 4031 7613
TIME...MOT...LOC 1357Z 242DEG 45KT 4064 7561 4037 7573
          4024 7589 4008 7604

$$

GORSE

1 follow-up statement

835 
WWUS51 KPHI 281433
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1033 AM EDT THU APR 28 2011

PAC011-017-029-077-091-281500-
/O.CON.KPHI.SV.W.0030.000000T0000Z-110428T1500Z/
CHESTER PA-MONTGOMERY PA-BERKS PA-LEHIGH PA-BUCKS PA-
1033 AM EDT THU APR 28 2011

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1100 AM EDT
FOR WEST CENTRAL BUCKS...SOUTHERN LEHIGH...EASTERN BERKS...
NORTHWESTERN MONTGOMERY AND NORTH CENTRAL CHESTER COUNTIES...

AT 1030 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO
INDICATE A LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING QUARTER 
SIZE HAIL...AND DAMAGING WINDS TO 60 MPH. THESE STORMS WERE LOCATED 
ALONG A LINE EXTENDING FROM 9 MILES NORTHEAST OF EMMAUS TO PENNSBURG 
TO STOWE TO HONEY BROOK...OR ALONG A LINE EXTENDING FROM ALLENTOWN 
TO 15 MILES SOUTH OF ALLENTOWN TO 14 MILES SOUTHEAST OF READING TO 
16 MILES SOUTH OF READING...MOVING NORTHEAST AT 50 MPH.

SEVERE THUNDERSTORMS WILL BE NEAR...
  CEDARVILLE...SOUTH POTTSTOWN...POTTSTOWN AND POTTSGROVE BY 1040 AM
  EDT...
  KENILWORTH BY 1045 AM EDT...
  GLENMOORE...TRUMBAUERSVILLE...SANATOGA AND GREEN LANE BY 1050 AM
  EDT...
  RICHLANDTOWN BY 1055 AM EDT...

SOME OF THESE STORMS HAVE HAD A HISTORY OF PRODUCING WIND DAMAGE     
IN SOUTHEASTERN PENNSYLVANIA.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 400 PM EDT
THURSDAY AFTERNOON FOR NORTHERN DELAWARE AND NORTHEASTERN MARYLAND
AND NEW JERSEY AND EASTERN PENNSYLVANIA.

&&

LAT...LON 4066 7563 4052 7533 4036 7513 3998 7598
      3999 7599 4003 7595 4011 7595 4014 7590
      4029 7612
TIME...MOT...LOC 1432Z 252DEG 45KT 4065 7539 4038 7551
          4025 7567 4011 7591

$$

GORSE

The office that day

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

Issued	Product	Office	Counties	Lasted
Apr 28, 4:24 AM EDT	Special Weather Statement	PHI	Berks, Carbon, Lehigh, Northampton	66 min
Apr 28, 4:36 AM EDT	Severe Thunderstorm Warning	PHI	Berks, Carbon, Lehigh, Monroe, Northampton	54 min
Apr 28, 5:31 AM EDT	Special Weather Statement	PHI	Carbon, Monroe	59 min
Apr 28, 5:49 AM EDT	Special Weather Statement	PHI	Carbon	56 min
Apr 28, 5:58 AM EDT	Areal Flood Advisory	PHI	Berks, Carbon, Lehigh, Monroe, Northampton	3 hr
Apr 28, 6:12 AM EDT	Special Weather Statement	PHI	Chester, Delaware, Philadelphia	63 min
Apr 28, 6:18 AM EDT	Severe Thunderstorm Warning	PHI	Carbon, Monroe	57 min
Apr 28, 6:23 AM EDT	Special Weather Statement	PHI	Berks, Chester, Lehigh, Montgomery	52 min
Apr 28, 6:56 AM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Chester, Delaware, Lehigh, Montgomery and 2 more	34 min
Apr 28, 7:06 AM EDT	Flash Flood Warning	PHI	Carbon, Monroe	6 hr
Apr 28, 7:35 AM EDT	Special Weather Statement	PHI	Bucks	55 min
Apr 28, 8:17 AM EDT	Special Weather Statement	PHI	Berks	58 min
Apr 28, 8:55 AM EDT	Severe Thunderstorm Warning	PHI	Berks, Lehigh	65 min
Apr 28, 8:59 AM EDT	Areal Flood Advisory	PHI	Berks, Lehigh	4 hr
Apr 28, 9:11 AM EDT	Special Weather Statement	PHI	Carbon, Monroe	49 min
Apr 28, 9:33 AM EDT	Severe Thunderstorm Warning	PHI	Carbon, Lehigh, Monroe, Northampton	57 min
Apr 28, 10:25 AM EDT	Severe Thunderstorm Warning	PHI	Bucks, Carbon, Lehigh, Monroe, Northampton	50 min
Apr 28, 10:48 AM EDT	Areal Flood Advisory	PHI	Bucks, Chester, Montgomery, Northampton	3 hr
Apr 28, 10:57 AM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Chester, Lehigh, Montgomery, Northampton	63 min
Apr 28, 10:58 AM EDT	Tornado Warning	PHI	Bucks, Northampton	32 min
Apr 28, 11:11 AM EDT	Severe Thunderstorm Warning	PHI	Northampton	64 min
Apr 28, 12:03 PM EDT	Special Weather Statement	PHI	Montgomery, Philadelphia	57 min
Apr 28, 12:11 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Chester, Delaware, Montgomery	31 min
Apr 28, 12:42 PM EDT	Special Weather Statement	PHI	Delaware	63 min
Apr 28, 12:45 PM EDT	Special Weather Statement	PHI	Bucks, Delaware, Montgomery, Philadelphia	60 min
Apr 28, 1:23 PM EDT	Areal Flood Advisory	PHI	Philadelphia	103 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.