Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2008

Severe Thunderstorm Warning 149, NWS Philadelphia/Mount Holly

July 23, 2008Chester County, Delaware County, Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Jul 23, 2008, 3:58 PM EDT for Chester County, Delaware County, Montgomery County, Pennsylvania. It was in force for 62 min. 4 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: Jul 23, 2008, 3:58 PM EDT (19:58 UTC)
Expired: Jul 23, 2008, 5:00 PM EDT
In force: 62 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties Chester County, PA, Delaware County, PA, Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 92 km from the middle of the area, began a volume at 19:59 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
Jul 23, 4:10 PM EDT	TSTM WND GST 55	Royersford, PA
Jul 23, 4:20 PM EDT	HAIL 0.25	1 S Phoenixville, PA
Jul 23, 4:20 PM EDT	HAIL 0.88	Royersford, PA
Jul 23, 4:50 PM EDT	HAIL 0.75	East Greenville, PA

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 23, 2:34 PM EDT	Severe Thunderstorm Watch	SPC	7 hr

The nearest sounding before it

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 8.0 hours before the alert went out and 89 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: 1012 J/kg
Mixed-layer CIN: -98 J/kg
Mixed-layer LCL: 980 m above ground
0-6 km bulk shear: 43 kt
0-1 km storm-relative helicity: -61 m²/s²
0-3 km storm-relative helicity: -48 m²/s²
Significant tornado parameter: -0.4
Supercell composite: -7.5

Open this sounding in Storm Lab

The text

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

000 
WUUS51 KPHI 231958
SVRPHI
PAC029-045-091-232100-
/O.NEW.KPHI.SV.W.0149.080723T1958Z-080723T2100Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
358 PM EDT WED JUL 23 2008

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  NORTHEASTERN CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...
  NORTH CENTRAL DELAWARE COUNTY IN SOUTHEAST PENNSYLVANIA...
  MONTGOMERY COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 500 PM EDT

* AT 355 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM CAPABLE OF PRODUCING NICKEL SIZE HAIL...AND
  DAMAGING WINDS IN EXCESS OF 60 MPH.  THIS STORM WAS LOCATED NEAR
  PAOLI...AND MOVING NORTH AT 25 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
  PAOLI BY 405 PM...
  RADNOR TOWNSHIP BY 410 PM...
  VALLEY FORGE BY 415 PM...
  KING OF PRUSSIA AND PHOENIXVILLE BY 420 PM...
  NORRISTOWN BY 425 PM...
  COLLEGEVILLE BY 430 PM...

IN ADDITION TO LARGE HAIL AND DAMAGING WINDS...CONTINUOUS CLOUD TO
GROUND LIGHTNING IS OCCURRING WITH THIS STORM. MOVE INDOORS
IMMEDIATELY LIGHTNING IS ONE OF NATURES NUMBER ONE 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 WEDNESDAY
EVENING FOR DELAWARE AND NORTHEASTERN MARYLAND AND NEW JERSEY AND
SOUTHEAST PENNSYLVANIA.

LAT...LON 4044 7553 4021 7516 3997 7535 3999 7545
      3995 7551 3992 7554 3994 7566
TIME...MOT...LOC 1958Z 201DEG 21KT 4000 7550

$$

IOVINO

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 23, 3:51 AM EDT	Flash Flood Watch	PHI	Berks, Carbon, Delaware, Lehigh, Monroe, Northampton and 1 more	25 hr
Jul 23, 4:23 AM EDT	Areal Flood Advisory	PHI	Bucks, Chester, Montgomery	3 hr
Jul 23, 2:55 PM EDT	Severe Thunderstorm Warning	PHI	Bucks	35 min
Jul 23, 2:58 PM EDT	Severe Thunderstorm Warning	PHI	Bucks	47 min
Jul 23, 3:30 PM EDT	Severe Thunderstorm Warning	PHI	Delaware, Philadelphia	60 min
Jul 23, 4:27 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	38 min
Jul 23, 4:47 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Lehigh, Montgomery, Northampton	58 min
Jul 23, 5:03 PM EDT	Severe Thunderstorm Warning	PHI	Bucks	57 min
Jul 23, 5:13 PM EDT	Severe Thunderstorm Warning	PHI	Bucks	62 min
Jul 23, 7:00 PM EDT	Severe Thunderstorm Warning	PHI	Delaware	60 min
Jul 23, 7:48 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Delaware, Montgomery, Philadelphia	57 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2008 Every severe thunderstorm warning in 2008

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.