Alert archive / Pennsylvania / Tornado Warnings in 2004

Tornado Warning 10, NWS Philadelphia/Mount Holly

August 11, 2004Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this tornado warning at Aug 11, 2004, 3:12 PM EDT for Chester County, Pennsylvania. It was in force for 78 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Aug 11, 2004, 3:12 PM EDT (19:12 UTC)
Expired: Aug 11, 2004, 4:30 PM EDT
In force: 78 min
Issued by: NWS Philadelphia/Mount Holly
Area: Counties, with a storm outline in the text

County Chester County, PA

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 11, 12:55 PM EDT	Severe Thunderstorm Watch	SPC	7 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 7.2 hours before the alert went out and 160 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: 253 J/kg
Mixed-layer CIN: -107 J/kg
Mixed-layer LCL: 1194 m above ground
0-6 km bulk shear: 26 kt
0-1 km storm-relative helicity: 51 m²/s²
0-3 km storm-relative helicity: 95 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

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

000 
WFUS51 KPHI 111912
TORPHI
PAC029-112030-

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
311 PM EDT WED AUG 11 2004

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS UPGRADED
THE SEVERE THUNDERSTORM WARNING TO A TORNADO WARNING FOR 
CHESTER COUNTY. 

* TORNADO WARNING FOR...
  CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA

* UNTIL 430 PM EDT

* AT 307 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO 9 MILES
  SOUTHWEST OF PARKESBURG MOVING EAST AT 25 MPH.

* THE TORNADO IS EXPECTED TO BE NEAR...
  PARKESBURG BY 340 PM EDT
  WEST GROVE BY 355 PM EDT
  6 MILES SOUTH OF COATESVILLE BY 405 PM EDT

WHEN A TORNADO WARNING IS ISSUED BASED ON DOPPLER RADAR...IT MEANS
THAT STRONG ROTATION HAS BEEN DETECTED IN THE STORM. A TORNADO MAY
ALREADY BE ON THE GROUND...OR IS EXPECTED TO DEVELOP SHORTLY. IF YOU
ARE IN THE PATH OF THIS DANGEROUS STORM...MOVE INDOORS AND TO THE
LOWEST LEVEL OF THE BUILDING. STAY AWAY FROM WINDOWS. IF DRIVING...DO
NOT SEEK SHELTER UNDER A HIGHWAY OVERPASS.

THE SAFEST PLACE TO BE DURING A TORNADO IS IN A BASEMENT. GET UNDER A
WORKBENCH OR OTHER PIECE OF STURDY FURNITURE. IF NO BASEMENT IS
AVAILABLE...SEEK SHELTER ON THE LOWEST FLOOR OF THE BUILDING IN AN
INTERIOR HALLWAY OR ROOM SUCH AS A CLOSET. USE BLANKETS OR PILLOWS TO
COVER YOUR BODY AND ALWAYS STAY AWAY FROM WINDOWS.

IF IN MOBILE HOMES OR VEHICLES...EVACUATE THEM AND GET INSIDE A
SUBSTANTIAL SHELTER. IF NO SHELTER IS AVAILABLE...LIE FLAT IN THE
NEAREST DITCH OR OTHER LOW SPOT AND COVER YOUR HEAD WITH YOUR HANDS.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 800 PM EDT
WEDNESDAY EVENING FOR NORTHWESTERN NEW JERSEY AND EASTERN
PENNSYLVANIA. A SEVERE THUNDERSTORM WATCH ALSO REMAINS IN EFFECT
UNTIL 800 PM EDT WEDNESDAY EVENING FOR SOUTHWESTERN DELAWARE AND
NORTHEASTERN MARYLAND AND SOUTHERN NEW JERSEY.

LAT...LON 3996 7616 3979 7614 3979 7575 4001 7578

$$

TFG

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 11, 2:21 PM EDT	Severe Thunderstorm Warning	PHI	Bucks	54 min
Aug 11, 2:40 PM EDT	Severe Thunderstorm Warning	PHI	Chester	95 min
Aug 11, 4:04 PM EDT	Severe Thunderstorm Warning	PHI	Bucks	41 min
Aug 11, 5:09 PM EDT	Special Marine Warning	PHI		81 min
Aug 11, 5:25 PM EDT	Severe Thunderstorm Warning	PHI	Berks	65 min
Aug 11, 5:28 PM EDT	Severe Thunderstorm Warning	PHI	Philadelphia	32 min
Aug 11, 5:37 PM EDT	Severe Thunderstorm Warning	PHI	Bucks	53 min
Aug 11, 5:56 PM EDT	Severe Thunderstorm Warning	PHI	Montgomery	34 min

Nearby

Tornado Warnings in Pennsylvania, 2004 Every tornado warning in 2004 Tornadoes in 2004

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive.