Alert archive / Maryland / Severe Thunderstorm Warnings in 2009

Severe Thunderstorm Warning 187, NWS Philadelphia/Mount Holly

August 9, 2009Cecil County, Maryland; New Castle County, Delaware; Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 9, 2009, 5:53 PM EDT for Cecil County, Maryland; New Castle County, Delaware; Chester County, Pennsylvania. It was in force for 82 min. 3 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: Aug 9, 2009, 5:53 PM EDT (21:53 UTC)
Expired: Aug 9, 2009, 7:15 PM EDT
In force: 82 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties New Castle County, DE, Cecil County, MD, Chester County, PA

The radar

The Dover AFB radar (KDOX), 98 km from the middle of the area, began a volume at 21:57 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 9, 6:25 PM EDT	TSTM WND DMG	Conowingo, MD	SEVERAL TREES KNOCKED DOWN ACROSS THE NORTHERN HALF OF THE COUNTY FROM CONOWINGO TO FAIR HILL. TREE FELL ONTO A TRAILER IN NORTH EAST. TREE ONTO A HOME NEAR FAIR HILL. NO INJURIES REPORTED.
Aug 9, 6:35 PM EDT	TSTM WND GST 65	4 Ne Elkton, DE	60 TO 65 MPH WIND GUST ESTIMATED BY FORMER NWS EMPLOYEE.
Aug 9, 6:40 PM EDT	TSTM WND GST 45	Wilmington, DE	45 MPH WIND GUST AT NEW CASTLE COUNTY AIRPORT.

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 9, 3:18 PM EDT	Severe Thunderstorm Watch	SPC	5 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 9.9 hours before the alert went out and 156 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: 255 J/kg
Mixed-layer CIN: -88 J/kg
Mixed-layer LCL: 1087 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 243 m²/s²
0-3 km storm-relative helicity: 282 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 6.6

Open this sounding in Storm Lab

The text

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

000 
WUUS51 KPHI 092153
SVRPHI
DEC003-MDC015-PAC029-092315-
/O.NEW.KPHI.SV.W.0187.090809T2153Z-090809T2315Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
553 PM EDT SUN AUG 9 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...
  NEW CASTLE COUNTY IN NORTHERN DELAWARE...
  THIS INCLUDES THE CITIES OF...WILMINGTON...NEWARK...MIDDLETOWN...
  SOUTHERN CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 715 PM EDT

* AT 549 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 17
  MILES NORTHWEST OF PARKESBURG...OR 11 MILES NORTHEAST OF
  LANCASTER...AND MOVING SOUTHEAST AT 35 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
  PARKESBURG AROUND 615 PM EDT...
  COCHRANVILLE AND HOMEVILLE AROUND 625 PM EDT...
  MOUNT VERNON AROUND 630 PM EDT...
  WEST GROVE AND OXFORD AROUND 635 PM EDT...
  BLAKE...LOMBARD AND LADENBERG AROUND 640 PM EDT...
  FAIR HILL AROUND 645 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

NUMEROUS TREES AND WIRES WERE KNOCKED DOWN WITH THIS THUNDERSTORM
COMPLEX THROUGHOUT BERKS COUNTY. PLEASE TAKE THIS STORM SERIOUSLY.

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 GREATEST KILLERS.
REMEMBER...IF YOU CAN HEAR THUNDER...YOU ARE CLOSE ENOUGH TO BE
STRUCK BY LIGHTNING.

HEAVY RAIN WILL OCCUR WITH THESE STORMS AND CAUSE LOW-LYING 
AND POOR DRAINAGE FLOODING.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 1000 PM EDT
SUNDAY EVENING FOR NORTHERN DELAWARE AND NORTHEAST MARYLAND AND NEW
JERSEY AND EASTERN PENNSYLVANIA. A SEVERE THUNDERSTORM WATCH ALSO
REMAINS IN EFFECT UNTIL 1100 PM EDT SUNDAY EVENING FOR SOUTHERN
DELAWARE AND NORTHEASTERN MARYLAND.

&&

LAT...LON 3976 7609 3987 7601 4011 7594 3993 7578
      3987 7562 3984 7559 3980 7542 3962 7560
      3959 7559 3960 7555 3946 7558 3939 7551
      3939 7552 3938 7605 3944 7600 3946 7602
      3953 7599 3954 7607 3962 7616 3972 7619
TIME...MOT...LOC 2151Z 333DEG 31KT 4013 7612

$$

TFG

1 follow-up statement

000 
WWUS51 KPHI 092238
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
638 PM EDT SUN AUG 9 2009

PAC029-092247-
/O.CAN.KPHI.SV.W.0187.000000T0000Z-090809T2315Z/
CHESTER PA-
638 PM EDT SUN AUG 9 2009

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHERN CHESTER COUNTY IS
CANCELLED...

THE LINE OF SEVERE THUNDERSTORMS HAS MOVED SOUTH OF THE COUNTY.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 1000 PM EDT
SUNDAY EVENING FOR NORTHERN DELAWARE AND NORTHEAST MARYLAND AND NEW
JERSEY AND EASTERN PENNSYLVANIA. A SEVERE THUNDERSTORM WATCH ALSO
REMAINS IN EFFECT UNTIL 1100 PM EDT SUNDAY EVENING FOR SOUTHERN
DELAWARE AND NORTHEASTERN MARYLAND.

LAT...LON 3973 7578 3979 7574 3984 7563 3980 7542
      3962 7560 3959 7559 3959 7557 3946 7558
      3939 7551 3939 7552 3938 7605 3944 7600
      3946 7602 3953 7599 3954 7607 3962 7616
      3972 7619
TIME...MOT...LOC 2237Z 333DEG 38KT 3981 7547 3967 7613

$$

DEC003-MDC015-092315-
/O.CON.KPHI.SV.W.0187.000000T0000Z-090809T2315Z/
CECIL MD-NEW CASTLE DE-
638 PM EDT SUN AUG 9 2009

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 715 PM EDT
FOR NEW CASTLE AND CECIL COUNTIES...

AT 635 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO
INDICATE A LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING
WINDS IN EXCESS OF 60 MPH.  THESE STORMS WERE LOCATED ALONG A LINE
EXTENDING FROM ARDEN TO RICHARDSMERE...OR ALONG A LINE EXTENDING FROM
8 MILES NORTH OF WILMINGTON TO 18 MILES WEST OF ELKTON...MOVING
SOUTHEAST AT 45 MPH.

SEVERE THUNDERSTORMS WILL BE NEAR...
  CHERRY HILL...BAY VIEW...BARKSDALE AND PORT DEPOSIT BY 645 PM
  EDT...
  GLASGOW...BEAR...ELKTON AND CHARLESTOWN BY 650 PM EDT...
  HOLLYWOOD BEACH AND BRANTWOOD BY 655 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS STORM HAS A HISTORY OF PRODUCING WIND DAMAGE ACROSS CHESTER
COUNTY. THIS IS AN EXTREMELY DANGEROUS SITUATION. SEEK SHELTER 
NOW INSIDE A STURDY STRUCTURE AND STAY AWAY FROM
WINDOWS AND TREES

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 1000 PM EDT
SUNDAY EVENING FOR NORTHERN DELAWARE AND NORTHEAST MARYLAND AND NEW
JERSEY AND EASTERN PENNSYLVANIA. A SEVERE THUNDERSTORM WATCH ALSO
REMAINS IN EFFECT UNTIL 1100 PM EDT SUNDAY EVENING FOR SOUTHERN
DELAWARE AND NORTHEASTERN MARYLAND.

&&

LAT...LON 3973 7578 3979 7574 3984 7563 3980 7542
      3962 7560 3959 7559 3959 7557 3946 7558
      3939 7551 3939 7552 3938 7605 3944 7600
      3946 7602 3953 7599 3954 7607 3962 7616
      3972 7619
TIME...MOT...LOC 2237Z 333DEG 38KT 3981 7547 3967 7613

$$
 
TFG

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 9, 11:57 AM EDT	Flash Flood Watch	PHI	Cecil	11 hr
Aug 9, 1:56 PM EDT	Heat Advisory	PHI	Caroline, Cecil, Kent, Queen Anne's, Talbot	30 hr
Aug 9, 6:03 PM EDT	Areal Flood Advisory	PHI	Cecil	117 min
Aug 9, 6:48 PM EDT	Severe Thunderstorm Warning	PHI	Caroline, Cecil, Kent, Queen Anne's	72 min
Aug 9, 1:56 PM EDT	Excessive Heat Warning	PHI	New Castle	30 hr
Aug 9, 7:36 PM EDT	Severe Thunderstorm Warning	PHI	Kent, Sussex	69 min
Aug 9, 9:23 AM EDT	Areal Flood Advisory	PHI	Chester, Delaware, Montgomery, Philadelphia	83 min
Aug 9, 9:33 AM EDT	Areal Flood Warning	PHI	Philadelphia	51 min
Aug 9, 4:30 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Carbon, Lehigh, Monroe, Northampton	90 min
Aug 9, 5:17 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester, Montgomery	76 min
Aug 9, 6:10 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware, Montgomery, Philadelphia	80 min

Nearby

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