Alert archive / Delaware / Severe Thunderstorm Warnings in 2009

Severe Thunderstorm Warning 165, NWS Philadelphia/Mount Holly

July 31, 2009Kent County, New Castle County, Sussex County, Delaware

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Jul 31, 2009, 4:12 PM EDT for Kent County, New Castle County, Sussex County, Delaware. It was in force for 73 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: Jul 31, 2009, 4:12 PM EDT (20:12 UTC)
Expired: Jul 31, 2009, 5:25 PM EDT
In force: 73 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties Kent County, DE, New Castle County, DE, Sussex County, DE

The radar

The Dover AFB radar (KDOX), 35 km from the middle of the area, began a volume at 20:14 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.

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

Wallops Is Stn, VA (KWAL), launched 12:00Z, 8.2 hours before the alert went out and 135 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: 969 J/kg
Mixed-layer CIN: -11 J/kg
Mixed-layer LCL: 484 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 53 m²/s²
0-3 km storm-relative helicity: 101 m²/s²
Significant tornado parameter: 0.3
Supercell composite: 2.0

Open this sounding in Storm Lab

The text

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

000 
WUUS51 KPHI 312012
SVRPHI
DEC001-003-005-312145-
/O.NEW.KPHI.SV.W.0165.090731T2012Z-090731T2145Z/

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

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  KENT COUNTY IN CENTRAL DELAWARE...
  THIS INCLUDES THE CITY OF DOVER...
  SOUTHERN NEW CASTLE COUNTY IN NORTHERN DELAWARE...
  THIS INCLUDES THE CITY OF MIDDLETOWN...
  NORTHERN SUSSEX COUNTY IN SOUTHERN DELAWARE...
  THIS INCLUDES THE CITY OF GEORGETOWN...

* UNTIL 545 PM EDT

* AT 411 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 10 MILES NORTHWEST OF DELANEY CORNER TO 18 MILES WEST OF
  SANDTOWN TO 31 MILES WEST OF ANDREWSVILLE...OR ALONG A LINE
  EXTENDING FROM 11 MILES SOUTHWEST OF MIDDLETOWN TO CENTERVILLE TO 6
  MILES WEST OF EASTON...AND MOVING SOUTHEAST AT 35 MPH.

* SEVERE THUNDERSTORMS WILL BE NEAR...
  DELANEY CORNER AROUND 425 PM EDT...
  CLAYTON AROUND 435 PM EDT...
  SANDTOWN AROUND 440 PM EDT...
  HAZLETTVILLE AROUND 445 PM EDT...
  DOVER SPEEDWAY AND ANDREWSVILLE AROUND 450 PM EDT...
  DOVER AROUND 455 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

DOPPLER RADAR HAS INDICATED SOME WEAK ROTATION WITHIN THIS LINE.
WHILE NOT IMMEDIATELY LIKELY...A TORNADO MAY STILL DEVELOP. IF A
TORNADO IS SPOTTED...ACT QUICKLY AND MOVE TO A PLACE OF SAFETY IN A
STURDY STRUCTURE...SUCH AS A BASEMENT OR SMALL INTERIOR ROOM.

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

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 3956 7579 3957 7557 3954 7555 3946 7558
      3935 7548 3932 7543 3924 7538 3916 7540
      3907 7539 3903 7533 3898 7529 3893 7530
      3883 7521 3879 7513 3880 7507 3870 7507
      3867 7570
TIME...MOT...LOC 2011Z 304DEG 32KT 3937 7591 3901 7605
          3876 7619

$$

TFG

1 follow-up statement

000 
WWUS51 KPHI 312125
SVSPHI

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

DEC001-003-005-312134-
/O.CAN.KPHI.SV.W.0165.000000T0000Z-090731T2145Z/
KENT DE-SUSSEX DE-NEW CASTLE DE-
525 PM EDT FRI JUL 31 2009

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHERN NEW CASTLE...NORTHERN
SUSSEX AND KENT COUNTIES IS CANCELLED...

THE SQUALL LINE WHICH PROMPTED THE WARNING HAS MOVED EAST OF THE 
AREA AND IS 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 3956 7579 3957 7557 3954 7555 3946 7558
      3935 7548 3932 7543 3924 7538 3916 7540
      3907 7539 3903 7533 3898 7529 3893 7530
      3883 7521 3879 7513 3880 7507 3870 7507
      3867 7570
TIME...MOT...LOC 2124Z 304DEG 32KT 3901 7522 3865 7536
          3840 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, 4:03 PM EDT	Severe Thunderstorm Warning	PHI	New Castle	57 min
Jul 31, 4:08 PM EDT	Flash Flood Warning	PHI	New Castle	3 hr
Jul 31, 4:36 PM EDT	Severe Thunderstorm Warning	PHI	Sussex	54 min

Nearby

Severe Thunderstorm Warnings in Delaware, 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.