Alert archive / Delaware / Severe Thunderstorm Warnings in 2009

Severe Thunderstorm Warning 84, NWS Philadelphia/Mount Holly

June 20, 2009New Castle County, Delaware; Chester County, Pennsylvania; Cecil County, Maryland

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Jun 20, 2009, 4:27 PM EDT for New Castle County, Delaware; Chester County, Pennsylvania; Cecil County, Maryland. It was in force for 53 min. 1 report 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: Jun 20, 2009, 4:27 PM EDT (20:27 UTC)
Expired: Jun 20, 2009, 5:20 PM EDT
In force: 53 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), 108 km from the middle of the area, began a volume at 20:27 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
Jun 20, 4:40 PM EDT	TSTM WND DMG	3 Nw Lombard, PA	TREES AND WIRES DOWN IN NOTTINGHAM TOWNSHIP.

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
Jun 20, 3:05 PM EDT	Tornado Watch	SPC	5 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 8.5 hours before the alert went out and 143 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: 1441 J/kg
Mixed-layer CIN: -83 J/kg
Mixed-layer LCL: 978 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: 90 m²/s²
0-3 km storm-relative helicity: 123 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 3.2

Open this sounding in Storm Lab

The text

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

000 
WUUS51 KPHI 202027
SVRPHI
DEC003-MDC015-PAC029-202130-
/O.NEW.KPHI.SV.W.0084.090620T2027Z-090620T2130Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
427 PM EDT SAT JUN 20 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...
  NORTHWESTERN NEW CASTLE COUNTY IN NORTHERN DELAWARE...
  THIS INCLUDES THE CITY OF NEWARK...
  SOUTHWESTERN CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...

* UNTIL 530 PM EDT

* AT 425 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 6 MILES
  NORTH OF ROCK SPRINGS...OR 18 MILES SOUTH OF LANCASTER...AND MOVING
  SOUTHEAST AT 30 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
  ROCK SPRINGS AND MOUNT VERNON AROUND 435 PM EDT...
  GLEN ROY...RISING SUN AND RICHARDSMERE AROUND 440 PM EDT...
  FARMINGTON...WEST NOTTINGHAM AND OXFORD AROUND 445 PM EDT...
  CALVERT AND ZION AROUND 450 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A TORNADO WATCH REMAINS IN EFFECT FOR THE WARNED AREA. 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.

&&

LAT...LON 3973 7623 3973 7615 3976 7609 3987 7601
      3991 7600 3979 7555 3940 7590 3948 7601
      3954 7599 3954 7607 3970 7624
TIME...MOT...LOC 2027Z 304DEG 27KT 3979 7616

$$

KRUZDLO

1 follow-up statement

000 
WWUS51 KPHI 202120
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
520 PM EDT SAT JUN 20 2009

DEC003-MDC015-PAC029-202130-
/O.CAN.KPHI.SV.W.0084.000000T0000Z-090620T2130Z/
CECIL MD-CHESTER PA-NEW CASTLE DE-
520 PM EDT SAT JUN 20 2009

...THE SEVERE THUNDERSTORM WARNING FOR NORTHWESTERN NEW CASTLE...
SOUTHWESTERN CHESTER AND CECIL COUNTIES IS CANCELLED...

LAT...LON 3973 7623 3973 7615 3976 7609 3987 7601
      3991 7600 3979 7555 3940 7590 3948 7601
      3954 7599 3954 7607 3970 7624
TIME...MOT...LOC 2120Z 304DEG 27KT 3957 7574

$$

KRUZDLO

The office that day

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

Issued	Product	Office	Counties	Lasted
Jun 20, 5:01 PM EDT	Severe Thunderstorm Warning	PHI	Kent, New Castle	59 min
Jun 20, 5:46 PM EDT	Severe Thunderstorm Warning	PHI	Kent, Sussex	59 min
Jun 20, 6:23 PM EDT	Severe Thunderstorm Warning	PHI	Sussex	27 min
Jun 20, 6:55 PM EDT	Coastal Flood Advisory	PHI	Kent, New Castle, Sussex	5 hr
Jun 20, 3:57 PM EDT	Severe Thunderstorm Warning	PHI	Kent, Queen Anne's, Talbot	66 min
Jun 20, 4:06 PM EDT	Tornado Warning	PHI	Kent, Queen Anne's, Talbot	32 min

Nearby

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