Alert archive / Delaware / Severe Thunderstorm Warnings in 2011

Severe Thunderstorm Warning 281, NWS Philadelphia/Mount Holly

August 21, 2011Kent County, Delaware

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 21, 2011, 10:33 AM EDT for Kent County, Delaware. It was in force for 57 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: Aug 21, 2011, 10:33 AM EDT (14:33 UTC)
Expired: Aug 21, 2011, 11:30 AM EDT
In force: 57 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

County Kent County, DE

The radar

The Dover AFB radar (KDOX), 30 km from the middle of the area, began a volume at 14:36 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 21, 10:40 AM EDT	TSTM WND DMG	Dover, DE	TREE LIMBS DOWN.
Aug 21, 10:40 AM EDT	TSTM WND GST 60	Dover, DE	TRAINED SPOTTER ESTIMATED WINDS TO 60 MPH NEAR THE DOVER SPEEDWAY.
Aug 21, 10:50 AM EDT	TSTM WND DMG	Dover Afb, DE	WIND DAMAGE REPORTED AT THE DOVER AFB BUT DETAILS ARE UNKNOWN AT THIS TIME.
Aug 21, 10:50 AM EDT	TSTM WND GST 77	Dover Afb, DE	A 77 MPH THUNDERSTORM WIND GUST WAS MEASURED AT THE DOVER AFB.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Wallops Is Stn, VA (KWAL), launched 12:00Z, 2.6 hours before the alert went out and 130 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: 1010 J/kg
Mixed-layer CIN: -15 J/kg
Mixed-layer LCL: 773 m above ground
0-6 km bulk shear: 26 kt
0-1 km storm-relative helicity: 56 m²/s²
0-3 km storm-relative helicity: 84 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 1.0

Open this sounding in Storm Lab

The text

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

158 
WUUS51 KPHI 211433
SVRPHI
DEC001-211530-
/O.NEW.KPHI.SV.W.0281.110821T1433Z-110821T1530Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1033 AM EDT SUN AUG 21 2011

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  CENTRAL KENT COUNTY IN CENTRAL DELAWARE...
  THIS INCLUDES THE CITY OF DOVER...

* UNTIL 1130 AM EDT

* AT 1032 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE HAIL...AND
  DAMAGING WINDS IN EXCESS OF 60 MPH.  THIS STORM WAS LOCATED NEAR
  DOVER...AND MOVING EAST AT 20 MPH.

* OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
  RISING SUN...BOWERS AND BIG STONE BEACH

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS IS A DANGEROUS STORM. IF YOU ARE IN ITS PATH...PREPARE
IMMEDIATELY FOR DAMAGING WINDS...LARGE HAIL...AND DEADLY CLOUD
TO GROUND LIGHTNING. PEOPLE OUTSIDE SHOULD MOVE TO A SHELTER...
PREFERABLY INSIDE A STRONG BUILDING BUT AWAY FROM WINDOWS.

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.

PLEASE REPORT HAIL OR STRONG WINDS TO THE NATIONAL WEATHER SERVICE BY
CALLING TOLL FREE...1-877-633-6772...WHEN YOU CAN DO SO SAFELY.

&&

LAT...LON 3908 7567 3924 7553 3921 7538 3916 7540
      3912 7539 3907 7539 3903 7533 3901 7531
      3895 7535
TIME...MOT...LOC 1434Z 283DEG 15KT 3915 7551

$$

ROBERTSON

1 follow-up statement

133 
WWUS51 KPHI 211504
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1104 AM EDT SUN AUG 21 2011

DEC001-211530-
/O.CON.KPHI.SV.W.0281.000000T0000Z-110821T1530Z/
KENT DE-
1104 AM EDT SUN AUG 21 2011

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1130 AM EDT
FOR EAST CENTRAL KENT COUNTY...

AT 1058 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO
INDICATE A SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE
HAIL...AND DAMAGING WINDS IN EXCESS OF 70 MPH.  THIS STORM WAS 
LOCATED 3 MILES NORTHWEST OF BOWERS...OR 7 MILES SOUTHEAST OF 
DOVER...MOVING SOUTHEAST AT 15 MPH.

OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO BIG 
STONE BEACH.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

PLEASE REPORT HAIL OR STRONG WINDS TO THE NATIONAL WEATHER SERVICE BY
CALLING TOLL FREE...1-877-633-6772...WHEN YOU CAN DO SO SAFELY.

&&

LAT...LON 3910 7549 3920 7542 3921 7538 3916 7540
      3912 7539 3907 7539 3903 7533 3901 7531
      3895 7535
TIME...MOT...LOC 1502Z 297DEG 14KT 3909 7540

$$

ROBERTSON

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 21, 3:28 AM EDT	Flash Flood Watch	PHI	New Castle	17 hr
Aug 21, 8:41 AM EDT	Special Weather Statement	PHI	New Castle	64 min
Aug 21, 9:19 AM EDT	Special Weather Statement	PHI	Kent	56 min
Aug 21, 9:36 AM EDT	Areal Flood Advisory	PHI	Kent, New Castle	2 hr
Aug 21, 10:15 AM EDT	Special Weather Statement	PHI	Kent	60 min
Aug 21, 5:20 PM EDT	Areal Flood Advisory	PHI	Kent, Sussex	115 min
Aug 21, 6:29 PM EDT	Special Weather Statement	PHI	Sussex	61 min
Aug 21, 7:03 PM EDT	Severe Thunderstorm Warning	PHI	Kent, Sussex	42 min
Aug 21, 7:17 PM EDT	Areal Flood Advisory	PHI	Kent, Sussex	118 min

Nearby

Severe Thunderstorm Warnings in Delaware, 2011 Every severe thunderstorm warning in 2011

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.