Alert archive / Delaware / Severe Thunderstorm Warnings in 2011

Severe Thunderstorm Warning 17, NWS Philadelphia/Mount Holly

April 16, 2011Kent County, Sussex County, Delaware; Caroline County, Maryland; Cumberland County, New Jersey

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Apr 16, 2011, 8:38 PM EDT for Kent County, Sussex County, Delaware; Caroline County, Maryland; Cumberland County, New Jersey. It was in force for 52 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
Apr 16, 2011, 8:38 PM EDT (00:38 UTC)
Expired
Apr 16, 2011, 9:30 PM EDT
In force
52 min
Issued by
NWS Philadelphia/Mount Holly
Area
Storm-based polygon

Counties Kent County, DE, Sussex County, DE, Caroline County, MD, Cumberland County, NJ

The radar

The Dover AFB radar (KDOX), 13 km from the middle of the area, began a volume at 00:38 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

TimeReportWhereRemark
Apr 16, 8:50 PM EDTTSTM WND DMGLaurel, DETREES DOWN

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.

IssuedProductOfficeLasted
Apr 16, 4:41 PM EDTTornado WatchSPC6 hr

The nearest sounding before it

Wallops Is Stn, VA (KWAL), launched 00:00Z, 0.6 hours before the alert went out and 111 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-pSkew-T log-p diagram, Wallops Is Stn, VA at 00:00Z on 2011-04-17Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 56 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Wallops Is Stn, VA at 00:00Z on 2011-04-17The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 537 square meters per square second.1939587897Sfc1 km3 km6 km9 kmRMLM
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
56 J/kg
Mixed-layer CIN
-92 J/kg
Mixed-layer LCL
542 m above ground
0-6 km bulk shear
46 kt
0-1 km storm-relative helicity
537 m²/s²
0-3 km storm-relative helicity
663 m²/s²
Significant tornado parameter
0.0
Supercell composite
2.5

Open this sounding in Storm Lab

The text

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

833 
WUUS51 KPHI 170038
SVRPHI
DEC001-005-MDC011-NJC011-170130-
/O.NEW.KPHI.SV.W.0017.110417T0038Z-110417T0130Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
838 PM EDT SAT APR 16 2011

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  EASTERN KENT COUNTY IN CENTRAL DELAWARE...
  THIS INCLUDES THE CITY OF DOVER...
  EXTREME SOUTHEASTERN CAROLINE COUNTY IN EASTERN MARYLAND...
  SUSSEX COUNTY IN SOUTHERN DELAWARE...
  THIS INCLUDES THE CITY OF GEORGETOWN...
  SOUTH CENTRAL CUMBERLAND COUNTY IN SOUTHERN NEW JERSEY...

* UNTIL 930 PM EDT

* AT 834 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 DOVER SPEEDWAY TO ANDREWSVILLE TO 10 MILES SOUTHWEST OF
  LAUREL...OR ALONG A LINE EXTENDING FROM DOVER TO 16 MILES NORTHWEST
  OF GEORGETOWN TO 9 MILES NORTHWEST OF SALISBURY...AND MOVING EAST
  AT 40 MPH.

* SEVERE THUNDERSTORMS WILL BE NEAR...
  MILFORD AND BOWERS AROUND 845 PM EDT...
  SYCAMORE...BIG STONE BEACH AND ELLENDALE AROUND 850 PM EDT...
  MILTON...SLAUGHTER BEACH AND GEORGETOWN AROUND 855 PM EDT...
  FORTESQUE AND GUMBORO AROUND 900 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

A TORNADO WATCH REMAINS IN EFFECT UNTIL 1100 PM EDT SATURDAY EVENING
FOR NORTHERN DELAWARE AND NORTHEASTERN MARYLAND AND SOUTHERN NEW
JERSEY AND SOUTHEASTERN PENNSYLVANIA.

&&

LAT...LON 3846 7570 3865 7573 3931 7555 3930 7542
      3921 7538 3927 7524 3922 7491 3920 7493
      3917 7491 3920 7505 3917 7514 3923 7518
      3926 7526 3921 7538 3909 7540 3883 7521
      3879 7513 3880 7507 3846 7503
TIME...MOT...LOC 0037Z 280DEG 35KT 3921 7546 3886 7555
          3846 7567

$$

MPD
1 follow-up statement
296 
WWUS51 KPHI 170052
SVSPHI

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
852 PM EDT SAT APR 16 2011

MDC011-170102-
/O.CAN.KPHI.SV.W.0017.000000T0000Z-110417T0130Z/
CAROLINE MD-
852 PM EDT SAT APR 16 2011

...THE SEVERE THUNDERSTORM WARNING FOR EXTREME SOUTHEASTERN CAROLINE
COUNTY IS CANCELLED...

A TORNADO WATCH REMAINS IN EFFECT UNTIL 1100 PM EDT SATURDAY EVENING
FOR NORTHERN DELAWARE AND NORTHEASTERN MARYLAND AND SOUTHERN NEW
JERSEY AND SOUTHEASTERN PENNSYLVANIA.

LAT...LON 3894 7551 3908 7540 3905 7536 3919 7516
      3923 7518 3927 7525 3922 7491 3920 7493
      3916 7493 3920 7504 3918 7515 3905 7537
      3896 7530 3893 7530 3883 7521 3880 7516
      3879 7507 3846 7503 3846 7570
TIME...MOT...LOC 0052Z 280DEG 35KT 3918 7527 3883 7537
          3844 7555

$$

DEC001-005-NJC011-170130-
/O.CON.KPHI.SV.W.0017.000000T0000Z-110417T0130Z/
KENT DE-CUMBERLAND NJ-SUSSEX DE-
852 PM EDT SAT APR 16 2011

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 930 PM EDT
FOR SUSSEX...SOUTH CENTRAL CUMBERLAND AND SOUTHEASTERN KENT
COUNTIES...

AT 851 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO 
INDICATE A LINE OF THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS 
IN EXCESS OF 60 MPH.  THESE STORMS WERE LOCATED ALONG A LINE 
EXTENDING FROM 7 MILES SOUTHWEST OF FORTESQUE TO ELLENDALE TO 8 MILES
SOUTH OF LAUREL...OR ALONG A LINE EXTENDING FROM 13 MILES EAST OF 
DOVER TO 10 MILES NORTH OF GEORGETOWN TO SALISBURY...MOVING EAST AT 
40 MPH.

SEVERE THUNDERSTORMS WILL BE NEAR...
  FORTESQUE AND MILTON BY 900 PM EDT...
  GUMBORO AND MILLSBORO BY 905 PM EDT...
  LEWES AND DAGSBORO BY 910 PM EDT...
  LONG NECK AND FRANKFORD BY 915 PM EDT...
  REHOBOTH BEACH AND MILLVILLE BY 920 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A TORNADO WATCH REMAINS IN EFFECT UNTIL 1100 PM EDT SATURDAY EVENING
FOR NORTHERN DELAWARE AND NORTHEASTERN MARYLAND AND SOUTHERN NEW
JERSEY AND SOUTHEASTERN PENNSYLVANIA.

&&

LAT...LON 3894 7551 3908 7540 3905 7536 3919 7516
      3923 7518 3927 7525 3922 7491 3920 7493
      3916 7493 3920 7504 3918 7515 3905 7537
      3896 7530 3893 7530 3883 7521 3880 7516
      3879 7507 3846 7503 3846 7570
TIME...MOT...LOC 0052Z 280DEG 35KT 3918 7527 3883 7537
          3844 7555

$$

MPD

The office that day

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

IssuedProductOfficeCountiesLasted
Apr 16, 8:08 PM EDTAreal Flood WarningPHINew Castle8 hr
Apr 16, 8:30 PM EDTSpecial Weather StatementPHISussex30 min
Apr 16, 8:42 PM EDTRiver Flood WarningPHINew Castle6 hr
Apr 17, 9:51 AM EDTCoastal Flood AdvisoryPHINew Castle3 hr
Apr 16, 9:11 PM EDTSevere Thunderstorm WarningPHICecil64 min
Apr 17, 5:55 PM EDTRiver Flood WarningPHICecil, Harford26 hr
Apr 16, 8:46 PM EDTSpecial Marine WarningPHI59 min
Apr 16, 9:39 PM EDTSpecial Weather StatementPHIAtlantic, Burlington, Ocean51 min
Apr 16, 10:09 PM EDTAreal Flood WarningPHIAtlantic, Burlington, Cape May, Cumberland, Monmouth, Ocean6 hr
Apr 16, 10:19 PM EDTSpecial Weather StatementPHIMonmouth, Ocean41 min
Apr 16, 11:21 PM EDTRiver Flood WarningPHIMorris, Somerset42 hr
Apr 17, 12:04 AM EDTRiver Flood WarningPHIMorris, Passaic42 hr
Apr 17, 12:37 AM EDTSmall Craft AdvisoryPHI34 hr
Apr 17, 12:40 AM EDTRiver Flood WarningPHIPassaic69 hr
Apr 17, 12:45 AM EDTRiver Flood WarningPHIMercer10 hr
Apr 17, 12:50 AM EDTRiver Flood WarningPHIHunterdon, Somerset6 hr
Apr 17, 12:50 AM EDTRiver Flood WarningPHISomerset11 hr
Apr 17, 12:50 AM EDTRiver Flood WarningPHIMiddlesex, Somerset23 hr
Apr 17, 12:50 AM EDTRiver Flood WarningPHIMiddlesex, Somerset23 hr
Apr 17, 3:03 AM EDTRiver Flood WarningPHIEssex, Morris, Passaic5 days
Apr 17, 3:03 AM EDTRiver Flood WarningPHIEssex, Passaic5 days
Apr 17, 3:19 AM EDTRiver Flood WarningPHIMorris, Passaic43 hr
Apr 17, 3:19 AM EDTRiver Flood WarningPHIBergen, Morris, Passaic32 hr
Apr 17, 3:19 AM EDTRiver Flood WarningPHIMorris32 hr
Apr 17, 3:19 AM EDTRiver Flood WarningPHIMorris49 hr
Apr 17, 5:39 AM EDTRiver Flood WarningPHISomerset38 hr
Apr 17, 8:39 AM EDTRiver Flood WarningPHIBurlington30 hr
Apr 17, 9:51 AM EDTCoastal Flood WarningPHIBurlington, Camden, Gloucester, Mercer4 hr

Nearby

Severe Thunderstorm Warnings in Delaware, 2011Severe Thunderstorm Warnings in Maryland, 2011Severe Thunderstorm Warnings in New Jersey, 2011Every 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.