Alert archive / Maryland / Severe Thunderstorm Warnings in 2011

Severe Thunderstorm Warning 18, NWS Philadelphia/Mount Holly

April 16, 2011Cecil County, Maryland; Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Apr 16, 2011, 9:11 PM EDT for Cecil County, Maryland; Chester County, Pennsylvania. It was in force for 64 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, 9:11 PM EDT (01:11 UTC)
Expired
Apr 16, 2011, 10:15 PM EDT
In force
64 min
Issued by
NWS Philadelphia/Mount Holly
Area
Storm-based polygon

Counties Cecil County, MD, Chester County, PA

The radar

The Dover AFB radar (KDOX), 118 km from the middle of the area, began a volume at 01:12 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, 10:05 PM EDTTSTM WND DMGCecilton, MDTREES DOWN FROM NORTHEAST TO WEST OF CECILTON

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

Washington/Dulle, VA (KIAD), launched 00:00Z, 1.2 hours before the alert went out and 168 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, Washington/Dulle, VA at 00:00Z on 2011-04-17Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 132 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, Washington/Dulle, VA at 00:00Z on 2011-04-17The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 574 square meters per square second.1939587897117Sfc1 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
132 J/kg
Mixed-layer CIN
-18 J/kg
Mixed-layer LCL
547 m above ground
0-6 km bulk shear
77 kt
0-1 km storm-relative helicity
574 m²/s²
0-3 km storm-relative helicity
593 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.5

Open this sounding in Storm Lab

The text

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

675 
WUUS51 KPHI 170111
SVRPHI
MDC015-PAC029-170215-
/O.NEW.KPHI.SV.W.0018.110417T0111Z-110417T0215Z/

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

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...
  CHESTER COUNTY IN SOUTHEAST PENNSYLVANIA...
  THIS INCLUDES THE CITY OF WEST CHESTER...

* UNTIL 1015 PM EDT

* AT 908 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 15 MILES NORTHWEST OF HONEY BROOK TO ROCK SPRINGS TO 22 MILES
  SOUTHWEST OF OCTORARO...OR ALONG A LINE EXTENDING FROM 13 MILES
  NORTHEAST OF LANCASTER TO 20 MILES SOUTH OF LANCASTER TO 13 MILES
  NORTHEAST OF BALTIMORE...AND MOVING EAST AT 40 MPH.

* SEVERE THUNDERSTORMS WILL BE NEAR...
  MOUNT VERNON...GLEN ROY...WEST NOTTINGHAM AND RISING SUN AROUND 920
  PM EDT...
  HOMEVILLE...FARMINGTON...OXFORD AND HONEY BROOK AROUND 925 PM
  EDT...
  COCHRANVILLE AND ZION AROUND 930 PM EDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS SEVERE THUNDERSTORM MAY CONTAIN LITTLE OR NO LIGHTNING. DO NOT
WAIT FOR THUNDER BEFORE TAKING COVER. SEEK SHELTER IMMEDIATELY INSIDE
A STURDY STRUCTURE AND STAY 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 3973 7615 3978 7607 3987 7601 3992 7601
      4013 7593 4026 7566 4019 7555 4013 7551
      4007 7537 4004 7543 3999 7545 3987 7562
      3984 7560 3982 7570 3972 7579 3939 7577
      3938 7604 3953 7599 3956 7610 3972 7624
TIME...MOT...LOC 0111Z 269DEG 37KT 4019 7611 3976 7616
          3942 7640

$$

MPD
1 follow-up statement
910 
WWUS51 KPHI 170145
SVSPHI

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

MDC015-PAC029-170215-
/O.CON.KPHI.SV.W.0018.000000T0000Z-110417T0215Z/
CECIL MD-CHESTER PA-
945 PM EDT SAT APR 16 2011

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1015 PM EDT
FOR CHESTER AND CECIL COUNTIES...

AT 942 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 ELVERSON TO OXFORD TO 9 MILES SOUTHWEST OF 
PERRYVILLE...OR ALONG A LINE EXTENDING FROM 8 MILES SOUTHEAST OF 
READING TO 11 MILES NORTHWEST OF NEWARK TO 21 MILES SOUTHWEST OF 
ELKTON...MOVING EAST AT 35 MPH.

THIS LINE OF STORMS HAS A HISTORY OF WIND DAMAGE OVER SOUTH CENTRAL 
PENNSYLVANIA. 

SEVERE THUNDERSTORMS WILL BE NEAR...
  GLENMOORE...PLEASANT HILL...BAY VIEW AND WEST GROVE BY 950 PM
  EDT...
  LADENBERG...KEMBLESVILLE...FAIR HILL AND ANDORA BY 955 PM EDT...
  PUGHTOWN AND CEDARVILLE BY 1000 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.

THIS SEVERE THUNDERSTORM MAY CONTAIN LITTLE OR NO LIGHTNING. DO NOT
WAIT FOR THUNDER BEFORE TAKING COVER. SEEK SHELTER IMMEDIATELY INSIDE
A STURDY STRUCTURE AND STAY AWAY FROM WINDOWS.

&&

LAT...LON 3979 7601 4011 7595 4026 7566 4020 7556
      4013 7551 4006 7538 4004 7543 3999 7545
      3987 7562 3984 7560 3982 7570 3972 7579
      3941 7578 3939 7604 3953 7599 3955 7609
      3961 7614
TIME...MOT...LOC 0144Z 265DEG 29KT 4023 7584 3980 7589
          3946 7614

$$

MPD

The office that day

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

IssuedProductOfficeCountiesLasted
Apr 16, 8:38 PM EDTSevere Thunderstorm WarningPHICaroline52 min
Apr 17, 5:55 PM EDTRiver Flood WarningPHICecil, Harford26 hr
Apr 16, 8:08 PM EDTAreal Flood WarningPHIBucks, Delaware, Montgomery, Philadelphia8 hr
Apr 16, 9:18 PM EDTRiver Flood WarningPHIChester11 hr
Apr 16, 9:32 PM EDTRiver Flood WarningPHIDelaware6 hr
Apr 16, 9:49 PM EDTSpecial Weather StatementPHIBerks, Lehigh56 min
Apr 16, 11:09 PM EDTRiver Flood WarningPHIBucks13 hr
Apr 16, 11:11 PM EDTRiver Flood WarningPHIMontgomery6 hr
Apr 17, 1:05 AM EDTAreal Flood WarningPHIBerks5 hr
Apr 17, 3:56 AM EDTAreal Flood WarningPHIBucks, Chester, Delaware, Montgomery, Philadelphia6 hr
Apr 17, 6:07 AM EDTAreal Flood WarningPHIChester3 hr
Apr 17, 6:37 AM EDTRiver Flood WarningPHIChester, Delaware7 hr
Apr 17, 9:51 AM EDTCoastal Flood WarningPHIDelaware, Philadelphia4 hr

Nearby

Severe Thunderstorm Warnings in Maryland, 2011Severe Thunderstorm Warnings in Pennsylvania, 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.