Alert archive / Delaware / Flash Flood Warnings in 2013

Flash Flood Warning 40, NWS Philadelphia/Mount Holly

July 21, 2013Sussex County, Delaware

NWS Philadelphia/Mount Holly issued this flash flood warning at Jul 21, 2013, 4:50 PM EDT for Sussex County, Delaware. It was in force for 4 hr. 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: Jul 21, 2013, 4:50 PM EDT (20:50 UTC)
Expired: Jul 21, 2013, 8:45 PM EDT
In force: 4 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

County Sussex County, DE

The radar

The Dover AFB radar (KDOX), 30 km from the middle of the area, began a volume at 20:53 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
Jul 21, 5:30 PM EDT	FLASH FLOOD	Millsboro, DE	WIDESPREAD PONDING OF WATER ON ROADWAYS... CONSTRUCTION EQUIPMENT FLOATING IN WATER. DOPPLER RADAR STORM TOTAL ESTIMATES EXCEEDED FOUR INCHES SOUTHWEST OF MILLSBORO.

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, 8.8 hours before the alert went out and 84 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: 1209 J/kg
Mixed-layer CIN: -73 J/kg
Mixed-layer LCL: 739 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: 59 m²/s²
0-3 km storm-relative helicity: 55 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.7

Open this sounding in Storm Lab

The text

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

749 
WGUS51 KPHI 212050
FFWPHI
DEC005-220045-
/O.NEW.KPHI.FF.W.0040.130721T2050Z-130722T0045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
450 PM EDT SUN JUL 21 2013

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  EASTERN SUSSEX COUNTY...

* UNTIL 845 PM EDT...

* AT 444 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
  VERY HEAVY RAIN FROM A THUNDERSTORM OVER EASTERN SUSSEX COUNTY.
  THE HEAVIEST RAIN HAS FALLEN HEAR SELBYVILLE.

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO GEORGETOWN.

ADDITIONAL RAINFALL AMOUNTS OF 1 TO 3 INCHES ARE POSSIBLE IN THE 
WARNED AREA. PLEASE ALSO BE CAREFUL ALONG DELAWARE STATE ROUTE 1 AS 
THE HIGH TIDE CYCLE IS STARTING. 
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLASH FLOOD WARNING MEANS THAT FLOODING IS IMMINENT OR OCCURRING.
IF YOU ARE IN THE WARNING AREA MOVE TO HIGHER GROUND IMMEDIATELY.
RESIDENTS LIVING ALONG STREAMS AND CREEKS SHOULD TAKE IMMEDIATE
PRECAUTIONS TO PROTECT LIFE AND PROPERTY. NEVER ATTEMPT TO CROSS
SWIFTLY FLOWING WATERS OR WATERS OF UNKNOWN DEPTH BY FOOT OR IN AN
AUTOMOBILE. TURN AROUND DON'T DROWN!

FLOODING IS OCCURRING OR IS IMMINENT. MOST FLOOD RELATED DEATHS OCCUR
IN AUTOMOBILES. DO NOT ATTEMPT TO CROSS WATER COVERED BRIDGES...
DIPS...OR LOW WATER CROSSINGS. TURN AROUND...DON'T DROWN! NEVER TRY
TO CROSS A FLOWING STREAM...EVEN A SMALL ONE...ON FOOT. TO ESCAPE
RISING WATER MOVE UP TO HIGHER GROUND.

&&

LAT...LON 3845 7544 3867 7544 3884 7521 3879 7515
      3879 7511 3880 7509 3880 7508 3870 7506
      3866 7505 3866 7506 3860 7505 3860 7504
      3845 7504

$$

1 follow-up statement

391 
WGUS71 KPHI 212309
FFSPHI

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
709 PM EDT SUN JUL 21 2013

DEC005-220045-
/O.CON.KPHI.FF.W.0040.000000T0000Z-130722T0045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
SUSSEX DE-
709 PM EDT SUN JUL 21 2013

...A FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 845 PM EDT FOR
EASTERN SUSSEX COUNTY...

AT 702 PM EDT...THE THUNDERSTORMS THAT PRODUCED THE VERY HEAVY RAIN
HAVE DISSIPATED. ADDITIONAL HEAVY RAIN APPEARS UNLIKELY. 
DOPPLER RADAR STORM TOTAL ESTIMATES THOUGH EXCEEDED FOUR INCHES 
SOUTHWEST OF SELBYVILLE AND MILLSBORO.  

PRECAUTIONARY/PREPAREDNESS ACTIONS...

FLOODING IS OCCURRING OR IS IMMINENT. MOST FLOOD RELATED DEATHS OCCUR
IN AUTOMOBILES. DO NOT ATTEMPT TO CROSS WATER COVERED BRIDGES...
DIPS...OR LOW WATER CROSSINGS. NEVER TRY TO CROSS A FLOWING STREAM...
EVEN A SMALL ONE...ON FOOT. TO ESCAPE RISING WATER MOVE UP TO HIGHER
GROUND.

&&

LAT...LON 3845 7544 3867 7544 3884 7521 3879 7515
      3879 7511 3880 7509 3880 7508 3870 7506
      3866 7505 3866 7506 3860 7505 3860 7504
      3845 7504

$$

TFG

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 20, 8:56 PM EDT	Special Weather Statement	PHI	New Castle	64 min
Jul 20, 10:17 PM EDT	Severe Thunderstorm Warning	PHI	Kent, New Castle	58 min
Jul 20, 10:55 PM EDT	Areal Flood Advisory	PHI	New Castle	3 hr
Jul 21, 3:17 PM EDT	Special Weather Statement	PHI	Sussex	58 min
Jul 21, 3:44 PM EDT	Special Weather Statement	PHI	New Castle	2 hr
Jul 21, 4:25 PM EDT	Special Weather Statement	PHI	Sussex	95 min
Jul 21, 4:58 PM EDT	Areal Flood Advisory	PHI	Kent	3 hr
Jul 21, 5:45 PM EDT	Special Weather Statement	PHI	Sussex	60 min
Jul 21, 6:28 PM EDT	Areal Flood Advisory	PHI	Kent, Sussex	3 hr

Nearby

Flash Flood Warnings in Delaware, 2013 Every flash flood warning in 2013

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.