Alert archive / New Jersey / Special Marine Warnings in 2021

Special Marine Warning 8, NWS Philadelphia/Mount Holly

April 21, 2021

NWS Philadelphia/Mount Holly issued this special marine warning at Apr 21, 2021, 1:30 PM EDT. It was in force for 60 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Apr 21, 2021, 1:30 PM EDT (17:30 UTC)
Expired: Apr 21, 2021, 2:30 PM EDT
In force: 60 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Hail: 0.75 in
Wind: 49.0 mph

The radar

The Dover AFB radar (KDOX), 50 km from the middle of the area, began a volume at 17:34 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.

The nearest sounding before it

Wallops Is Stn, VA (KWAL), launched 12:00Z, 5.5 hours before the alert went out and 148 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: 12 J/kg
Mixed-layer CIN: -142 J/kg
Mixed-layer LCL: 1437 m above ground
0-6 km bulk shear: 35 kt
0-1 km storm-relative helicity: 136 m²/s²
0-3 km storm-relative helicity: 126 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

044 
WHUS51 KPHI 211730
SMWPHI
ANZ430-431-211830-
/O.NEW.KPHI.MA.W.0008.210421T1730Z-210421T1830Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Special Marine Warning
National Weather Service Mount Holly NJ
130 PM EDT Wed Apr 21 2021

The National Weather Service in Mount Holly NJ has issued a

* Special Marine Warning for...
  Delaware Bay...

* Until 230 PM EDT.

* At 129 PM EDT, severe thunderstorms were located along a line
  extending from 11 nm southwest of Woodland Beach to 13 nm east of
  Miles River, moving east at 30 knots.

  HAZARD...Wind gusts to nearly 50 knots and large hail.

  SOURCE...Radar.

  IMPACT...Small craft could be damaged in briefly higher winds and 
           suddenly higher waves. Large hail could result in 
           structural damage.

* Locations impacted include...
  Fortesque Beach, Sea Breeze, Fourteen Foot Bank Light, Slaughter
  Beach, East Point, Woodland Beach, Miah Maull Light, Ship John
  Shoal Light, Brandywine Shoal Light, Cross Ledge Light and Bowers
  Beach.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Move to safe harbor until hazardous weather passes.

&&

LAT...LON 3944 7539 3930 7522 3916 7484 3886 7529
      3936 7557
TIME...MOT...LOC 1729Z 268DEG 28KT 3925 7569 3890 7594 

HAIL...>.75IN
WIND...49KTS

$$

JEO

1 follow-up statement

447 
FZUS71 KPHI 211822
MWSPHI

Marine Weather Statement
National Weather Service Mount Holly NJ
222 PM EDT Wed Apr 21 2021

ANZ430-431-211832-
/O.EXP.KPHI.MA.W.0008.000000T0000Z-210421T1830Z/
222 PM EDT Wed Apr 21 2021

...THE SPECIAL MARINE WARNING WILL EXPIRE AT 230 PM EDT...

The affected areas were... 
Delaware Bay...

The thunderstorms have moved out of the area and no longer pose a
significant threat to boaters.

A Severe Thunderstorm Watch remains in effect until 600 PM EDT for
central and southern Delaware...southern New Jersey...and the
adjacent coastal waters.

LAT...LON 3944 7539 3930 7522 3916 7484 3886 7529
      3936 7557
TIME...MOT...LOC 1822Z 268DEG 28KT 3925 7569 3890 7594 

$$

JEO

The office that day

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

Issued	Product	Office	Counties	Lasted
Apr 20, 8:48 PM EDT	Freeze Watch	PHI	Hunterdon, Morris, Somerset, Sussex, Warren	7 hr
Apr 21, 3:26 AM EDT	Freeze Warning	PHI	Hunterdon, Morris, Somerset, Sussex, Warren	30 hr
Apr 21, 12:25 PM EDT	Severe Thunderstorm Warning	PHI	Warren	50 min
Apr 21, 12:51 PM EDT	Severe Thunderstorm Warning	PHI	Sussex, Warren	21 min
Apr 21, 12:55 PM EDT	Severe Thunderstorm Warning	PHI	Hunterdon, Warren	27 min
Apr 21, 1:10 PM EDT	Severe Thunderstorm Warning	PHI	Burlington, Camden, Gloucester, Mercer, Salem	50 min
Apr 21, 1:17 PM EDT	Special Weather Statement	PHI	Hunterdon, Morris, Somerset, Sussex	58 min
Apr 21, 1:28 PM EDT	Severe Thunderstorm Warning	PHI	Atlantic, Burlington, Camden, Gloucester	36 min
Apr 21, 1:43 PM EDT	Severe Thunderstorm Warning	PHI	Hunterdon, Middlesex, Morris, Somerset	33 min
Apr 21, 1:58 PM EDT	Special Weather Statement	PHI	Burlington, Camden, Monmouth, Ocean	62 min
Apr 21, 2:02 PM EDT	Severe Thunderstorm Warning	PHI	Burlington, Camden, Monmouth, Ocean	43 min
Apr 21, 2:03 PM EDT	Special Weather Statement	PHI	Cumberland	27 min
Apr 21, 2:17 PM EDT	Severe Thunderstorm Warning	PHI	Atlantic, Cumberland, Gloucester, Salem	43 min
Apr 21, 2:28 PM EDT	Special Weather Statement	PHI	Middlesex, Monmouth	47 min
Apr 21, 2:30 PM EDT	Special Marine Warning	PHI		60 min
Apr 21, 2:38 PM EDT	Severe Thunderstorm Warning	PHI	Monmouth, Ocean	37 min
Apr 21, 2:40 PM EDT	Special Marine Warning	PHI		55 min
Apr 21, 2:43 PM EDT	Special Weather Statement	PHI	Cape May	32 min
Apr 21, 2:50 PM EDT	Severe Thunderstorm Warning	PHI	Atlantic, Burlington, Ocean	40 min
Apr 21, 3:02 PM EDT	Severe Thunderstorm Warning	PHI	Atlantic	28 min
Apr 21, 3:07 PM EDT	Special Marine Warning	PHI		53 min
Apr 21, 12:03 PM EDT	Special Weather Statement	PHI	Chester, Lehigh	42 min
Apr 21, 12:17 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Chester, Lehigh, Montgomery, Northampton	43 min
Apr 21, 12:54 PM EDT	Special Weather Statement	PHI	Delaware	36 min
Apr 21, 1:23 PM EDT	Severe Thunderstorm Warning	PHI	Kent	37 min
Apr 21, 2:09 PM EDT	Special Weather Statement	PHI	Sussex	36 min
Apr 21, 2:18 PM EDT	Severe Thunderstorm Warning	PHI	Kent, Sussex	42 min
Apr 21, 2:47 PM EDT	Severe Thunderstorm Warning	PHI	Sussex	16 min

Nearby

Special Marine Warnings in New Jersey, 2021 Every special marine warning in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.