Alert archive / New Jersey / Special Marine Warnings in 2021

Special Marine Warning 9, NWS Philadelphia/Mount Holly

April 21, 2021

NWS Philadelphia/Mount Holly issued this special marine warning at Apr 21, 2021, 2:30 PM EDT. It was in force for 60 min. 5 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: Apr 21, 2021, 2:30 PM EDT (18:30 UTC)
Expired: Apr 21, 2021, 3:30 PM EDT
In force: 60 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Hail: 0.75 in
Wind: 50.0 mph

The radar

The Dover AFB radar (KDOX), 43 km from the middle of the area, began a volume at 18:33 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
Apr 21, 2:45 PM EDT	TSTM WND GST 46	Cape May, NJ
Apr 21, 2:45 PM EDT	MARINE TSTM WIND 46	Cape May, NJ
Apr 21, 2:55 PM EDT	TSTM WND GST 44	1 Nw Sea Isle City, NJ	LUDLUM BAY.
Apr 21, 2:55 PM EDT	MARINE TSTM WIND 44	1 Nw Sea Isle City, NJ	LUDLUM BAY.
Apr 21, 3:00 PM EDT	MARINE TSTM WIND 48	North Wildwood, NJ

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, 6.5 hours before the alert went out and 91 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.

784 
WHUS51 KPHI 211830
SMWPHI
ANZ430-431-452>455-475-211930-
/O.NEW.KPHI.MA.W.0009.210421T1830Z-210421T1930Z/

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

The National Weather Service in Mount Holly NJ has issued a

* Special Marine Warning for...
  Delaware Bay...
  Coastal waters from Little Egg Inlet NJ to Fenwick Island DE out 20
  nm...
  Outer waters from Cape May NJ to Fenwick Island DE out 20 to 40
  nm...

* Until 330 PM EDT.

* At 230 PM EDT, severe thunderstorms were located along a line
  extending from near Brown Shoal Light to 13 nm west of Assawoman
  Bay, moving northeast at 40 knots.

  HAZARD...Wind gusts in excess of 50 knots and large hail.

  SOURCE...Radar.

  IMPACT...Boats could suffer significant structural damage in high 
           winds and hail. Small craft could capsize in suddenly 
           higher waves.

* Locations impacted include...
  Five Fathoms Buoy, Buoy 2fb, Brown Shoal Light, Fenwick Island,
  Buoy 4fb, Buoy 3fb, Fourteen Foot Bank Light, Cape Henlopen,
  Rehoboth Beach, Cape May Point, Brandywine Shoal Light, Ocean City
  Reef, Indian River Inlet Bridge, Wildwood, Overfalls Shoal, The
  Lump, Cape May Reef, Sea Isle City, Bethany Beach and Buoy 2ms.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Move to safe harbor immediately as gusty winds and high waves are
expected.

&&

LAT...LON 3845 7510 3851 7511 3853 7513 3907 7523
      3905 7499 3931 7442 3872 7456 3845 7502
      3846 7504 3845 7507
TIME...MOT...LOC 1830Z 238DEG 39KT 3894 7519 3845 7536 

HAIL...>.75IN
WIND...50KTS

$$

JEO

2 follow-up statements

065 
FZUS71 KPHI 211913
MWSPHI

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

ANZ430-431-452-211923-
/O.CAN.KPHI.MA.W.0009.000000T0000Z-210421T1930Z/
313 PM EDT Wed Apr 21 2021

...THE SPECIAL MARINE WARNING IS CANCELLED...

The affected areas were...
Delaware Bay...
Coastal waters from Little Egg Inlet to Great Egg Inlet NJ out 20
nm...

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

A Severe Thunderstorm Watch remains in effect until 600 PM EDT for
the adjacent coastal waters.

LAT...LON 3882 7477 3926 7446 3925 7445 3925 7444
      3872 7456 3848 7497
TIME...MOT...LOC 1913Z 239DEG 44KT 3920 7459 3869 7487 

$$

ANZ453>455-475-211930-
/O.CON.KPHI.MA.W.0009.000000T0000Z-210421T1930Z/
313 PM EDT Wed Apr 21 2021

...A SPECIAL MARINE WARNING REMAINS IN EFFECT UNTIL 330 PM EDT...

For the following areas...
Coastal waters from Cape Henlopen to Fenwick Island DE out 20 nm...
Coastal waters from Cape May NJ to Cape Henlopen DE out 20 nm...
Coastal waters from Great Egg Inlet to Cape May NJ out 20 nm...
Waters from Cape May NJ to Fenwick Island DE out 20 to 40 nm...

At 313 PM EDT, strong thunderstorms were located along a line
extending from near Ocean City Reef to 9 nm south of Buoy 2ms, moving
northeast at 45 knots.

HAZARD...Wind gusts to 40 knots and small hail.

SOURCE...Radar indicated.

IMPACT...Small craft could be damaged in briefly higher winds and 
         suddenly higher waves.

Locations impacted include...
Five Fathoms Buoy, Buoy 2fb, Buoy 4fb and Cape May Reef. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Move to safe harbor immediately as gusty winds and high waves are
expected.

&&

LAT...LON 3882 7477 3926 7446 3925 7445 3925 7444
      3872 7456 3848 7497
TIME...MOT...LOC 1913Z 239DEG 44KT 3920 7459 3869 7487 

HAIL...<.75IN
WIND...40KTS

$$

JEO

709 
FZUS71 KPHI 211920
MWSPHI

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

ANZ453>455-475-211930-
/O.EXP.KPHI.MA.W.0009.000000T0000Z-210421T1930Z/
320 PM EDT Wed Apr 21 2021

...THE SPECIAL MARINE WARNING WILL EXPIRE AT 330 PM EDT...

The affected areas were... 

Coastal waters from Great Egg Inlet NJ to Fenwick Island DE out 20
nm...
Outer waters from Cape May NJ to Fenwick Island DE out 20 to 40 nm...

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
the adjacent coastal waters.

LAT...LON 3882 7477 3926 7446 3925 7445 3925 7444
      3872 7456 3848 7497
TIME...MOT...LOC 1920Z 238DEG 39KT 3924 7451 3873 7479 

$$

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, 1:30 PM EDT	Special Marine Warning	PHI		60 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, 2:38 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.