Alert archive / New Jersey / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 242, NWS Philadelphia/Mount Holly

August 10, 20215 counties in New Jersey; Bucks County, Montgomery County, Philadelphia County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Aug 10, 2021, 5:09 PM EDT for 5 counties in New Jersey; Bucks County, Montgomery County, Philadelphia County, Pennsylvania. It was in force for 51 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: Aug 10, 2021, 5:09 PM EDT (21:09 UTC)
Expired: Aug 10, 2021, 6:00 PM EDT
In force: 51 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

Counties Burlington County, NJ, Hunterdon County, NJ, Mercer County, NJ, Somerset County, NJ, Warren County, NJ, Bucks County, PA, Montgomery County, PA, Philadelphia County, PA

The radar

The Philadelphia radar (KDIX), 73 km from the middle of the area, began a volume at 21:08 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
Aug 10, 6:05 PM EDT	TSTM WND DMG	Bensalem, PA	A FEW SHINGLES BLOWN OFF, ALONG WITH 2 INCH DIAMETER LIMBS. TIME ESTIMATED FROM RADAR.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Brookhaven, NY (KOKX), launched 12:00Z, 9.2 hours before the alert went out and 192 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: 73 J/kg
Mixed-layer CIN: -51 J/kg
Mixed-layer LCL: 635 m above ground
0-6 km bulk shear: 12 kt
0-1 km storm-relative helicity: 74 m²/s²
0-3 km storm-relative helicity: 103 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

444 
WUUS51 KPHI 102109
SVRPHI
NJC005-019-021-035-041-PAC017-091-101-102200-
/O.NEW.KPHI.SV.W.0242.210810T2109Z-210810T2200Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
509 PM EDT Tue Aug 10 2021

The National Weather Service in Mount Holly NJ has issued a

* Severe Thunderstorm Warning for...
  Hunterdon County in northwestern New Jersey...
  Southwestern Warren County in northwestern New Jersey...
  Northwestern Mercer County in central New Jersey...
  Northwestern Burlington County in southern New Jersey...
  Southwestern Somerset County in northern New Jersey...
  East central Montgomery County in southeastern Pennsylvania...
  Bucks County in southeastern Pennsylvania...
  Northeastern Philadelphia County in southeastern Pennsylvania...

* Until 600 PM EDT.

* At 509 PM EDT, severe thunderstorms were located along a line
  extending from near Riegelsville to Fricks, moving southeast at 25
  mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Damage to roofs, siding, trees, and power lines is 
           possible.

* Locations impacted include...
  Philadelphia, Trenton, Somerville, Bensalem, Ewing, Lansdale,
  Manville, Burlington, Bristol, Perkasie, Doylestown, Byram,
  Riverside, Hatboro, Souderton, Bedminster, Flemington, Chalfont,
  Tinicum and Hatfield.

This includes the following highways...
 Pennsylvania Turnpike between mile markers 340 and 358.
 Northeast Extension between mile markers 29 and 30.
 Interstate 95 in Pennsylvania between mile markers 32 and 40.
 Interstate 295 in New Jersey between mile markers 70 and 76.
 Interstate 287 in New Jersey between mile markers 15 and 16.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

Wind damage with these storms will occur before any rain or
lightning. Do not wait for the sound of thunder before taking cover.
SEEK SHELTER IMMEDIATELY inside a sturdy structure and stay away from
windows.

&&

LAT...LON 4000 7492 4024 7535 4062 7520 4062 7519
      4064 7519 4058 7456
TIME...MOT...LOC 2109Z 301DEG 23KT 4057 7515 4028 7525 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

SFJ

2 follow-up statements

207 
WWUS51 KPHI 102126
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
526 PM EDT Tue Aug 10 2021

NJC041-102136-
/O.CAN.KPHI.SV.W.0242.000000T0000Z-210810T2200Z/
Warren NJ-
526 PM EDT Tue Aug 10 2021

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHWESTERN WARREN COUNTY IS
CANCELLED...

The storms which prompted the warning have weakened. Therefore, the 
warning has been cancelled. Gusty winds to 40 mph are still a 
concern though.

LAT...LON 4023 7533 4063 7511 4058 7456 4000 7492
TIME...MOT...LOC 2126Z 296DEG 25KT 4052 7499 4023 7513 

$$

NJC005-019-021-035-PAC017-091-101-102200-
/O.CON.KPHI.SV.W.0242.000000T0000Z-210810T2200Z/
Hunterdon NJ-Mercer NJ-Burlington NJ-Somerset NJ-Montgomery PA-
Bucks PA-Philadelphia PA-
526 PM EDT Tue Aug 10 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 600 PM EDT
FOR HUNTERDON...NORTHWESTERN MERCER...NORTHWESTERN BURLINGTON...
SOUTHWESTERN SOMERSET...EAST CENTRAL MONTGOMERY...BUCKS AND
NORTHEASTERN PHILADELPHIA COUNTIES...

At 526 PM EDT, severe thunderstorms were located along a line
extending from near Frenchtown to near Ivyland, moving southeast at
30 mph.

HAZARD...60 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...Damage to roofs, siding, trees, and power lines is 
         possible.

Locations impacted include...
Philadelphia, Trenton, Somerville, Bensalem, Ewing, Lansdale,
Manville, Burlington, Bristol, Doylestown, Byram, Riverside, Hatboro,
Bedminster, Flemington, Chalfont, Tinicum, Hatfield, Pennington and
Beverly.

This includes the following highways...
 Pennsylvania Turnpike between mile markers 340 and 358.
 Interstate 95 in Pennsylvania between mile markers 32 and 40.
 Interstate 295 in New Jersey between mile markers 70 and 76.
 Interstate 287 in New Jersey between mile markers 15 and 16.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

Wind damage with these storms will occur before any rain or
lightning. Do not wait for the sound of thunder before taking cover.
SEEK SHELTER IMMEDIATELY inside a sturdy structure and stay away from
windows.

&&

LAT...LON 4023 7533 4063 7511 4058 7456 4000 7492
TIME...MOT...LOC 2126Z 296DEG 25KT 4052 7499 4023 7513 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

SFJ

552 
WWUS51 KPHI 102157
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
557 PM EDT Tue Aug 10 2021

NJC005-019-021-035-PAC017-091-101-102207-
/O.EXP.KPHI.SV.W.0242.000000T0000Z-210810T2200Z/
Hunterdon NJ-Mercer NJ-Burlington NJ-Somerset NJ-Montgomery PA-
Bucks PA-Philadelphia PA-
557 PM EDT Tue Aug 10 2021

...THE SEVERE THUNDERSTORM WARNING FOR HUNTERDON...NORTHWESTERN
MERCER...NORTHWESTERN BURLINGTON...SOUTHWESTERN SOMERSET...EAST
CENTRAL MONTGOMERY...BUCKS AND NORTHEASTERN PHILADELPHIA COUNTIES
WILL EXPIRE AT 600 PM EDT...
            
The storms which prompted the warning have weakened below severe
limits, and no longer pose an immediate threat to life or property.
Therefore, the warning will be allowed to expire.  However gusty
winds to 40 mph are still possible with these thunderstorms.

LAT...LON 4023 7533 4063 7511 4058 7456 4000 7492
TIME...MOT...LOC 2157Z 301DEG 23KT 4043 7479 4014 7493 

$$

SFJ

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 10, 1:02 AM EDT	Special Weather Statement	PHI	Burlington	28 min
Aug 10, 3:33 AM EDT	Excessive Heat Warning	PHI	Burlington, Camden, Gloucester, Hunterdon, Mercer, Middlesex and 5 more	4 days
Aug 10, 3:33 AM EDT	Heat Advisory	PHI	Atlantic, Cape May, Cumberland, Monmouth, Ocean, Salem and 2 more	4 days
Aug 10, 3:54 AM EDT	Areal Flood Advisory	PHI	Atlantic	80 min
Aug 10, 4:59 AM EDT	Areal Flood Advisory	PHI	Burlington	60 min
Aug 10, 5:58 AM EDT	Flash Flood Warning	PHI	Burlington, Mercer	2 hr
Aug 10, 2:07 PM EDT	Special Weather Statement	PHI	Salem	38 min
Aug 10, 4:52 PM EDT	Special Weather Statement	PHI	Monmouth	23 min
Aug 10, 4:54 PM EDT	Special Marine Warning	PHI		26 min
Aug 10, 5:05 PM EDT	Special Weather Statement	PHI	Somerset, Warren	25 min
Aug 10, 5:30 PM EDT	Special Weather Statement	PHI	Warren	30 min
Aug 10, 5:58 PM EDT	Special Weather Statement	PHI	Mercer, Middlesex, Morris, Somerset, Warren	32 min
Aug 10, 6:27 PM EDT	Special Weather Statement	PHI	Burlington, Mercer, Middlesex, Monmouth, Morris	33 min
Aug 10, 6:59 PM EDT	Special Weather Statement	PHI	Middlesex, Monmouth	31 min
Aug 10, 7:09 PM EDT	Special Marine Warning	PHI		66 min
Aug 10, 7:27 PM EDT	Special Weather Statement	PHI	Monmouth	33 min
Aug 9, 10:10 PM EDT	Areal Flood Advisory	PHI	Carbon	3 hr
Aug 10, 3:06 PM EDT	Special Weather Statement	PHI	Berks	24 min
Aug 10, 3:33 PM EDT	Special Weather Statement	PHI	Berks	27 min
Aug 10, 3:52 PM EDT	Special Weather Statement	PHI	Berks, Carbon, Lehigh	23 min
Aug 10, 4:01 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Carbon, Chester, Lehigh, Montgomery, Northampton	44 min
Aug 10, 4:18 PM EDT	Areal Flood Advisory	PHI	Berks, Carbon, Lehigh	3 hr
Aug 10, 4:33 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Carbon, Chester, Lehigh, Monroe and 2 more	42 min
Aug 10, 5:11 PM EDT	Special Weather Statement	PHI	Chester, Montgomery, Philadelphia	34 min
Aug 10, 5:40 PM EDT	Special Weather Statement	PHI	Chester	35 min
Aug 10, 6:36 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester	39 min
Aug 10, 7:10 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester, Montgomery	65 min
Aug 10, 7:54 PM EDT	Severe Thunderstorm Warning Considerable damage threat	PHI	Chester	51 min

Nearby

Severe Thunderstorm Warnings in New Jersey, 2021 Severe Thunderstorm Warnings in Pennsylvania, 2021 Every severe thunderstorm 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.