Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2021
Severe Thunderstorm Warning 289, NWS Philadelphia/Mount Holly
NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at Sep 1, 2021, 5:13 PM EDT for 5 counties in Pennsylvania; Hunterdon County, Mercer County, New Jersey. It was in force for 47 min. 7 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
- Sep 1, 2021, 5:13 PM EDT (21:13 UTC)
- Expired
- Sep 1, 2021, 6:00 PM EDT
- In force
- 47 min
- Issued by
- NWS Philadelphia/Mount Holly
- Area
- Storm-based polygon
- Tornado
- Possible
- Hail
- 0.75 in
- Wind
- 60.0 mph
Counties Hunterdon County, NJ, Mercer County, NJ, Bucks County, PA, Chester County, PA, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA
The radar
The Philadelphia radar (KDIX), 70 km from the middle of the area, began a volume at 21:17 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 |
|---|---|---|---|
| Sep 1, 5:35 PM EDT | TORNADO | 2 Nne Whitemarsh Twp, PA | *** 1 FATAL, 2 INJ *** A SEMI-DISCRETE SUPERCELL THUNDERSTORM BEGAN TO EXHIBIT ROTATION OVER DELAWARE COUNTY, PA AROUND 5:15 PM ON SEPTEMBER 1. THE ROTATION CONTINUED NORTH-NORTHEAST INTO MONTGOMERY COUNTY, AND EVENTUALLY STRENGTHENED ENOUGH TO PRODUCE A TORNA |
| Sep 1, 5:39 PM EDT | TSTM WND DMG | 1 S Furlong, PA | NUMEROUS TREES DOWN AND MINOR DAMAGE TO STRUCTURES IN A SWATH GENERALLY PARALLEL TO AND JUST NORTH OF YORK ROAD BETWEEN SUGAR BOTTOM ROAD AND ROUTE 202. |
| Sep 1, 5:39 PM EDT | TSTM WND DMG | Fort Washington, PA | SINGIFICANT TREE DAMAGE IN THE FORT WASHINGTON AREA. POSSIBLE TORNADO. TIME ESTIMATED FROM RADAR. |
| Sep 1, 5:39 PM EDT | TSTM WND DMG | Upper Dublin Twp, PA | CONSIDERABLE TREE DAMAGE IN FORT WASHINGTON NEAR THE HIGH SCHOOL. POSSIBLE TORNADO. TIME ESTIMATED FROM RADAR. |
| Sep 1, 5:44 PM EDT | TSTM WND DMG | 1 Se Lower Gwynedd Twp, PA | TREE AND POWER LINE DAMAGE AROUND MAPLE GLEN. POSSIBLE TORNADO. TIME ESTIMATED FROM RADAR. |
| Sep 1, 5:46 PM EDT | TSTM WND DMG | 2 Wnw Horsham, PA | MULTIPLE BUILDINGS HAD THEIR ROOFS BLOWN OFF ALONG NORRISTOWN ROAD. NORRISTOWN ROAD IS COMPLETELY BLOCKED WITH DEBRIS. POSSIBLE TORNADO. TIME ESTIMATED FROM RADAR. |
| Sep 1, 5:59 PM EDT | TORNADO | 1 Wnw Warwick Twp, PA | THE STORM WHICH PRODUCED A STRONG TORNADO IN MONTGOMERY COUNTY, PA, CYCLED AND PRODUCED ANOTHER TORNADO IN BUCKS COUNTY, PA. DAMAGE BEGAN NEAR IN THE AREA OF NESHAMINY CREEK BETWEEN VALLEY RD AND PEBBLE HILL RD IN DOYLESTOWN. THE TORNADO TRACKED NORTH-NORTHEAS |
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.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| Sep 1, 12:40 PM EDT | Tornado Watch | SPC | 9 hr |
The nearest sounding before it
Washington/Dulle, VA (KIAD), launched 12:00Z, 9.2 hours before the alert went out and 220 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.
- Mixed-layer CAPE
- 558 J/kg
- Mixed-layer CIN
- -21 J/kg
- Mixed-layer LCL
- 575 m above ground
- 0-6 km bulk shear
- 48 kt
- 0-1 km storm-relative helicity
- 122 m²/s²
- 0-3 km storm-relative helicity
- 223 m²/s²
- Significant tornado parameter
- 0.4
- Supercell composite
- 2.6
The text
As transmitted.
220
WUUS51 KPHI 012113
SVRPHI
NJC019-021-PAC017-029-045-091-101-012200-
/O.NEW.KPHI.SV.W.0289.210901T2113Z-210901T2200Z/
BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
513 PM EDT Wed Sep 1 2021
The National Weather Service in Mount Holly NJ has issued a
* Severe Thunderstorm Warning for...
South central Hunterdon County in northwestern New Jersey...
Southwestern Mercer County in central New Jersey...
Montgomery County in southeastern Pennsylvania...
Southern Bucks County in southeastern Pennsylvania...
Northeastern Chester County in southeastern Pennsylvania...
Philadelphia County in southeastern Pennsylvania...
Delaware County in southeastern Pennsylvania...
* Until 600 PM EDT.
* At 513 PM EDT, a severe thunderstorm was located over Newtown
Square, or 12 miles east of West Chester, moving northeast at 55
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, Camden, Bensalem, Ewing, Norristown,
Chester, Phoenixville, Lansdale, West Norriton, East Norriton,
Yeadon, Westtown, Bristol, Doylestown, Byram, Conshohocken,
Palmyra, Hatboro and Souderton.
This includes the following highways...
Pennsylvania Turnpike between mile markers 312 and 359.
Northeast Extension between mile markers 21 and 33.
Interstate 95 in Pennsylvania between mile markers 0 and 40.
Interstate 76 in Pennsylvania between mile markers 327 and 351.
Interstate 195 in New Jersey near mile marker 0.
Interstate 295 in New Jersey near mile marker 60, and between mile
markers 75 and 76.
Interstate 676 in Pennsylvania between mile markers 0 and 1.
Interstate 476 in Pennsylvania between mile markers 0 and 19.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
A Tornado Watch remains in effect until 1000 PM EDT for northern
Delaware...southern, central and northwestern New Jersey...and
southeastern Pennsylvania.
For your protection move to an interior room on the lowest floor of a
building.
A Tornado Watch remains in effect until 1000 PM EDT for northern
Delaware...southern, central and northwestern New Jersey...and
southeastern Pennsylvania.
&&
LAT...LON 4014 7573 4046 7501 4018 7471 4007 7492
4005 7497 4002 7501 3996 7513 3989 7514
3988 7519 3985 7525 3985 7533 3980 7541
3981 7543 3982 7546
TIME...MOT...LOC 2113Z 239DEG 47KT 4000 7538
TORNADO...POSSIBLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH
$$
JEO2 follow-up statements
859
WWUS51 KPHI 012129
SVSPHI
Severe Weather Statement
National Weather Service Mount Holly NJ
529 PM EDT Wed Sep 1 2021
NJC019-021-PAC017-029-045-091-101-012200-
/O.CON.KPHI.SV.W.0289.000000T0000Z-210901T2200Z/
Hunterdon NJ-Mercer NJ-Montgomery PA-Bucks PA-Chester PA-
Philadelphia PA-Delaware PA-
529 PM EDT Wed Sep 1 2021
...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 600 PM EDT
FOR SOUTH CENTRAL HUNTERDON...SOUTHWESTERN MERCER...MONTGOMERY...
SOUTHERN BUCKS...NORTHEASTERN CHESTER...PHILADELPHIA AND EASTERN
DELAWARE COUNTIES...
At 529 PM EDT, a severe thunderstorm was located over Jenkintown, or
near Philadelphia, moving northeast at 55 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, Camden, Bensalem, Ewing, Norristown, Chester,
Phoenixville, Lansdale, West Norriton, East Norriton, Yeadon,
Bristol, Doylestown, Byram, Conshohocken, Palmyra, Hatboro, Souderton
and Folcroft.
This includes the following highways...
Pennsylvania Turnpike between mile markers 326 and 359.
Northeast Extension between mile markers 21 and 33.
Interstate 95 in Pennsylvania between mile markers 0 and 40.
Interstate 76 in Pennsylvania between mile markers 327 and 351.
Interstate 195 in New Jersey near mile marker 0.
Interstate 295 in New Jersey near mile marker 60, and between mile
markers 75 and 76.
Interstate 676 in Pennsylvania between mile markers 0 and 1.
Interstate 476 in Pennsylvania between mile markers 0 and 19.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
A Tornado Watch remains in effect until 1000 PM EDT for northern
Delaware...southern, central and northwestern New Jersey...and
southeastern Pennsylvania.
For your protection move to an interior room on the lowest floor of a
building.
Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.
&&
LAT...LON 4019 7560 4046 7501 4018 7471 4007 7492
4005 7497 4002 7501 3996 7513 3989 7514
3988 7519 3985 7525 3985 7533 3980 7541
3981 7543 3982 7546 4005 7536
TIME...MOT...LOC 2129Z 239DEG 47KT 4011 7515
TORNADO...POSSIBLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH
$$
JEO209
WWUS51 KPHI 012154
SVSPHI
Severe Weather Statement
National Weather Service Mount Holly NJ
554 PM EDT Wed Sep 1 2021
NJC019-021-PAC017-029-045-091-101-012204-
/O.EXP.KPHI.SV.W.0289.000000T0000Z-210901T2200Z/
Hunterdon NJ-Mercer NJ-Montgomery PA-Bucks PA-Chester PA-
Philadelphia PA-Delaware PA-
554 PM EDT Wed Sep 1 2021
...THE SEVERE THUNDERSTORM WARNING FOR SOUTH CENTRAL HUNTERDON...
SOUTHWESTERN MERCER...MONTGOMERY...SOUTHERN BUCKS...NORTHEASTERN
CHESTER...PHILADELPHIA AND EASTERN DELAWARE COUNTIES WILL EXPIRE AT
600 PM EDT...
The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning will be allowed to expire.
A Tornado Watch remains in effect until 1000 PM EDT for northern
Delaware...southern, central and northwestern New Jersey...and
southeastern Pennsylvania.
LAT...LON 4019 7560 4046 7501 4018 7471 4007 7492
4005 7497 4002 7501 3996 7513 3989 7514
3988 7519 3985 7525 3985 7533 3980 7541
3981 7543 3982 7546 4005 7536
TIME...MOT...LOC 2154Z 239DEG 47KT 4027 7481
$$
JEOThe office that day
Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 1, 6:19 AM EDT | Areal Flood Advisory | PHI | Chester, Delaware | 116 min |
| Sep 1, 6:49 AM EDT | Flash Flood Warning | PHI | Chester, Delaware, Philadelphia | 86 min |
| Sep 1, 11:24 AM EDT | Areal Flood Advisory | PHI | Berks, Carbon, Lehigh, Monroe, Northampton | 3 hr |
| Sep 1, 12:07 PM EDT | Flash Flood Warning | PHI | Carbon, Monroe | 4 hr |
| Sep 1, 1:29 PM EDT | Flash Flood Warning | PHI | Berks, Lehigh | 6 hr |
| Sep 1, 2:53 PM EDT | Flash Flood Warning | PHI | Berks, Chester, Delaware, Montgomery | 9 hr |
| Sep 1, 3:55 PM EDT | River Flood Warning | PHI | Montgomery | 36 hr |
| Sep 1, 3:55 PM EDT | River Flood Warning | PHI | Chester, Montgomery, Philadelphia | 43 hr |
| Sep 1, 3:55 PM EDT | River Flood Warning | PHI | Montgomery, Philadelphia | 41 hr |
| Sep 1, 3:55 PM EDT | River Flood Warning | PHI | Philadelphia | 39 hr |
| Sep 1, 3:55 PM EDT | River Flood Warning | PHI | Berks | 24 hr |
| Sep 1, 4:02 PM EDT | River Flood Warning | PHI | Monroe | 24 hr |
| Sep 1, 4:04 PM EDT | Areal Flood Warning | PHI | Carbon, Monroe, Northampton | 24 hr |
| Sep 1, 4:10 PM EDT | River Flood Warning | PHI | Monroe | 19 hr |
| Sep 1, 4:12 PM EDT | Flash Flood Warning | PHI | Berks, Bucks, Lehigh, Montgomery, Northampton | 7 hr |
| Sep 1, 4:12 PM EDT | River Flood Warning | PHI | Lehigh, Northampton | 25 hr |
| Sep 1, 4:12 PM EDT | River Flood Warning | PHI | Lehigh, Northampton | 24 hr |
| Sep 1, 4:12 PM EDT | River Flood Warning | PHI | Carbon | 15 hr |
| Sep 1, 4:13 PM EDT | Tornado Warning | PHI | Chester | 32 min |
| Sep 1, 4:20 PM EDT | River Flood Warning | PHI | Montgomery | 22 hr |
| Sep 1, 4:21 PM EDT | River Flood Warning | PHI | Bucks | 29 hr |
| Sep 1, 4:42 PM EDT | Flash Flood Warning | PHI | Chester, Delaware, Montgomery | 6 hr |
| Sep 1, 5:07 PM EDT | River Flood Warning | PHI | Chester | 17 hr |
| Sep 1, 5:15 PM EDT | Tornado Warning | PHI | Delaware, Montgomery, Philadelphia | 30 min |
| Sep 1, 5:26 PM EDT | Flash Flood Warning | PHI | Bucks, Delaware, Montgomery, Philadelphia | 9 hr |
| Sep 1, 5:34 PM EDT | Tornado Warning | PHI | Bucks, Montgomery, Philadelphia | 26 min |
| Sep 1, 5:42 PM EDT | Flash Flood Warning | PHI | Bucks | 10 hr |
| Sep 1, 5:57 PM EDT | Tornado Warning | PHI | Bucks | 33 min |
| Sep 1, 6:08 PM EDT | Flash Flood Warning | PHI | Monroe, Northampton | 6 hr |
| Sep 1, 6:20 PM EDT | Tornado Warning | PHI | Bucks | 40 min |
| Sep 1, 6:22 PM EDT | Tornado Warning | PHI | Philadelphia | 23 min |
| Sep 1, 6:38 PM EDT | River Flood Warning | PHI | Chester, Delaware | 26 hr |
| Sep 1, 6:42 PM EDT | Tornado Warning | PHI | Bucks, Philadelphia | 33 min |
| Sep 1, 6:59 PM EDT | Severe Thunderstorm Warning | PHI | Bucks | 61 min |
| Sep 1, 7:04 PM EDT | Tornado Warning | PHI | Bucks | 26 min |
| Sep 1, 7:05 PM EDT | Flash Flood Warning | PHI | Bucks | 8 hr |
| Sep 1, 7:22 PM EDT | Tornado Warning | PHI | Bucks | 11 min |
| Sep 1, 7:23 PM EDT | Areal Flood Warning | PHI | Berks, Lehigh | 14 hr |
| Sep 1, 7:31 PM EDT | Flash Flood Warning | PHI | Bucks | 4 hr |
| Sep 1, 7:53 PM EDT | River Flood Warning | PHI | Delaware | 13 hr |
| Sep 1, 3:23 AM EDT | Gale Warning | PHI | 32 hr | |
| Sep 1, 3:23 AM EDT | Small Craft Advisory | PHI | 41 hr | |
| Sep 1, 4:34 AM EDT | Rip Current Statement | PHI | Atlantic, Cape May, Monmouth, Ocean | 39 hr |
| Sep 1, 7:58 AM EDT | Severe Thunderstorm Warning | PHI | Burlington, Ocean | 47 min |
| Sep 1, 8:39 AM EDT | Severe Thunderstorm Warning | PHI | Monmouth, Ocean | 39 min |
| Sep 1, 9:11 AM EDT | Special Marine Warning | PHI | 64 min | |
| Sep 1, 4:27 PM EDT | River Flood Warning | PHI | Morris, Somerset | 6 days |
| Sep 1, 4:27 PM EDT | River Flood Warning | PHI | Essex, Morris, Passaic | 8 days |
| Sep 1, 4:27 PM EDT | River Flood Warning | PHI | Essex, Morris, Passaic | 6 days |
| Sep 1, 4:27 PM EDT | River Flood Warning | PHI | Essex, Passaic | 21 days |
| Sep 1, 4:33 PM EDT | River Flood Warning | PHI | Morris, Passaic | 46 hr |
| Sep 1, 4:40 PM EDT | River Flood Warning | PHI | Hunterdon, Somerset | 36 hr |
| Sep 1, 4:40 PM EDT | River Flood Warning | PHI | Somerset | 22 hr |
| Sep 1, 4:40 PM EDT | River Flood Warning | PHI | Middlesex, Somerset | 42 hr |
| Sep 1, 4:40 PM EDT | River Flood Warning | PHI | Middlesex, Somerset | 48 hr |
| Sep 1, 4:41 PM EDT | River Flood Warning | PHI | Somerset | 61 hr |
| Sep 1, 5:33 PM EDT | Special Marine Warning | PHI | 27 min | |
| Sep 1, 5:35 PM EDT | Tornado Warning | PHI | Cumberland, Salem | 25 min |
| Sep 1, 5:57 PM EDT | Tornado Warning | PHI | Gloucester, Salem | 33 min |
| Sep 1, 6:05 PM EDT | Flash Flood Warning | PHI | Hunterdon, Mercer, Middlesex, Morris, Somerset | 10 hr |
| Sep 1, 6:14 PM EDT | Special Marine Warning | PHI | 61 min | |
| Sep 1, 7:28 PM EDT | Tornado Warning | PHI | Mercer, Middlesex, Morris, Somerset | 47 min |
| Sep 1, 7:44 PM EDT | Special Marine Warning | PHI | 61 min |
Nearby
Severe Thunderstorm Warnings in Pennsylvania, 2021Severe Thunderstorm Warnings in New Jersey, 2021Every 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.