Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2018

Severe Thunderstorm Warning 8, NWS Philadelphia/Mount Holly

May 12, 2018Chester County, Delaware County, Pennsylvania; New Castle County, Delaware; Gloucester County, Salem County, New Jersey

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at May 12, 2018, 7:30 PM EDT for Chester County, Delaware County, Pennsylvania; New Castle County, Delaware; Gloucester County, Salem County, New Jersey. It was in force for 45 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: May 12, 2018, 7:30 PM EDT (23:30 UTC)
Expired: May 12, 2018, 8:15 PM EDT
In force: 45 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Tornado: Possible
Hail: 1.75 in
Wind: 60.0 mph

Counties New Castle County, DE, Gloucester County, NJ, Salem County, NJ, Chester County, PA, Delaware County, PA

The radar

The Philadelphia radar (KDIX), 110 km from the middle of the area, began a volume at 23:30 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
May 12, 7:35 PM EDT	HAIL 1	1 Ne Toughkenamon, PA	MPING REPORT OF QUARTER SIZED HAIL.
May 12, 7:36 PM EDT	HAIL 1	Hockessin, DE
May 12, 7:37 PM EDT	HAIL 0.75	Concord Hills, DE	DIME-SIZED HAIL ON ROUTE 202 NEAR NAAMANS ROAD.
May 12, 7:46 PM EDT	HAIL 0.75	Elsmere, DE	HAIL UP TO PENNY SIZE IN ELSMERE. TIME APPROXIMATED FROM RADAR.
May 12, 7:58 PM EDT	HAIL 0.75	1 Ne Cleland Heights, DE

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
May 12, 4:58 PM EDT	Tornado Watch	SPC	5 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 11.5 hours before the alert went out and 180 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1390 m above ground
0-6 km bulk shear: 38 kt
0-1 km storm-relative helicity: 178 m²/s²
0-3 km storm-relative helicity: 201 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

202 
WUUS51 KPHI 122330
SVRPHI
DEC003-NJC015-033-PAC029-045-130015-
/O.NEW.KPHI.SV.W.0008.180512T2330Z-180513T0015Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
730 PM EDT SAT MAY 12 2018

The National Weather Service in Mount Holly NJ has issued a

* Severe Thunderstorm Warning for...
  Northern New Castle County in northern Delaware...
  Northwestern Salem County in southern New Jersey...
  West central Gloucester County in southern New Jersey...
  Southeastern Chester County in southeastern Pennsylvania...
  Southwestern Delaware County in southeastern Pennsylvania...

* Until 815 PM EDT.

* At 729 PM EDT, a severe thunderstorm was located near Kennett
  Square, or near West Chester, moving east at 45 mph.

  HAZARD...Golf ball size hail and 60 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...People and animals outdoors will be injured. Expect hail 
           damage to roofs, siding, windows, and vehicles. Wind 
           damage to roofs, siding, trees, and power lines is 
           possible.

* Locations impacted include...
  Wilmington, West Chester, Chester, Pennsville, Coatesville,
  Westtown, Carneys Point, Downingtown, Swarthmore, Elsmere, Kennett
  Square, New Castle, Penns Grove, West Grove, Newport, Arden,
  Stanton, Cheyney, Talleyville and Elam.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

This storm is producing large hail. SEEK SHELTER NOW inside a sturdy
structure and stay away from windows!

In addition to large hail and damaging winds, frequent cloud to
ground lightning is occurring with this storm. Move indoors
immediately. Remember, if you can hear thunder, you are close enough
to be struck by lightning.

&&

A tornado watch remains in effect until 100 AM EDT for northern
Delaware...southern New Jersey...and southeastern Pennsylvania.

LAT...LON 4002 7579 3998 7534 3965 7541 3978 7595
      3993 7588
TIME...MOT...LOC 2329Z 280DEG 38KT 3989 7568 

TORNADO...POSSIBLE
HAIL...1.75IN
WIND...60MPH
 
$$

LF

2 follow-up statements

646 
WWUS51 KPHI 122348
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
748 PM EDT SAT MAY 12 2018

DEC003-NJC015-033-PAC029-045-130015-
/O.CON.KPHI.SV.W.0008.000000T0000Z-180513T0015Z/
New Castle DE-Salem NJ-Gloucester NJ-Chester PA-Delaware PA-
748 PM EDT SAT MAY 12 2018

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 815 PM EDT
FOR NORTHERN NEW CASTLE...NORTHWESTERN SALEM...WEST CENTRAL
GLOUCESTER...SOUTHEASTERN CHESTER AND SOUTHWESTERN DELAWARE
COUNTIES...

At 747 PM EDT, a severe thunderstorm was located over Chester
Township, or 10 miles northeast of Wilmington, moving east at 40 mph.

HAZARD...60 mph wind gusts and quarter size hail.

SOURCE...Trained weather spotters.

IMPACT...Minor damage to vehicles is possible. Wind damage to roofs, 
         siding, trees, and power lines is possible.

Locations impacted include...
Wilmington, Chester, Pennsville, Westtown, Carneys Point, Swarthmore,
Elsmere, New Castle, Penns Grove, Newport, Arden, Stanton, Cheyney,
Talleyville, Elam, Chelsea, Gradyville, Greenville, Broomall and
Chester Township.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

In addition to large hail and damaging winds, frequent cloud to
ground lightning is occurring with this storm. Move indoors
immediately. Remember, if you can hear thunder, you are close enough
to be struck by lightning.

&&

A tornado watch remains in effect until 100 AM EDT for northern
Delaware...southern New Jersey...and southeastern Pennsylvania.

LAT...LON 4000 7554 3998 7534 3965 7541 3974 7575
TIME...MOT...LOC 2347Z 270DEG 38KT 3986 7543 

TORNADO...POSSIBLE
HAIL...1.00IN
WIND...60MPH
 
$$

882 
WWUS51 KPHI 130011
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
811 PM EDT SAT MAY 12 2018

DEC003-NJC015-033-PAC029-045-130021-
/O.EXP.KPHI.SV.W.0008.000000T0000Z-180513T0015Z/
New Castle DE-Salem NJ-Gloucester NJ-Chester PA-Delaware PA-
811 PM EDT SAT MAY 12 2018

...THE SEVERE THUNDERSTORM WARNING FOR NORTHERN NEW CASTLE...
NORTHWESTERN SALEM...WEST CENTRAL GLOUCESTER...SOUTHEASTERN CHESTER
AND SOUTHWESTERN DELAWARE COUNTIES WILL EXPIRE AT 815 PM EDT...
        
The storm which prompted the warning has moved out of the area.
Therefore, the warning will be allowed to expire.

A tornado watch remains in effect until 100 AM EDT for northern
Delaware...southern New Jersey...and southeastern Pennsylvania.

LAT...LON 4000 7554 3998 7534 3965 7541 3974 7575
TIME...MOT...LOC 0011Z 280DEG 38KT 3982 7512 

$$

The office that day

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

Issued	Product	Office	Counties	Lasted
May 12, 6:51 PM EDT	Special Weather Statement	PHI	Chester	39 min
May 12, 6:53 PM EDT	Special Weather Statement	PHI	Montgomery, Philadelphia	52 min
May 12, 7:00 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware	45 min
May 12, 7:10 PM EDT	Areal Flood Advisory	PHI	Chester, Delaware	2 hr
May 12, 7:16 PM EDT	Severe Thunderstorm Warning	PHI	Chester	44 min
May 12, 7:37 PM EDT	Areal Flood Advisory	PHI	Bucks, Chester, Delaware, Montgomery, Philadelphia	2 hr
May 12, 7:45 PM EDT	Severe Thunderstorm Warning	PHI	Delaware	45 min
May 12, 7:25 PM EDT	Severe Thunderstorm Warning	PHI	Kent, New Castle	50 min
May 12, 7:57 PM EDT	Areal Flood Advisory	PHI	Kent, New Castle	4 hr
May 12, 6:26 AM EDT	Special Weather Statement	PHI	Atlantic	49 min
May 12, 7:02 AM EDT	Special Marine Warning	PHI		58 min
May 12, 7:48 PM EDT	Special Marine Warning	PHI		57 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2018 Severe Thunderstorm Warnings in New Jersey, 2018 Severe Thunderstorm Warnings in Delaware, 2018 Every severe thunderstorm warning in 2018

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.