Alert archive / Pennsylvania / Tornado Watches in 2015

Tornado Watch 397

July 9, 20158 counties in Maryland; 37 counties in Pennsylvania; 14 counties in West Virginia

The Storm Prediction Center issued this tornado watch at Jul 9, 2015, 1:27 PM EDT for 8 counties in Maryland; 37 counties in Pennsylvania; 14 counties in West Virginia. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Jul 9, 2015, 1:27 PM EDT (17:27 UTC)
Expired: Jul 9, 2015, 7:33 PM EDT
In force: 6 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1 in
Strongest gust expected: 60 kt

All 59 counties

Allegany County, MD, Baltimore County, MD, Carroll County, MD, City of Baltimore, MD, Frederick County, MD, Garrett County, MD, Harford County, MD, Washington County, MD, Adams County, PA, Armstrong County, PA, Bedford County, PA, Blair County, PA, Cambria County, PA, Cameron County, PA, Centre County, PA, Clarion County, PA, Clearfield County, PA, Clinton County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Elk County, PA, Fayette County, PA, Forest County, PA, Franklin County, PA, Fulton County, PA, Greene County, PA, Huntingdon County, PA, Indiana County, PA, Jefferson County, PA, Juniata County, PA, Lancaster County, PA, Lebanon County, PA, Lycoming County, PA, Mifflin County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Schuylkill County, PA, Snyder County, PA, Somerset County, PA, Sullivan County, PA, Union County, PA, Westmoreland County, PA, York County, PA, Barbour County, WV, Berkeley County, WV, Grant County, WV, Hampshire County, WV, Hardy County, WV, Harrison County, WV, Jefferson County, WV, Marion County, WV, Mineral County, WV, Monongalia County, WV, Morgan County, WV, Preston County, WV, Taylor County, WV, Tucker County, WV

The radar

The State College radar (KCCX), 53 km from the middle of the area, began a volume at 17:29 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 SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes: 40%
One or more EF2 to EF5 tornadoes: 20%
Ten or more severe wind reports: 50%
One or more gusts of 65 knots or more: 10%
Ten or more severe hail reports: 5%
One or more hailstones of 2 inches or more: 5%
Six or more combined severe hail and wind reports: 90%

Warnings issued inside it

18 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Jul 9, 1:27 PM EDT	Tornado Warning	PBZ	Fayette, Greene	18 min
Jul 9, 1:44 PM EDT	Severe Thunderstorm Warning	PBZ	Garrett	46 min
Jul 9, 1:54 PM EDT	Tornado Warning	PBZ	Indiana, Jefferson	21 min
Jul 9, 2:05 PM EDT	Severe Thunderstorm Warning	CTP	Centre, Clearfield	70 min
Jul 9, 2:21 PM EDT	Severe Thunderstorm Warning	CTP	Cambria, Somerset	54 min
Jul 9, 2:28 PM EDT	Severe Thunderstorm Warning	PBZ	Fayette, Westmoreland	32 min
Jul 9, 2:30 PM EDT	Severe Thunderstorm Warning	PBZ	Garrett	45 min
Jul 9, 2:43 PM EDT	Severe Thunderstorm Warning	PBZ	Armstrong, Butler, Clarion, Venango	47 min
Jul 9, 3:12 PM EDT	Severe Thunderstorm Warning	CTP	Lycoming, Tioga	63 min
Jul 9, 3:29 PM EDT	Severe Thunderstorm Warning	PBZ	Armstrong, Clarion, Indiana, Jefferson	46 min
Jul 9, 4:50 PM EDT	Severe Thunderstorm Warning	CTP	Adams, Cumberland, Franklin	55 min
Jul 9, 5:07 PM EDT	Severe Thunderstorm Warning	CTP	Dauphin, York	98 min
Jul 9, 5:20 PM EDT	Severe Thunderstorm Warning	CTP	Columbia, Lycoming, Montour, Northumberland, Sullivan, Union	29 min
Jul 9, 5:23 PM EDT	Severe Thunderstorm Warning	LWX	Carroll, Frederick	52 min
Jul 9, 5:34 PM EDT	Severe Thunderstorm Warning	CTP	Lancaster, Lebanon, York	86 min
Jul 9, 6:01 PM EDT	Severe Thunderstorm Warning	CTP	Dauphin, Lebanon, Schuylkill	74 min
Jul 9, 6:24 PM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Harford	36 min
Jul 9, 6:55 PM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Harford	20 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Pittsburgh, PA (KAGC), launched 12:00Z, 5.5 hours before the alert went out and 145 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: 104 J/kg
Mixed-layer CIN: -48 J/kg
Mixed-layer LCL: 631 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 208 m²/s²
0-3 km storm-relative helicity: 233 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

208 
WWUS20 KWNS 091724
SEL7  
SPC WW 091724
MDZ000-PAZ000-VAZ000-WVZ000-CWZ000-100100-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 397
NWS STORM PREDICTION CENTER NORMAN OK
125 PM EDT THU JUL 9 2015

THE NWS STORM PREDICTION CENTER HAS ISSUED A

* TORNADO WATCH FOR PORTIONS OF 
  NORTHERN MARYLAND INCLUDING THE PANHANDLE
  SOUTHWEST THROUGH CENTRAL PENNSYLVANIA
  FAR NORTHERN VIRGINIA
  NORTHEAST WEST VIRGINIA INCLUDING THE EASTERN PANHANDLE
  COASTAL WATERS

* EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 125 PM UNTIL
  900 PM EDT.

* PRIMARY THREATS INCLUDE...
  A COUPLE TORNADOES POSSIBLE
  SCATTERED DAMAGING WIND GUSTS TO 70 MPH POSSIBLE

SUMMARY...THUNDERSTORMS ARE EXPECTED TO INCREASE IN COVERAGE AND
INTENSITY ACROSS THE AREA WITH A MIXTURE OF SUPERCELLS AND BOWING
LINE SEGMENTS PRODUCING DAMAGING WINDS AND PERHAPS A COUPLE OF
TORNADOES.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 70 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 30 MILES WEST OF LATROBE
PENNSYLVANIA TO 45 MILES EAST NORTHEAST OF HARRISBURG
PENNSYLVANIA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

&&

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 450.
MEAN STORM MOTION VECTOR 25035.


...MEAD

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 9, 11:27 AM EDT	Mesoscale Discussion	SPC	Garrett	2 hr
Jul 9, 12:59 PM EDT	Mesoscale Discussion	SPC	Allegany, Anne Arundel, Baltimore, Carroll, Cecil, Frederick and 7 more	2 hr
Jul 9, 3:09 PM EDT	Mesoscale Discussion	SPC	Allegany, Anne Arundel, Baltimore, Caroline, Carroll, Cecil and 10 more	96 min
Jul 9, 4:55 PM EDT	Mesoscale Discussion	SPC	Allegany, Baltimore, Carroll, Cecil, Frederick, Garrett and 5 more	95 min
Jul 9, 4:57 PM EDT	Severe Thunderstorm Watch	SPC	Caroline, Cecil, Kent, Queen Anne's, Talbot	5 hr
Jul 9, 6:25 PM EDT	Mesoscale Discussion	SPC	Cecil, Harford	95 min
Jul 9, 7:04 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Calvert, Caroline, Charles, Dorchester, Prince George's and 6 more	86 min
Jul 9, 12:15 PM EDT	Mesoscale Discussion	SPC	Boone, Logan, McDowell, Mingo, Wyoming	3 hr
Jul 9, 5:58 PM EDT	Mesoscale Discussion	SPC	McDowell	2 hr

Nearby

Tornado Watches in Pennsylvania, 2015 Tornado Watches in West Virginia, 2015 Tornado Watches in Maryland, 2015 Every tornado watch in 2015

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.