Tornadoes · United States · Pennsylvania · 2017

EF1 tornado, Needmore to Gem, Pennsylvania, August 4, 2017

From Needmore to Gem, this EF1 tornado ran 1.2 miles across Fulton County on August 4, 2017, touching down at 5:55 PM EDT and reaching 200 yards wide. It killed nobody, and did $5,000 of property damage.

The rating scale

Tracks are drawn in the color of the rating. The Enhanced Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.

  1. EF065 to 85 mph

    Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

  2. EF186 to 110 mphthis tornado

    Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

  3. EF2111 to 135 mph

    Considerable damage. Roofs torn off well-built houses, frame homes shifted on their foundations, mobile homes destroyed, large trees snapped or uprooted, cars lifted off the ground.

  4. EF3136 to 165 mph

    Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

  5. EF4166 to 200 mph

    Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

  6. EF5over 200 mph

    Incredible damage. Strong frame houses swept off their foundations, car-sized missiles thrown more than 100 meters, steel-reinforced concrete badly damaged, high-rise buildings deformed.

  7. Unrated

    The survey recorded a tornado but could not put a number on it, most often because it crossed open country and damaged nothing a rating can be read from.

The record

Rating
EF1
Date
August 4, 2017
Touchdown
5:55 PM EDT (21:55 UTC)
Lifted
6:01 PM EDT (22:01 UTC)
On the ground
6 minutes
Path length
1.2 miles (2.0 km)
Path width
200 yards (183 m)
Deaths
0
Injuries
0
Property damage
$5,000
County
Fulton County
Touchdown point
39.855, -78.150
Lift-off point
39.865, -78.131
Record number
1708041555-01

What the Weather Service recorded

An EF1 tornado touched down briefly near Needmore in Fulton County during the early evening of August 4, 2017.

An EF1 tornado with an estimated maximum wind speed of 100 mph was confirmed by a NWS survey team to have touched down in Fulton County on August 4, 2017. The tornado touched down near Pleasant Grove Road (State Road 3007) and traveled northeastward for about 5 minutes, snapping and uprooting several swaths of trees along its path. It was estimated that approximately 150 trees were snapped or downed by the tornado.

From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.

The warnings

19 minutes of warning. NWS CTP issued a tornado warning for this county at 21:36 UTC, 19 minutes before the tornado touched down, in force until 22:15 UTC.

The county was under a severe thunderstorm watch, issued at 17:26 UTC and running to 01:00 UTC.

Issued (UTC)ExpiredProductOffice
17:26 UTC01:00 UTCSevere Thunderstorm WatchCTP
21:28 UTC22:30 UTCSevere Thunderstorm WarningCTP
21:36 UTC22:15 UTCTornado WarningCTP
22:18 UTC23:15 UTCSevere Thunderstorm WarningCTP
22:29 UTC01:30 UTCFlood AdvisoryCTP
01:42 UTC04:45 UTCFlood AdvisoryCTP

Every warning and watch covering the touchdown point that day, from the Iowa Environmental Mesonet's archive of National Weather Service products. Lead time is measured from the issue of the warning in force to the touchdown time in the database, both of which were recorded to the minute by different people.

The forecast that day

The Storm Prediction Center had this point in a Slight Risk. The outlook in force was issued at 19:57 UTC.

SPC's Day 1 convective outlook as it stood when the tornado began, read at the touchdown point. The same archive is on the radar archive.

The air that afternoon

The radiosonde launches on either side of the tornado, from the nearest station that was launching then, drawn and analyzed the way Storm Lab does: the same diagram, the same parcel and shear definitions SPC's mesoanalysis uses.

Washington/Dulle, VA (KIAD), 12:00Z

9.9 hours before the tornado, 120 km from the path. August 4, 2017.

Skew-T log-pSkew-T log-p diagram, Washington/Dulle, VA at 12:00Z on 2017-08-04Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 166 joules per kilogram, CIN -125, lifted condensation level 1412 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Washington/Dulle, VA at 12:00Z on 2017-08-04The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity 45 square meters per square second, 0 to 6 km bulk shear 21 knots.1939Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
166 J/kg
Mixed-layer CIN
-125 J/kg
Surface CAPE
90 J/kg
Mixed-layer LCL
1412 m above ground
0-6 km bulk shear
21 kt
0-1 km bulk shear
13 kt
0-1 km storm-relative helicity
45 m²/s²
0-3 km storm-relative helicity
46 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
5.1 K/km

Open this sounding in Storm Lab

Washington/Dulle, VA (KIAD), 00:00Z

2.1 hours after it, 120 km from the path. August 5, 2017.

Skew-T log-pSkew-T log-p diagram, Washington/Dulle, VA at 00:00Z on 2017-08-05Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 786 joules per kilogram, CIN -29, lifted condensation level 1447 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Washington/Dulle, VA at 00:00Z on 2017-08-05The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity 128 square meters per square second, 0 to 6 km bulk shear 33 knots.193958Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
786 J/kg
Mixed-layer CIN
-29 J/kg
Surface CAPE
1142 J/kg
Mixed-layer LCL
1447 m above ground
0-6 km bulk shear
33 kt
0-1 km bulk shear
17 kt
0-1 km storm-relative helicity
128 m²/s²
0-3 km storm-relative helicity
202 m²/s²
Significant tornado parameter
0.3
Supercell composite
3.7
0-3 km lapse rate
7.0 K/km

Open this sounding in Storm Lab

The radar

The Sterling radar (KLWX), 113 km away, was scanning. The volume nearest the touchdown began at 21:56 UTC.

Open the radar archive at this moment, over the track

Reflectivity and velocity, decoded from the Level II archive in the browser. Volumes take a few seconds to open the first time.

What was reported nearby

Local storm reports within 60 km of the path, in the three hours either side.

Time (UTC)ReportWhereCountyRemark
21:50 UTCTSTM WND DMG2 W AndoverFulton, PASEVERAL TREES DOWN
21:50 UTCTSTM WND DMG3 Sse BreezewoodFulton, PATREES AND WIRES REPORTED DOWN NEAR INTERSECTION OF ROUTE 915 AND PLEASANT VALLEY ROAD NEAR THE CRYSTAL SPRING EXIT ON I-70.
21:55 UTCTORNADO1 Nw NeedmoreFulton, PAEF1 TORNADO CONFIRMED NEAR NEEDMORE.
22:20 UTCTSTM WND DMG2 Sw MetalFranklin, PAMULTIPLE TREES REPORTED TO BE DAMAGED JUST EAST OF COWNAS GAP.
22:20 UTCTSTM WND DMGMcconnellsburgFulton, PATREES AND WIRES REPORTED DOWN NEAR MCCONNELLSBURG.
22:34 UTCTSTM WND DMGUpper StrasburgFranklin, PATREE AND WIRES REPORTED DOWN NEAR UPPER STRASBURG.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

This ground now

The live radar over the trackEvery 2017 tornado in PennsylvaniaEvery tornado in Pennsylvania since 1950Warnings in force in Pennsylvania nowThe forecast where you are

The other tornadoes of August 4, 2017

2 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
August 42:50 PM EDTUnratedSaratoga, NY0.120
August 47:46 PM EDTEF1Bibb, GA1.9200$100,000

What this means

Ratings are the survey's, read off the damage rather than measured; the rating scale is above. Tornado counts rise through the record as reporting improved, so a year in the 1950s is not comparable with one today except for the strongest tornadoes, which were always noticed.

Sources

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.