EF1 tornado, East Waterford to Academia, Pennsylvania, April 28, 2011

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.

Rating

EF1

Date

April 28, 2011

Touchdown

2:53 AM EDT (06:53 UTC)

Lifted

3:00 AM EDT (07:00 UTC)

On the ground

7 minutes

Path length

8.5 miles (13.6 km)

Path width

100 yards (91 m)

Deaths

0

Injuries

0

Property damage

$25,000

County

Juniata County

Touchdown point

40.380, -77.590

Lift-off point

40.467, -77.476

Record number

1104280053-01

4 damage points were recorded along this path by NWS CTP, in the Damage Assessment Toolkit the survey teams carry. The highest wind the damage implies is 74 mph.

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

A total of six tornadoes were confirmed over from the early evening on the 27th through the early morning hours of the 28th. This was the most significant tornado outbreak in central Pennsylvania since 2005. The last event with 6 confirmed tornadoes was September 2004 with Hurricane Ivan. The large scale weather pattern that contributed to this outbreak featured a fast-moving upper level impulse and attendant surface low pressure system that moved across the Great Lakes Region. An unseasonably warm and relatively moist air mass /surface temperatures in the 70s to low 80s and dewpoints in the upper 50s/ resided over central Pennsylvania in advance of this system and aided in strong destabilization. Moderate instability combined with strong vertical wind shear profiles promoted a convective environment favorable for organized thunderstorms with supercells and bowing line segments. Although large hail and damaging winds were the main threats, sufficient low-level wind shear was present to support isolated tornadoes. A tornado watch was issued around 1500 EDT on 27 April 2011. The tornado threat continued through the evening and into the overnight and early morning hours on 28 April 2011. By this time, thunderstorms had evolved into largely north-south oriented clusters or broken lines with embedded supercell structures. The storms finally exited the region by mid-morning on 28 April 2011.

The NWS in State College confirmed an EF1 tornado near East Waterford in Juniata County. The tornado occurred between 0253 and 0300 AM EDT on 28 April 2011. The EF1 tornado first produced damage on the east side of East Waterford, then skirted northeast along SR 75 producing sporadic damage along a well-defined path from Honey Grove to Seven Pines in Spruce Hill Township. The Hancock farm in Honey Grove sustained the most significant damage, as the farm house roof and several barns and farm sheds were destroyed. Numerous tree damage was observed along the tornado track which covered approximately 8 miles. Two barns were also damaged along Laurel Run near SR 850 at Burnt Church Road. Additional barns along SR 75 suffered minor to moderate roof damage, with roof debris scattered up to 200 yards away from its source location. The damage indicators, primarily those observed at the Hancock farm, were consistent with a maximum wind speed between 105 to 110 mph, putting the tornado in the upper-bound of the EF1 rating category.

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

No tornado warning for this county appears in the archive as in force at the moment the tornado touched down.

The county was under a severe thunderstorm watch, issued at 03:50 UTC and running to 08:51 UTC.

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 Storm Prediction Center had this point in a General Thunderstorms Risk, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 06:09 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 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.

The State College radar (KCCX), 68 km away, was scanning. The volume nearest the touchdown began at 06:53 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.

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

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

The live radar over the trackEvery 2011 tornado in PennsylvaniaEvery tornado in Pennsylvania since 1950Warnings in force in Pennsylvania nowThe forecast where you are

39 more were confirmed in the United States that day.

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.

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