EF1 tornado in Allegheny County, Pennsylvania

A damage survey confirmed that a tornado tracked across the

southern portion of Hampton Township, PA. This tornado was

associated with the same circulation that initially produced a

brief tornado earlier in Mount Nebo. Damage was first noted in the

area of Auld and Forest Avenues, in the form of light structural

damage to homes. The tornado strengthened on Linden Drive, with

several snapped hardwood and softwood trees, as well as the

uplift of a roof. Damage in this area was consistent with wind

speeds of 90 to 95 MPH. Snapped and uprooted trees were seen as

the tornado continued across Parkview Lane and then to Duncan

Avenue. Farther east, in the Church Hill area, snapped and

uprooted trees were observed, with one large tree on a house on

Cole Avenue, and some other minor structural damage where Cole

intersects with Miller Avenue as well as Cella Lane, representing

a rough tornado track width of 200 yards. The tornado weakened

considerably after it crossed Route 8 and into Bryant, before

causing more damage in the vicinity of Middle Road. Widespread

snapped hardwood trees were seen between John Giel Drive and

Green Valley Drive, and a cinder-block outbuilding was destroyed,

with debris being blown downwind 1/4 mile. Damage here was

consistent with 100 to 105 MPH wind. Tree damage continued ENE

into Hartwood Acres Park and then to Dorseyville Road, where the

damage path finally ended as the tornado dissipated. NWS

Pittsburgh is grateful to Hampton Township and Allegheny County

EMA for their assistance with this damage survey.

Damage cost was estimated using information from the local emergency manager.

A broken line of supercells, which formed along a front, moved quickly through the Ohio River Valley the evening of October 21st and spun off several tornadoes. The number of tornadoes, time of year, and intensity (one long track EF2 tornado) will mark this event as very rare and significant for this region.

Prior to tornado development, surface temperatures warmed into the low-mid 60s; dew points topped out near 60F. Forecast soundings indicated modest levels of mean layer CAPE, and a relatively straight hodograph yielding marginal but sufficient storm relative helicity. The overall quick track of the broken line and eastward propagation helped cells sustain rotating updrafts.