Thunderstorm Wind — Delaware, Pennsylvania

2020-06-03 · near Crum Creek Manor, Delaware, Pennsylvania

Event narrative

A tree fell on a power line that fell on a house near Wallingford, which then started a house fire, killing one individual. Time estimated from radar.

Wider weather episode

An area of thunderstorms, some of them severe, moved from northwest to southeast across southeastern Pennsylvania during the mid-morning hours on Wednesday, June 3rd. Then a derecho, which developed just southeast of Lake Erie during the early morning hours, moved rapidly southeast across Pennsylvania before exiting off the New Jersey coast by early afternoon (130 PM). Damaging winds associated with this derecho were sporadic over western and central Pennsylvania, but as the thunderstorm complex moved into increasingly unstable air in the eastern part of the state just before noon, wind damage reports became more numerous and widespread. Most of these reports were confined within a 50-mile wide swath extending from Berks County eastward to the Philadelphia metro area, then further east to the Ocean County shoreline in New Jersey. Wind gust reports between 60 and 70 MPH were common within this swath, with some of the highest gusts as follows: 83 MPH at Reading Regional Airport (Berks County), 76 MPH in Pottstown (Montgomery County), 75 MPH in Malvern (Chester County), and 71 MPH in the Holmesburg section of Philadelphia. In addition to these destructive wind gusts, frequent to continuous cloud to ground lightning, heavy rain, and a few instances of hail were also reported throughout the area.

Tragically, four deaths were reported in eastern Pennsylvania as a result of these severe wind gusts. Three fatalities in Montgomery County were due directly to falling trees. The fourth fatality in Delaware County was due to a house fire caused by an electrical malfunction from a fallen tree. This is the highest number of fatalities from a derecho event in Pennsylvania since 1950.

Over 208,000 power outages were reported in southeastern Pennsylvania as a result

of fallen trees on power lines. Some localities were without power for several days. Numerous road closures were also reported due to fallen trees.

A seven story 150 unit apartment building took severe roof damage in Lansdale Borough, Montgomery County. The Montgomery County Community Based COVID-19 Testing Site shut down at noon due to the storms. Personnel took shelter and reported minor property damage.

Because this derecho moved off the coast by 130 PM, the warm afternoon sun was able to sufficiently destabilize the atmosphere for the formation of another round of severe thunderstorms over some of the same areas that experience them earlier in the day. Reported wind gusts associated with these thunderstorms generally ranged between 45 and 65 MPH, with a 65 MPH wind gust measured at the Philadelphia International Airport. The remaining thunderstorms then moved offshore by 1000 PM, which brought an end to the day's severe weather.

View location on OpenStreetMap → (39.8800, -75.3700)

Source: NOAA Storm Events Database, event_id 885522. Narrative written by the NWS forecast office that issued the report.