EF0 tornado in Philadelphia County, Pennsylvania

A brief tornado occurred in the Bustleton section of Northeast

Philadelphia. Damage was first observed near Grant Ave at the

Grant Gardens apartment complex, where some minor loss of roofing

material was noted and debris was tossed in a chaotic manner

consistent with tornadic winds. The tornado moved east-southeast

across Roosevelt Blvd. Continued minor structural damage was noted

along a narrow path, mainly consisting of sporadic losses of

siding and insulation. Minor tree damage was also noted. One

building also had ceiling tiles pulled downward with insulation

removed in a car park area, a strong indicator of tornadic

pressure gradient forces. Near Blue Glass Rd, a couple of slightly

larger trees had their trunks snapped, and winds of around 80 mph

likely occurred in that area. The damage path ended near there,

however, after a track length of only around half a mile. Radar

data indicates this was an anticyclonic tornado.

A strong shortwave trough moved east-southeastward out of the Great Lakes region on July 29. An associated, strengthening surface low also tracked out of the Great Lakes and into upstate New York. A warm front associated with this low moved through most of New Jersey and eastern Pennsylvania during the late morning and early afternoon hours. This front, combined with the remains of widespread convection to the west from the previous overnight and morning hours, brought significant cloud cover to the eastern mid-Atlantic for much of the day on the 29th. This was mainly in the form of mid and high level cloud cover, however, and temperatures still warmed to near seasonal levels behind the warm front, allowing moderate to strong instability to build. Meanwhile, the robust surface and upper level disturbances approaching the region brought both strong forcing and unseasonably strong wind shear. By mid-afternoon, an unusually favorable convective environment existed over eastern Pennsylvania and New Jersey.

The result of this environment was a rare tornado outbreak across the area. Initially, during the mid-afternoon hours, mixed convective modes over east-central Pennsylvania produced a couple instances of damaging wind and brief tornadoes as storms attempted to overcome cloud cover and some light stratiform rain in the area. With time, as storms moved into better instability and a less contaminated environment over far eastern Pennsylvania and New Jersey, they took on more supercellular structures. Multiple cyclic supercells would go on to produce several tornadoes, three of them strong (EF2+) over eastern Pennsylvania and New Jersey. Convection persisted past the sunset hour with little to no loss in intensity due to the strong forcing. The only thing that put an end to the outbreak was the coastline, as storms moved offshore towards 9 to 10PM local time. Even offshore, one supercell continued to exhibit strong rotation and likely produced a strong waterspout for tens of miles over the Atlantic.

Fortunately, and miraculously, no serious injuries or loss of life occurred as a result of this outbreak. With the passage of a cold front late on the evening of the 29th, cooler, drier, and much less active weather would grace the region for several days as clean-up efforts began.