Ten Year Anniversary of Allison

Ten years ago today the region was soaked, socked, and pounded by the tropical remnants of Tropical Storm Allison, a soggy and slow-moving rainmaker that flooded countless places from Houston northeast to New Jersey. Allison was not a potent storm in terms of intensity, not on the scale of a major hurricane as it did not even exceed 60 mph winds at its fiercest, but it was a prolific rainmaker in the Delaware Valley, killing seven in causing over $200 million in damage to the Delaware Valley.   One of the more notable items damaged in the storm was the R5 bridge over the Wissahickon Creek in Fort Washington, knocking out SEPTA service in that immediate area.

Allison's rains were copious and rather equal in opportunity, producing nearly five inches along the coastal plain in Atlantic County but upwards of ten or more inches fell in Chalfont, Willow Grove, and Horsham, with 7.30" of rain falling in a six hour window at Willow Grove.  The heaviest of rains fell generally across Delaware, New Jersey, and Eastern Pennsylvania as Allison interacted with a frontal boundary that was approaching from the west.  This front enhanced rainfall as Allison moved northeast as the boundary provided additional lift for the system as it moved up the coast.

Allison is more noteworthy nationally for what it did to Houston in terms of flooding, thanks to the storm stalling out as it moved onshore.   However, locally Allison has not been completely forgotten even after ten years.