After encountering some resistance, losing its hurricane status, and slowing down Saturday, Hurricane Isaias was forecast to track up the East Coast, perhaps making landfall in or near New Jersey and generate potentially flooding rains in the Philadelphia region in the coming days.
The National Weather Service said that Isaias or whatever is left of it could generate 2 to 4 inches of rain on either side of the I-95 corridor, with isolated amounts of up to 6 inches possible. In addition, the waxing moon could enhance any coastal flooding at the Shore.
The track forecast, which has been jogging westward, on Saturday night suggested that Isaias could pass quite make a landfall in New Jersey, as did Fay on July 10; Sandy, in 2012; and Irene, in 2011.
Roughed up by its encounters with land and wind shear in the atmosphere, Isaias’ timetable has been pushed back slightly, and the most likely time for its impacts reaching the Philadelphia region would be sometime Tuesday into Tuesday night, Nicholas Carr, a meteorologist with the weather service office in Mount Holly, said late Saturday afternoon.
“The system hasn’t looked particularly healthy today,” he said. And with the 5 p.m. update, the National Hurricane Center demoted it to a tropical storm, with peak winds at 70 mph, or four under what it needed to keep the “Hurricane” in front of its name (which is pronounced ees-ah-EE-ahs, by the way, the Spanish form of Isaiah.)
Late Saturday night it was about 80 miles of Fort Lauderdale and moving ponderously northwest at about 9 mph. Tropical storm watches extended as far north as South Carolina.
The hurricane center said that Isaias would regroup after it gets a jolt from warm Gulf Stream waters and become at least a minimal hurricane again.
Regardless, the storm could present a flooding threat both at the Shore and the mainland, the weather service said. Carr said the rains would be enhanced by Isaias’ interaction with another system, as often happens with tropical storms or their remnants.
That was the case with Floyd in 1999, which inundated the region with up to a foot of rain.
“Definitely rainfall is our chief concern,” Carr said. The Shore could see some tropical-storm-force winds, and the full moon would be adding an extra foot of water to tide levels.
While Isaias is attracting all the attention, the weather service warns that rains without names could be problematic late Sunday.
With water-vapor levels increasing, parts of the region are under a heat advisory Sunday for heat indexes in triple digits possible. That also would leave the atmosphere primed for severe storms as an Isaias appetizer.