Early nor’easter prompts flood warnings for the Shore and Philly into the weekend

Flood warnings are up for the Jersey Shore into early Saturday as that very early-season nor’easter matures off the Southeast coast.

But, perhaps ironically, in the early going what has been happening at the Shore has had more to do with an extraordinary system to the north that normally is associated with dry and tranquil weather, said John Gyakum, an atmospheric scientist and coastal-storm expert at McGill University in Montreal.

Yes, he said, the developing storm, which continues to bedevil computer models, was “unusual” for occurring so early in the autumn — actually, make that Day One. And it may foreshadow what is to come later in the fall and winter.

The National Weather Service was warning of potentially damaging “moderate flooding” on the oceanfront and along back bays during several high tides into Saturday. In addition, winds could gust up to 45 mph at the beaches and 35 mph inland.

What’s more, the growing influence of the moon, which reaches fullness Saturday, is going to provide an astronomical tug to the tides.

The weather service also has issued an advisory for minor flooding along the Delaware River that could approach moderate levels late Wednesday and Thursday nights.

At the Shore, the flooding may be most problematic along the back bays, the weather service warned, and officials in the beach towns were making preparations.

Ocean City was advising residents to “move vehicles to safe places,” spokesperson Doug Bergen said. And the Army Corps of Engineers moved its beach-fill equipment in Avalon and Ocean City to safe harbors.

The weather service said moderate flooding could be expected on the oceanfront for four consecutive high-tide cycles starting Thursday evening.

Moderate flooding was forecast in the back bay areas Friday evening and Saturday morning.

Along the Delaware River, moderate flooding was predicted for late Wednesday night into early Thursday in Philly, and again late Thursday night into early Friday.

At the moderate level, “many roads” can become “impassable,” and some houses could incur damage, the weather service said.

No rain is expected until the weekend, with the amounts very much dependent on whether the storm makes a westward jog toward the coast or stays farther out to sea. As of late Wednesday, the computer models still were disputing the issue.

For now, the weather service has a chance of rain both in the immediate Philly region and at the Shore.

It is likely to stay breezy through the weekend, but the winds are forecast to take a more northerly turn, rather than howling onshore. The switch would be gentler on the beaches, which will have lost considerable sand.

Temperatures in the region Wednesday were in the mid-60s, about 10 degrees below normal and close to what they would normally be in late October.

The chilly conditions were the result of a massive area of high pressure, or heavier air, over southeastern Canada.

Winds circulate clockwise around centers of high pressure, and thus the Shore and the Philly region have been getting brisk winds from the northeast.

The high is also supplying the cool air that is contrasting with the warm air off the Southeast coast, thus igniting the nor’easter, said Gyakum, who is credited with minting the term bomb cyclone.

Winds circulate counterclockwise around storm centers, so areas to the northwest of the center (see: Jersey Shore, Philadelphia) experience onshore winds from the northeast (thus the term nor’easter).

The two systems working in tandem are conspiring to generate gusts and potential rains likely to peak along the New England coast, said Bob Oravec, senior branch meteorologist at the federal Weather Prediction Center.

Still, the Jersey Shore impacts are likely to be significant.

The nor’easter in all likelihood has nothing to do with the intensifying El Niño warming of waters in the equatorial Pacific.

Typically, that does not start to affect the Northeast until later in the fall and into the winter.

However, the storm could foreshadow what is to come.

“There tends to be an increased number of nor’easters during El Niño events, particularly strong El Niños,” said Samantha Borisoff, climatologist with the Northeast Regional Climate Center at Cornell University.

Although this nor’easter is a precocious one, on the first full day of the astronomical fall, it is a clear indication the seasons have changed.

Said Oravec: “You can’t fool the sun. Eventually the atmosphere responds.”