Ophelia’s marathon rains wiped out the Philly region’s precipitation deficits, but more Shore flooding is possible

Tropical Storm Ophelia and its remnants, which may continue to pester the region the next few days, conspired to ruin a weekend with a succession of downpours and gale-force gusts and turned the sun into a rumor.

Yet, while remarkable for their staying power, the Ophelia-related rains and winds were perhaps surprisingly short on trauma and overall had a benign effect on the region’s water supplies, meteorologists said Monday.

Some of the rain totals were prodigious. Nearly 7.5 inches of rain was reported in Ocean County, and the Shore, where wind gusts to 60 mph were measured, endured some minor and moderate flooding during the weekend, with perhaps more to come.

Elsewhere, in Philadelphia and its neighboring counties, totals of 2.5 to 4 inches were common from early Saturday into Monday.

While the storm’s effects have backed off, the coastal flooding threat hasn’t. Ophelia’s remains, centered near the Jersey coast Monday, were forecast to continue to exercise some influence on the beaches into midweek.

With onshore winds continuing, said meteorologist Patrick O’Hara, more coastal flooding is possible this week with the harvest moon reaching fullness on Friday and making one of its closest approaches to Earth of the year with a supermoon.

The weather service said it’s possible that with high tide Tuesday, around 6 p.m., the Shore flooding could approach or exceed that of Saturday’s high tides as winds off the ocean continue. It has issued a warning for moderate flooding Tuesday, and minor flooding on Wednesday, when high tide is 7 p.m.

A flood advisory was also up for areas along the Delaware River and tributaries for nuisance flooding from 10 p.m. Tuesday until 3 p.m. Wednesday.

But for the mainland, overall, Ophelia essentially was a rainstorm with a name, with no significant freshwater flooding reported and limited numbers of power outages.

What might explain the lack of impacts?

Rains began during the early-morning hours of Saturday and continued off and on in Philadelphia until Monday morning.

At times it poured, but not at those flash-flood-producing rates of an inch or two an hour so prevalent during the summer.

What resulted was a generous region-wide watering that dampened drought deficits that built during the previous month in parts of the region, said O’Hara.

The northern half of Chester County and south-central Montgomery County were in the “abnormally dry” zones in the weekly analysis by the U.S. Drought Monitor, posted Thursday. On the Jersey side, so were most of Burlington County and parts of Atlantic, Cape May, and Cumberland Counties.

All of Ocean County was so designated, and a portion near the weekend rain jackpot zone was declared in moderate drought.

The dryness had an upside: Stream and river levels were quite low heading into the weekend, thus resistant to flash flooding.

In addition, the vegetation at this time of year is still fairly robust, and that helped to limit runoff.

Ophelia, said Stephen Travis, a meteorologist at the National Weather Service Office in State College, had its plus side.

“It’s good for the surface water,” he said, although, “the groundwater might take a little longer to respond.”

Ophelia got all the celebrity, but a huge factor in the coastal flooding was an area of high pressure, or heavier air, centered to the north. Winds circulate clockwise around highs, so areas to the south of the center experience winds from the east.

Winds are driven by differences in pressure, or weight, and given the low pressure of Ophelia to the south, the region was caught in a wind channel during the first weekend of fall.

Ophelia’s remains were forecast to drop off the coast and drift southward, but the high is expected to gain strength and keep generating breezes off the Atlantic, pushing water onshore.

The sun is due to make a cameo Wednesday, but the clouds and shower chances return Thursday and Friday with cool temperatures in the 60s.

After 48-plus hours of generally benign rain, said O’Hara, “If we could get 48 hours of sunshine, that would be fine, too.”

That could well happen this weekend.