Hurricane Helene targets Florida, and its leftovers could bring some rain to ultra-dry Philly

After it crashes into the Florida coast, what remains of what is now Hurricane Helene is forecast to produce a prodigious amount of rain in a large, globular area of the Southeast and Mid-Atlantic. But it’s unclear whether the storm’s remnants eventually will target Philly’s rain deficits that have induced an early start to the foliage show.

Significant rains sometime during the weekend are at least a possibility, said Bob Smerbeck, senior meteorologist with AccuWeather Inc. But as of Thursday morning, the forecasts had more hedges than Longwood Gardens.

The weekend forecast remained “tricky,” the National Weather Service Office in Mount Holly said in its morning discussion. “The models seem all over the road with what to do with the remnants of Helene.” it said on Wednesday.

For now, both the weather service and AccuWeather are calling for a chance of showers Saturday. The weather service has Sunday dry, but AccuWeather sees an 80% chance of a few hours of rain.

That amount wouldn’t do much to wipe out the rain shortages. With its weekly update, the interagency U.S. Drought Monitor which has most of the entire region in the “abnormally dry” zone, with the Main Line, extreme southwestern Chester County and portions of Atlantic, Burlington, and Ocean Counties in “moderate drought.”

A mere 0.16 inches of rain has been measured in Camden County in the last 30 days, which is 3% of normal, according to the weather service’s Middle Atlantic River Forecast Center. Philly has had just 6% of normal precipitation.

» READ MORE: What Helene could mean for the Eagles-Bucs game and the fans

Helene-related rains in the South are due to make pushes east and north, but drying high pressure to the north might repel them, Smerbeck said. He said that a 50-mile shift would “put Philadelphia in the downpours.”

One thing is evident: What has been a surprisingly unexceptional Atlantic hurricane season is getting a second wind.

Said Smerbeck: “The lid came off.”

NOAA hurricane specialists and others had warned that this could be a historic season in the Atlantic Basin, which includes the Gulf of Mexico and the Caribbean Sea.

Helene, however, is the eighth named storm of the season — those with winds of at least 39 mph — and this marks the longest wait for an eighth storm in 10 years, according to Philip Klotzbach, hurricane expert at Colorado State University. On average 10 have formed by now.

» READ MORE: Is the hurricane season getting a second wind?

Smerbeck said that during a lull period that continued through the first week of September, a large area of sinking air over the hurricane basin discouraged the development of storms, which live on rising air currents. But that area has shifted eastward.

“Now,” he said, “we have upward motion” that will continue into the first week of October.

Computer models still are debating precisely where Helene will go and how it will behave once it ravages northern Florida. The National Hurricane Center said it expects landfall in the Big Bend region, and it may reach Category 3 strength with peak winds of 120 mph.

Smerbeck said that it appeared the remnants would migrate toward the Tennessee Valley and merge with an upper-air system.

Heavy rains are likely to set off “catastrophic flooding” in Georgia and the southern Appalachians, he said.

The center of the remnant storm is then forecast to shift toward the Carolina coast, he said.

The National Weather Service on Wednesday had chances of showers Friday night and Saturday, with lower probabilities on Sunday.

The AccuWeather forecast was similar, but Smerbeck said recent models have been less bullish on that protective high pressure to the north. This far out, a far greater likelihood would be changes in the forecast.

» READ MORE: The dryness may help the fall color ... at least to a point

The region has undergone a browning in the last month and rainfall deficits have been growing, which helps explain why some of the trees are shedding leaves and changing colors prematurely, said Vincent A. Marrocco, horticulture director at Chestnut Hill’s Morris Arboretum.

Given the dryness, “trees are beginning to cut their losses for the season by dropping their leaves early,” he said. “With so little water in the soil, a lot of trees are deciding it’s time to call the 2024 season done and get ready to go dormant for the year. That means an early fall season.”

In addition, he said, the recent warm nights may have a dampening effect on the colors, “but things could still change if we get some decent rain.”