What Philly’s growing dry spell has to do with Hurricanes Milton and Helene

With the Gulf of Mexico on simmer, for the people on Florida’s West Coast the reality horror show that is an approaching hurricane reached a climax Wednesday night on Florida’s west coast when Milton made landfall near Siesta Key, just south of Sarasota, with peak winds of 120 mph.

This, less than two weeks after much of the Sunshine State was soaked by downpours from Helene that went on to deluge the South from Tallahassee to Charlottesville, Va. Rainfall amounts exceeded 20 inches in some areas, raising fresh concerns about the role of worldwide warming.

By contrast, Philadelphia’s citywide rainfall in the last 30 days — 0.34 inches — has been about 8% of normal, according to the Middle Atlantic River Forecast Center. The interagency U.S. Drought Monitor has a significant portion of the region, including all of Chester County and most of the state of Delaware, in “moderate drought.” Dry conditions could stretch into November, says AccuWeather Inc. long-range forecaster Paul Pastelok.

And the fact that October is producing a harvest of dust around here evidently has something to do with Helene and Milton and what’s been happening to our south.

Lacking summer thunderstorms and the more-organized storms characteristic of late fall, rains associated with moisture-bearing tropical-storm remnants are important sources of precipitation in the Philadelphia region in September and October.

“You have to rely a lot of times on tropical systems getting this far north,” said Tom Kines, an AccuWeather senior meteorologist. “It’s not happening.”

These days, that prime precipitation supplier — the Gulf of Mexico — in brimming with moisture-laden air. Sea-surface temperatures are running as high as 5 degrees Fahrenheit above normal, the National Oceanic and Atmospheric Administration (NOAA) says.

But the pattern hasn’t favored exporting rain to the Northeast, said Kines, and Helene and Milton, as it prowls the Gulf, have been significant factors lately.

“Those systems robbed the moisture,” he said.

Helene-devastated Asheville, N.C. — home of the government’s national climate center, which effectively has been shut down — measured 17.9 inches of rain in September. Areas to the east experienced over 20 inches, with double-digit rain totals as far north as Charlottesville, according to the Southeast Regional Climate Center.

But the rains have been reaching a dry wall somewhere near the Mason-Dixon Line. Philly finished September with 0.77 inches of rain officially at Philadelphia International Airport, the eighth driest on record, and still awaits the first drop of October.

Meanwhile, since Sept. 1, Tampa has had over 15 inches of rain, more than double its normal total, with the National Hurricane Center calling for 12 to 16 inches more from Milton.

On Wednesday night, the center of Milton, with peak winds of 120 mph, came ashore just south of Sarasota.

Milton has been powered by ultra-warm waters, said Philip Klotzbach, hurricane expert at Colorado State University.

“The Gulf of Mexico is just so much warmer than normal right now,” he said. “There is tons of fuel there.”

Typically, hurricanes stir up warm surface water and allow colder, below surface waters to rise, diluting the storms’ strength.

But, said Lew Gramer, a NOAA physical oceanographer, Milton wasn’t able to tap those waters.

After it buzzsaws through Florida, Milton is forecast to weaken and sail into the North Atlantic, the center passing near or south of Bermuda.

“I don’t think there’s any way Milton’s moisture” gets anywhere near the Philly area, said Kines.

A good question.

No rain is in the short-term forecast, and the Climate Prediction Center outlook through Oct. 23 sees the odds continuing to favor below-normal precipitation.

While a likely disaster unfolds in Florida, the next several days in the Philly region are forecast to be full of that oblique October sunlight with daytime temperatures in the 60s and 70s.