Ophelias remnants to soak New York as Philippe and Rina roam tropics

Hurricane season might have taken a breather, but that doesn’t mean we’re out of the woods yet. The remnants of Tropical Storm Ophelia, which hit North Carolina over the weekend, could spawn flooding rains Friday in parts of the Northeast, while tropical storms Philippe and newly formed Rina meander east of the Caribbean.

Ophelia’s rain eases D.C. area dryness, but drought holds to the west

A particularly challenging forecast is materializing in parts of the Acela corridor and southern New England, particularly around New York City. That’s where weather models paint a swath of anywhere from 1 to 8 inches of rainfall as showers and thunderstorms roll through between Thursday night and early Saturday. The downpours will tap into moisture left in the wake of Ophelia, which disintegrated several days ago.

Tropical Storm Philippe, meanwhile, is throwing equally burdensome curveballs at forecasters as it approaches the Lesser Antilles, which mark the divide between the Atlantic and Caribbean. Initially it was expected to approach Puerto Rico as a ragged tropical depression, but newer forecasts suggest it may hover to the east as Rina curls around it.

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The storms come as the calendar prepares to flip to October, an infamous month for storms that develop near the United States. While the Atlantic’s Main Development Region between Africa and the Caribbean tends to shut down, the Gulf of Mexico and Caribbean become notorious for churning out some sneaky, quick-forming storms.

The Atlantic hurricane season has been a busy one. It was the most jam-packed Aug. 20-Sept. 28 on record, according to tropical weather researcher Phil Klotzbach at Colorado State University. He also noted that the 18 named storms that have formed so far this year signify the third most to date.

Tropical storms and hurricanes so far have churned through a full season’s worth of “accumulated cyclone energy,” or storm fuel. Klotzbach leans toward a continuation of above-normal activity over the next two weeks.

A tricky forecast in the Northeast

Heavy rain risk

A stubborn meteorological setup is frustrating meteorologists in the Northeast, and it is making for a “boom or bust” forecast for cities like Philadelphia, New York City, Hartford, Conn., and even Albany, N.Y.

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The reason? A small but intense corridor of downpours will likely become established into Friday night, with downpours training, or repeating, over the same areas. Some of the downpours could produce rainfall rates of 2 inches or more per hour, leading to isolated 6 inch totals.

Some models suggest that northeast New Jersey to New York City might be the zone to watch, whereas others depict a more expansive zone of moderate rains across the majority of southern New England. There will be a sharp northern and western cutoff, and uncertainty remains unusually high.

The National Weather Service declared a Level 3 out of 4 risk for excessive rainfall around New York City.

“Numerous flash flood are likely,” the Weather Service warned.

🌧️ A slow-moving coastal low will bring heavy rainfall to parts of the Northeast (including NYC) on Friday, which could cause numerous flash floods, especially in urban areas. Remain weather-aware, have multiple ways to receive warnings, and remember to turn around, don’t drown! pic.twitter.com/anYHRDW4Nb

Flood watches were issued for 2 to 4 inches of rain and a few instances of over 5 inches from northeast Pennsylvania through western Connecticut.

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“Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations,” the Weather Service wrote. “Extensive street flooding and flooding of creeks and rivers are possible.”

[Flood Watch]: Heavy rainfall is expected with potential of scattered to numerous flash flooding late tonight into Friday night for portions of the area. 2 to 4 inches of rain are forecast with localized higher amounts in excess of 5 inches possible. pic.twitter.com/gC6oxMnE63

An unusual setup

A broad zone of low pressure evolved from the remnants of Ophelia earlier in the week, and has been languishing off the Northeast coast. That’s why there have been days of cool, dreary conditions and onshore flow for the Mid-Atlantic and southern New England.

Stuck weather pattern keeps coasts unsettled and middle warm and dry

Within that zone, a smaller, more concentrated area of low pressure stretching northward out of the parent low will come together. Meteorologists call that an “inverted trough.” Surface winds converge, or gather, along that trough, forcing air upward into heavy downpours.

Inverted troughs are difficult to forecast, and weather models likewise have a tough time handling them. As such, it’s reasonable to anticipate that some area will see a potentially significant flood event, but pinpointing where is a big challenge.

Trouble in the tropics

Philippe, meanwhile, is a disorganized storm 560 miles east of the Lesser Antilles. It has 50 mph winds, but on satellite looks scrappy. It has an exposed low-level center, and all the convection, or thunderstorm activity, is displaced east of that center. That “misalignment” stems from shear, or a disruptive change of wind speed and/or direction with height.

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Models suggest that Philippe will head west in the near term before turning north — holding its current intensity. It could come very close to the northern Leeward Islands early next week as a tropical storm.

Newly formed Rina, a 40 mph tropical storm about 500 or 600 miles east of Philippe, is forecast to follow close behind before also turning more to the north, safely away from the islands. There is some chance, however, that Philippe and Rina interact in a dance called the “Fujiwhara.” That could push Rina farther west than initially forecast, but confidence remains low.

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