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Henri exiting after delivering extreme rain and damaging wind; more activity to brew by early September

The tropics look to remain relatively quiet for now, but activity could ramp up later this season

A vehicle travels through a flooded street during tropical storm Henri in the Brooklyn borough of New York on Aug. 22. (Ismail Ferdous/Bloomberg News)
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Henri may have been tamer than expected as it made landfall near Westerly, R.I., around noon Sunday, but the strong tropical storm still packed a punch with damaging winds, and prompted flash flooding around the northeastern coast.

Tens of thousands lost power around southern New England and Long Island, with 50,000 customers in the dark in Connecticut and Rhode Island as of Monday morning, according to PowerOutage.us. Although the outage is significant, power companies and emergency managers far and wide had planned for much worse.

Photos: the scenes as Tropical Storm Henry drenched the Northeast

The storm will probably be most remembered for the heavy rainfall it left behind, especially outside its path. Between six and 10 inches fell across New York City and the Tri-State area, spurring serious flooding in central and northern New Jersey.

Henri on its way toward the exit

The storm remained a decaying tropical depression as the workweek commenced, leaving one final arc of heavy tropical downpours swirling through Connecticut and western Massachusetts. That last gasp of heavy rainfall will drift east and begin to thin throughout Monday.

Henri exemplified that sometimes the biggest problems associated with a landfalling tropical cyclone can extend well beyond the “cone of uncertainty.”

While Henri’s cone accommodated the motion of its center into Westerly, R.I., which coincidentally was also hit by Tropical Storm Henri in 1985, extreme rain fell on its periphery. More than eight inches fell on New York’s Central Park, including 3.32 inches that came down in just two hours Saturday night.

That’s more than the Big Apple’s average August rainfall, which is 3.31 inches. The city remains under a flood watch through Tuesday.

Newark received 8.02 inches between Saturday and Monday morning, with 6.95 inches in Queens and 7.02 inches in Little Neck on western Long Island. Middlesex County, N.J., was also hit hard, with 7.71 inches in Plainsboro Township and 7.01 inches in Helmetta. At least 150 people were rescued there from rising floodwaters. New Jersey Gov. Phil Murphy (D) visited Monroe Township in Middlesex County on Monday morning.

The slug of rain that caused much of the flooding formed Saturday night, well ahead of then-Hurricane Henri. It was the result of a trough, or high-altitude disturbance to the west, featuring low temperatures aloft. It interacted with the edge of Henri’s moisture field and pulled the rain over land.

A second bull’s eye of rain occurred as Henri’s western rain bands stalled over central Connecticut, dropping 5.10 inches on Manchester and 5.12 on Hebron.

Much of the area west of Interstate 84 in southern New England and southwest down Interstate 95 to New York City and New Jersey remained under flash flood and flood watches Monday. Henri, a leftover swirl of clouds and showers, is set to fully decay as it drifts east and eventually out to sea through Tuesday.

Looking beyond Henri

Meanwhile, the remainder of the Atlantic is quiet — ominously so. But that respite may not last.

Water temperatures in the “main development region,” or tropical belt of the open Atlantic, are near average, but the Gulf of Mexico and Eastern Seaboard are running toasty. Hurricanes can develop in this zone in water temperatures exceeding 82 degrees. Sea surface temperatures in the northwest Gulf of Mexico are running about 86 or 87 degrees.

Two weak disturbances are being monitored over the Atlantic for potential development. One over the southern Windward Islands will push west over the coming days, perhaps bringing heavy rain to parts of Mexico and the Yucatán Peninsula. It may then arrive over the Bay of Campeche, possibly developing into a storm about a week from now.

Another system over the open Atlantic could also gradually acquire tropical characteristics as it slowly pushes northwest toward Bermuda.

There are signs to support an increase in favorable conditions for storm formation as soon as next week. While the Atlantic is under the fair-weather branch, which will quell hurricane activity for a bit, by early September, the ascending branch of the wave will pass over the Atlantic. It seems likely that hurricane activity will trend upward by late August.

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