Tropical Storm Henri on final approach to landfall in southern New England
After threatening to wobble west toward central Long Island, Henri has drifted slightly east. It now appears that the center of the circulation will just miss the eastern tip of Long Island and first make landfall in Rhode Island. The location of the center is important because its location changes the angle that the winds hit the coast. And that angle affects how high the ocean water is pushed over the coast, where the water is pushed inland, and where it’s pushed offshore.
The dangerous weather with Henri extends far to the west of the storm. Bands of torrential rain have already flooded roads and tunnels from New Jersey across New York City and over Long Island. Total rainfall amounts in the 5-to-10-inch range are forecast where the outer bands set up along and near the Hudson River, which includes northern New Jersey and New York City. The forecast is for 3 to 6 inches in other locations.
The winds with Henri have dropped just below hurricane strength. The peak winds in the storm never got quite as strong as forecast, in part because the system developed a fairly large eye. Like a figure skater doesn’t spin as fast with extended arms then spins faster when she pulls her arms in tight, hurricanes intensify as the eye contracts.
It’s not a win to have a bigger eye, however. Yes, the winds aren’t quite as strong, though still plenty strong enough to bring down trees and power lines. But the wider circulation more efficiently moves ocean water toward the coast. Like pushing water in the bathtub with your forearm instead of you hand, the larger radius transfers more energy from the wind to the ocean and the waterways it’s blowing over.
This is why the storm surge forecast is still for water to be pushed 3 to 5 feet above normal high-tide levels in areas where the wind is blowing toward the coast, even though the peak winds have decreased a little.
As an example of the importance of wind direction, as long as the center of the eye is south of Long Island, the east wind on the north side of the circulation will be pushing water into Long Island Sound, which runs east to west north of the island. This may cause flooding as far west as New York City. This applies to all the harbors, bays, and inlets along the coastline of southern New England.
Once the center comes ashore, the system is forecast to move slowly over eastern Connecticut, Rhode Island, Massachusetts, and northern New England. Overall, the winds will quickly decrease, but bands of heavy rain will continue rotating around the system. Some gusts will still take down trees, especially since the ground is saturated by the heavy rains from Fred combined with the excessive rainfall earlier in the summer.
The best advice is to be informed about local conditions before you head out. Normally tame creeks can turn into raging torrents in this kind of situation. Let the danger pass.
As always, many people who took action to be safe before the storm will realize they would have been okay if they hadn’t. But you take action based on risk, not what happened in retrospect. Since a slight unforecastable wobble or eye contraction makes such a dramatic difference in who is affected and how they're affected, there is nothing to do but to prepare in advance based on possibilities, not on absolutes. You never know which way the cookie is going to crumble, or in this case, the hurricane is going to wobble.
In Central America, Grace has died out over the Sierra Madre mountains that run the length of Mexico.
Out in the Atlantic, the National Hurricane Center is identifying a disturbance that might develop when it moves north and combines with another system. It would not be a threat.
Elsewhere, some long-range computer forecast models predict a system will form in the western Caribbean toward the end of the week. But there is no indication it would be a threat to the U.S. if it did form.