The year’s first hurricane watches for the U.S. East Coast were posted Friday in an unusual area – New York and New England – as Tropical Storm Henri was predicted to intensify and move toward a potential landfall late in the weekend. Meanwhile, after hammering the coast of the Yucatan Peninsula, a restrengthened Hurricane Grace was moving across the Bay of Campeche toward a second landfall expected late Friday.

As of 2 p.m. EDT Friday, August 20, a hurricane watch was in effect along the south and north shores of Long Island, New York, east of Fire Island Inlet and Port Jefferson Harbor, respectively, and also from New Haven, Connecticut, to Sagamore Beach, Massachusetts. The watch also included the islands of Nantucket and Martha’s Vineyard in Massachusetts and Block Island in Rhode Island. Tropical storm watches extended westward along the Long Island and Connecticut coastlines to near the New York City suburbs. Update (5 p.m. EDT Friday): A hurricane warning is now in effect on the north and south Long Island shorelines east of Fire Island Inlet and Port Jefferson Harbor, as well as the coastline from New Haven, Connecticut, east through Rhode Island.

After arcing around the east and south sides of Bermuda, Henri has now embarked on a long-anticipated turn toward the north. At 2 p.m. EDT, Henri was moving north-northwest at 6 mph and was positioned about 720 miles south of the eastern end of Long Island. Top sustained winds had increased to 70 mph, putting Henri on the threshold of hurricane strength.

Henri has held its own as a strong tropical storm over the past couple of days despite relentless wind shear of 20-25 knots. The northerly shear has tilted Henry’s circulation toward the south with height, but the storm’s core of intense thunderstorms has remained robust and fairly well organized, helping it to resist the shear.

Forecast for Henri

Henri is being blocked from the usual northeastward, out-to-sea motion of storms at its location by a ridge of high pressure from eastern Canada into the northwest Atlantic. At the same time, a weak but sharply elongated upper low near the U.S. East Coast will establish a northward steering current that will guide Henri toward New York and New England. Henri may actually angle slightly westward around the low as it approaches the coast. Computer model forecasts for Henri’s track have shifted notably westward since Thursday, and ensembles are now in closer agreement. The 12Z Friday runs of our top three track models – the GFS, Euro, and UKMET – all predict that Henri will come ashore over or near Long Island. It appears Henri could move well inland into southern New England on Sunday night before taking a right-hand turn toward the east on Monday.

Wind shear over Henri will relax markedly by Friday night and Saturday, giving the storm a chance to become a category 1 hurricane as it passes over warm waters of 29 degrees Celsius (84°F), about 0.5°C above average. Rapid intensification does not appear to be favored, and top short-range intensity models, the HWRF and HMON, agree that Henri most likely will strengthen into the category 1 range, as predicted by the National Hurricane Center (NHC).

If Henri does make landfall in New England as a hurricane, it will be the region’s first since Bob in 1991.

What makes Henri so unusual, a ‘striking exception’?

It’s quite uncommon for a tropical storm to become a hurricane this far north en route to New England.  It’s unusual in part because Henri was born so far north: it developed from a jet-stream impulse that dipped into the subtropics near Bermuda after triggering severe weather over the United States. As we showed in our August 19 post, all other other systems on record that have affected New York or Long Island as hurricanes originated in the tropics, as opposed to Henri’s formation in the subtropics north of 30°N.

Henri’s window to reach hurricane strength, and its damage potential, will be limited by the sharp dropoff in sea surface temperatures (SSTs) north of the Gulf Stream. SSTs along Henri’s path will decrease from around 28°C on Saturday night east of North Carolina to less than 24°C near the coast of Long Island, where Henri is expected to be on Sunday afternoon and evening. As it spends roughly a day traversing these cool waters, Henri is expected to weaken, and it most likely will reach the coast of Long Island or southern New England as a strong tropical storm or a minimal hurricane. The 12Z runs of the HMON and HWRF high-resolution models both weaken Henri below hurricane strength prior to landfall.

Nevertheless, Henri could bring damaging storm surge, and if it arrives near high tide, any tidal effects will be accentuated by Sunday’s full moon. Potential inundations at high tide include 2-4 feet on most of Long Island and Connecticut, with 3-5 feet possible in Rhode Island and southeast Massachusetts.

Most storms that reach New England as hurricanes are rapidly accelerating, carried by a strong meridional (south-to-north) jet stream and moving at speeds of 40 mph or more. Henri is a striking exception, as the steering flow will be notably weaker than usual for this type of setup. Henri is actually predicted by NHC to be decelerating rather than accelerating as it reaches the coast, perhaps moving at 15-20 mph on Sunday morning but less than 10 mph on Sunday night. On the downside, this will prolong the immediate landfall and related impacts, and it will allow for a longer period of heavy rains close to Henri’s track. However, on the plus side, Henri will likely be weakening more rapidly than usual near landfall because of its more gradual approach over the cooler waters just offshore.

Because Henri is not moving into a preexisting frontal zone, its heaviest rains are expected to be limited to areas near the immediate track, although Henri’s slow motion will add to those rainfall totals. Local amounts could reach 8 inches, with more widespread 2-5” amounts possible. Overall, one can expect a relatively concentrated area of peak wind and rain impacts with Henri.

Hurricane Grace restrengthens, heads toward a second landfall in Mexico

Hurricane Grace made landfall in Mexico’s hurricane-weary Yucatan Peninsula at 5:45 a.m. EDT Thursday, just south of Tulum, as a category 1 hurricane with 80 mph winds and a central pressure of 986 mb. Grace knocked out power to 180,000 customers and did considerable damage to trees and power poles, but there were no deaths or injuries reported near the landfall zone.

Grace is the fourth hurricane to hit the Yucatan Peninsula in the past 12 months. In 2020, Hurricane Zeta hit near Tulum as a category 1 storm with 80 mph winds; Hurricane Gamma made landfall within 10 miles to the north of Tulum on October 3 as a category 1 storm with 75 mph winds; and Hurricane Delta hit Cancun on October 7 as a category 2 storm with 110 mph winds.

Forecast for Grace

Grace emerged over the southern Gulf of Mexico on Thursday night and quickly re-organized, taking advantage of favorable conditions for intensification: warm waters near 30 degrees Celsius (86°F), an atmosphere with a mid-level relative humidity of 60%, and moderate wind shear of 10-15 knots. At 2 p.m. EDT Friday, Grace was an intensifying category 1 hurricane with 90 mph winds.

Grace likely will undergo additional strengthening before landfall occurs on Friday night in Mexico’s Veracruz state near Poza Rica (metro population 450,000). In its 11 a.m. EDT advisory, the NHC predicted Grace would be a category 2 hurricane with winds of 105 mph several hours before reaching the coast, with some additional strengthening possible just before landfall. The 12Z Friday run of the SHIPS statistical model shows a 45% chance that Grace will reach peak winds of 115 mph (low-end category 3).

Grace has the potential to inflict considerable damage, as it may be one of the strongest hurricanes on record in this area. A storm surge of 4 to 6 feet and rainfall totals of 6-12” are expected, with local amounts as high as 18” likely leading to flash flooding and mudslides. The only cat 3 hurricane on record to strike this section of the Mexican coastline is Karl (2010), which followed a track roughly similar to the one Grace is following. Karl made landfall just north of Veracruz after becoming the strongest hurricane on record in the Bay of Campeche up to that point (125 mph peak winds several hours before landfall). Karl led to 22 deaths and caused roughly $5.6 billion US in damage in the Veracruz area.

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