Hurricane Henri gathered strength east of the Carolinas on Saturday, August 21, as it moved north toward a landfall on Sunday that will affect southeast New York and southern New England. Henri will bring a corridor of torrential rains and potential flash flooding well inland, and it could drive a substantial storm surge into parts of the Atlantic coast between New York and Boston. Widespread gales may lead to major power outages.
The National Hurricane Center (NHC) upgraded Henri to hurricane strength at 11 a.m. EDT Saturday as top winds reached 75 mph, or minimum category 1 strength. At 2 p.m. EDT, Henri was located about 400 miles south of the eastern end of Long Island, New York, moving north-northeast at 17 mph.
Intensity forecast for Henri
Henri has successfully fought off multiple days of strong wind shear. The effort left the storm somewhat lopsided, though, and at midday Saturday most of Henri’s strongest thunderstorms were displaced well southeast of the center. Wind shear dropped to a light 5-10 knots on Saturday, and the atmosphere around Henri was moistening, with the mid-level relative humidity rising from around 50% to 60%. Until early Sunday, Henri will be passing over warm waters over and south of the Gulf Stream, around 28-29 degrees Celsius (82-84°F). Together, these conditions will favor Henri’s consolidation and some further strengthening. Rapid intensification is not expected.
On Sunday, as Henri nears New England, it will be passing over dramatically cooler waters, around 24°C (75°F). In most cases, this is too cool to sustain a tropical cyclone for long periods. Henri will be approaching the coast more slowly than have earlier hurricanes in the area (see below), so it will have more of an opportunity to weaken. The main questions shaping whether Henri makes landfall as a hurricane are how strong Henri gets on Saturday and how quickly its motion slows prior to landfall. Two top intensity models, the HMON and HWRF, insist that Henri will be only a tropical storm when it makes landfall. It’s important to note that there will be little difference in the anticipated impacts between a strong tropical storm and a minimal hurricane.
Henri’s strength will diminish quickly as it moves inland, but the storm will still be capable of dumping torrential rain and producing gale-force winds that can knock down trees and knock out power lines. While Henri’s winds will be similar to those of a strong nor’easter, tree damage will be much more severe than in a winter storm, since the trees are currently in full leaf and the leaves will act like sails to catch the wind.
Track forecast for Henri
Henri is expected to reach the Connecticut/Rhode Island coast on Sunday afternoon or evening, likely crossing Long Island, New York, just beforehand. Henri’s overall steering will be controlled by a weak but sharply elongated upper-level low close to the U.S. East Coast. This low will guide Henri northward in much the same fashion as classic New England hurricanes of the past. However, with the steering flow unusually weak, Henry’s forward speed will be far less than that of such storms as the catastrophic 1938 Hurricane and 1985’s Gloria, the latter the most recent hurricane to make landfall on Long Island. New England’s most recent hurricane landfall was Bob (1991).
After accelerating north to north-northeast on Saturday, Henri is predicted to arc north-northwest and slow markedly on Sunday. Henri will likely be moving at only about 10 mph as it nears the coast, a forward speed that would make it by far the slowest moving hurricane on record to approach Long Island (Figure 1). Henri is expected to be crawling at only about 5 mph as it moves across southern New England on Sunday night and Monday. With a pronounced turn to the right on Monday, Henri is expected to reach coastal Maine as a tropical depression or post-tropical low by Tuesday.
Rainfall and flooding threat from Henri
Henri’s exceptionally slow movement through New England will allow for unusually large rainfall totals along and left of its path. A corridor of 4- to 6-inch rainfall totals can be expected, with isolated pockets of 6-10” amounts. Soils across much of eastern New York and New England are saturated from the passage of ex-Tropical Storm Fred several days ago, together with substantial moisture through the summer. This will lead to an enhanced flash flood threat, perhaps roughly comparable in some areas to the flooding produced by Hurricane Irene in 2011 as it reached the New York City area as a tropical storm and pushed north.
The saturated soils will also make it easier for Henri’s winds to uproot trees, even with winds in most areas below hurricane strength. Falling trees are often one of the leading causes of death and injury in systems like Henri. Widespread power outages are quite possible.
Henri’s landfall will also produce substantial storm surge on Sunday afternoon and evening, with the highest astronomical tides intensified by this weekend’s full moon. If the highest surge arrives during the Sunday evening high tide, the following inundations above ground level are possible:
Flushing, NY to Chatham, MA, including Narragansett Bay, Buzzards Bay, Vineyard Sound, and Nantucket Sound…3-5 ft
North shore of Long Island from Flushing to Montauk Point, NY, including Long Island Sound…3-5 ft
South shore of Long Island from Mastic Beach to Montauk Point, NY…3-5 ft
Chatham, MA to Sagamore Beach, MA, including Cape Cod Bay…2-4 ft
South shore of Long Island from East Rockaway Inlet to Mastic Beach, NY…2-4 ft
Cape May, NJ, to East Rockaway Inlet, NY…1-3 ft
Sagamore Beach, MA, to Merrimack River including Massachusetts Bay…1-3 ft
Grace becomes Bay of Campeche’s strongest landfalling hurricane on record
Hurricane Grace outdid itself on Friday night, August 20, rapidly intensifying from category 1 to high-end category 3 strength just before it roared ashore near Tecolutla, Mexico, shortly before 1:00 a.m. CDT Saturday. Grace’s top sustained winds were 125 mph, making it the Atlantic’s first major hurricane of 2021 and the strongest hurricane landfall on record for Mexico’s entire Bay of Campeche coast south of Tampico. The former record of 120 mph was held by Hurricane Karl (2010), which 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, a record now tied by Grace). Karl led to 22 deaths and caused roughly $5.6 billion US in damage in the Veracruz area.
The Bay of Campeche is well known to support fast-strengthening tropical cyclones, owing to its concave geography, which helps focus winds in a cyclonic fashion, and the frequent presence of very warm SSTs. Grace took advantage of both features in the few hours before landfall, rapidly clearing out a large 35-mile-wide eye surrounded by intense thunderstorms.
La Prensa reported at least eight deaths from Grace as of midday Saturday, with three people missing. Severe flooding was reportedly ongoing in Xalapa, the state capital of Veracruz, according to Reuters. The worst of Grace’s winds and storm surge likely arrived in the northern eyewall in the sparsely populated coastal area near Barra de Cazones. Storm surge was predicted to be as high as 9 feet.
Grace, which had weakened to a 70-mph tropical storm as of 11 a.m. EDT Saturday, will be a troublemaker throughout the weekend as it weakens while pushing west across the rugged terrain of central Mexico. Widespread rainfall of 6-12” can be expected along its path, with localized totals of 18” or more likely causing intense and dangerous flash flooding and mudslides. Even Mexico City can expect 1-3” rainfall totals, with isolated amount of up to 5”. In fact, at 2 p.m. EDT, Grace was a 45-mph tropical storm located just 35 miles northwest of Mexico City. No tropical storm in modern times has passed so close to the sprawling city.
After eventually moving back offshore into the Eastern Pacific, the remnants of Grace are expected to reorganize into a new tropical cyclone next week. In its 5 am PDT tropical weather outlook for the region, the NHC gave an 80 percent chance of redevelopment by Wednesday. If Grace’s remnants do consolidate into a new Eastern Pacific tropical storm, they will take on a new name: Marty. Such crossovers tend to happen every year or two. Only if a recognizable circulation survives the trek from Atlantic to Pacific, or vice versa, is the original name kept, based on a 2000 decision from the World Meteorological Organization. The only tropical cyclones thus far to retain their names in such a crossing are Hermine (2010, Pacific to Atlantic) and Otto (2016, Atlantic to Pacific).
Grace made its first landfall in Mexico’s hurricane-weary Yucatan Peninsula early Thursday morning, August 19, 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.
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