Tropical Storm Henri, now spinning between Bermuda and Florida, is likely to increase to hurricane strength on Friday as it accelerates northward. A much bigger question is whether it will move onto or near the New England coast by Sunday night before taking a sharp right turn to the east. Models agree on at least a close approach to Cape Cod, Massachusetts, but it’s too soon to know with confidence where the sharp right turn will happen. Coastal residents from New York to Maine, plus the Canadian Maritime Provinces, need to keep a close eye on Henri over the next few days as forecasts evolve.

As of 11 a.m. EDT Thursday, Henri was about 500 miles southeast of Cape Hatteras, North Carolina, and about 800 miles south of Nantucket, Massachusetts, moving west at 10 mph. Top sustained winds remained at 70 mph.

Henri has been a well-organized storm with a resilient core of thunderstorms despite northerly wind shear that has intensified since Wednesday. The shear is predicted to continue at between 20 and 25 knots through Friday, which will keep the storm tilted southward with height. Henri has maintained a solid inner core despite the tilt, suggesting it could survive as a strong tropical storm until Friday with only modest degradation, allowing it to intensify when wind shear relaxes.

Henri’s approach to New England will result from an unusual steering pattern. An upper-level high will strengthen across eastern Canada, with a weak ridge extending into the Northwest Atlantic, preventing Henri from doing the quick recurvature out to sea more typical of systems in its location. Instead, Henri will be pulled north by flow around a sharply elongated upper-level low taking shape near the U.S. East Coast (see image below). The ultimate strength and configuration of this low will help determine how strongly Henri affects New England.

Figure 1. Steering currents guiding Henri at the 250-mb level (about 34,000 feet) predicted by the 06Z Thursday run of the GFS model and valid at 8 p.m. EDT Friday, August 20 (left), and Saturday, August 21 (right). (Image credit: tropicaltidbits.com)

Another important cofactor is how strong and well-structured Henri can stay and how far west it gets. Model ensembles over the last day or so have shown a distinct pattern: The stronger Henri gets and the further west it moves, the more likely it will reach New England.

Conditions for intensification will improve markedly on Friday and Saturday, as wind shear will be light to moderate, 5-15 knots, and Henri will be near the warm waters of the Gulf Stream, with sea surface temperatures of 28-29 degrees Celsius (82-84°F). Upper-level winds will be very supportive for intensification, allowing plenty of room for Henri to strengthen its upper-level outflow. The National Hurricane Center predicts Henri will become a Category 1 hurricane on Friday night and remain at that strength through at least Sunday. This forecast is consistent with two of the best intensity models, the HWRF and HMON, both of which suggested Henri might briefly hit Cat 2 strength. Henri is expected to weaken quickly on Sunday, however, and would likely reach the New England coast (if it makes it onshore) early Monday as a tropical storm rather than as a hurricane.

Figure 2. Track of Henri atop sea surface temperatures in the northwest Atlantic (degrees Celsius). (Image credit: SSEC/CIMMS/UW-Madison).

A key reason so few hurricanes hit New England as powerful systems is the rapid drop-off in sea surface temperatures (SSTs) in the chilly waters north of the Gulf Stream. From Saturday to Sunday, as shown above, Henri will be moving over waters cooler than 26 degrees Celsius (79°F), the standard minimum to support tropical cyclones. Some of the most destructive storms in New England history, such as the 1938 Hurricane, were being hauled northward by a strong jet stream at speeds of 50 mph or more, limiting how long they spent over cool water before making landfall.

In the case of Henri, the steering flow is on the weaker side. So, after experiencing very favorable conditions on Friday and early Saturday, including warm SSTs, Henri would spend at least 24 hours atop these cool waters, likely denting its peak winds substantially. There are even suggestions in the model output that Henri could slow down on approach, which would provide even more time for weakening.

That said, if Henri moves far enough west on its expected approach to New England, it could still be pushing a large amount of water on the right side of its path even as its circulation is weakening. Hurricane Sandy (a much larger storm than Henri) produced one of the worst storm surges on record along the New York and New Jersey coast, even though its peak sustained winds had weakened to minimal Category 1 strength at landfall. If Henri’s path is close to current forecasts, the most likely area for damaging surge would be the south and east shores of Cape Cod. However, it is too soon to be too specific, and residents throughout coastal New York and New England ought to keep monitoring Henri over the next several days.

Keep in mind that Henri’s wind field will expand as the storm progresses northward – in part, because of the increased spin Henri will receive from Earth’s spin as a result of its being farther from the equator. When Henri makes its closest approach to the New England coast on Sunday night and Monday morning, the storm’s tropical storm-force wind field may be close to 200 miles in diameter. With Sunday’s full moon bringing some of the highest astronomical tides of the month, the potential exists for widespread coastal flooding from Henri. The 6Z Thursday run of the HWRF model predicted that Henri would bring a swath of 2-6″ of rain to the coast from Connecticut to New Hampshire, which would increase flooding near the coast.

Figure 3. Track of all tropical cyclones on record, going back to 1851, that passed within 120 nautical miles of Hartford, Connecticut, while still classified as hurricanes. (Image credit: NOAA Historical Hurricane Tracks)

It would be a true historical fluke if Henri were to make it to or near the New England coast while at hurricane strength, after having originated in the subtropics and spent its whole life near or north of 30°N. The graphic above shows that no tropical cyclones on record have made it to this area as hurricanes without having originated in the tropics – far south of Henri’s birthplace as a tropical depression near Bermuda.

Figure 4. Visible satellite image of Tropical Storm Grace at 12:20 p.m. EDT August 19, 2021. (Image credit: NOAA/RAMMB/Colorado State University)

Hurricane Grace makes first of its two landfalls in Mexico

Hurricane Grace made landfall at 5:45 a.m. EDT Thursday in Mexico’s hurricane-weary Yucatan Peninsula, just south of Tulum, as a category 1 hurricane with 80 mph winds and a central pressure of 986 mb. Near the time of landfall, Xcaret Park near Playa del Carmen, Mexico, measured sustained winds of 60 mph, gusting to 85 mph, and Cancun measured sustained winds of 59 mph, gusting to 80 mph. Grace passed just south of Cozumel Island shortly before landfall, bringing sustained winds of 41 mph, gusting to 68 mph, to the Cozumel Lighthouse.

Figure 5. Radar image of Hurricane Grace at landfall near Tulum, Mexico at 5:45 a.m. EDT August 19, 2021. (Image credit: National Meteorological Service of Belize, h/t to Acelo Pedroso for saving it)

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 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.

Figure 6. Predicted wind speed (colors) and sea level pressure (black lines) for Tropical Storm Grace at 11 p.m. EDT Friday, August 20, from the 6Z Thursday, August 19, run of the HWRF model. The model predicted Grace would be approaching landfall near Poza Rica, Mexico, as a category 2 hurricane with 100 mph winds. (Image credit: Tropical Tidbits)

Forecast for Grace

Grace is expected to emerge over the southern Gulf of Mexico on Thursday night and head westward for a second Mexican landfall Friday night in Veracruz state near Poza Rica, population 200,000.

With 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, Grace is expected to undergo at least modest strengthening over the Gulf of Mexico after it recovers from its trek over the Yucatan Peninsula.

The 12Z Thursday run of the SHIPS model gave a 12% chance that Grace would intensify into a 120-mph category 3 hurricane by Friday night. However, Grace’s initial disorganization after emerging over the Gulf of Mexico, combined with an atmosphere that is somewhat on the dry side for rapid intensification, make it more likely that Grace will make its second landfall in Mexico as a strong category 1 or weak category 2 hurricane. NHC predicted a landfall intensity of 85 mph in its 11 a.m. EDT Thursday forecast, but noted the possibility of Grace being be slightly stronger than that.

Figure 7. Damage to U.S. 276 in western North Carolina on August 18 due to flooding from Tropical Depression Fred. (Image credit: NCDOT Western Mountains)

Two dead, 20 missing in North Carolina after Fred’s rains

Tropical depression Fred caused major flooding in western North Carolina on Tuesday after dumping torrential rains of 6-10 inches; Asheville reported a four-day rainfall total of 8.10”, its fifth-wettest four-day period on record. According to weather.com, two people are dead and 20 missing in western North Carolina because of the flooding, and multiple roads and bridges have been washed out. An additional death occurred in Florida, from a car crash caused by hydroplaning. Fred made landfall in the Florida Panhandle on Monday afternoon as a tropical storm with 65 mph winds.

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Jeff Masters

Jeff Masters, Ph.D., worked as a hurricane scientist with the NOAA Hurricane Hunters from 1986-1990. After a near-fatal flight into category 5 Hurricane Hugo, he left the Hurricane Hunters to pursue a...

Bob Henson

Bob Henson is a meteorologist and journalist based in Boulder, Colorado. He has written on weather and climate for the National Center for Atmospheric Research, Weather Underground, and many freelance...