On August 14, a non-tropical low developed north-northeast of Bermuda in the subtropical Atlantic. It developed surprisingly quickly and had an impressive, if small, satellite signature by the next afternoon. The low was navigating around a high pressure ridge to its west, which was located over the U.S. east coast. This clockwise flow unusually pushed the system south, bringing it just east of Bermuda late on August 15. At that time, it was designated Tropical Depression Eight. Despite its proximity to the island, Eight was so small that Bermuda experience little more than showers.
Anomalously warm waters allowed the system to intensify and become Tropical Storm Henri by the afternoon of August 16. The storm continued its loop around Bermuda and turned west-southwest on the 17th. Curved bands near the center became better defined throughout that day and the storm steadily strengthened. Hints of an eye appeared on satellite imagery on August 18, bringing Henri to the verge of hurricane strength. However, wind shear out of the north increased that evening, squashing the cyclone's cloud shield and halting intensification. The storm proved resilient since it had access to warm ocean temperatures and ample moist air, and only weakened slightly over the next day in the face of 25 knots of shear.
Meanwhile, it continued westward along the 30°N parallel. As the shear abated during the afternoon of August 19, Henri's structure began to improve again. The next morning, it began a long-anticipated turn toward the north as the ridge steering it collapsed and was replaced by a trough along the eastern seaboard. The next morning, Henri strengthened into a hurricane as it accelerated north-northeastward. An eye even opened up briefly on August 21, though it was a bit ragged, and most deep convection was south and east of the center.
Normally, a cyclone in Henri's position would have recurved out to sea, but the setup in this case was quite different. A ridge was building to the system's east, while simultaneously an elongated upper-level low over the mid-Atlantic exerted a pull toward the west. This allowed Henri to defy climatology and continue northward toward land. While located over the Gulf stream, the storm deepened a little more, reaching its peak intensity of 75 mph winds and a minimum pressure of 986 mb early on August 22. The storm began to slow down upon nearing the coast, yet another unusual feature of its track: tropical cyclones that do manage to hit the northeast are typically accelerated to forward speeds of over 30 mph by mid-latitude jet streams. Henri, in contrast, was hemmed in by the ridge and continued to swirl around the upper-level low, turning left around landfall.
Colder waters weakened the storm down to a strong tropical storm before the center made landfall along the coast of Rhode Island that afternoon. Along with some minor storm surge, Henri was primarily a rainmaker. It looped slowly west, weakened to a tropical depression, and stalled over New York state before turning east on August 23. The storm finally became post-tropical that afternoon. What was left of Henri accelerated eastward and moved out to sea the next day.
The above image shows Henri as a minimal hurricane moving north toward New England on August 22.
It's hard to overstate how odd Henri's track was: the cyclone even originated in the subtropics east of Bermuda. For a storm with such an origin to loop back west and hit North America was unprecedented.
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