Henri (2015)

A small, non-tropical low developed a few hundred nautical miles southeast of Bermuda on 7–8 September 2015 and quickly organized into a tropical depression by 1800 UTC 8 September. The system became Tropical Storm Henri around 0000 UTC 9 September and moved generally northward and then northeastward ahead of an upper-level trough. Henri was short-lived, accelerating northeast and weakening; its circulation was declared a trough and the tropical cyclone dissipated by 1200 UTC 11 September, after which the remnant trough merged with a larger extratropical cyclone over the North Atlantic.

Henri did not make any landfalls. It remained well offshore of the U.S. East Coast and Atlantic Canada for its entire life, staying several hundred miles southeast to south of Bermuda and then tracking northward into the open Atlantic as it weakened.

The storm’s peak intensity was 45 kt (about 52 mph) with a minimum central pressure near 1003 mb, reached around 1800 UTC 9 September. That peak corresponds to a moderate tropical storm; at no time did Henri reach hurricane strength.

Because Henri stayed over open water, no storm surge reports, coastal inundation, or significant rainfall impacts were attributed to the cyclone in populated areas. There were no reports of notable surge heights or heavy rainfall totals tied to Henri at named cities or counties in the NHC record.

No damage or casualties were reported in association with Henri—no direct or indirect deaths were recorded. The storm’s main impacts were limited to open-ocean conditions where scatterometer and satellite observations documented its winds and expanding wind field.

Two noteworthy points from the analysis: the system developed from a non-tropical frontal zone and its genesis was poorly predicted in advance, illustrating challenges forecasting tropical formation from non-tropical origins; and Henri’s wind field expanded while it interacted with the nearby upper-level trough, even though the peak wind speeds remained modest.