Tropical Storm Henri

Summary of Tropical Storm Henri August 21-23, 2021

Summary

Henri best track, courtesy of NOAA's National Hurricane Center

Tropical storm Henri (pronounced ON-Ree) developed at 5 pm AST on Monday August 16, 2021 about 145 miles southeast of Bermuda. Henri remained a tropical storm over the next several days as it slowly tracked westward. By Friday August 20, 2021, Henri began to turn towards the north as the storm felt the steering of an upper level trough over the eastern United States. Henri tracked towards the north-northeast on Saturday August 21, 2021 and strengthened to a Category 1 Hurricane as it moved over the relatively warm waters of the Atlantic Gulf Stream. The steering pattern would not allow Henri to move out to sea. The storm was forced to make a turn back to the north and then northwest as it approached Long Island and New England early on Sunday, August 22, 2021. Henri encountered increasing wind shear and cooler water temperatures as it moved north, weakening to a tropical storm as it made landfall. Henri made landfall on the coast on Rhode Island, near Westerly, at 12:30pm EDT Sunday August 22, 2021 with maximum sustained winds of 60 mph. Henri then continued turning to the west as the storm weakened over Connecticut. Henri meandered towards the Lower Hudson Valley as the storm continued to interact with the upper level trough, before being swept eastward off the New England coast late in the day on Monday August 23, 2021.

Tropical storm, hurricane, and storm surge watches were issued for portions of Long Island and southern Connecticut were issued with the 5:00am EDT Advisory on Friday August 20, 2021. Watches were expanded inland with the 11:00am EDT Advisory and then upgraded to warnings with the 5:00pm EDT Advisory. Tropical storm watches were also expanded a bit westward due to the shifting forecast track. Henri's ended up not making landfall on eastern Long Island. The storm also weakened faster than anticipated, which limited the tropical storm conditions to mainly southeast Connecticut and the twin forks of Long Island. The storm surge was also muted due to the offshore flow around the storm with the landfall occurring further east in Rhode Island.

Deep tropical moisture interacting with an upper level trough led to significant flash flooding in the New York City metro well ahead of the landfall of Henri. This rainfall was not directly tied to the core of Henri and occurred Saturday Night August 21, 2021. More flash flooding occurred after landfall and as Henri slowed down and weakened on Sunday evening. See the rainfall totals and flash flooding sections below for more information.

NHC Advisory and Other Storm Summary Links

Many archived reports below are courtesy of the Iowa State University Iowa State Mesonet (IEM)  National Weather Service Text Product Archive .

Storm Reports

The map below displays locations of flooding reports during the predecessor rainfall leading up to the arrival of Tropical Storm Henri. The reports are from 8pm EDT on August 21, 2021 through 7am EDT on August 22, 2021. Click any circle on the map below to give more detailed information. A full summary of these reports can also be found  here .

Tropical Storm Henri Predecessor Rainfall Reports from 8pm EDT on August 21, 2021 through 7am EDT on August 22, 2021.

The map below displays locations of storm reports associated directly with Tropical Storm Henri from 7am EDT August 22, 2021 through the morning of August 23, 2021. Click any circle on the map below to give more detailed information. A full summary of these reports can also be found  here .

Tropical Storm Henri Storm Reports from 7am EDT August 22, 2021 through the morning of August 23, 2021.

Satellite

Below is an animation of visible imagery from GOES-East of Henri as the storm is making landfall. The animation begins at 8 am and ends at 12:20 pm EDT Sunday August 22, 2021. The data also includes GOES-East Visible Imagery and Geostationary Lightning Mapper (GLM) group energy density and was created by  Colorado State University Regional and Mesoscale Meteorology Branch .

GOES-East Visible and Geostationary Lightning Mapper (GLM) beginning at 8 am and ending 12:20 pm EDT Sunday August 22, 2021.

Radar

Below is a radar animation of the full event beginning 2 pm EDT August 21, 2021 and ending 4:15 pm EDT August 23, 2021. The animation includes the predecessor rainfall, the core of Henri making landfall, and the dissipating circulation. The radar animation was created courtesy of the  National Weather Service Eastern Region Headquarters . Warning polygons are also indicated in the loop.

NWS regional radar animation beginning 2 pm EDT August 21, 2021 and ending 4:15 pm EDT August 23, 2021.

Rainfall Totals

The following graphic displays the total observed rainfall from Henri.

Observed Rainfall during Henri from August 21, 2021 through August 23, 2021.

A significant amount of the rainfall across the NYC metro fell in the predecessor rain event which will be described in more detail in the next section. The graphic below is the Multi Radar Multi Sensor (MRMS) Quantitative Precipitation Estimate (QPE) ending at 3 am EDT August 22, 2021. While the data is from the previous 12 hours, much of the rain depicted in the graphic occurred in a 3 to 6 hour time frame.

12-hr MRMS Q3 multi-sensor precipitation analysis ending 3am EDT August 22, 2021.

Central Park, NY observed 4.45 inches of rain on Saturday August 21, 2021, with the majority of this rain coming from 9pm EDT to midnight. This rainfall is now the record for daily rainfall on August 21, 2021. Hourly rainfall rates were about 1 to 2 inches an hour. Overall, the highest totals in the predecessor rainfall were around 2 to 5 inches. An additional 2 to 4 inches of rain fell when the main core of Henri made landfall and then slowly dissipated over New England.

Flash Flooding/Predecessor Rainfall

Henri was moving north-northeast from the Middle Atlantic coast on Saturday August 21, 2021. At the same time, an upper level low/trough was situated over the Middle Atlantic. The 500 mb analysis below valid at 8 pm August 22, 2021 illustrates the close proximity of the two systems. The wind barbs also depict the air blowing away from Henri towards the northeast, with enhancement from the upper level trough to its west.

500 mb analysis valid at 8pm EDT Saturday August 21, 2021.

The 300 mb analysis below, valid at 8 pm EDT August 22, 2021, also illustrates how the flow was coming out of Henri and towards the northeast states around the trough. The yellow contours indicate divergence, which is a mechanism helping to lift the tropical moisture that led to heavy showers and thunderstorms.

300 mb analysis valid at 8pm EDT Saturday August 21, 2021.

The GOES-EAST Water Vapor imagery just before 9 pm EDT August 22, 2021 shows the plume of moisture being advected northwestward away from Henri and towards the northeast states. This moisture was then precipitated out in bands of showers and thunderstorms that moved from east to west across the New York City metro well ahead of Henri. The rainfall was determined to be a predecessor rainfall event following the classification used in the  Galarneau et al. 2010  paper found in the  American Meteorological Society's Monthly Weather Review  journal.

GOES East Water Vapor Imagery valid at 8:50pm EDT Saturday August 21, 2021

Here is a radar animation of the showers and thunderstorms that caused significant flash flooding in the New York City ahead of Henri. The radar animation starts at 7 pm EDT August 21, 2021 and ends at 3 am EDT August 22, 2021. Flash Flood Warnings are highlighted by the green polygons as they were issued in real time during the event.

KOKX Radar Animation from 7pm August 21, 2021 ending at 3am EDT August 22, 2021

Winds

Peak wind gusts occurred with Henri the morning and afternoon on Sunday August 22, 2021. The following image is select peak wind gusts from Henri at NWS Automated Surface Observing Systems (ASOS) across the region. A full list of peak wind gusts from the event can be found  here .

Select peak winds gusts from Henri. Data courtesy of the the  NOAA/NWS Hazards Viewer .

Coastal and Marine Summary

Coastal and marine impacts were mostly limited to the east due to the more eastward track and weaker storm at landfall. However, there was still beach erosion and some isolated minor coastal flooding/surge impacts. The NY State Parks reported flooding on all the oceanfront beaches at Jones Beach State Park. There was also minor water intrusion into some of the buildings and the Administration parking lot was flooded. Gilgo State Park also received flooding to the dune line and some erosion occurred. The erosion conditions impacted the reopening of the park after the storm. Robert Moses State Park had beach flooding to the dune lines and some minor erosion. Hither Hills, Montauk, and Orient State parks all had beachfront flooding and some minor erosion. Minor erosion was also reported at Hecksher State Park.

Here are some photos of the rough conditions at some of the parks and beaches described above.

Montauk State Park Courtesy of NY State Parks on August 22, 2021

Hither Hills Center Beach Courtesy of NY State Parks on August 22, 2021

Jones Beach Courtesy of NY State Parks on August 22, 2021

Gilgo State Park Courtesy of NY State Parks on August 22, 2021

Hecksher State Park Courtesy of NY State Parks on August 23, 2021

Ocean seas peaked around 5 ft near the New York Harbor Entrance Buoy to around 14 ft on the ocean waters east of Moriches Inlet. Peak wind gusts ranged from 35 to 55 mph, strongest along the Forks of Long Island and coastal New London Connecticut.


You can check out more of our storm summaries back on our NWS New York, NY  Local Storm Archive .

Henri best track, courtesy of NOAA's National Hurricane Center

Observed Rainfall during Henri from August 21, 2021 through August 23, 2021.

12-hr MRMS Q3 multi-sensor precipitation analysis ending 3am EDT August 22, 2021.

500 mb analysis valid at 8pm EDT Saturday August 21, 2021.

300 mb analysis valid at 8pm EDT Saturday August 21, 2021.

GOES East Water Vapor Imagery valid at 8:50pm EDT Saturday August 21, 2021

Select peak winds gusts from Henri. Data courtesy of the the  NOAA/NWS Hazards Viewer .

Montauk State Park Courtesy of NY State Parks on August 22, 2021

Hither Hills Center Beach Courtesy of NY State Parks on August 22, 2021

Jones Beach Courtesy of NY State Parks on August 22, 2021

Gilgo State Park Courtesy of NY State Parks on August 22, 2021

Hecksher State Park Courtesy of NY State Parks on August 23, 2021