Subtropical Storm Ana Forms, 2021’s First Named Atlantic System

What you need to know:
— The Atlantic’s first named tropical cyclone for 2021 has formed northeast of Bermuda.
— Tropical storm conditions are possible on the island later today, with a tropical storm watch in effect for the country
— The system poses no threat to T&T or the Lesser Antilles.

Subtropical Storm Ana has formed in the North Atlantic Ocean, after days of being monitored by the National Hurricane Center. This early-season tropical cyclone has followed the pattern of the last six years (2015-2020) where at least one system formed before the official June 1st start to the Atlantic Hurricane Season.

This subtropical storm is forecast to have slow and erratic motion in the North Atlantic Ocean over the next few days, gradually dissipating by early next week according to the National Hurricane Center. Still, tropical storm conditions are possible across Bermuda, hence a tropical storm watch is in effect for the country.

This tropical cyclone is not forecast to impact Trinidad, Tobago, or the Lesser Antilles.

What is a subtropical storm?

GOES-16 IR-13 Imagery of the Subtropical Storm Ana northeast of Bermuda (Weathernerds)
GOES-16 IR-13 Imagery of the Subtropical Storm Ana northeast of Bermuda (Weathernerds)

subtropical cyclone is a non-frontal low-pressure system that has characteristics of both tropical and extratropical cyclones. Subtropical cyclones originate over tropical or subtropical waters and have a closed circulation about a well-defined center. Across the North Atlantic, they require central convection fairly near the center and a warming core in the mid-levels of the troposphere.

Those with sustained winds below 62 KM/H (33 knots or 38 MPH) are called subtropical depressions, while those at or above this speed are referred to as subtropical storms.

At 5:00 AM AST, the center of Subtropical Storm Ana was located near latitude 34.2 North, longitude 62.2 West. The storm is moving toward the west-southwest near 6 KM/H. A continued slow and erratic motion is expected through tonight, followed by a faster northeastward motion on Sunday and Monday.

Maximum sustained winds are near 75 KM/H with higher gusts. Little change in strength is forecast today, but gradual weakening is expected tonight and Sunday. Ana is expected to dissipate in a couple of days.

Winds of 75 KM/H extend outward up to 335 kilometers north of the center. The estimated minimum central pressure is 1006 millibars.

Subtropical Storm Ana Forecast Track as of 5:00 AM Saturday 22nd May 2021. (National Hurricane Center)
Subtropical Storm Ana Forecast Track as of 5:00 AM Saturday 22nd May 2021. (National Hurricane Center)

Watches & Warnings

Subtropical Storm Ana Watches and Warnings as of 5:00 AM Saturday 22nd May 2021. (National Hurricane Center)
Subtropical Storm Ana Watches and Warnings as of 5:00 AM Saturday 22nd May 2021. (National Hurricane Center)

A tropical storm watch is in effect for Bermuda. A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, in this case within 24 hours.

Hazards Affecting Land

Subtropical Storm Ana probabilities for tropical-storm-force winds as of 5:00 AM Saturday 22nd May 2021, as well as the most likely time of arrival of tropical-storm-force winds. (National Hurricane Center)
Subtropical Storm Ana probabilities for tropical-storm-force winds as of 5:00 AM Saturday 22nd May 2021, as well as the most likely time of arrival of tropical-storm-force winds. (National Hurricane Center)

WIND: Tropical storm conditions are possible on Bermuda today.

This system is of no direct threat to the Windward Islands, including Trinidad and Tobago.

Subtropical Storm Ana Forecast Discussion

Satellite images indicate that the low-pressure system that is located a couple of hundred miles northeast of Bermuda has become better organized overnight. The low now has a well-defined center of circulation, some central deep convection, and thunderstorms that are organized in curved bands to the north and northeast of the center. The system is considered a subtropical cyclone rather than a tropical cyclone since it is still entangled with an upper-level
low as evident in water vapor satellite images, but it does have some tropical characteristics as well. The initial intensity is estimated to be 40 knots, which makes the system Subtropical Storm Ana.

Ana is moving slowly to the west-southwest with the initial motion estimated to be 240/3 kt. An even slower motion is expected later this morning, and Ana is forecast to meander through tonight while it remains embedded within the upper-level low in weak steering currents. However, a mid-to upper-level trough moving off of Atlantic Canada should cause Ana to turn northeastward thereafter and accelerate in that direction on Sunday and Monday. The NHC track forecast lies close to the HCCA and TVCA consensus models.

Ana will likely change little in strength in the short term, but a combination of increasing shear, dry air, and decreasing SSTs should cause the storm to gradually weaken tonight and Sunday. Nearly all of the models show Ana opening up into a trough of low pressure in about 48 to 60 hours, and so does the NHC forecast. The remnant trough will likely be absorbed by a front shortly thereafter.

Forecast discussion by NHC Forecaster Cangialosi.

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