Tropical Depression Five Forms East of The Lesser Antilles

At 11:00 AM Saturday 24th August 2019, advisories were initiated by the National Hurricane Center for newly formed Tropical Depression Five. This tropical cyclone is slated to become our next named Tropical Storm in the Atlantic Basin, Dorian.

On its present track, it poses no direct threat to Trinidad and Tobago. However, it is becoming increasingly likely that we may experience periphery effects from Tropical Depression Five’s (future Tropical Storm Dorian) outer convective bands (feeder bands).

The National Hurricane Center's forecast track for Tropical Depression Five as of 11:00 AM Saturday 24th August 2019.
The National Hurricane Center’s forecast track for Tropical Depression Five as of 11:00 AM Saturday 24th August 2019.

The center of newly formed Tropical Depression Five was located near latitude 10.4 North, longitude 47.9 West. The depression is moving toward the west near 19 KM/H and this general motion is expected to continue today.

A turn toward the west-northwest is forecast on Sunday, and that motion is expected to continue through Tuesday. On the forecast track, the tropical cyclone is expected to be near the central Lesser Antilles on Tuesday.

Maximum sustained winds are near 55 KM/H with higher gusts. Gradual strengthening is forecast during the next few days and the depression is forecast to become a tropical storm later tonight or on Sunday.

The estimated minimum central pressure is 1010 millibars.

There are no coastal watches or warnings in effect.

Interests in the central and northern Lesser Antilles should monitor the progress of this system.

The small low-pressure system that the NHC has been tracking the past several days across the tropical Atlantic Ocean has acquired enough deep convection to be classified as a tropical depression, the fifth tropical cyclone of the 2019 hurricane season.

Two ASCAT passes between 1200-1300Z this morning indicated that the system had a closed circulation and surface winds of at least 30 kt, and that is the intensity set for this advisory. Upper-level outflow is fair to the northwest and restricted to the southeast due to moderate easterly vertical wind shear.

The initial motion estimate is 280/10 kt. The NHC model guidance is in very good agreement that the cyclone will move in a general west-northwestward direction along the southern periphery of a deep-layer ridge for the next 5 days, bring the system through the central or northern Lesser Antilles on Tuesday, and into the northeastern Caribbean Sea on Wednesday and Thursday.

 The National Hurricane Center's forecast earliest reasonable arrival time of tropical-storm-force winds as of 11:00 AM Saturday 24th August 2019.
The National Hurricane Center’s forecast earliest reasonable arrival time of tropical-storm-force winds as of 11:00 AM Saturday 24th August 2019.

The official forecast track is close to the consensus model TVCN, which is a little north of the NOAA HCCA corrected-consensus model.

The small cyclone is currently experiencing easterly to southeasterly shear of about 15 kt. The shear is forecast to steadily decrease over the next 24 h and be around 5 kt in the 24-to-72-hour time period. Although the depression is expected to remain embedded in a fairly dry mid-level environment, the small overall circulation, small radius of maximum winds, low shear regime, and warm SSTs of 28.0-28.5 deg C should allow for slow but steady intensification through the 5-day period despite occasional intrusions of dry air.

The NHC intensity forecast is a blend of the statistical-dynamical SHIPS and LGEM models, and the more robust HWRF model.

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