Tropical Depression Five Forms, Takes Aim At The Windward Islands

After being tracked for several days as Invest 97L, and then Potential Tropical Cyclone Five, Tropical Depression Five has formed 1,600 kilometers east-southeast of Trinidad and Tobago.

Based on available forecast data, this system is expected to become Tropical Storm Elsa later today and traverse the Windward Islands on Friday morning through the afternoon as a strong tropical storm.

Specifically for Trinidad and Tobago, while direct impacts are not expected, periphery impacts such as an atypical wind regime, feeder bands (strong showers, thunderstorms, and gusty winds associated with Tropical Storm Elsa), and agitated seas are likely on Friday into Saturday.

The Latest From The National Hurricane Center

Tropical Depression Five's Forecast Track as of 11:00 PM June 30th, 2021. (National Hurricane Center)
Tropical Depression Five’s Forecast Track as of 11:00 PM June 30th, 2021. (National Hurricane Center)

At 11:00 PM AST on June 30th, the center of Tropical Depression Five was located near latitude 9.6 North, longitude 46.3 West. The depression is moving toward the west near 37 KM/H. An even faster motion to the west-northwest is expected over the next 24 to 36 hours. On the forecast track, the system will pass near or over portions of the Windward Islands or the southern Leeward Islands on Friday, move into the eastern Caribbean Sea late Friday and Friday night, and move near the southern coast of Hispaniola on Saturday.

The center of Tropical Depression Five is located approximately 1,600 kilometers east-southeast of Trinidad and Tobago.

According to the National Hurricane Center, maximum sustained winds are near 55 KM/H with higher gusts to 74 KM/H. Strengthening is forecast, and the tropical depression is expected to become a tropical storm early Thursday. The estimated minimum central pressure is 1008 millibars.

Tropical Depression Five's Forecast Track as of 11:00 PM June 30th, 2021. (National Hurricane Center)
Tropical Depression Five’s Forecast Track as of 11:00 PM June 30th, 2021. (National Hurricane Center)

Tropical Depression Five Watches & Warnings

Tropical Depression Five’s Tropical Storm Watches and Warnings as of 11:00 PM June 30th, 2021. (National Hurricane Center)

A Tropical Storm Warning is in effect for Barbados, Martinique and St. Lucia.

A Tropical Storm Watch is in effect for St. Vincent and the Grenadines and Guadeloupe.

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours. A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours.

Other Alerts Issued For Several Islands

A number of other alerts are in effect for several islands across the Lesser Antilles, though some may not be under direct threat from Tropical Depression Five’s eventual track as Tropical Storm Elsa.

Trinidad and Tobago, Grenada and its dependencies.

There are no alerts, watches, or warnings in effect for Trinidad and Tobago as of June 30th, 2021. However, the Trinidad and Tobago Meteorological Service issued a statement on Wednesday afternoon advising, “It is likely that feeder band activity associated with the system will produce periods of rain/showers and isolated thunderstorm activity with possible gusty winds on Friday (2nd July 2021) into Saturday (3rd July 2021) over Trinidad and Tobago.”

Grenada’s Meteorological Office has issued a Severe Weather Advisory for Grenada and its dependencies. The Advisory warms of cloudy to overcast conditions with showers (which may become heavy) and thundershowers, accompanied by gusty winds by Friday afternoon. The likelihood of significant impacts is greater for the sister isles of Carriacou and Petite Martinique. According to the advisory, potential impacts are expected to be most significant across the northern section of the state, with a medium chance of flash flooding; downed trees and powerlines, landslides, and rockfalls.

St. Vincent and the Grenadines

In addition to a Tropical Storm Watch, St. Vincent and the Grenadines (SVG) also have a yellow-level marine advisory warning of above normal swells and gusty winds. SVG’s National Emergency Management Organization NEMO is also warning of lahars, mudflows, and flooding.

According to NEMO, “It is expected that whenever rain falls, there will be significant steaming, particularly in the valleys where Pyroclastic Density Currents have come down.  The Pyroclastic Density Currents can result in warm or hot mudflows, which will also steam.  This means that it would not be unusual to have significant steaming in some or all of the valleys on the volcano.  Also, while this steaming would be mainly focused in the upper parts of the valleys, due to the fact that the mudflows can also steam, the steaming can extend all the way down the valley to the coastline.”

Barbados

Alerts in effect from the Barbados Meteorological Service for Barbados as of Wednesday morning

There are several advisories in effect for Barbados over the next 72 hours, concerning excess rainfall, marine interests, severe thunderstorms, and wind.

In addition to the Tropical Storm Warning, the Barbados Meteorological Service has issued a High Surf Advisory, a Small Craft Advisory, and a Flash Flood Warning. The latter will be terminated at 6:00 AM on Thursday.

Martinique, Guadeloupe and the French Antilles

Alerts in effect from Meteo France for the French Antilles (Meteo France)

Dominica

While this country is not under any tropical storm watches or warnings at this time, the Dominica Meteorological Service has placed the country under a flood warning until 6:00 AM Thursday as Invest 95L continues to move westward, but still producing heavy rainfall in the region.

The Met Service in that country is warning of “tropical storm-like conditions with winds gusting to tropical storm force from Friday afternoon. Rainfall amounts of 60 mm to 100 mm (2.5 in to 4 in) in moderate to heavy showers are projected with waves near 4.0 m/13.0ft.” A Small Craft Warning is in effect for Dominica.

Tropical Depression Five’s Tropical Storm Watches and Warnings as of 11:00 PM June 30th, 2021. (National Hurricane Center)

According to the National Hurricane Center, interests elsewhere in the Windward Islands, Leeward Islands, the Virgin Islands, Puerto Rico, the Dominican Republic, and Haiti should monitor the progress of this system. Warnings and additional watches will likely be required tonight and on Thursday.

Tropical Depression Five: Hazards Affecting Land

Tropical Depression Five probabilities for tropical-storm-force winds as of 11:00 PM Wednesday 30th June 2021. (National Hurricane Center)
Tropical Depression Five probabilities for tropical-storm-force winds as of 11:00 PM Wednesday 30th June 2021. (National Hurricane Center)

WIND: Tropical-storm conditions are expected in portions of the Windward and the southern Leeward Islands within the warning area beginning late Thursday night into Friday. Tropical storm conditions are possible in the watch area beginning late Thursday night into Friday.

RAINFALL: The system will produce rainfall totals of 3 to 6 inches with maximum totals of 8 inches on Friday across the Windward and the southern Leeward Islands, including Barbados. This rain may produce isolated flash flooding and mudslides.

Additional island-specific impacts have been mentioned above.

Tropical Depression Five probabilities for hurricane-force winds as of 11:00 PM Wednesday 30th June 2021. (National Hurricane Center)
Tropical Depression Five probabilities for hurricane-force winds as of 11:00 PM Wednesday 30th June 2021. (National Hurricane Center)

This system is of no direct threat to Trinidad and Tobago at this time.

Tropical Depression Five Forecast Discussion

Tropical Depression Five (Weathernerds.org)

The satellite presentation of the system over the last 6-12 hours has gradually improved, with a prominent banding feature to the west of the estimated center. An ASCAT-A pass received at 2323 UTC revealed that the low-level circulation has become a bit better defined than earlier today, though still somewhat elongated to the south and west. The peak wind retrievals from this instrument were 30-32 kt. While subjective satellite estimates from TAFB and SAB were a bit higher, the latest estimated intensity was held at 30 kt for this advisory in agreement with the slightly lower scatterometer data.

The initial motion has accelerated a bit tonight at 280/20 kt. A strong subtropical ridge is situated poleward of the tropical depression, and this feature should steer the system quickly to the west-northwest over the next several days. After 72 hours, the tropical cyclone will reach the westward extent of the ridge and begin to move more poleward and slow down as the ridge also becomes eroded by a mid-latitude trough over the eastern US. The track guidance in the latter portion of the forecast continues to exhibit a large spread, with the GFS and HWRF/HMON models along the left side of the guidance envelop, while the ECMWF and its ensemble mean on the right side. The latest NHC track forecast is a shade right of the previous one and also slightly faster, but given the spread in the models, the latter portion of the track is more uncertain than usual.

While the depression is currently in a favorable environment of low vertical wind shear, warm sea-surface temperatures, and high mid-level relative humidity, the expected acceleration in forward motion could cause the system to outrun the favorable upper-level easterlies currently overhead after 36 hours. In addition, the system could be near or over some of the Greater Antilles in the latter portions of the forecast. For these reasons, the intensity
remained capped at 50 kt after 36 hours and is still on the lower end of the intensity guidance suite, though this forecast could be somewhat conservative.

Key Messages:

  1. The tropical depression is expected to become a tropical storm before reaching the Lesser Antilles. Tropical storm conditions are expected to begin late Thursday night in portions of the Windward and the southern Leeward Islands.
  2. Heavy rainfall will move quickly across the Windward and the southern Leeward Islands, including Barbados, on Friday. Isolated flash flooding and mudslides are possible.
  3. There is a risk of wind and rainfall impacts in portions of the Virgin Islands, Puerto Rico, Hispaniola, Cuba, the Turks, and Caicos, and the southeastern Bahamas through early next week. Interests in these areas should monitor the system’s progress, and updates to the forecast.
  4. Interests in Florida should monitor updates to the forecast for this system, but it is too soon to determine what if any impacts could occur there next week given the uncertainty in the long-range forecast.

Forecast discussion by NHC Forecasters Papin and Brown

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