Tammy has strengthened east of the Lesser Antilles and is taking aim at the northern half of the Lesser Antilles, forecast to bring tropical-storm and hurricane conditions, hazardous seas, and surge, as well as potentially flooding rainfall mere weeks after Tropical Storm Philippe caused destructive floods across Antigua and Barbuda and Guadeloupe.
For the southern Windward Islands, though, we remain on the lookout for feeder band activity, near calm winds, warm temperatures with slow-moving late morning through afternoon showers/thunderstorms are likely to occur through Saturday and Sunday, with agitated seas.
Over the last day, a persistent feeder band remained south of Barbados and north of Tobago, extending into the Grenadines on Friday night with most of the rainfall remaining offshore.
What you need to know
— What has happened: Tammy strengthened from a tropical storm to a hurricane on Friday, east of the Lesser Antilles, with multiple islands north of Barbados and Dominica under tropical cyclone watches and warnings.
— Where is it forecast to move: Forecast models have consistently shown Tammy remaining north of Trinidad and Tobago and the southern Windwards. The latest models and the National Hurricane Center forecast show the center of the system moving near or even across the northern Windwards and Leewards on Saturday into Sunday, much slower than initially forecast.
— The Intensity & Impacts: The National Hurricane Center brings Hurricane Tammy’s circulation near or directly over the Leewards by Saturday morning through Sunday afternoon. Damaging winds, flooding rainfall, and hazardous seas are forecast for the Leewards and northern Windwards over the weekend. For the southern Windwards, including T&T, feeder band activity could bring periods of inclement weather, interrupting generally settled and near-calm conditions, with isolated daytime thunderstorms from the late morning through the afternoon.
— Latest from officials: There are multiple alerts, watches, and warnings in effect for the Lesser Antilles. See below for more information. For Trinidad and Tobago, there are no alerts, watches, or warnings in effect from the Trinidad and Tobago Meteorological Service.
The latest
At 8:00 PM Friday, October 20th, 2023, the center of Hurricane Tammy was located near latitude 14.5 North, longitude 59.7 West. Tammy is moving toward the west-northwest near 11 KM/H.
According to the National Hurricane Center (NHC), a turn toward the northwest is anticipated by tonight, followed by a north-northwestward and northward turn Saturday night through Sunday night. On the forecast track, the center of Tammy will move near or over portions of the Leeward Islands tonight through Saturday night and then move north of the northern Leeward Islands on Sunday.
Maximum sustained winds are near 120 KM/H with higher gusts. Gradual strengthening is forecast during the next couple of days, and Tammy is expected to be a hurricane while it moves near or over portions of the Leeward Islands. Hurricane-force winds extend outward up to 35 km from the center and tropical-storm-force winds extend outward up to 205 km. The estimated minimum central pressure is 990 millibars.
Alerts, Watches, & Warnings
There are multiple alerts, watches, and warnings in effect for the Lesser Antilles as of 8:00 PM Friday, October 20th, 2023. From south to north:
- Trinidad and Tobago: None
- Grenada: Small Craft Advisory
- St. Vincent and the Grenadines: Small Craft Advisory (Orange), Flooding and Landslide Advisory (Yellow)
- St. Lucia: Small Craft Advisory, Advisory for flooding and landslides
- Barbados: Tropical Storm Watch, Small Craft Warning, High Surf Advisory
- Martinique: Tropical Storm Watch, Yellow Alert: Heavy Rainfall, Winds, Orange Alert: Hazardous Seas
- Dominica: Hurricane Watch, Tropical Storm Warning, Small Craft Warning, High Surf Advisory
- Guadeloupe: Hurricane Warning, Orange Alert: Tropical Cyclones
- Montserrat: Hurricane Warning, High Surf Warning, Small Craft Warning
- Antigua and Barbuda: Hurricane Warning, High Surf Warning, Small Craft Warning
- St. Kitts and Nevis: Hurricane Warning, High Surf Warning, Small Craft Warning
- St. Barthelemy & St. Martin: Hurricane Warning, Orange Alert: Tropical Cyclones
- Saba & St. Eustatius: Tropical Storm Warning, Severe Wind Gusts, Flooding, Small Craft Advisory
- Sint Maarten: Hurricane Warning, Small Craft Warning
- Anguilla: Hurricane Warning, High Surf Warning, Small Craft Warning
- British Virgin Islands: High Surf Warning, Small Craft Warning
A Hurricane Warning means that hurricane conditions are expected somewhere within the warning area, in this case within the next 24 hours. Preparations to protect life and property should be rushed to completion. A Hurricane Watch means that hurricane conditions are possible within the watch area, in this case within the next 24 hours. A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area. A Tropical Storm Watch means that tropical storm conditions are possible within the watch area.
Where is it going?
Hurricane Tammy has slowed down east of the Lesser Antilles as forecast, but is finally beginning to take the northwestward turn that models have indicated over the last few days. Tammy is forecast to continue moving along the western periphery of a high-pressure system anchored over the North Atlantic, taking it more northwestward on Saturday and Sunday as a sharp, mid-latitude trough moves in from the west, eroding the high-pressure ridge. Tammy’s motion could bring the center of circulation near or over the Leeward Islands by Saturday morning with a fairly slow movement.
As it stands on Thursday evening, Tropical Storm Tammy is no direct threat to Trinidad and Tobago. While forecast models keep this low-pressure system north of the southern Windwards, those north of Barbados and St. Vincent and the Grenadines, feeder band activity could impact the region, including T&T. However, feeder bands are notoriusly difficult to forecast (in location, intensity and duration.)
How strong could it get?
Tammy continues to organize with winds of 120 KM/H and gusts to 150 KM/H. The environment ahead of Tammy is not predicted to change much during the next day or so, according to the NHC. Warm waters and moderate shear are expected to allow for some modest strengthening during the next couple of days, and the NHC intensity forecast during that time is similar to the last few forecasts. After Tammy moves north of the Leeward Islands, increasing vertical wind shear is likely to initiate weakening as Tammy moves northward.
What does this mean for the Lesser Antilles?
For the northern half of the Lesser Antilles, tropical cyclone preparedness plans should be rushed to completion, mainly north of Barbados and St Lucia, where Tropical Storm Watches and Warnings and Hurricane Watches and Warnings are in effect. There is an increasing risk of heavy rainfall that will produce floods, landslides, and mudslides, as well as strong winds and gusts that can produce wind damage and agitated seas. See the local alerts above for more information.
For the southern half of the Lesser Antilles, mainly from Barbados and St. Vincent and the Grenadines southward, the main hazards from Friday night into the weekend will be localized, heat-driven, heavy showers/thunderstorms along western and northern areas of islands, and potentially hazardous seas, mainly for the northern islands. Stronger southerly winds may also lead to isolated thunderstorms being enhanced by topography, and with near-calm to light winds over the weekend and clockwise turning winds through the atmosphere, the potential for funnel clouds will also exist.
Wind
Based on the latest guidance and forecasts, tropical-storm-force winds and gusts (above 34 knots, 39 MPH, 63 KM/H) are forecast to primarily affect the northernmost Leewards, mainly north of Barbados and Martinique and east of the U.S. Virgin Islands where countries are forecast to experience stronger wind gusts in heavy showers/thunderstorms, where Tropical Storm and Hurricane Warnings are in effect. Hurricane-foce wind gusts are possible, and stronger tropical-storm-force winds are likely, mainly for areas north of Dominica towards Anguilla.
For the central Lesser Antilles (Martinique to St. Vincent and the Grenadines, including Barbados), a low-level to surface trough extending southwestward from the eventual low-pressure system will create slack to near-calm winds, leading to hot daytime temperatures and isolated late-morning through afternoon showers/thunderstorms along western and hilly areas. However, in feeder band activity, wind gusts to tropical-storm-force strength are possible.
For the southern Lesser Antilles (south of the Grenadines, including T&T), the pressure gradient between the low-pressure system north of the Lesser Antilles and a high-pressure system over northern South America will lead to strong low-level southeasterly winds across the area through Sunday, which can make it to the surface in showers or thunderstorms. Wind gusts exceeding 35 KM/H are likely during this period. In feeder band activity, even stronger winds and gusts are likely.
Rainfall
The highest rainfall accumulations are forecast to occur across the northernmost Leewards and the northern half of the Lesser Antilles, with rainfall totals through Monday, October 23rd, 2023, ranging between 100 and 200 millimeters (4-8 inches) with isolated totals up to 300 millimeters (12 inches) based on the current forecast track.
For the southern half of the Lesser Antilles, for Martinique and St. Lucia, rainfall totals are forecast to be between 50 to 100 millimeters (2-4 inches), with isolated totals of up to 150 millimeters (6 inches).
For Barbados, between 25 to 75 millimeters (1-3 inches) are forecast with isolated higher totals possible, with the remainder of the southern Windwards, including T&T, forecast to see up to 50 millimeters (2 inches) with isolated totals up to 75 millimeters (3 inches).
Seas and Storm Surge
Based on the latest model guidance:
- For Trinidad and Tobago, and Grenada to St. Vincent and the Grenadines: Open water waves are forecast to reach as high as 3.0 meters, particularly Friday into Saturday night.
- For Barbados to Martinique: Open water waves are forecast to be near 3.5 meters, nearing 5.5 meters in channels between islands and Atlantic-facing coasts, with the highest waves forecast on Friday night through Sunday morning.
- For Dominica to Anguilla (not including St. Kitts & Nevis and the Leeward Dutch Antilles): 3.5 meters to 5 meters, reaching as high as 7 meters in channels and Atlantic-facing coasts of Antigua and Barbuda.
For islands north of Martinique, storm surge could raise sea levels by 1-3 feet (up to 1 meter) above sea level near coastal areas.
For Trinidad and Tobago
Latest Forecast
Forecast: Isolated Showers, Thunderstorms Ahead of Significant Saharan Dust Surge
Trinidad and Tobago is NOT under any tropical storm or hurricane threat, watch, or warning at this time.
Pay close attention to official forecasts in the coming hours and days from your respective authorities. For Trinidad and Tobago, official forecasts and early warnings come from the Trinidad and Tobago Meteorological Service.
