Between June and November, a sailor in Grenada watches the weather in a different way. Most days are fine, but every few days a tropical wave rolls in from the east, bringing squalls, a wind shift and heavy rain, and a few times each season one of those waves shows signs of organising into something more serious. The skill lies in telling the two apart early enough to act, without moving the boat every time a cloud bank appears.
This page explains the weather systems that affect Grenada in the season, the forecast products that matter most, how to read them without being misled, and how to set personal triggers for action. Official warnings for Grenada come from the Grenada Meteorological Service, and public safety instructions from the National Disaster Management Agency (NaDMA). The United States National Hurricane Center (NHC) provides the forecasts that most sailors use for tracking.
Tropical waves: the season's everyday weather
A tropical wave is a trough of low pressure moving westward in the trade winds, typically starting over West Africa and crossing the Atlantic over a week or more. Dozens pass through the Caribbean each season. Most never develop into a storm, but nearly all bring a band of cloud, showers and squalls, often followed by a shift of the wind towards the south-east and then back to east.
For a boat at anchor, the squalls are the main concern. Gusts in a strong line squall can exceed 30 or 40 knots for a short time, rain can reduce visibility to near zero, and the wind can swing suddenly through a large arc, testing every anchor in the bay. Boats with short scope or poor holding drag in these squalls more often than in any named storm.
Waves are tracked in the NHC's Tropical Weather Discussion and on surface analysis charts, and many cruisers follow them through the morning net's weather report. The practical routine is simple: when a wave is due, check your anchor and snubber, put loose gear away, close hatches before you go ashore and keep the dinghy secured or lifted.
The forecast products that matter
Tropical Weather Outlook. Issued by the NHC several times a day during the season, it marks areas of disturbed weather and gives the probability that each will form a tropical cyclone within 48 hours and within seven days. A disturbance east of the islands with rising probabilities is the first signal worth tracking.
Advisories and the forecast cone. Once a system forms, or is designated a potential tropical cyclone because it threatens land, the NHC issues regular advisories with a forecast track and cone. The cone shows where the centre is likely to go, based on historical forecast errors; it says nothing about the size of the storm or where the strongest winds will be.
Wind speed probabilities. The NHC publishes probabilities of tropical-storm-force (34 knot), 50 knot and hurricane-force (64 knot) winds at specific locations over the next five days. For a boat owner, the chance of 34-knot winds at Grenada is often more useful than the cone.
National watches and warnings. The Grenada Meteorological Service issues watches and warnings for Grenada, Carriacou and Petite Martinique. A watch means storm or hurricane conditions are possible, generally within about 48 hours; a warning means they are expected, generally within about 36 hours.
Forecast discussions. Alongside each advisory, the NHC publishes a forecast discussion explaining the forecasters' reasoning, the level of confidence and where the models disagree. Reading it tells you whether a track is firm or a best guess between very different scenarios, which is exactly what a boat owner needs to judge how early to act.
Marine and local forecasts. The Grenada Met Service also issues marine forecasts, and NaDMA communicates public safety measures, shelter openings and curfews through radio, television and official channels.
Reading the cone without fooling yourself
The cone is the most widely shared and most misunderstood graphic in hurricane season. It represents the probable track of the storm's centre, built so that the centre stays inside it roughly two thirds of the time. One third of the time, the centre goes outside. And because hurricane winds and rain extend well beyond the centre, damaging conditions often occur far outside the cone's edges.
Forecast track errors grow with time. A five-day position can be several hundred miles off, which is why a storm forecast to pass north of Grenada five days out can end up passing over it, or the reverse. Intensity forecasts are even less certain: storms in warm water can strengthen rapidly, as Beryl did in 2024, going from a newly formed system to a major hurricane within a few days.
For low-latitude systems approaching the Windward Islands, small shifts in track matter enormously. A difference of 50 miles can decide whether Grenada gets a brush of squalls or a direct hit. Treat a forecast track that passes close to Grenada as a threat to Grenada, not as a miss.
Setting your own action triggers
Experienced owners decide in advance what will make them act, so that the decision is not made in a rush. One workable framework, to be adapted to your boat and plan:
- Season start: strategy chosen (haul-out, hurricane hole or going south), storage or shelter booked, insurer's approval in writing, gear for storm preparation aboard.
- Disturbance in the outlook with a track towards the southern islands: review the plan, check fuel, water and provisions, and keep up with each outlook.
- Seven-day formation probability high and a track towards Grenada: begin preparing the boat; if going south, start looking for a weather window.
- Named system forecast to pass within a set distance of Grenada within about 72 hours: act. Move to the hurricane hole, haul out if a slot exists, or leave for Trinidad if conditions allow a safe passage.
- Watch issued: complete preparation of the boat. Arrange your shelter ashore.
- Warning issued: boat secured, crew off the boat unless there is an overriding reason, follow NaDMA instructions.
Sources and habits that work
A small number of reliable sources, checked consistently, beats a dozen apps checked in a panic.
- The NHC's outlooks, advisories and wind speed probabilities, read directly rather than through social media screenshots.
- The Grenada Meteorological Service for official national watches and warnings, and NaDMA for public safety measures.
- The morning cruisers' net on the south coast, which summarises weather and coordinates local arrangements.
- A way to receive forecasts without mobile data, such as satellite messaging or a long-range radio, in case networks fail.
- A barometer aboard, logged every few hours when a system approaches; a steady fall is an unmistakable signal.
- Weather model viewers, used with caution: individual model runs can swing wildly, and an ensemble or official forecast is a better basis for decisions.
Mistakes in reading the weather
Watching the line, not the cone and the winds. The centre line of the forecast track is only the most likely path. Plan for the whole cone and beyond.
Waiting for a name. A disturbance can become a named storm close to the islands with little warning. Track disturbances, not just named systems.
Over-reacting to every wave. Moving the boat for every tropical wave wears out crews and gear. Know the difference between a routine wave and a developing system.
Ignoring the squalls. Most anchor-dragging incidents in Grenada's bays happen in ordinary squalls. Set anchors for them.
Forgetting the land side. Supermarkets, fuel stations and banks get busy as a storm approaches, and they close when a warning is issued. Fill tanks, draw cash and stock up while the forecast is still uncertain; the cost of doing so for a storm that misses is small.
Trusting a single model run. One run showing a storm passing harmlessly can lull you; the next may show the opposite. Use official forecasts and ensembles.
Frequently asked questions
What is a tropical wave?
A tropical wave is a trough of low pressure moving westward across the Atlantic in the trade winds. Dozens cross the Caribbean each season, bringing cloud, squalls, heavy rain and wind shifts. Most do not become storms, but a few develop into tropical depressions, storms or hurricanes.
What does the hurricane forecast cone show?
The cone shows the likely path of the storm's centre, sized so the centre stays inside it about two thirds of the time. It does not show the size of the storm, and strong winds, rain and surge often extend well outside it. Treat a nearby cone as a direct threat.
What is the difference between a hurricane watch and a hurricane warning?
A watch means hurricane conditions are possible, generally within about 48 hours. A warning means they are expected, generally within about 36 hours. In Grenada they are issued by the Grenada Meteorological Service. By the time of a warning, boat preparations should be complete.
Where do Grenada's official storm warnings come from?
The Grenada Meteorological Service issues official watches and warnings for Grenada, Carriacou and Petite Martinique. The National Disaster Management Agency (NaDMA) handles public safety measures and shelters. Many sailors also follow the US National Hurricane Center's forecasts for tracking.
How much warning do you get before a hurricane in Grenada?
Typically several days for systems tracked across the Atlantic, but storms can form close to the islands or strengthen rapidly. Disturbances often appear in outlooks a week ahead with low probabilities. Acting on a credible threat about three days out gives time to prepare or move a boat.
Are squalls from tropical waves dangerous at anchor?
They can be. Gusts may exceed 30 or 40 knots briefly, and the wind can swing through a large arc, causing boats with short scope or poor holding to drag. Set anchors well, use generous scope, close hatches when leaving the boat and secure the dinghy.
