The Wind Does Not Care About Your Itinerary

Generic weather apps show a sun icon and 15 knots for a week straight. They are lying. You need to understand trade wind acceleration, island blanketing, and the Christmas Winds.

The Trade Winds Reality

The Caribbean is dominated by the Easterly Trade Winds. In the winter (Dec-Feb), these are known as the "Christmas Winds" and frequently blow 25-30 knots for days on end. If you are a novice, this is terrifying on a 45ft catamaran.

Island Effects

Wind Acceleration Zones (WAZs): Wind funnels between mountainous islands (e.g., between St. Vincent and Bequia). A 15-knot forecast becomes 25 knots in the channel.
Blanketing: The leeward side of an island (the west side) is calm, but gusts (williwaws) can shoot down the valleys at double the ambient wind speed.

The Tools You Actually Need

Do not use Apple Weather. Use marine-specific models.

Windy.com: Specifically, compare the ECMWF model with the high-resolution GFS.
PredictWind: The gold standard for routing, but the free version is sufficient for basic squall tracking.
VHF Weather Reports: Every morning at 0800, tune into the local cruiser net (usually VHF Ch 68 or 83). They provide the only hyper-local, observed data.

Apparent Wind Calculator

Understand how your boat speed changes the wind you feel on deck.

True Wind Speed (knots)

True Wind Angle (degrees from bow)

Boat Speed (knots)

JavaScript required.

Fallback: If you are sailing upwind at 7 knots in 15 knots of true wind, it will feel like 20+ knots on deck. If you are sailing downwind, it will feel like 8 knots. Reef accordingly.

Common Mistakes

Mistake	The Reality
Ignoring squalls	A dark cloud approaching fast can pack 40-knot gusts. Reef early, start the engines, and point upwind.
Trusting the anchor in a blow	If the forecast calls for 25+ knots overnight, 5:1 scope is not enough. Let out 7:1 or find a mooring.