Advanced Scenario Check: Forecast Mismatch and Tidal Gate

At 1200 in this fictional exercise, the yacht is 18.0 nautical miles from an exposed entrance that must be reached by 1545. The forecast increase to Force 6 has arrived early, pressure has fallen 5.3 hPa in three hours, the sea is building against the stream and monitored speed over the ground has reduced to 4.5 knots. One crew member is seasick and the easier harbour is 7.5 nautical miles away on a route expected to make 5.0 knots.

Separate the evidence. The pressure tendency is falling quickly; the early Force 6 and building sea contradict the expected timing; the reduced speed is measured progress; the crew limitation is operational. None alone dictates the destination, but together they remove the original timing and workload margin.

Test the exposed route before debating the weather-system label. Eighteen miles at 4.5 knots takes four hours, giving a 1600 arrival — fifteen minutes after the fictional 1545 gate and before adding any manoeuvring or contingency allowance. The original route therefore fails on the monitored case.

The easier harbour is 7.5 miles away. At 5.0 knots the estimate is one hour thirty minutes, giving a 1330 arrival from 1200. That figure is not a guarantee; it shows why the fallback remains substantially easier now than after another hour towards the exposed entrance.

Brief the diversion, sail and watch plan, casualty care, weather-update task and a review point. Reopen the original route only if a fresh information set, observed conditions, crew state and a recalculated arrival all restore the chosen margin. This is written revision, not a live forecast or route recommendation.