This example illustrates how a tropical cyclone can cause significant stalling to ship movement—an occurrence that is replicated around the world.
While accurate forecasts depend on a blend of technology and experience, ship captains know that storms have navigable and dangerous semi-circles. The image below shows a classic northern hemisphere storm and indicates that when sailing north and east of a cyclone, a ship is in the dangerous semi-circle due to a cyclone’s propensity for recurvature. Storms may track WNW at 5-10 knots for days before recurvature starts, and that recurvature process starts out slowly. However, the recurving cyclone typically speeds up, sometimes in excess of 40 knots, which would bring all ships in its path into a dangerous situation.
There are exceptions to this rule, thus all available data should be scrutinized when determining the best course of action for storm avoidance. Take the following situation from October 4, 2018:
The ship is heading eastbound towards the Mediterranean Sea, and proceeding along the shortest route seems to place the vessel into the dangerous semi-circle of the storm. However, forecasts were very consistent in indicating that the storm would not take the typical NE course and would instead turn ESE-ward in the days to come.
If the ship were to attempt to pass south of the storm’s track (seen below), an additional 2.5 days of sailing and 80 MT of fuel oil would be needed.
Case Study 2: