Marine Glossary

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navigable semicircle

That half of a cyclonic storm area in which the rotary and progressive motions of the storm tend to counteract each other and the winds are in such a direction as to tend to blow a vessel away from the storm track. In the Northern Hemisphere this is to the left of the storm center and in the Southern Hemisphere it is to the right. The opposite is dangerous semicircle.

Often it is shifts in the wind direction of the approaching Low that tells us the relative course of the storm and which side would be the better choice if we have a choice. Here a key element is that on the navigable side the building wind is in the direction toward pushing us away from the path of the storm, as shown in G171.

ART-1 discusses the sides of a storm in detail. See also G103.