weather and water wisdom 269
“Your Call, Skipper”
You’re the skipper or most knowledgeable crewmember in each
of the following situations. What actions would you take?- You were sailing southbound for the islands but decided to anchor
to wait out a storm to the south. What two signs would indicate the
storm center has passed and it’s safe to proceed? - The latest weather forecast calls for 2- to 3-foot seas this afternoon,
building to 5 feet by evening. What average wave height would you ex-
pect this evening? What is the highest possible sea after nightfall? - A 20-knot breeze is predicted to blow onto the 1,200-foot cliffs
close to your trackline. How far away should you stay to avoid a pos-
sible dangerous “ricochet” zone? - You are approaching a mountainous island in a gusty 15-knot breeze.
Winds will increase later this afternoon. A low cloud layer has settled
over the island on all sides. What effect could this have in the anchorage
on the lee side? - You’re sailing in the Caribbean and need to find a good anchorage
for this evening. You pull out the largest scale chart and study the
area. What features would warn you to expect a heavy groundswell
caused by refraction?
Answers - The winds will back to the northeast (in the Northern Hemisphere)
after the eye passes. The barometer will begin to rise slowly. - The smallest seas should average 3 feet (60% × 5 feet). Occasion-
ally, you may experience a 10-foot sea (200% × 5 feet). - Two miles: 1,200 feet × 10 = 12,000 feet; 12,000 feet ÷ 6,000 feet
(per mile) = 2 miles - Expect a rough anchorage. A low cloud layer on all sides funnels high
winds around the island. Use storm ground tackle or tie up pierside. - A roundish island with gently sloping bottom contours all around
its circumference is a candidate for heavy groundswell caused by
refraction. Try to find long, narrow islands or islands with protected
coves or lagoons or their lee sides.