TravelTalkOnline Forums Travel and Vacation Forums British Virgin Islands BVI DDM - Unstableather Alert - May 22nd

"DDM has sent out communication indicating there is a high probability of unstable weather affecting the BVI beginning next Wednesday, May 22"

WindGuru showing clouds and some rain as well

Don't fret folks ! The flash flood came without warning. They are hopefully just covering their arse. Eastern canada term for [censored]

The weather forecasts are all very benign for next week - apart from the cloud cover and north swell. I cannot fathom why a disaster alert organization would issue a warning; they risk a "chicken little" effect if they do that. "Unstable Air" just means that there is a high potential for cumulus to develop, which could overdevelop into thunderstorms. Kind of standard fare for tropical climes...

Zanshin or others: can you elaborate on how to read VGR's windguru illustration to understand the north swell? What data indicates that the swell is significant? I assume the "Wave" and "wave direction" are the primary indicators, but if so, at what number does "wave" become significant? > 1? Is the period relevant?

appreciate the expert insights.

Keep in mind that in many oceans you have both swell and wind driven waves. Often they come from different directions. The BVI is prone to swell from the North usually generated by storms in the North Atlantic. If you hear of a big Nor’easter in the US expect a big North swell in the BVI a few days later. Those swells in the BVI have virtually no impact when you are in open water sailing. They become a factor when they reach shallow water and turn into breaking waves. Wind driven chop on the other hand is what makes things nasty when out sailing creating short duration steep waves. Usually however it has little effect on anchorages as good ones provide both shelter from the wind and not enough fetch for the waves to build. Cane Garden Bay can be a great anchorage in 30 knots of wind when you are getting hammered out on the open water. CGB is however not a good place to be in a North swell even with calm winds. The North swell is monitored by a series of buoys along the Eastern US. This leads to very accurate swell forecasts. Wind forecasts are more iffy.
As far as the impact a swell might have on a anchorage there are no set rules. Slight changes in direction can have a big impact. Each anchorage will be affected differently. In the BVI a N swell primarily impacts Cane Garden Bay for overnights. My general rule is just go somewhere else if it’s over 1.2 meters give or take. A swell will also impact day stops like the Baths, Dogs, Savannah Bay, Guana, Monkey Point ect.. A swell can also produce large loads on shallow water mooring balls if the swell lifts the boat when its position is such that the mooring line snaps tight as the boat rises. This is probably what led to a well publicized ball failure by a big Utuber. Never leave a boat on a mooring unattended in a North swell. When the swell builds to 2 meters or more it can cause issues in places you don’t expect as it wraps around land masses or reflects off others. White Bay on Jost is an example and I have seen Cooper Island impacted in a big swell. If in the USVI and moderate or larger swell will take out all the great North side anchorages on St John.