Ground swells

Does anyone know of a reliable way to predict ground swells in CGB or CIBC short of waking up at 2AM and saying, "they're here!"? <img src="http://www.traveltalkonline.com/forums/images/graemlins/duh.gif" alt="" />

http://www.windguru.cz/int/index.php?sc=58

http://magicseaweed.com/Cane-Garden-Bay-Surf-Report/480/


These are the sites I use.

This is for the USVI, but it should apply to the BVI as well:
http://forecast.weather.gov/shmrn.php?mz=amz715

The forecasts above should give you warning many hours before any swell coming from hundreds if not thousands of miles away. You also can give yourself greater buffer from real harm and risk of damage by never putting yourself as the inside row of boats. Deeper water provides a buffer, distance also provides you a buffer against a sudden change to a lee shore.

I have never been in CGB when a sudden set of unsafe swell or surf showed up. I was in Salt Whistle Bay , Mayreau when the swell and surf showed up instantly.




Most of the cats closest to the shore in shallow water ended up on the beach in single digit minutes. Middle of the afternoon! Several boats with the crew on the boats were incapable of saving themselves. The swell simply came in and put the boats on the beach. The boats in the middle of the bay where safe. I have been in White Bay shortly after a sudden storm where a boat was up on the rocks or beach.

If any anchorage is wide open. You should always asked yourself why? If you see a sandy beach. Surf threw that sand up there. Someday the wind and waves will come along a throw a boat up there just like the sand.

Another helpful website: http://www.stormsurfing.com/cgi/display.cgi?a=natla_height

Here is a simple chart of Cane Garden Bay with North marked. One location in this anchorage may be the safest place to be with a sudden North swell. That same mooring or anchor spot could be a disaster if the swell shows up from a storm to the south or the west.



Note: Settled weather so often referenced in the cruising guide does not translate to "good weather" or "favorable weather" it means conditions that will not change for the period in question.


I edited this to try and be more clear. Local Sailor is correct in many of his statements. I was just trying to be clear in my personal experience. CGB is not protected. It is never the place to be in a North Swell. Some spots will give you more time to recover than others is my point. As to the buoy referenced. That single device will give you a heads up to a North Swell, But not a west or south swell from a different storm in a different location. Again my point is to give yourself space to recover from a change in conditions. The closer to the sand, the closer to the rock, the shallower the water. The less time your crew will have to recover to a change in conditions.

I disagree most wholeheartedly that Cane Garden Bay :

" A location in this anchorage may be the safest place to be with a sudden North swell."


That is contrary to my experience of 40 years of sailing here.

"I have never been in CGB when a sudden set of unsafe swell or surf showed up."

I certainly have and it is NOT a pleasant anchorage at that point.

http://www.ndbc.noaa.gov/show_plot.php?s...;time_label=GMT

This buoy is almost 200 nm North of the BVI and a fairly predictive and accurate look at swell conditions in real time there and approaching in 8-12 hours..

I wholeheartedly agree. CGB is one of the last places I want to be in a North swell.

look at the source, Chris. If there is any swell and it was tenable, we would anchor inside the gas station.

For general forecast, I use the Stormsurf Caribbean Sea Height Forecast. http://www.stormsurfing.com/cgi/display.cgi?a=carib_height

<img src="http://www.traveltalkonline.com/forums/images/graemlins/Clapping.gif" alt="" />Thanks everyone - great advice. Gotta love TTOL

One thing to keep in mind. I often see lots of confusion between swell and wind driven wave action. They are very different animals. Swell can occur in any wind condition including dead calm winds. It is usually generated in the N Atlantic and the swells run down to the Caribbean. Even in large swells the sailing is just fine. They make for a nice smooth ride with a gentle up and down motion. The bad stuff happens when swell hits shallow water like CDB. That gentle swell starts to steepen and turns into a breaking wave. Essentially swell is a anchorage not a sailing problem. Swell in the Caribbean is almost always out of the NNW to NNE.
Wind driven waves on the other hand come from the direction of the prevailing wind and are generally short and steep waves with whitecaps starting around 15 knots of wind. Wind above 15 to 20 knots can make for miserable sailing with the boat pitching heavily sailing into the wind and cats giving lessons in slap. Anchorages on the other hand are usually fine because most are sheltered from the prevailing E wind in the BVI. CDB is a fantastic place to be when the wind is howling.
G