Crossing Dynamics

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Our sea surface temperature information overlaid on the NOAA chart (click for large), and our track. The swell and wind information were not adjusted for the Stream. So, the 3-4 footers with 11 second periods predicted were 5-6 with six seconds in the core of the Stream. The West winds 5 kts were more NW at 7 in the core. When the wind shifted through NE to SE its speed never increased enough to be usable.

Sailing East across the Gulf Stream from Fort Lauderdale to West end is pretty easy to predict. Go to the beach look at the horizon. if it’s a nice straight line (no humps and lumps) and the wind is fair for the duration, go. Sailing back from West End or Memory Rock is more of a challenge. Looking out at the horizon tells one nothing. Here one has to rely on weather forecasts, swell predictions, and sea surface temperature information. We are able to receive all three through our satellite weather terminal. Generally they are correct in the “core” information, however, there are things one must infer from the products based on outside sources and experience.

Some thoughts:

  • A fair wind for a sailboat sailing is a moveable feast. The crabbing angle required through the trip can vary by as much as 50 degrees. That nice reach on departure can turn into a beat into stacked up swells by mid-Stream. For us it is better to leave the Little Bahama Bank on a run and be reaching by mid Stream. This means a S to SSW breeze…but these can bring squalls.
  • Swells from one direction are highly preferable. With the Stream is preferable. With the Stream is rare. In the Spring NE is common as large weather systems north of the Bahamas as far as Nova Scotia can send long period swells into the southern US coast for as much as a week at a time, and frequent storms can extend this to weeks. They become almost unavoidable. Recognize they will stack up and come closer together in mid-Stream. Plan for it and shape course accordingly.
  • Sea Surface Temperature isn’t discussed much, but on the edges of the Stream it is a current speed map. Each gradation in color away from the core represents some degree of slowing. Where these decelerations occur, small but persistent eddies can form. Don’t be surprised by momentary loss of speed. Also these deceleration zones tend to be seaweed, jelly fish and trash traps, keep an eye peeled.
  • Lastly. Because of the Stream and the general shape of the coast, even though tides from Port Canaveral south don’t have a lot of range, the tidal flow in the jettied inlets can get quite high (4+kts). Riding these currents in is better than bucking an ebb — especially if it is breaking because of a breeze blowing from the ocean. In addition to having a weather window for crossing it is a good idea to have a current window for arriving. Good current windows will last about seven days and can be copied straight from the Tidal Current Tables.

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