Month: November 2021

Getting across the Gulf Stream without undue drama is often a challenge in late Fall. Our tytpical approach is to get down to Lake Worth and hang out till conditions fit our criteria. More on that later.

Privateer plans

Normally we are in no particular hurry to get across. Usually our first schedule commitment is to meet up with our sons in the Exumas for Christmas. But this year we planned a major family reunion for Thanksgiving in Spanish Wells. Still not a problem if there were no boat mechanical issues and the weather pattern was typical. Unfortunately, that is not how it worked out. We spent a week on the hard in early November dealing with a propeller vibration issue.

As the work progressed we watched the weather, hoping the boat would be ready when a weather window opened up. By the 9th we were seeing a possible window for the 12th, but at that point we had neither props or shafts installed. Since this post is about the GS and not our mechanical issues, I will skip the details and just say that the last technician left the boat at 6pm on the 11th and we departed the morning of the 12th. Our sea trial would be conducted as we motored out Lake Worth inlet.

Gulf stream crossing strategy

Back to our criteria for GS crossings. Our usual navigation approach is to cross perpendicular to the current, with constant course over ground (COG) and speed through the water (STW, while varying heading (HDG) as required to hold course and letting speed over ground (SOG) be what it will be. We let the autopilot drive the boat.

This method, sailing the shortest distance from one side of the stream to the other, is the most efficient for our boat speed of 8+ knots, versus the typical GS current of 2- 2.5 knots. Normally we cruise a bit slower for fuel efficiency, but the greater the speed differential between the boat and the current, the less effect the current has on the overall trip. With a slower boat, or significantly stronger current, the shortest time approach, holding HDG and accepting the set, might be more efficient. Back to our criteria for crossing conditions.

Weather and seas

A forecast of NE 5-10G15 and 3′ seas will keep us in port. These conditions will create a rather nasty set of steep, short period seas near the nose, often much higher than the forecast suggests. Change the wind direction to NW and we will accept a little more wind. Winds with a southerly component still seem to stir up the stream more than they would on no-current waters so even with a southerly wind we avoid anything over 20 knots.

So lets get back to this crossing. By Wednesday the forecast for Friday was looking better. We use Windy and Predict Wind for their presentation of the various GRIB models. If the GRIBS are not in agreement, we tend to place more stock in the Euro model. We rely on NOAA for a summary and Chris Parker for a sanity check. Chris’ approach is to forecast the worst conditions one would likely encounter, so if his forecast meets our criteria we are good to go. We usually start looking a week out and then watch the trends. On Tuesday, NOAA was predicting NW10-15G20 and 4-5′, a no-go, but by Wednesday had dropped back to 5-10G15, a favorable trend.

Here is what the GRIB models were forecasting, courtesy of Windy:

A minor risk of squalls and maybe a thunderstorm but otherwise a great forecast. This forecast pretty much held through Friday morning and was supported by both NOAA and Chris Parker. All the forecasts suggested a NE swell at 3′ and 9 seconds, coming down to 2′ later in the day. We were a GO!

Geluf stream current forecasts

The GS forecast for current speeds also looked pretty good. We use Passage Weather for these stream forecasts. The max current of 2.5-3 knots looked to be for a fairly narrow slice of the stream, with mostly 1 to 2 knots. We have encountered as much as 4 knots but that is more typical closer to the Keys.

We cleared the break wall at Lake Worth inlet at about 8am and in less than five miles we began to pick up a little current. Luckily, the swell was already 2′ or less and just got better from then on. The following table lays out our trip with mileage, speeds courses and headings. From this data I was able to calculate the set and drift of the current. Using the Passage Weather chart I estimated the current at intervals along the route and compared them to actual performance.

Actual Set and drift

I was surprised to see that despite a maximum crab angle of 21 degrees at 1000am, our speed over ground was still pretty good at 7.9 knots. That can be explained by the NNE set during the strongest portion of the stream. All this assumes our speed through the water was in fact a steady 8.3 knots, which may have been a bit low. We had essentially flat seas and at times a bit of a tail wind which might have improved speed through the water.

Once we were within sight of West End the current was minimal so we cut the corner a bit and headed straight for Spanish Wells, arriving at about 9am on Saturday. I had been so rushed when we were leaving that I never checked on the moon phase. I was happy to see a half moon near overhead just after sunset that lasted until the early ours of the next day. Plenty of tankers and cruise ships (yes, they are back) on this route but they all played nice and dodging them gave us something to do.

Now that we are here we appreciate how lucky we were to find any window at all. Wishing all of you will find equally pleasant weather windows.