Tag Archives: Offshore

Whoa, Where Did That One Come From?

SwellHow many times have you said that or dreaded it? Well, wave behavior is predictable, but forecasts only tell one part of the story. Remember grading on the curve and the normal distribution? Well, it doesn’t apply to waves. Wave height distributions follow a Rayleigh curve. Which looks like the one below. Click pics for details.

RayleighCurveThat wave forecast is for the significant “H” — the average of the highest 1/3. Beyond that are the highest 1/10, 1/100, 1/1000, etc.

So how big are these larger waves?

HeightDistrA 3-5 foot forecast will include at least some ~6 to ~10 footers!

Frequency

And if the wave period is predicted to be 6-7 seconds, those larger waves could occur every 1.7 to 1.9 hours… or three could come in a row; remember this is statistical behavior.

This is why the heights and periods found in forecasts need to be more fully understood. And yes, there are 1/10000, 1/100000 and so on waves out there. but conditions usually change before these are seen, unless they don’t, and seen they are.

What We Didn’t Do Yesterday

WE DIDN’T
♦ …sleep late (up at 0550).
♦…get stuck circling at the Sisters Creek Bridge with an adverse current.
♦…get stuck behind the Kingsley Creek unattended, automatic railroad bridge with an adverse current.
♦…have to wait for high tide to clear the shoal in the Amelia River below Fernandina.
♦…have to mess with the Cumberland Dividings at low tide.
♦…drone through the winding creeks and sloughs of Georgia fighting an adverse current.
♦…have to deal with Jekyll Creek at low tide.

Instead

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WE DID
♦…make good time up the waterway to the St Johns on a fading ebb.
♦…enter the St Johns with less cross current than we have ever experienced here.
♦…go down the St Johns with no large traffic until the very end, and we left the ship channel before it got to us.
♦…have a very nice motorsail — SE wind 6-8 knots on the starboard quarter,  swell from the SE all the way to the entrance to St Simons Sound where the wind shifted E and increased to 18 knots.
♦…get a 0.5-1.2 knot push from the coastal current all the way.
At the entrance to St Simons, the tide switched and we fought a similar or greater current all the way in with our ground speed around 4.8 at times. There were no breakers across our path, but there were to the north.
♦…make it into Brunswick Landing Marina at 1700 — an hour early — and went from 79 degrees offshore to 90 in a hurry — ouch.

♦We traded 11 hours offshore (three of them just getting through the St Simons Inlet to the Marina) for 36 or more that would have been required in the waterway.

♦We saw lots of shrimpers — visual or on radar — and we followed another sailboat and a freighter into St Simons. Otherwise it was a very low stress day.

So, now we are above Cumberland Island before 1 June — an insurance requirement — and the rest of our trip will be more tuned to nature’s rhythms. Oh, and there appears to be something tropical heading our way in the next few days.

Lumpy and Grumpy, The Gulf Stream and Us.

We returned from the Bahamas to Fort Pierce, Florida May 13th. With an inaccurate forecast, it was not a fun crossing, the way our trip over on March 1 was. Click on first pic for gallery, more text below.

The high pressure area moving east stalled. The inverted trough to the south dissipated in place; Northeast winds lingered and built a NE swell N of the Bahamas.  When we left Mangrove Cay at 4 am, the updated forecast was for East winds, with SSE the following day. Wrong. [Had the original forecast held, we would have gone to West End on Sunday and crossed on Monday. Ah, well.]

When we crossed the edge of the Little Bahama Bank at Memory Rock, there was a southerly component in the wind we attributed to a local effect of wind being bent by the shape of the west end of Grand Bahama Island–we thought it temporary. Wrong.

We motorsailed with main only because the downwind rolling would have made the genoa jib useless (and worse).  We had  criss-crossing 3-5 foot swells from S, SE and NE. “Rolling” is generous. Drunken lurching would be closer to the truth.

We pressed on, on port tack, toward the center of the Gulf Stream. But the Stream was running further west than predicted. We jibed near the geographic middle of the Florida Strait. On starboard tack we sought out the fastest flowing current and saw our speed over the bottom go up to 10 knots. But the lurching continued and was now augmented with swooping as we got into the NE swells. When these added to the other swells we would sometimes see 7 foot walls of water loom next to us and then disappear.

The only water we took aboard all day was through the scuppers when we rolled so deeply the water came up the drain hose. No waves or heavy spray came aboard.

We jibed again where the western wall of the Stream was supposed to be. Unfortunately, we had to fight the Stream for about ten miles crabbing as much as 40 degrees off course to make Fort Pierce. The northerly winds from the stalled high had nudged the Stream west.

The Fort Pierce ebb started early, and was running at about 2.5 knots and was breaking when we arrived. They were 3-4 footers at right angles to the channel and about sixty feet apart. So we positioned ourselves on the back side of one and used throttle to stay there. It lasted about five minutes. Only had to reposition twice. It was easier than the prior ten hours, but at no time was I tempted to hang ten.

We made the 14.5 hour trip in 14.6 hours.

Starting with getting up at 0330, the day was not fun, but neither was it especially dangerous. The boat handled it superbly. The autopilot deserves a medal. We were never out of control. And when sailing maneuvers were required (jibes, furling sails, etc) they were not particularly difficult. And we had a great homemade deli tuna salad with whole wheat egg noodles.

Cleared Customs with a three minute phone call.

We slept till 1000 the next morning.

New Links for Weather/Oceanographic Visualization

klaxonstrongThese sites do a good job of providing derivative info. I would not use them for stand-alone support, but for getting the gestalt of conditions expected, they do the job. While I have shown the links relevant to us here and now, in the links list they are higher level links.

Windfinder – Wind & weather forecast Green Turtle Cay / Gillam Bay

Swellfinder – Waves & swell forecast Atlantic Ocean

Animated North West Atlantic Wave / Swell Chart (WAM) » Yo Surfer!

 

Crossing the Stream

The sail over was spectacular. We left the dock at 0554. We exited the Port Everglades breakwater 0645 (dodging a Carnival cruise ship in the process of docking).

It was a little lumpy for the first three hours as the tide met the swell that had built in the Gulf Stream overnight. We sailed all the way from the Port Everglades outer buoy to a mile off West End (68 miles). The water was cobalt blue and garlanded with Sarrgasso Weed the whole way. Six maybe seven rain drops fell. We motorsailed through some light spots, but we had 12-14 knots of almost due south wind the whole day. Shipping traffic was remarkably light and never a problem. Toward the end, small flying fish put on their skittery show of avoiding the boat.

We tied up here in Old Bahama Bay Marina (West End) at 1715. The Dockmaster was waiting with a lawn cart to take me to customs. The Customs officer didn’t seem the least put out we arrived past duty hours. The Marina office was just as cheerful.

We met Steve and Mary Ann (sp?) from “Air Force Won,” a Hunter 46. They leave tomorrow morning to return to the US for the birth of grand children. As is usually the case, they were a great source of specifics the guides often omit.

We replaced our yellow quarantine flag with the Bahamian courtesy ensign. And now onward…

Departing Fort Lauderdale

Well, WordPress continues to disappoint. Now, I have discovered their application has failed in the same way on our other laptop.

We are planning to slip the lines about 0600 on Thursday to head for West End, Grand Bahama. We have a favorable weather situation starting tomorrow, but other things prevent us from leaving then.

With the kick from the Gulf Stream, we are looking at around 10 hours to get there and hope we can do better than than that (for clearing Customs reasons). Southerlies on Thursday may encourage a surface drift current that will add a bit to our speed. Although the Stream runs around 2.5 kts, our course will only allow us to take advantage of about 1 knot as we must crab to get there.

While this crossing must be taken seriously, it is also useful to remember at 69 nm, it is less distance than we sailed to get from Deale to Sandy Point on the Great Wicomico.

Still, the boat gets a thrice over before we leave. A problem on this route has different consequences than a problem on that one.