Tactics and Sunset Wind Shift

Day: 70 — Odometer: about 2,262M
Position: N22 44’ W152 45’
Distance from start: 1,831M
Nearest land: NE shores of Big Island 215M due 219T
Waikiki Yacht Club by my course: 310M due WSW
ETA: Sept 9-10, maybe not at all, see below

RECORDS as running totals
Solo career total in days at launch: 845 now 915
Overall career total in days at launch: 928 now 998
Solo career total in miles at launch: 27,595M now about 29,857M
Overall career total in miles at launch: 31,083M now about 33,345M
==> Ralph Tuijn (NL) leads the last one with 35,635M

Actual distance rowed in miles will append to my existing career totals at launch in solo and overall categories; to become official, London based Ocean Rowing Society must adjudicate supporting GPX files from my chart plotter and YB Tracker.

—-oOo—-

After my last update, Dr. Jay Barlow wrote an urgent plea to his NOAA colleagues on Oahu. I am collecting ambient sound data for Dr. Barlow and I need to swap his external drive in loan on my rowboat with a blank one to use beyond Hawaii. There was a possibility that NOAA assets could be used to assist in this process to rendezvous at sea north of Oahu. Alas, all NOAA vessels are dockside, operations suspended on account of COVID.

One of his colleagues Amanda Bradford wrote that they own a Boston Whaler based near Haleiwa Harbor and could help. That lifeline by Amanda was all I needed to lift my spirits. We now had a solution in case I had to route north of Oahu.

Since then I was able to bring my rowboat south some taking advantage of a wind hole which developed south of me. This was a welcome break from my steady loss of ground due west. As a result, my positional advantage to reach the west end of Molokai improved from 245T to 249T. This means that I can now tolerate winds four degrees more southerly and still maintain my course… So the farther south, the better at this time to improve my odds of clearing Koko Head at the southeast corner of Oahu, guarding the west end of Kaiwi Channel, my gateway to Waikiki.

When winds turned ESE at sunset last night I was no longer tracking 249T even when I rowed, so I deployed the para anchor and found a convenient southerly flow under my rowboat. Despite a steady 7-10 knot ESE wind, my rowboat tracked 3.3M due SSE over the following 11 hours, an average of 0.3 knots. So it seems that I will be able to not only hold my position but register some free southing while I wait for this inconvenient ESE-SE wind pattern to blow through midnight on Wednesday. Then through Sunday, I will have favorable winds bookended by yet another bout of ESE winds starting on Monday. My hope is that I will by then be close enough to Molokai to better control my destiny. I will see what The Ocean offers at that time to leverage toward Waikiki. Else, thanks to Amanda, I have a vessel that can meet me north of Oahu to deliver parts and supplies at sea. If I cannot pull into Haleiwa, I now have the option to continue nonstop.

As I wrote in my last update, while the overall strategy requires understanding of prevailing seasonal patterns, taking advantage of the daily patterns falls under the realm of tactical decision making. Near shore, one must negotiate the tides and the onshore effects on winds. Unless I am presented with unusual wind patterns that just don’t belong like that southerly wind spell which hit me on Aug 14th, or the present southeasterly nuisance, the trade winds in the 20 latitudes typically are reliable.

One daily wind pattern offshore which I observe in the north 20s has been that by mid afternoon, the wind would back and increase by at least 5 knots. This is probably due to hotter air at lower latitudes rising to draw the relatively cooler air from the north across my latitude. Then as the sun approaches the horizon about an hour or two before sunset, the wind would veer some (in the northern hemisphere, backing means wind direction shifts CCW, veering means CW). This is the gradually cooling air in the east where the sun has already set, chasing the sun’s heat.

So I have a fine work day, putting in decent rowing at 15-20 knots of winds to maintain an acceptable westerly course. Then when I am ready for dinner, the wind veers helping the boat track the course that earlier I could only maintain by rowing. Remember that in all reality, I can only change the boat’s course by about 20 degrees toward the weather. This wind shift makes rest possible. This is also how I will maintain my westerly course steady at around 21N latitude beyond Hawaii with predictably ENE winds.

Jason Christensen had read that New Zealand yachtsmen call this the “sunset lefty” while sailing in the south 20 latitudes. In this hemisphere, that sunset wind shift would be a “sunset righty” to me as I described above. He referenced the book that describes the reason for the sunset wind shift from a weather standpoint as "Bernot on Breezes" by Jean-Yves Bernot.

Erden