Tuesday, November 21, 2023

Hilton Head Island: anchored upon; hot; AI weather forecasting and ‘rogue’ waves

Carol and I went for a brief sail Sunday afternoon. 

The wind was gusty from the northeast, sometimes heading us as we went out Skull Creek, so at times we sailed under mainsail alone, at times motorsailed with the Evo engaged.  As we entered Port Royal Sound the wind increased to 20 knots, which on or aft the beam would have made for good sailing in the open ocean, but was a handful, literally, in close quarters and roughed up the sound beyond anchoring except in an emergency.  So we turned around and sailed back up Skull Creek and anchored a half hour before sunset in 15’ of smooth water a couple of hundred yards northwest of the marina.

Between the marina and the Port Royal Sound are almost a mile of sand patches barely above the surface at high tide.  The Intracoastal curves west of those islets, but there is also water to the east which in theory is deep enough for GANNET to pass on that side.  Some boats do.  Mostly small power boats and multihulls.  I have always followed the Intracoastal.  A multihull, about 45’, was anchored a half mile away from us on that shallow waterway.

Carol and I were sitting on deck sipping margaritas I had made at the condo when we saw a mast approaching.  As it came nearer and passed the anchored multihull it was revealed to be another about 45’ catamaran being towed by a small red hulled TowBoat US, heading directly for us.  The sun was setting, but it was still full daylight.  Carol said, “He is going to come over and anchor on top of us.”  And that’s just what he did.  We watched the tow boat slow and drift back beside the catamaran for consultation, then go forward and take the strain again and with a clear half mile of empty water in all directions bring the catamaran to within a few boat lengths of GANNET where the cat, whose crew of a man and a woman, dropped anchor.  Sigh.

The man, who was at the helm, which on that boat was at least fifteen feet above the water, shouted to us, “Are you staying the night?”

Carol hears better than I and relayed the message.  I shouted back, ‘Yes.”

“Then I guess I’ll have to move.”

I did not reply but thought, I guess you will.

He shouted again, “We lost a rudder and an engine.”

I am not aware of any severe weather around here recently and have never sailed on such a boat so do not know how they handle, yet I wonder if one rudder and one engine are not enough.  They are all I have ever had, if I’ve had an engine at all.

So they raised anchor, which of course only required pushing a button, and the tow boat hauled them a quarter mile back from where they had approached and they anchored again.  Why they didn’t stop there the first time I do not know.

We finished our margaritas and went below to share a good bottle of red wine and excellent chicken breast sandwiches Carol had made ashore, followed by half a brownie each, and a good night’s sleep.

You may have heard of Brazil’s current extreme heat wave because a fan died at a Taylor Swift concert there.  However the heat is startling as well as deadly.

The heat index in Rio set a record a few days ago of 58.5C/137F.  And this is Rio de Janeiro, not Death Valley.  Or wasn’t.  I know from personal experience in Hilton Head summers that a heat index of 105F/40.5C is dangerous.  At least for this old man.


No conclusion here, just observation.

Of weather and waves I have recently come across two articles of interest about AI.

As you know during hurricane season I download both the US and European GRIBs daily.  The European, ECMWF, has the reputation of being the more accurate.  Now there is a study that shows that an AI model named GraphCast has outperformed ECMWF in 90% of 1,380 metrics.  This is very good news for better weather forecasting in the future.  Whether it is good or bad news that AI may make our species obsolete is a matter of opinion.


I thank Mark for the other AI article, this one about the much greater frequency of ‘rogue’ waves than had been believed.


I put ‘rogue’ in quotes because that is an example of the pathetic fallacy, humans applying human characteristics to insentient forces, and I note a shift in the rather modest definition of such waves as being “at least twice the height of a formation’s ’significant wave height’ or the mean of the largest one-third of a wave pattern.’  That doesn’t seem very unusual to me and such waves are not likely ‘monsters’.

In nine or ten years at sea I have never seen a huge wave.  I do not doubt they exist, but the biggest waves I have seen were I judge about 30’ high, which is big enough.

However I have often seen waves that meet the above definition.

Some of you may remember that the most dangerous moments of GANNET’s circumnavigation did not come in her two 55 knot gales, but on a sunny, moderate wind day in the South Pacific on the passage between Honolulu and Apia, Samoa, when suddenly two 10’/3 meter waves appeared at right angles to the prevalent 3’/1 meter wave pattern, knocked GANNET onto her beam and held her there for long moments with the ocean almost reaching the opened companionway.  Had it done so we would have gone down.

Those waves were three times the significant wave height and meet the ‘rogue’ definition.  They were dangerous, but they were not the 80’ walls of water of the article writer’s imagination.  

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