Archive for July 19th, 2008

Riding out a Storm on the Open Sea

Saturday, July 19th, 2008

The Scarlett Knight is being impacted by the storm, given its slow speed there are only a few strategies, such as sling shotting forward in favorable currents, etc., but for the most it is just a time of  riding out the storm.  Whether you read the Perfect Storm, Sloccum's diary, or experincing it live, there are few things as epic as being at sea during large storms.  These are violent and quite often organic experiences.  Along those lines, i found a few passages from Captain Joshua Sloccum's mission around the world, that can captures exerpeince in fine form as we relax knowing we are not in the North Atlantic being buffted by Bertha. 

Passages from the "Sailing alone around the world" by Capt. Joshua Slocum (Sheridan House Publishers).  The Scarlett Knight is a Webb Glider named after Joshua Slocum.  The passage starts after taking his provisions at the Azores.

"Plums seemed the most plentiful on the Spray  and these I ate without stint.  I had also a Pico white cheese that General Manning, the American consul-general had given me, which I supposed was to be eaten, and of this I partook with the plums.  Alas! by night-time I was double up with cramps.  The wind, which was already a smart breeze, was increasing somewhat, with a heavy sky to the sou'west.   Reefshad been turned out, and I must turn them in again somehow.  Between cramps I got the mainsail down, hauled out the earings as best i could, and tied away point by point, in the double reef.  There being sea-room, I should, in strict prudence, have made all snug and gone down at once to my cabin. I am a careful man at sea, but this night, in the coming storm, I swayed up my sails, which, reefed though they were, werre still too much in such heavy weather; and i saw to it that the sheets were securely belayed.  In a word, I should have laid to, but did work.  I gave her the double-reefed mainsail and whole jib instead, and set her on her course.  Then i went below, and threw myself upon the cabin floor in great pain.  How long i lay there I could not tell, for I became delirious.  When I came to, as I thought, from my swoon, I realized that sloop was plunging into a heavy sea, and looking out the companionway, to my amazement I saw a tall man at helm.  His rigid hand hand, grasping the spokes of the wheel in a vise.  One may imagine my astonishment.  His rig was that of a foriegn salior, and large red cap he wore was cockbilled over his his left ear, and all was set off with shaggy black whiskers.  He would have taken been taken as a pirate in any part of the world.  While I gazed upon his threatening aspect I forgot the sotrm, and wondered if he had come to cut my throat.  This he seemed to divine.  "Senor" said he, doffing his cap, " I have come to do you no harm." And a smile, the faintest in the world, but still a smile, played on his face, which seemed no unkind when he spoke. I have sailed free," he said, "but was never worse than a contrabandista. I am one of Columbus's crew," he continued. "I am the pilot of the Pinta come to aid you. Lie quiet, senor captain," he added, "and i will guide your ship to-night.  You have a calentura, but you will be all right to-morrow." I thought waht a very devil he was to carry sail.  Again, as if he read my mind, he exclaimed: "Yonder is the Pinta ahead: we must overtake her. Give her sail; give her sail! Vale vale muy vale!" Biting off a large quid of black twist, he said: "You did worng captain to mix cheese with plums.  White cheese is safe unless you know whence it comes. Quien sabe it have been from leche de Capra and becoming capricious---"

"Avast there" I cried. "I have no mind for moralizing."

I made shift to spread a mattress and lie on that instead of the hard floor, my eyes all the while fastened on my strange guest, who, remarking again that I would only "only pains and calentura," cuckled as he chanted a wild song:

High are the waves, fierce, gleaming,

High is the tempest roar!

High is the sea-bird screaming!

High the Azore!

I suppose I was now on the mend, for I was peevish, and complained" "I detest your jingle. Your Azore should be at roost, and would have been were it a respectable bird!" O begged he would tie a rope-yarn on the rest of the song, if there was more of it.  I was still in agony.  Great sea were boarding the Spray, but in my fevered brain I thought they were boats falling on deck, that careless draymen were throwing from wagons on the pier to I imagined the Spray was now moored, and without fender to breast her off. "You"ll smash your boats!" I called out again and again, as the sea crashed on the cabon over my head.  "You'll smash your boats, but you can't hurt the Spray.  She is strong!" I cried.

I found, when my pains and calentura had gone, that the deck, now as white as a shark's tooth from sea washing over it, had swept of ervything moveable.  To my astonishment, I saw now at broad day that the Spray was still heading as I had left her, and was going like a race-horse.  Colombus could not have held her more exactly on her course.  The sloop had made ninety mile in the night through a rough sea.  I felt grateful to the old pilot that I marveled some that he had not taken in the jib.  The gale was moderating, and by noon the sun was shining."

So in the spirit of Captian Slocum we hope the wayward spirit of the Pinta is with the Scarlett Knight today riding out the remnant of Bertha.  If the ghost pilot of Columbus is not available, well we will be happy having the Rutgers undergraduate glider pilots! 

 

 

Hurricane Bertha heads off to the Northeast

Saturday, July 19th, 2008

That was fast.  Hurricane Bertha is now over the colder waters to the north of RU17.

The forecast below shows the hurricane is going to continue tracking rapidly to the northeast

Amazing how as it was approaching us, Bertha dediced to reintensify, going back to Hurricane force winds.  RU17 was in the region with the tropical storm winds (orange), with the hurricane winds just to our west (red).

Waves are now peaked at about 30 foot significant wave height.  Wow.  We were in 10 foot waves during yesterday's glider deployment in Hawaii.  30 footers in the North Atlantic, hard to imagine.

With the storm now past, we can go back to our more efficient flight pattern, and head into those stronger currents we see in the Navy NLOM model.  Justin loves to take the wheel.  Lets see where he takes us.

 

Weathering the Strom, Riding the Rings

Saturday, July 19th, 2008

Gulf Stream forecasters love storms.  The storms mix up the surface layers, and instead of looking at a uniformly warm but thin surface layer, you get to see the horizontal gradients associated with the deeper flows.  In the case below, the eddy structure is clearly visible in the sea surface temperature image.  When you get images like this, they are very valuable, because they are instantaneous.  They show the actual shape of the features.  Our eventual goal is that strong cold eddy near 42 N between 40 W and 43 W.  We want to ride its southern side.  You also can see some of the warmer eddy to the northwest of the cold eddy.  RU17 is in clouds (the black regions in this enhancement).

Below the altimetry is in excellent agreement with the satellite sea surface temperature The cold eddy (low in blue) we are going for is clearly outlined, and we see the warm eddy (high in red to the northwest).  The problem here is that the cold eddy RU17 is trying to use today is located under the clouds near 39 N,47 W.  According to the altimetry, RU17 is crossing through the strongest nortward currents associated with that eddy.  We know that is not the case.  RU17's currents remain below 20 cm/sec, very week.  So the altimetry, a several day composite, is smearing this feature and we need to wait for another overpass to refine our current estimates in this region.

Once refinement is to use a dynamical model, in this case the Navy's NLOM model that does the dynamic interpolation of the altimetric field to try to eliminate the smearing in time and space you get from raw altimetry.  The dynamic constraint is the the interpolation requires F=m*a, a significant constraint since the apple hit Newton on the head. In this dynamically constrained interpolation (current speed contoured below), the eddy we are looking to ride is still to our east.

Below is the countours of north/south velocity, and we still want to steer into those strong currents to the north. 

And find those strong currents to the east (bright red) we see here associated with that eddy.

Bertha crosses our track

Saturday, July 19th, 2008

Bertha is moving northeast, crossing the track of RU17.  We are just to the right of this propagation direction, about 200 km from the eye wall, in the outer cloud bands.  Looking down through the eye, Bertha will soon cross into the colder water to our north.

 

Rigged and Ready

Saturday, July 19th, 2008

Hugh sent RU17 straight north.  Justin's blue line indicates RU17's course.  We are on the right side of the Tropical Storm, the side with the most intense winds.  RU17 reported increasing currents to the north.