Thursday, January 24, 2013

Progress report Jan 24-25

The little blue dot is us at the moment. There is clearly a lot of traffic around, but just as we can see them, the ships can also. This is an AIS picture from marine traffic.  There are receiver antennas on the coast who participate with Marine Traffic by sending back their live data to the Marine Traffic HQ. After they get 100 mi or so offshore, this will no longer work.


Team is underway and doing well  in  difficult conditions, not to mention that everyone has to adjust to the life at sea, which takes a couple days.

You can see their position updated every 1.5 hr at the oarnw site.  click any position point to get more data. Making on average about a knot to toward about 300 T.  Once things settle down and the wind and waves clock back around to the east, progress will pick up.

Check the wx map to see that there is a trough over coast of Africa that has cranked the isobars and winds around to the north and freshened them–they who would otherwise be lighter trade winds from the NE.

These trough winds brings with them larger waves, which slows down progress.

My guess of the waves from the ww3 model is about 3.5 m from just west of north, which means they might be rowing with seas on the starboard bow... we have to learn later what real conditions are.

My guess is they might take a somewhat more westerly course when the wind and seas allow them.

Currents do not become an issue for a couple days i would guess, but we will keep an eye on it.

For next day or two waves are still predicted at from 350 (actually slipping a bit more to the west 340), but they should diminish. Sat down to 2.2 or so (down 40%), and by sunday start to move to the east, meaning from 010 or so.   200 miles west of you they are from almost NE.

PS normally we describe waves as the direction they move toward, but in our application it seems more logical to think of the direction they are coming from.... we will see as we progress here what is the best way to describe the seas in this application.  Generally wind and waves should be from the same direction, but there are multiple reasons that get them out of sync.

for one, the wind can change directions relatively quickly, but it takes half a day or longer for the seas to follow.

Also if there are any prevailing swells in the neighborhood, they combine with the wind waves to make a combined sea state which will have some combined height and direction.  Generally if the period of the waves are much longer than 12s or so, these are mostly swells, if less than 10 or so, they are mostly wind waves.  The boat is now experiencing something in between these two ends.

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