Sunday, January 1, 2017

Short Survey of Ocean Currents

These three environmental sources surveys cover key resources available to mariners who have not taken our Marine Weather Course, which covers each of these in depth, along with the background needed to use them efficiently. Our goal here is to be sure that you do not leave one of our other courses without at least knowing what the basic tools are and how to find them. 

All three surveys (weather, waves, and currents) take advantage of viewing forecasts or actual data in GRIB format using dedicated GRIB viewing software or a navigation program with that functionality. A discussion of those programs and sources of GRIB formatted data are in the Weather Survey, so that one is needed to understand the Currents Survey and Waves Survey.


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We have a page dedicated to ocean and coastal currents at http://www.starpath.com/currents.  It is extensive, but not well organized as an introduction, and it covers more than we need now. So we make this list.

Climatic averages

(1) Climatic ocean currents are given on pilot charts, which you can download from links at  http://www.starpath.com/navpubs, monthly by ocean. 

http://www.opencpn.org offers these charts as RNC echarts that can be loaded in any nav program. )

Pilot charts are historically the mariners first guess of what current to expect. 

(2) A survey of the various global current patterns in given in Bowditch (starpath.com/navpubs)

(3) A short pictorial description is at http://www.srh.noaa.gov/jetstream/ocean/currents_max.html

(4) for more detail on each system see http://oceancurrents.rsmas.miami.edu


Live Current Forecasts

There are several models that do global ocean current forecasts, but we will stick with the most popular one RTOFS, which is likely as good as any of them.

(1) See graphic forecasts online at http://www.opc.ncep.noaa.gov/Current_fcasts.shtml  Note that this site gives NCOM as well for adjacent US waters, and they only show RTOFS for the Northern Hemisphere, but you can use RTOFS for all waters. And that is good, because the RTOFS digital data is readily available, and only special programs can access the NCOM data.

(2) You can request and view digital RTOFS current forecasts in Zygrib, LuckGrib, OpenCPN, and other programs.  Most ECS, and indeed most ECDIS programs will display this data. For the ECDIS apps you may have to provide the data yourself, see (3) below.

(3) The data are also available directly from saildocs (see Weather Survey). For example, you would send this email to query@saildocs.com

send RTOFS:34N,43N,77W,68W|0.08,0.08|0,3..72|CUR,WTMP

This gets you the currents and seawater temps in 3-hr steps out to 72 hr, for the lat-lon box indicated. the 0.08 part is a fixed notation for the resolution.  See saildocs.com for more specs. You can request and get this file now, but you need a grib viewer to see it.  if using Zygrib or LuckGrib you can ask for this from within the program and do not need this external email.

(4) To view historic images and animations of global currents see this comprehensive Navy Link.


Generally this link will require you to give your browser permission, so say yes every where, then you have a real encyclopedia of currents around the world.

Live coastal current measurements

(1) See the HF radar data coordinated at this link: http://cordc.ucsd.edu/projects/mapping/maps/

These installations are mostly in US coastal waters, but there are a few stations overseas as well.


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For those who do not have time for our full Marine Weather Course, we have available our textbook Modern Marine Weather  and our Weather Workbook for study on your own.






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