If you are regularly traveling around a fixed location, you might want a five day forecast for that position. But vessels under way do not need a five day prediction for the place they just left. The passage forecast is a system that provides predictions for the places you expect to be in the future. A message gets sent to the passage-responder with five set of lat/long points. The points represent your current position and where you expect to be over the next 4 days. Returned is a valuable look into the future weather of your passage.

The graphic shows how you can use the forecast to help plan a passage to Hawaii from Los Angeles. A program like Visual Passage Planner can make finding the points you need easy by providing estimated daily position along the route. The points shown are what you would use the day you left LA. Or if you were deciding if you want to leave.

If you were leaving June 24, 2002, this is what you would have been looking forward to:

		BUOYWEATHER.COM Marine Voyage Forecast  
  Cycle    : 20020624 t12z              
  Time Zone: GMT - 7 hours              
  Current Location : 34.0N  -119.0W     
-------------------------------------------------------
                    WIND                  SEAS
             dir/deg  range(kt)   dir/per   range(ft)
             ------------------   -------------------
6/24  11am   WSW 231   3 -  4     WNW  7sec   3 -  6
6/24   5pm   WSW 256  10 - 14       W 12sec   3 -  5
6/24  11pm    NW 319   8 - 11       W 12sec   3 -  5
6/25   5am   NNE  13   1 -  2     WNW 11sec   3 -  5


		24hr position forecast for : 33.5N  -122.0W
-------------------------------------------------------
                    WIND                  SEAS
             dir/deg  range(kt)   dir/per   range(ft)
             ------------------   -------------------
6/25  11am    NW 322  13 - 18      NW  7sec   7 - 11
6/25   5pm    NW 315  16 - 22      NW  8sec   7 - 11
6/25  11pm    NW 317  16 - 21      NW  7sec   7 - 11
6/26   5am    NW 319  17 - 23      NW  6sec   7 - 11


		48hr position forecast at : 33.0N  -124.75W
-------------------------------------------------------
                    WIND                  SEAS
             dir/deg  range(kt)   dir/per   range(ft)
             ------------------   -------------------
6/26  11am    NW 325  11 - 15     NNW  6sec   5 -  8
6/26   5pm    NW 319  13 - 18       N  6sec   5 -  8
6/26  11pm   NNW 330  13 - 18     WNW 10sec   5 -  9
6/27   5am    NW 328  12 - 17     WNW  9sec   5 -  9


		72hr position forecast at : 32.25N  -128.5W
-------------------------------------------------------
                    WIND                  SEAS
             dir/deg  range(kt)   dir/per   range(ft)
             ------------------   -------------------
6/27  11am   NNW 343   7 -  9     WNW  9sec   5 -  8
6/27   5pm    NW 320   7 -  9     WNW 12sec   5 -  8
6/27  11pm    NW 326   9 - 13     WNW 11sec   5 -  9
6/28   5am   WNW 296   7 - 10     WNW 10sec   5 -  8


		96hr position forecast at : 31.5N  -132.0W
-------------------------------------------------------
                    WIND                  SEAS
             dir/deg  range(kt)   dir/per   range(ft)
             ------------------   -------------------
6/28  11am     W 271   4 -  6     WNW 10sec   5 -  8
6/28   5pm   WNW 293   7 -  9     WNW  9sec   5 -  8
6/28  11pm   WNW 304   5 -  7     WNW  9sec   5 -  8
6/29   5am   WNW 295   4 -  5     WNW  9sec   4 -  7

Passage forecast requests are sent to this email:

voyage@buoyweather.com

You can leave the message subject line blank. Here is the format:

Each day along the passage, a new forecast should be requested reflecting the new current position and expected future positions.

Line 2 - This is your username. The same username you use to access your Pro account online. The program will check to make sure you have an account with credits left before the data gets sent. Your password will not work here. Make sure it is your username which is probably an email address.

Line 3 - The email address you want the data sent to. You are welcome to send data to a friend. Any email address is acceptable. Just make sure there is no typo! Everyday, someone makes the mistake of entering their own email incorrectly.

Line 4- Select the grib file. Valid inputs are “nww3”, “wna”, “enp”, "med", or "gfs". nww3 is the global 1.25 X 1.0 file which is most often used. See the about WAVEWATCHIII section for which file to use. It is important that this is correct! If you use the wna or enp setting and any of your points are outside their domain, you will get an error message instead of a forecast. You may also find this more useful in some tropical regions where a convective analysis may be more important than wave height data.

Line 5 - You can adjust the time on the report to local time by entering the hours from GMT. Enter a 0 if you want the forecast report in GMT. Enter 8 if you want it for Singapore (i.e. 8 hours later than GMT) or -4 if you want it for Peru (i.e. 4 hours earlier than GMT). Never put a plus sign. "+8" for example will cause an error.

The next five lines each contain a latitude and a longitude separated by at least one space. The space between the lat & long is very important. Without it, the forecast will come back corrupt. The five sets of lat/long must be in every request. If you are due in port in 2 days, just repeat the final destination’s lat/long until you have exactly five lat/long sets.

When you are in the western hemisphere, enter the longitude as a negative like the sample above. The program will round off to the nearest longitude model grid point depending on which grib file you choose. Do not put a plus sign for eastern longitudes! Just a number.

Finding points near land can be tricky. There are points on the grid that are over water, which are not covered by the model. If you are coastal cruising, we strongly suggest that you plan ahead and find the near land points you will need using the online data browser before departing.