I like to use Weather4D on an
iPad to display my GRIB files.
You can easily intergrate it with the Iridium Axxess Point which is a
WIFI attachment for your phone. Now you can place the phone and Axxess Point outside on
deck with clear view of the sky and keep you
iPad or
laptop inside.
Weather4D makes it easy to create and send your request.
Iridium | Products | Iridium AxcessPoint
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You can select which method you want to use to get your GRIB file, including Axxess Point.
The best feature on Weather4D is that you can define a
route and select a projected SOG. Then you can show
wind, waves, CAPE and other values along the
route. See the
screen shot with
wind shown in the upper graph. You can easily slide the
boat along the route and see what
weather to expect.
It also offers the option to calculate an optimized route based on your GRIB and
boat polar.
For longer passages I get 5 days at 6 or 12 hour intervals, and 1 degree resolution. I then try to get an update evry 24 hours.
I get Wind (10m), Pressure, Temperature, Precipitation, Cloud Cover, CAPE, and Waves. Near the Gulfstream I also get the
current.
On my last
delivery the owner had an Iridium phone and used a
laptop to download GRIBS using saildocs either via Iridium or via
SSB. We then used Instashare to transfer the GRIB files from the laptop to my iPad.
As a general
rule add about 10% to the wind speed - at least. The prediction is for 10m and you are measuring at 20m above sea level. Also, GRIBs tend to underpredict; often. Very helpful are the CAPE values which are an indication of squall potential. On long passages you will run into squall areas and they call for caution due to high, erratic wind speeds and directions. Maybe best to the most put experienced crew on watch then.
Here is a picture of a squall that I could not avoid on my last trip. I tried fore-reaching at about 2 knots for 1/2 hour (see upwind track), but it kept on growing to windward. I finally had to go for it. As I did, it opened up right in the middle and brought some light rain and a little more wind, but nothing too bad.
hope this helps.