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
Weather4D makes it easy to create and send your request. Iridium | Products | Iridium AxcessPoint
Size: 173.7 KB
ID: 82037" style="margin: 2px" />
Size: 175.6 KB
ID: 82038" style="margin: 2px" />
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
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.