Weather4D still makes greater finesse

With the basic 1.3.3 and PRO versions 1.3.9 delivered last November, Weather4D had replaced the GRIB files fine grid from Great Circle by its own files based on the U.S. model WRF (¹), computed under his own steam. These files cover Europe, Greece, Canaria, Azores, Greater and Lesser Antilles, offer a resolution of 0.1° (6 NM) up to 96 hours by 1 hour steps. The data provided is the same as the GFS model (¹). At the same time, The annual subscription price has been reduced by 60 down to 30 €.

Thanks to the implementation of new means, the next updates that have just been submitted to Apple Store will provide even more details. Olivier Bouyssou explains :

« FYI, App4Nav uses 6 different servers, 2 for the calculation of WRF model and 4 for distributing GRIBs : 2 for the US+Asia region and 2 for Europe. At this time 8000 GRIBs are distributed per day and triple during the season… ”

This now enables to provide, for the French coasts, including Corsica, ultra-fine grid to 0.04 °, that to say 2,4 NM. It also adds to the GFS and WRF files new data evaluating wind gusts.

The WRF France model

With a resolution of 2,4 nautical miles (Latitude) Grid provides extremely tight data that will delight sailors along the shores.

Grid points spaced 2,4 MN in latitude and 1,6 MN in longitude (at the latitude of Cherbourg)

This weather network, added to the high-resolution current predictions provided by MyOcean (IBI model 1/36 ° either 1,7 NM) allows, with Weather4D PRO, a relatively small trip routing, as in the example in the Bay of Quiberon below :

Theoretical route prepared in iNavX

Routing done in W4D PRO from the imported route

Optimized route exported in iNavX ready to activate

It also allows for basic version users to have hourly coastal forecast (Winds, currents and waves) high precision, with high-level graphical display .

Wind strength and gusts

Experience has shown that the wind strength predicted in the GRIB files of the GFS and WRF models is often lower than the observed reality, especially above 25-30 knots. One method used by meteorologists is to predict the wind speeds of the atmospheric pressure surface 925 mb. At the average altitude of this pressure, environ 750 meters high, The wind is stronger than at ground level due to less friction. Ground gusts are often close to the average to 925 mb. In connection with these data a parameter Gusts is now available in GFS and WRF models, the values of which are used by Weather4D in addition to the wind speed at 10 meters high. These gusts values ​​are represented in meteograms text and graphics that are displayed for the activated target (Basic Version) and for ship positions in the Routes function (PRO version).

In darker blue, the gust curve and on the right, the two values : Ground wind/gusts.

In light blue the wind speed curve at sea level (10 meters high) and darker blue gusts speed giving a good risk assessment.

These improvements provide users with a new scale of accuracy in preparing for navigation, in regattas and cruising.

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(¹) See the entry "Forecast Models" in the Glossary.
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