Are GRIB files consistently optimistic ?

This question has been asked regularly, but until now I had never wanted to publicly give my opinion on the subject so as not to offend anyone and especially not to create unnecessary controversy. But by dint of doing it during my training, why not express it openly ?

My opinion, forged by observation and a long professional experience in pleasure boating (¹), is that this assertion of the systematic optimism of the GRIB forecasts regarding wind force, which unfortunately continues, no longer has a reason to be, and has not been verified in fact for some time. Read more …

Alternative weather models

For several years, forecast files in GRIB format have been widely used in meteorological applications.. The majority of forecast models have been made freely available by the meteorological services, all countries included. Applications like XyGrib, LuckGrib, SailGrib, Weather4D and others, offer a selection of atmospheric and oceanic models, up to 25 weather models and 15 wave and current models for Weather4D in example. But there are always others that can usefully complement the standard offerings of these applications.. Read more …

Predict thunderstorms with Weather4D


In Weather4D (all versions) most weather models provide a data calledCAPE.

Convective Available Potential Energy, in French : Energie potentielle de convection disponible. Behind this abstruse acronym hides a powerful tool for forecasting thunderstorms. The CAPE is measured in joules per kilogram of air (J / Kg) and defines the vertical thrust energy of a hot air particle in a colder atmosphere. In other words, vertical acceleration of the air particle will be directly related to this energy measurement. Read more …

Reading : "Clouds and other meteors" Météo-France

In an article updated in August 2020 (¹), I have described nautical books in digital format that can be usefully saved on iPad in the Apple Books app. Among them I mentioned the works of Météo-France available in PDF format for free download from their documentary portal.

In the “Courses and Manual” section of this site, we can download a new book, published 2020, entitled "Meteorological Observations and Measurements – Tome 1 / Clouds and other meteors ", a veritable mine of information on clouds, and all associated meteorological phenomena, called "meteors" (²). Read more …

You said « Medicane » ?

Many sailors who cross the "Big Blue" have known for ages that, if the navigation is relatively easy, the weather represents a particularly difficult constraint to deal. Indeed, if the coasts are mostly clean and the dangers very localized, if the tides are almost insignificant, if the currents are to be considered only in well defined areas, the major difficulty comes from a capricious meteorology, difficult to forecast, which can represent a real danger by its changing moods, sudden, even rough. Read more …

Training onboard with ACM Catamaran [2021]

Despite the uncertainties associated with the pandemic, we can hope to be able to resume nautical training. In any case, this is the positive will displayed by my partner ACM Catamaran. In 2021 the formations Weather4D are therefore renewed and scheduled. I will supervise these training sessions " Navigate with Weather4D Routing & Navigation with iPad »In onboard weekend on one of the cruising school catamarans departing from the base ofHyères – The Gapeau. From 3 up to 6 people in a private cabin for these intensive training courses which have been very successful for several years.

The Calendar 2021. is available and registrations open for april, May and October. Read more …

Prendre la météo par téléphone satellite [2021]

Following the tutorial " Introduction to Marine Weather" , the new tutorial " Prendre la météo par téléphone satellite "Just uploaded to the iBook Store.

A complete reworking of the originally published book in 2014, new layout, clearer and more readable in portrait mode, ful revision of the text, video update and illustrations. Read more …