Météo-France Sandwich product:a version tailored to the needs of all French users

Since September 26, 2024, Météo-France has been producing and making available to forecasters around 50 products derived from FCI and LI data. The newest ones are proving very successful. But popularity does not lie just in novelty.

The Sandwich product, already well known for many years, has become one of the flagship products used by forecasters. It was not distributed with MSG at Météo-France, taking its applications into account was a real eye-opener. The 500 m resolution adds great value, with a significantly increased amount of information when it comes to convective situations.

This product makes it possible to observe cloud top features, with a level of detail never seen before with a geostationary satellite at 0° position. These features can be linked to the occurrence of dangerous phenomena, such as severe gusts or large hail. While cloud top features were already well known to forecasters, partly because they were already visible with MSG, others proved to be more novel, as they had been little or not at all observed until then.

A skills upgrade is underway within the forecasting community, particularly at Météo-France, through MTG training courses. Identifying these storm systems is crucial for forecasters, who can then alert the relevant authorities in real time to the likelihood of severe weather.

Due to Météo-France's territorial presence in several overseas territories and the needs of the armed forces and civil security services, the Sandwich product had to be adapted so that it could remain usable on the entire FCI disk.

In literature, colour usually ranges only account for temperatures up to - 70 °C. The colour does not change beyond this value, which results in a loss of information about the temperature at the top of the coldest clouds. The colour palette has therefore been tuned for such very cold clouds frequently encountered in tropical latitudes, while remaining consistent with experts and community standards.

In addition, a new feature has been implemented: a night-time version, with infrared channel 10.5 taking over the visible channel as the background image. The result is a complete, smooth product, with consistent images between day and night, and a seamless transition between the two. Cloud top features have indeed specific thermal signatures, including at night.

Thus, after extensive consultation with users, a finalized and complete version of the Sandwich product was introduced at Météo-France.