NWCSAF: Meteosat IR10.8 with ASII NWP overlay

Up till this point the products of the NWC SAF thus seen only identified and characterised the areas in the cloudfree regions. Two products that identify and characterise clouds are ASII and ASII-NWP. Where ASII-NWP stands for Automatic Satellite Image Interpretation. Where the data from MSG SEVIRI satellite are supplemented by typical key parameters from the numerical model output of ECMWF

The basic concept of ASII-NWP is the identification of:

• Detection of frontal areas
• Detection of S-shaped lines
• Detection of circular-shaped cells
• Detection of narrow cloud fibres
• Detection of black stripes in WV images
• Detection of spiral cloud structures

A segmentation divides the IR and WV satellite images into sub-regions being coherent in terms of brightness and texture. The classification process assignes qualities of different conceptual models to these coherent areas using both SEVIRI as well as NWP. At 0630UTC the convection over Austria, Czech Republic and Poland has not started but concentrating on the frontal system on which the convection starts some interesting thing can be identified. The front is marked by c, • , w, m and ~ . Where

• c stands for Cold Front
• w denotes the Warm Front cloudiness
• ul indicates an upper level low.
• ~ is the sign for a developing wave on the cyclonic side of the frontal band.

In the next few hours not much changes within the forntal system. The move slowly moves northward along the frontal band. The c changes colour to c indicating the warm air advection derived from the model. South of the Alps and north of the Pyrenees lee clouds are embedded, indicated by >l. At 1130UTC ASII-NWP recognises the convective cells and indicates them as developing cb’s.