Forecasting Material and Methods

Fronts

"First of all we have a look into the overall weather situation. A very convinient tool for this is the SatRep (Satellite Report) which shows an analysis of the cloud features in terms of conceptual models and relates them to relevant numerical parameters."

This is the IR image of the frontal system at 18 May 06/06 UTC.

It shows a well developed cloud spiral north, northwest of Scotland and the cloud band of a cold front from Germany across France to Spain. At its rearward cloud boundary a typical wave bulge can be seen in the Bay of Biscay. Cloud fields over Switzerland, North Italy and Austria belong typically to a warm front and warm sector.

This is the IR image superimposed by the Satrep

The names refer to the relevant conceptual models which are represented by the cloud features. In this case the following conceptual models are of special interest: occlusion (OCCL), the Cold front (CF), the warm front (WF shield) and the warm sector (THR cloud) and the wave (Upper Wave).

This is the IR image superimposed by the height contours at 1000 hPa (red) and at 500 hPa (green)

There is a trough in the contourlines of 1000hPa in the area of the cloud band which indicates the cold front close to the surface. The contour lines at 500 hPa show a strong SW stream over the cold front cloud band and a trough far behind the cloud system.

This is the IR image superimposed by the Thermal Front Parameter TFP (blue), the thickness contours (green) and the field of warm advection (red)

In the cloud part extending from Spain to Denmark there is a distinct gradient of thickness within and behind the cloud band and a TFP within the cloud band. A warm advection maximum over South France is connected to the wave development.

This is the IR image superimposed by the lines of equivalent potential temperature at 850 hPa (red)

In the cloud part extending from Spain to Denmark there is a distinct gradient within and at the rear side of the cold front cloud band and a distinct ridge area at the leading edge of the frontal cloud band from Spain to Switzerland.

This is the IR image superimposed by the lines of the Showalter index (yellow and magenta)

Behind the frontal cloud band over the Atlantic stable values exist while the area at the leading edge from Spain across Switzerland to S-Germany show very unstable values. The cold front cloud band is a transition area with growing instability from west to east.

This is the IR image superimposed by the Thermal Front Parameter (TFP) (blue) and the zeroline of shear vorticity at 300 hPa (yellow)

In the cloud part extending from Spain to Denmark the zeroline of shear vorticity representing the jet axis is at the rearward edge of the cloud band and parallel to it. This is indicative of an Anafront cold front type. Only in the geographical latitude of Denmark the jet starts to cross the cloud band.

This is the IR image superimposed by the isolines of isotachs (yellow) and the Positive Vorticity Advection (PVA) (violett) both at 300 hPa

In the cloud part extending from Spain to Denmark there is a strong jet streak between Spain and Denmark and consequently a maximum of PVA in the left exit region of this jet streak between Denmark and Southern Norway.

This is the IR image at 06 UTC superimposed by the position of the Thermal Front Parameter (TFP) at 06 (yellow) and forecasted for 12 (green) and for 18 (blue)

Looking at about 48 degrees latitude the TFP moves from France eastward to Switzerland during the 12 hours between 06 and 18.

This is the IR image at 06 UTC superimposed by the position of the isolines of the Showalterindex at 06 (yellow) and forecasted for 12 (green) and for 18 (blue)

Looking at the leading side of the frontal cloud band where the strongest instability exists there is an eastward movement of this area but much weaker as the eastward movement of the TFP.

"Let us continue investigating fronts. Follow this link to go on!"

EUMeTrain: Nowcasting CAL Module - Basic Nowcasting

Fronts