Surface pressure (reduced to NN) and airmass composite, Time Sequence: 3h, 29 February to 01 March 2008     

This chapter contains a short description of the surface pressure (reduced to NN) in combination with the airmass RGB. The legend for the airmass RGB can be seen in the legend.

We will use model fields and will not consider possible model errors. We see in this image that the surface low (southwest of Iceland) is already situated north of the jet axis (transiton from purple to blue) and superimposed by high PV (purple colour). The rapid cyclogenesis has already started.

The surface low intensified (according ot the 3h-forecast of the model) by more than 5 hPa within only 3 hours.

The surface low continued intensifying. We see the split front which was near the surface trough's axis.

In the meanwhile the surface low's centre exhibited a pressure of about 965 hPa. A strong surface low trough extended to Scotland/Ireland, at a similar position as in 300 hPa. Orographic effects caused probably a short ridge over Scotland and North England.

The low continued intensifying and the trough's axis arrived over the British Islands. Near its axis we recognise a comma structure that was also connected to the upper air trough in 300 hPa.

The surface low exhibited a surface pressure of almost 960 hPa. We see a strong surface pressure gradient, especially at the west and southwest flanck.

The surface low pressure at the centre falled below 960 hPa and the storm field extended to South-England. The overruning jet can be seen over the Central Northsea. Northeast of it we find the left exit region of the jet streak (wind in 300 hPa (equivalent to positive vorticity advection)). It is likely that in that area surface pressure will decrease.

Whereas the surface low's centre did not intensify during the last 3 hours the surface pressure decreased over the eastern parts of the North Sea. We find a sharp surface trough extending from Southwest Norway to Northwest Germany.

A new surface low started to develop near the south edge of Norway yielding an increased surface pressure gradient over parts of the British Islands and Central Europe. Hints to a new trough can be seen east of the Scotish mountains (probably triggered by lee effects).

In the meanwhile the storm field covered big parts of UK, the North Sea and the northern parts of Middle Europe. A new surface low developed in the lee of Norwegian mountains that increased the surface pressure gradient over Middle Europe. Near the surface trough's axis the convective line can be seen, at a similar position as the upper air trough's axis in 300 hPa.

The surface low near Oslo intensified to less than 965 hPa. The big storm field extended from the Northeast Atlantic over the North Sea to many parts of Middle Europe. The surface trough's axis and the convective line arrived over Central Germany.

The storm field covered now almost entire Germany.

The trough's axis and the convective line arrived over the Alps. The surface low moved to Sweden and started weakening. With exception of the West parts, Germany was influenced by the storm field.

Hints to the most intense area of a storm field can be derived from the airmass RGB. In the violet to purple area and south to west of the surface low the highest wind gusts can be expected.

In the meanwhile the surface low arrived East Sweden and the storm field extended from West Norway to the Alps.

The general situation did not change significantly. The surface low and the gradient started weakening.

No significant changes occured over West, North and Central Europe. The cold front and the storm field arrived east Europe.

The storm over Germany weakened.