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Fig. 6.16.1. Pressure pattern over Europe and wind field over the Baltic Sea on 11 April 
1997, 18 UTC 
On 10 April, successive troughs of low pressure moved across Scandinavia and the Baltic 
Sea, causing a southeastward flow of warm air and an inflow of cold Arctic air in their rear. In 
front of the trough and in its southern part, a westerly gale followed by a westerly storm of 8- 
9 Bft developed over the eastern North Sea, Kattegat and the Western Baltic Sea in the 
afternoon. Around midnight and in the early hours of 11 April, wind speeds in front of the 
advancing cold front occasionally exceeded 10-11 Bft over the western basins, with 
directions backing temporarily west-southwest. The storm was less severe in the eastern 
basins of the Baltic Sea. 
Around 09 UTC on 11 April, the storm behind the cold front veered NW and reached 8 to 9 
Bft in gusts. At about 15 UTC, a secondary cold front crossed the coast, with winds veering 
NNW - N and reaching 10 Bft in gusts. In the afternoon and during the night, the winds from 
northerly directions were still gusty but decreased gradually to 7-5 Bft in the early hours of 12 
April. 
In the course of 12 April, a high pressure ridge began to develop over Scandinavia, which 
was later destroyed by a southward moving low-pressure trough on 13 April. In front of the 
warm front which crossed the southern coast at 18 UTC on 13 April and became stationary 
until 16 April, SW winds increased to about 6-7 Bft between 09 and 15 UTC on 14 April. 
Wind directions on 14 April generally veered from WSW to W - NNW, but in the central part 
of the Southern Baltic Sea they oscillated locally over a rather wide range due to squall-like 
disturbances generated in the pre-frontal zone. 
After the front had crossed the coastline at about 18 UTC on 14 April, the northerly air flow of 
force 6-7 Bft, which reached 8 Bft in gusts, established itself along the eastern edge of the 
high pressure ridge, which became stronger over Scandinavia. As the “old” quasi-stationary 
trough did not retreat (Fig. 6.16.2.), the pressure gradient zone with its northerly winds 
remained over Scandinavia and the Baltic Sea until 16 April, decreasing gradually.