Most severe negative surges on the southern Baltic Sea coast 
53 
5.16. December 1999 
Meteorological situation 
At the end of November, as a stationary anticy 
clone was centred over southern Europe, a suc 
cession of low pressure centres travelled across 
northern Europe. This provoked very strong 
winds in the northern Baltic Sea region which 
calmed only temporarily. 
On 1 December, one of the depressions moved 
eastward across central Scandinavia and the 
Gulf of Bothnia, deepening rapidly, with 953 hPa 
measured in its centre when it reached Finland at 
09 UTC. The depression continued tracking 
toward the White Sea, filling. The low pressure 
trough with its associated fronts provoked a 
southerly to southwesterly storm as early as the 
night of 30 November. Wind force reached more 
than 8 Bft. In the afternoon of 1 December, winds 
behind the cold front veered west to northwest 
and became increasingly gusty (Fig. 5.16. a). On 
2 December and in the morning of 3 December, 
winds backed and calmed to 7-5 Bft. In the 
meantime, however, another active depression, 
with 995 hPa in its centre, appeared northwest of 
Ireland after midnight on 3 December. Moving 
quickly east across Scotland and the North Sea, 
the depression, now with an atmospheric pres 
sure of 953 hPa, entered the Skagerrak at 
21 UTC on 3 December. The centre slowed over 
Denmark and stopped, deepening, then contin 
ued across southern Sweden and the Baltic Sea. 
It did not begin to fill until it reached the Latvian 
coast on 4 December, at 06 UTC, continuing on 
its eastward track (Fig. 5.16. b). 
Along its whole track across the North Sea, 
Scandinavia and the Baltic Sea, the depression 
was accompanied by hurricane-like winds. The 
passage of the frontal system resulted in a S-SW 
storm. After the cold front had passed toward 
noon on 4 December, the storm veered west, 
then northwest, increasing considerably in gusti 
ness. The intensity of the storm in the whole 
southwestern area of the Baltic Sea, from the 
Sounds to the coasts of Kotobrzeg, reached and 
at times exceeded 9 to 10 Bft. In the eastern part 
of the coast the storm was less violent. It was not 
until the late hours of 4 December that the storm 
calmed down slowly. 
On 5 December, moderate westerly winds be 
coming later variable prevailed over the Baltic 
Sea. On 6 December, another large low pressure 
trough approached from the British Isles. Early 
on 6 December, the winds backed southwest 
and increased to 8-9 Bft, reaching 10 Bft in gusts 
and dominating the entire Baltic Sea region. 
Around midnight on 7 December, the winds 
calmed down, veering slowly (Fig. 5.16. c). 
Hydrological response of sea level 
Towards the end of November, water levels oscil 
lated around the mean values in the western part 
of the Baltic Sea coast. Levels began to de 
crease in the afternoon of 30 November due to 
strong offshore winds. Water levels remained at 
their minimum until the morning hours of 
1 December, when the wind veered onshore and 
decreased. The minimum water levels were first 
reached in the eastern sections of the coast: 
416 cm in Kotobrzeg between 02 and 06 UTC, 
385 cm in Swinoujscie around 08 UTC, 377 cm 
at Sassnitz around 03 UTC, 359 cm at 
Warnemünde between 9 and 10 UTC, and 332 cm 
at Wismar around 09 UTC. 
Even deeper minima were forced by the storm of 
3 and 4 December. In the western part of the 
coast, water levels began to fall earlier than in the 
east because the hurricane-like offshore winds 
continued for a longer time over the western Bal 
tic Sea. As usual, deeper minima were recorded 
by the westernmost gauges: 309 cm and 333 cm 
in Wismar and Warnemünde, respectively, bet 
ween 9 and 10 UTC, 364 cm at Sassnitz, and 
379 cm at Swinoujscie between 7 and 8 UTC. In 
Kotobrzeg, where the wind was less severe and 
veered first, the minimum of 456 cm was reached 
between 5 and 6 UTC. 
Those two very deep drops of sea levels were 
followed by a third one hardly two days later. 
When the moderate westerly winds, which 
calmed down and became variable later on 5 De 
cember, backed again southwest in the morning 
of 6 December and increased to 8-9 Bft, sea lev 
els responded immediately and began to fall to 
ward noon on 6 December. Minima were reached 
between 18 UTC on 6 and 02 UTC on 7 Decem 
ber. The lowest value in Wismar was close to 
380 cm, and the level in Warnemünde was just 
below 400 cm. The other gauges recorded water 
levels between 415 cm and 450 cm. The com 
pensating increase which followed was assisted 
by a slight veering of the wind.