28 
Negative Surges in the Southern Baltic Sea 
By far the major part, 83.6 %, of all negative 
surge events during the period 1955-2005 co 
occurred with the zonal group. 32.5 % occurred 
during the West Cyclonic pattern Wz (Fig. 4.4. a), 
and 14.8% together with the Central European 
Ridge, BM. The third most important atmos 
pheric type is NWz with about 10 %, the other 
zonal and mixed situations showed co-occur 
rence with low sea levels of 6 % or lower. 
50 
45 - 
40 
35 
Q) 30 
> 
a> 
« 
<o 
W 25 
o 
>■ 
I 20 - 
15 -- 
10 
BM -14,8% 
Wa 
West Anticyclonic 
Wz 
West Cyclonic 
WS 
Southern West 
WW 
Angleformed West 
SWa 
South-West Anticyclonic 
SWz 
South-West Cyclonic 
NWa 
North-West Anticyclonic 
NWz 
North-West Cyclonic 
HM 
Central European High 
BM 
Central European Ridge 
TM 
Central European Low 
Na 
North Anticyclonic 
Nz 
North Cyclonic 
HNa 
North Iceland High Anticyclonic 
HNz 
North Iceland High Cyclonic 
HB 
British Isles High 
TrM 
Central European Trough 
NEa 
North-East Anticyclonic 
NEz 
North-East Cyclonic 
HFa 
Fennoscandian High Anticyclonic 
HFz 
Fennoscandian High Cyclonic 
HNFa 
Norwegian Sea - Fennoscandian High Anticyclonic 
HNFz 
Norwegian Sea - Fennoscandian High Cyclonic 
SEa 
South-East Anticyclonic 
SEz 
South-East Cyclonic 
Sa 
South Anticyclonic 
Sz 
South Cyclonic 
TB 
British Isles Low 
TrW 
Western European Trough 
U 
Unclassifiable 
Wa Wz WS WW SWa SWz NWa NWz HM BM TM Na Nz HNa HNz HB TrM NEa NEz HFa HFz HNFa HNFz SEa SEz Sa Sz TB TrW U 
Atmospheric situation type 
Fig. 4.4. a Co-occurrence frequency of particular atmospheric situations and negative surge events £440 cm 
at the southern Baltic Sea coast, 1955-2005 (in the inner frame: symbols and specification of atmospheric situations 
over Europe, according to G. Hess and H. Brezowski) 
Wz - West Cyclonic 
Fig. 4.4. b Atmospheric situation Wz (West Cyclonic), which causes most of the negative surges on the 
southern Baltic Sea coast (average surface level pressure anomaly chart, after G. Cawley)