52

Fig.  6.14.1.  Route  of  the  depression  from  00  UTC  on  7  April  to  00  UTC  on  10  April  1995;
pressure  pattern  and  wind  field  over  the  Baltic  Sea  on  8  April  1995,  06  UTC
The  steep  gradient  weakened  only  slowly  in  the  course  of  9  April  as  the  low  was  slowly  filling
within  24  hours,  from  03  UTC  on  8  April  to  03  UTC  on  9  April,  while  it  retreated  to  Lithuania,
northeastern  Poland  and  Western  Bielorussia,  from  where  its  path  backed  NE  -  N.  In  the  late
hours  of  9  April,  the  low  was  still  well  recognisable  near  Lake  Ladoga  (993  hPa),  from  where
it  travelled  north-northwest  across  Finland.  During  its  retreat,  the  depression  left  an
elongated  trough,  so  that  the  isobars  over  the  Baltic  Sea  retained  their  north-south  direction.
As  the  above  pressure  pattern  developed  on  7  April,  the  wind,  which  initially  had  been
blowing  from  westerly  directions  with  5-7  Bft  and  later  SW  with  6-8  Bft,  veered  W  -  NW  in  the
afternoon  (in  the  eastern  and  central  areas  at  first)  and  increased  to  7-9  Bft.  On  8  April,
northerly  and  northwesterly  winds  continued  to  blow  over  the  western,  southern  and
southeastern  Baltic  Sea,  whereas  over  the  central  and  northern  Baltic  N  -  NE  wind  directions
prevailed.  The  wind  speed  in  the  area  varied  between  7  and  9  Bft,  reaching  10  Bft  in  gusts.
The  wind  did  not  begin  to  abate  until  the  late  hours  of  8  April,  when  the  storm  centre  moved
slowly  towards  Bielorussia.
Hydrological  response  of  the  sea  level
The  surge  generated  by  the  meteorological  situation  described  above  overlapped  the  already
comparatively  high  (520-540  cm)  water  levels  on  the  coasts.  The  surge  rose  relatively
uniformly,  beginning  in  the  central  area  of  the  coast,  but  culmination  was  reached  nearly
simultaneously  (about  17  UTC  on  8  April)  on  the  entire  coast.  Maximum  water  levels  ranged
from  608  cm  in  Sassnitz  to  629  cm  in  Wismar.  The  mean  rate  of  increase  slightly  exceeded  6
cm/h  in  Wismar  and  Warnemünde,  and  3  cm/h  in  Swinoujscie  and  Kotobrzeg  (Fig.  6.14.2.).
The  high  water  levels  persisted  for  a  long  time:  the  warning  levels  were  maintained  for  12-25
hours.
In  relation  to  the  reference  level  indicator  (541  cm  on  7  April),  the  surge  lasted  from  27  hours
in  Wismar  and  Warnemünde  to  54  hours  in  Kotobrzeg.