56

Negative  Surges  in  the  Southern  Baltic  Sea

December  1999

Wismar  —•—Warnemünde  Sassnitz  ■»  Swinoujscie  —  —  Kotobrzeg  MSL
Fig.  5.16.  e  Variations  of  sea  level  decrease  during  the  storm  of  6-7  December  1999

5.17.  November  2001
Meteorological  situation
On  the  days  preceding  the  surge,  as  northwesterly ­
  air  flow  prevailed  over  the  Baltic  Sea,  a  depression ­
  developed  near  the  southeast  coast  of
Greenland.  Initially  tracking  east,  the  low  pressure ­
  centre  then  moved  quickly  southeastward
toward  northern  Norway.
It  then  tracked  across  the  northern  part  of  the
Gulf  of  Bothnia  and  central  Finland,  which  it  left
late  on  15  November.  Continuing  in  southeastern
direction,  the  low  pressure  centre  crossed  Lake
Ladoga,  filling  in  the  area  southeast  of  this  basin
around  noon  on  16  November.
As  the  pressure  trough  associated  with  this  centre ­
  moved  across  Scandinavia  and  the  Baltic
Sea,  the  moderate  northerly  winds  prevailing  in
the  western  Baltic  backed  west,  then  southwest,
as  wind  speeds  increased.  Early  on  15  November, ­
  winds  reached  7  Bft  in  the  entire  Baltic  Sea
region  and  soon  increased  to  8-9  Bft.  Between
14  and  22  UTC  on  15  November,  the  cold  front
crossed  the  southern  Baltic  coast,  first  in  the
east,  and  about  9  hours  later  in  the  west.  Behind

the  cold  front,  winds  veered  northwest  in  onshore ­
  directions,  calming  only  over  the  western
and  partly  over  the  southern  Baltic  Sea,  while  the
central,  northern  and  eastern  regions  of  the  Baltic ­
  remained  under  the  influence  of  stormy  northerly ­
  winds  (Fig.  5.17.  a).
Hydrological  response  of  sea  level
When  early  on  15  November  the  low  pressure
trough  was  moving  southeast,  the  stormy  winds
backed  in  offshore  directions,  causing  sea  levels
to  fall  gradually  and  nearly  simultaneously  along
the  whole  southern  coast,  first  at  the  easternmost ­
  water  gauges.
Thus,  the  minimum  value  at  Kotobrzeg  was
456  cm  at  about  15  UTC,  at  Swinoujscie  421  cm,
and  at  Sassnitz  407  cm,  both  around  18  UTC.  At
Warnemunde,  396  cm  was  measured  at  about
20  UTC,  and  at  Wismar  365  cm  at  21  UTC
(Fig.  5.17.  b).