© LEGMA, 2006

LATVIAN ENVIRONMENT, GEOLOGY ANDMETEOROLOGY AGENCY

Latvian Environment, Geology and Meteorology

Agency (LEGMA)

Maskavas street, 165,

Riga, LV-1019,

Latvia

Phone: +371 67032600

Fax: +371 67145154

www.lvgma.gov.lv

© LEGMA, 2006

LATVIAN

ENVIRONMENT, GEOLOGY AND

METEOROLOGY AGENCY

TYPICAL SYNOPTIC SITUATIONS CAUSING

EXTREMELY HIGH WATER LEVELS ALONG

THE LATVIAN COAST OF THE BALTIC SEA

AND IN THE GULF OF RIGA.

Alona Kuduresenior forecaster

LEGMA, Forecast Division

April 27-29, 2009

Delft, Netherlands

© LEGMA, 2006

LATVIAN ENVIRONMENT, GEOLOGY ANDMETEOROLOGY AGENCY

Samples of surges near Latvian coasts

Alona Kudure

senior forecaster

LEGMA, Forecast Division

MSOffice1

MSOffice2

In Latvia, regular water level monitoring since 1875.

7 marine stations - in the Gulf of Riga and 3- along the eastern coast of the Baltic Sea.

In 1996-2001 the stations were equipped with automatic sensors.

Maximum water levels at Latvian stations in

period 1947-2008.max water level, cm month, year period of observation

Daugavgriva +214 2 Nov 1969 from 1875

Andrejosta

(port Riga)

+229 2 Nov 1969 from 1930

Jurmala (RGS) +208 2 Nov 1969 from 1949

Salacgriva +228 2 Nov 1969 from 1929

Skulte +247 2 Nov 1969 from 1940

Mersrags +183 2 Nov 1969 from 1929

Roja +160 18 Oct 1967 from 1933

Kolka +134 18 Oct 1967 from 1884

Ventspils +148 18 Oct 1967 from 1887

Pavilosta +169 18 Oct 1967 from 1930

Liepaja +174 18 Oct 1967 from 1891

Frequency of water level heights, ports of

Riga and Ventspils

• Statistical analysis of surges implied water level data sets from the ports of Riga (exceeding +100 cm) and Ventspils (exceeding +60 cm) for the period 1961- 2008.

• Highest frequency have shown water levels of +60 to +80 cm.

• Storm surges above +100 cm for Ventspils, and above +140 cm for Riga ( “yellow level”) - 6-12 %.

• Extremely high surges of over +170 cm in Riga and +140 cm in Ventspils ( “orange level”) - less than 3 %. These surges cause maximum damages.

Monthly distribution of surges and wind

speed > 15 m/s

Maximum number of surges - in the autumn-winter period

0,0

5,0

10,0

15,0

20,0

25,0

30,0

35,0

40,0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Ventspils

Riga

wind

Number of days with the water level of more than

+60 cm in Ventspils and +100 cm in Riga.

• Frequency and the duration of storm surges have increased in the years 1961-2008.

• -Maximum number of surges was reported in 1990, 1983, 2002 and 2007. This is connected with a high cyclonic activity over the North Atlantic.

Synoptic situations promoting storm

surges

Extremely high water levels have been observed when cyclones moved close to

trajectory 1 or between trajectories 1 and 2.

-movement of a deep low over the Baltic Sea-the interaction of meteorological factors: atmospheric pressure and the wind, influences the water level in the sea.

Statistical analysis 1961-2008:

- 218 flood events above + 100 cm for Riga - 247 events above +60 cm for Ventspils- 30 episodes of extremely high water rising of above +140 cm have taken tolls in property.

Synoptic situations promoting storm surges

• The so-called "diving" north-western cyclones (trajectory 6) can also cause water level to rapidly increase, especially in the southern part of the Gulf of Riga.

• With a deep southern cyclone, the water level also rises ( up to +110…+120 cm).

• But both cases have been reported in only 8-10%.

In most of cases storm surges were

associated with western cyclones.

At low initial water levels, storm

surges began when a deep cyclone

moved from the southwest.

Floods usually are influenced by

W, SW, NW winds.

Synoptic parametres during storm surges.

• Water level in Ventspils peaked when the cyclone was passing its longitude.

• Atmospheric pressure of 955-980 mb prevailed

• in the centre of the cyclone during the peak of flood

• and during the intensive water level rise.

• Storm surges could be influenced by a less deep low

• when its center pass close to Ventspils or a bit to the north.

• In intensive rising water level and at its maximum, the baric

• gradient was 17-22 mb/500 km. In extremely high floods, it

• reached 24-27 mb /500 km ( January 9, 2005 and January 14-15, 2007).

• In changing of the wind for the north-westerly direction, in the southern part of the gulf and thereby in the port of Riga there is an abrupt rise of water level.

Trend of maximum water level +8 cm

Trend of average water level +5 cm

Maximum frequency of water level rising phase is 12-20 hours.Peak of storm surges - 2-4 hours

The empirical dependences are rather reliable in the cases when the wind of certain direction has had the whole possible length of fetch.

Water level forecasts in LEGMA

Intensity of water level rising in

Daugavgriva (NW wind)

Water level, cm/hour

Wind, m/s

20

80

6

40

cm

60

10

70

50

30

128 10

15

20

25

2 4

10

0

A high accuracy forecast of the cyclone’s evolution, its trajectory and barical

gradient are necessary as well.

Regression curves

Maximum water level in Daugavgriva Delay of maximum in Daugavgriva

50

100

NW

0

Water level in Ventspils, cm

50 100 150

SWNW after SW and W

200

Water level in

Daugavgriva, cm

W

50

100

Water level in Ventspils, cm

Hours

W

0 510

15

NW

SW

SSW

Floods January 9, 2005 and January 14-15, 2007

Maximum water level:

in Ventspils +132 cm, in Daugavgriva +208 cm

LATVIJAS

VIDES, ĂEOLOĂIJAS UN

METEOROLOĂIJAS AĂENTŪRA

ATLANTIJAS CIKLONS, KAS IZRAISĪJA

VIESUěVĒTRU LATVIJĀ 8.-9.JANVĀRĪ

Despite the fact that an absolute maximum of

+229 cm was not reached, water level in Riga

( Andrejosta) rose up to a very dangerous point +214 cm.

Flood in January 9, 2005 has caused damage

of about 20 million Euros.

© LEGMA, 2006

LATVIAN ENVIRONMENT, GEOLOGY AND

METEOROLOGY AGENCY

Flood January 9, 2005.

Autors: S. Preinberga

© LEGMA, 2006

LATVIAN ENVIRONMENT, GEOLOGY ANDMETEOROLOGY AGENCY

Latvian Environment, Geology and Meteorology

Agency (LEGMA)

THANK YOU FOR ATTENTION !

www.lvgma.gov.lv