Seaclub.lv also recommends:

http://www.windguru.cz

Other resources about weather forecasts:

http://latvian.wunderground.com                       (international)
http://weather.yahoo.com/regional/EUROPEX.html    (international)
http://www.ilm.ee                                       (EST)
http://www.emhi.ee                                     (EST)
http://www.meteoblue.ch                            (international)