looduskalender.ee

Week 15: a sunny high pressure area was replaced in the second half of the week with the ash cloud that arrived from Iceland and caused chaos in all Europe.

 

The high pressure zone stretching from the British Isles to northern Russia in the beginning of the week brought foggy nights (particularly around the islands) and sunny days to Estonia. On Monday (12.04) the maximum of the week was recorded in Pärnu and in Western Nigula: +16,3 °C. Enjoying the sun was disturbed at times by the low pressure trough with its cold front moving across Estonia on Tuesday (13.04) and Wednesday (14.04) towards southeast. It brought only little rain, but cooled the air markedly. When an edge of a high pressure area from the British Isles again spread over Estonia during Thursday night (15.04) the air temperature fell in Jõhvi to  -4,7 °C (minimum of the week). At the same timea low pressure area reigned over the northern part of Barents Sea, with its trough reaching over northern Finland and Scandinavia and moving by small steps towards east-southeast. The fact is that with the rain clouds an ash cloud also approached Estonia across the sea. It had been thrown up into the high atmosphere on 14.04 by the volcano that had been active on Iceland. Airports closed down, one after another; Estonian airports stopped activity early on Friday (16.04) morning as the first rain clouds reached north-western Estonia. During the day the trough moved on with the rain and ash clouds across Estonia towards east-southeast, and the westerly winds following it reached 12 m/s.

On Saturday night (17.04) a small high pressure ridge spread over Estonia and the weather cleared up in the morning. At the same time the next depression moved from Iceland to the north coast of Norway, and reached the Gulf of Bothnia in the evening. In Estonia the cloud cover became denser and the south and south-easterly winds gathered force up to 12-16 m/s. On Sunday night (18.04) the depression moved on to Finland and in Estonia there was rain at the southern edge of the cyclone. The wind turned westerly and increased to 18 m/s in gusts. In the morning the wind that had turned north-westerly following the cold front even brought snow slush to our north-western shore. In the south and east the rain squalls continued.

The average air temperature was mostly -2 to +3 °C at night, some rainy nights locally showed 5..6 °C. In daytime the indicator on the thermometer went up to  +8 to +14 °C , on the coasts open to winds to about +3 to +7 °C. 

 

Snow situation.

On April 15 all snow was gone from the observation sites.

 

Ice situation.

There is still some ice in the Gulf of Finland in the north-eastern corner (but not in Estonian waters); the Väinameri [between the islands and the mainland] and Pärnu Bay were free of ice this week and the icebreaker TARMO went on summer holidays. Compact ice, up to 15-20 cm thick, can still be seen in the Gulf of Riga near the Ruhnu island.

Ice on Lake Peipus has collected into the north-eastern corner, elsewhere the lake is free of ice.

 

Temperatures in inland waters.