WEATHER ANOMALIES IN LATVIA, 2013

The 2013 average air temperature was + 7.0ºC (1.3 degrees above the normal for the period of 1961-1990), putting it as the 15th warmest in the long term data row. In the 21st century 2013 was the 6th warmest (Fig.1).

After six consecutive years (2007-2012) with the rainfall above normal, the annual precipitation amount of the year 2013 was below normal. With a yearly precipitation amount of 622 mm (94% of normal) the year 2013 was the 30th driest in the last 90 years and the 4th driest in the 21st century (Fig.2).

After a close to normal calendar winter of 2012-2013, spring of the year 2013 in Latvia was rich in weather contrasts (Fig.3 and Fig.4).

March with an average air temperature of -5.5°C (4.2ºC below normal 1961-1990) was the 8th coldest in the history of air temperature observations and the coldest since 1987. With a precipitation amount of 11.3 mm (32% of normal) March was the 6th driest in the history of precipitation observations and the driest since 1974 as well. There was plenty of sunshine during the month – March was the second sunniest in Latvia as a whole and the sunniest in some places.

Persistently cold weather in March and the beginning of April continued to increase the snow depth and thickness of ice on rivers. Most of Latvia was covered with snow until the second 10-days period of April, which is on average, one month longer than normal. In the eastern part of Latvia the average snow depth in March was 2,5 times higher, but in the first 10-days period of April  - 10 times higher than normal. The snow depth for the first 10-days period of April was 40 cm, which was the thickest snow cover throughout all the winter season 2012-2013 (usually the thickest snow cover in Latvia is in the third 10-days period of February).

Due to the temperature rising in the second 10-days period of April, thick snow melted very quickly – in 6-9 days. The heat was rapidly breaking up ice and forming ice jams in rivers as well. These effects together resulted in a significant increase in water level and intense and extensive flooding. The highest water level rise was observed in the Ogre River near the town of Ogre. Estimates suggest that the maximum water level (24.5 m, which is 4 meters above the long-term average) had a probability of 0.5%, i.e. once every 200 years.

Typical spring weather in 2013 lasted only a little more than a month. With two hot periods in the first and second 10-days periods, May of the year 2013, with an average air temperature of +14,4ºC, was the warmest May ever recorded in Latvia. On the 9th of May air maximum temperature of +30ºC was observed. This was the first time of such a temperature for that date, and was also the earliest date in the year, that such a temperature had ever been recorded.

June 2013 was the second warmest June in the history of air temperature observations and the warmest in 21st century. July and August were moderately warm, but the whole calendar summer was the 9th warmest.

The weather at the end of the year was again significantly warmer than normal. November was the 5th warmest ever recorded and the warmest in 21st century, and December - the second warmest ever recorded and the warmest in 21st century. Autumn-like temperatures continued throughout December up to 12th of January 2014.

2013 as a whole had the slowest wind speed since the 1977 when throughout Latvia 10 minutes average wind speed observations were started. The 2013 annual wind speed was 0.6 m/s lower than the 1981 - 2010 period average. However 2013 was not without storms. They were recorded in eight months out of the twelve. On the night of the 28th and on the 29th October Latvia experienced the strongest storm in the last five years. The maximum wind gusts throughout the territory, with the exception of Bauska and Daugavpils, were above 20 m/s. The highest wind gust speed was on the Baltic Sea coast - 30 m/s. In October storm force wind gusts are not uncommon, so only the center of Riga had a new long term maximum wind gust record - 24 m/s – during this storm.