MAIN WEATHER AND CLIMATE TRAITS IN THE NORTHEN HEMISPHERE AS OF DECEMBER 2019
Air Temperature
All through December, abnormal warmth prevailed in the European territory of Russia. The average air temperatures in any decade exceeded the normal values by 3-7° or more. The unprecedented temperature maxima were recorded everywhere from the Barents Sea to the North Caucasus and Crimea, and ultimately, the monthly-averaged air temperatures from the western border to West Siberia turned out to be much higher than usual, e.g., by 8° and more in the Arkhangelsk Region. In the Central Federal District, this December became the second warmest in the history of meteorological observations: the weather was even warmer in 2006 only. Likewise, this month entered the Top Ten of warmest in the North-West, Volga and South Federal Districts.
East of the Urals, the weather was also warmer than usual, albeit that in the first half of the month only. In the first decade and at the beginning of the second one, the daily temperature maxima were recorded in Western Siberia. But later on, the eastern regions of the country were overwhelmed by bitter Arctic colds. Frosts down to -52° were observed in Yakutia, and down to -45° in the Irkutsk Region and in the Trans-Baikal. In South Siberia, new temperature minima were reached in the Kemerovo Region. The entire territory of Siberia and of the Far East was under the spell of cold. The anomalies of decade-averaged temperature were -2…-8° or larger, so that this December turned out to be generally colder than usual in the east of Siberia, in Yakutia, Trans-Baikal, Amur River Region and Primorye. Only the Far North-East of the country, notably, the Chukotka Autonomous District, succeeded in retaining the heat accumulated at the beginning of the month in spite of the cold in the third decade; there, the monthly-averaged air temperature was above its normal value.
The average annual air temperature in 2019 was above normal throughout Russia. Calculated for the whole country, it regained the maxima of 2007 and 2017 to an accuracy of 0.1°C, while in Central Russia, it reached the absolute maximum for the entire period of regular meteorological observations, i.e., since 1891. The second highest result in the meteorological chronicle was obtained for Siberia and the northern regions of the Far East where the largest anomalies of average annual temperature (+3…+4° and more) were recorded.
Six times this year, the monthly-averaged air temperatures in Russia were among the Top Ten of highest values in history (in March through June, in August and in October). Each federal district was marked by at least one month when the average air temperature either reached or approached its positive extremes. This was championed by the Siberian and Far East Federal Districts where such months were observed four times in 2019. In neither federal district, nor in Russia as a whole, did the monthly-averaged air temperature ever enter the Top Ten of coldest values. July in the Central Federal District was closest to that. Its average temperature was the lowest since 1985, and this July was among the fifteen coldest ones in the meteorological chronicle since 1891.
In East Asia, December was warm. The monthly-averaged air temperature was above normal everywhere. In some regions of Japan, Korea, northern and southern China, the normal value was exceeded by 2-3° or more.
A similar picture was observed in South-East Asia, yet the normal values were exceeded less significantly there.
In northern India, the average temperature in December was below normal, by 2° or more in some places. At the same time, the weather was warmer than usual in the south.
In the Near and Middle East, the weather was abnormally warm in general, with the monthly-averaged temperatures in excess of their normal values observed everywhere. It was especially noticeable in the north and west of Iran and in Kuwait, where this excess reached 2-3° or more. In Azerbaijan, new record-breaking temperature maxima were established.
It was very warm in Central Asia where the monthly-averaged temperatures were above normal all around: by 2-3° in most of this region, and by 3-5° in the east of Kazakhstan. In the last decade of December, new air temperature maxima were set all over Central Asia. The air in Turkmenistan heated to above +20°.
In North Africa, the weather was warmer than usual, particularly in Algeria where the anomalies of monthly-averaged air temperature were +2…3° or higher.
Europe was basking in the warmth again, and December proved to be warmer than usual in all its parts: by about 2-3° in the west and the centre of the continent, and by up to 3-5° and above in the east and the north. The monthly-averaged temperature exceeded the normal value by 2.8° in Barcelona, by 3.1° in Geneva, by 4.2° in Warsaw, by 5.1° in Kiev, and by 5.6° in Helsinki. New air temperature maxima were recorded in several countries. Sometimes, the air would warm up to +20° and above in Portugal and Malta, to +16-17° and above in Ukraine and Moldova, and to +10° and above in Moldova. Such warmth made December 2019 the second warmest one in the history of meteorological observations in Europe, after December 2015.
In most of the USA and Canada, the air temperature was well above normal, with the normal values of monthly-averaged temperatures exceeded by 2-3° or more. Individual regions of Alaska and the north-west of the Arctic zone in Canada were the only ones to demonstrate the figures slightly less than usual. In the USA, this December is in the Top Ten of warmest in the history of the country.
The average annual air temperature in the North Hemisphere matched (to an accuracy of 0.1°) the second highest values of 2015 and 2017 since 1891, with the record value of 2016 unsurpassed still.
In all parts of Europe, Asia or North Africa, the average annual temperatures were above normal. The highest anomalies (+3…+4°C and more) were in the north of Asia, in North America, and in Eastern Europe. As for the North American continent, this year was colder than usual in parts of the USA, and warmer than usual in the rest of the country. In the areas from North Carolina to Florida and Alabama, this year was the warmest one in the history of meteorological observations.
In Europe and in Alaska, this year was the warmest one in the history of meteorological observations, whereas China, its average annual temperature regained the record-breaking value observed in 2007, 2015 and 2017. The year 2019 was the second warmest in the Arctic, and the third warmest in North Africa (along with 2014 and 2017).
In Moscow, the monthly-averaged air temperature in December was +0.8°, and the anomaly was +6.9°. This December was the second warmest in the meteorological chronicle of the capital; only December 2006 was even warmer with its average temperature of +1.2°. The average December temperature in the history of Moscow was positive four times only: in 2006, 2019, 2015 and 1960. This year, it was greater than the normal value for November.
In 2019, the average annual air temperature in the capital was +7.8°. This means that 2019 was the warmest year in the history of Moscow. Four months (February, May, October and December) were among the Top Ten of the warmest months in this history. No extremely cold months were observed in the capital this year. Only July was colder than normal on the average, August matched the normal values, but the other months were warmer than usual.
Ocean Surface Temperature
The mean SST anomaly of the Pacific Ocean in the Northern Hemisphere decreased by 0.2° as compared to November. Large positive anomalies formed in the tropical zone of the Ocean, as well as in the north-east – in the Gulf of Alaska and to the south of it, in the west – in the Sea of Japan, and to the east of Japan. No large negative anomalies were observed. The neutral phase of the Southern Oscillation was active still.
In overall, the surface of the Pacific Ocean in the Northern Hemisphere warmed up to 0.6° above the normal value on the annual average. This is only 0.1° less than the highest value recorded in 2004.
As for the Atlantic Ocean in the Northern Hemisphere, the anomalies were still weaker than in the Pacific. Small-sized seats of positive anomalies were dispersed over the whole Ocean. Off the coast of Greenland in the Davis Strait, they reached +2°. Negative anomalies took place in the east of the tropical zone and at temperate latitudes.
Precipitation
In the ETR, most precipitation was observed in the north. In some places, e.g., in St. Petersburg, record-breaking daily precipitation totals were recorded. The monthly amounts of precipitation were twice the normal values in the Republic of Karelia, and 1.5 times greater than normal in the Leningrad, Novgorod, Arkhangelsk, Murmansk and Vologda Regions. In the rest of the ETR, precipitation was scarce and amounted to less than the monthly normal figure everywhere excluding the Kostroma and Kirov Region, the Perm Territory, and the Republics of Mari El and Udmurtia. Specifically, it was very dry in the south where less than half of the normal precipitation amount was accumulated during the month. Yet, heavy rains did pour down from time to time, such as in Sochi where 60 mm of precipitation was recorded one day.
In the Urals, precipitation was close to normal, and in Siberia, 1.5-2.0 times the normal value in most areas. The precipitation amounts were normal in the Far Eastern Federal District, namely, in the Trans-Baikal and Primorye, and sub-normal in the Amur River Region, in the north-east of the Magadan Region and in the Chukotka Autonomous District. One after the other, cyclonic vortices would deliver snowfalls to Kamchatka and the Kuril Islands.
Most of Asia received scanty precipitation in December. The rains that totalled their normal monthly amounts or exceeded them in places went to Japan, Korea, the east coast of China, the north of India, the Republic of Sri Lanka, and to the Near and Middle East where these amounts were sometimes dramatically exceeded. At the end of the month, showers descended upon Israel and lasted for almost two days bringing up to 50 mm of rainwater in certain areas during this time interval. New unprecedented precipitation totals were reported. At about the same time, intensive rains fell in Ceylon where 500 mm of precipitation was accumulated for one day. Rivers overflowed their banks, and landslides were triggered. Water flooded residential buildings and farming lands. On the New Year's Eve, tropical showers hit Indonesia. According to local weather services, 377 mm of atmospheric moisture fell in Jakarta on December 31, thus beating the previous record set in 1995.
The weather in Africa was dry; rains were only to be seen in some areas on the coast of the Mediterranean sea and the Gulf of Guinea.
Europe received plenty atmospheric moisture in December. The monthly precipitation totals in some western regions amounted to 1.5-2.0 times the normal value. Heavy showers hit the UK in the third decade. Rivers overflowed, flooded settlements and lead to a halt of railway communication. Heavy rains in Portugal, Spain and southern France also resulted in major floods that shut down electric power lines. Fatalities were reported. Venice was under water again. Less precipitation went to the east and north of the continent. In such countries as Denmark, Ukraine, Romania, Bulgaria and Serbia, its amounts were less than half of the normal value.
Abundant precipitation, both in the form of rains and in the form of snowfalls, went to the USA. In the western state of Oregon, rains caused river spates and blocked highways where local residents tried to reach each other on Christmas Eve, but were captured en route. The centre of the country, the states of Colorado, Nebraska, both Dakotas and Rocky Mountains were hit by snowfalls that caused severe problems and interruptions in transportation and in energy supply. Unprecedented amounts of snow were recorded in some places, with the snow depth in excess of 25 cm and the monthly precipitation totals exceeded by 1.5-2.0 times.
In Canada, scarce precipitation was observed in the south of the country, in contrast to the north where the precipitation quantities were much greater than normal.
As for the annual totals, the precipitation amounts in the Normal Hemisphere were close to their normal values. The latter values were noticeably exceeded in certain regions of the northern Russia, in the Far East and in the USA, but were not reached in western Africa, Mexico, Central Asia, some areas of China, and some European countries. The annual precipitation totals throughout the US were the second highest in the entire history of meteorological observations, and reached their absolute maximum everywhere from Montana and Wyoming to Ohio, Virginia and Tennessee.
In December, Moscow received 32 mm of precipitation, which is only about half the normal value. The annual figure was 552 mm, i.e., 80% of the normal amount.