THE MAIN WEATHER AND CLIMATE FEATURES OF THE NORTHERN HEMISPHERE IN APRIL 2018

Air Temperature.

April in the north-east of Russia commenced with the abnormally warm weather. In Chukotka and Yakutia in the first decade the new daily air temperature maximums were registered repeatedly. Decade norms were exceeded here by 4-10°. Then the warmth was spread in all east region of the country: from Urals to the Pacific ocean. In the second and third decades the air temperature noticeably exceeded the norms also in the south of Far East and in Siberia. As a result, the last April became here substantially warmer than usual – by 2-8°. In the north of Far East, it was the third warmest April on the record. Let us remind that April of the last year was recognized the warmest one in the region.
Quite another situation took place in the European territory of the country. Here the air temperature above the norm was kept all month only in the extreme west areas and in the north during the first decade. Other days of the month were fresh and sometimes – cold. In Central Russia and Chernozem area during the night the temperature dropped to -4°, in the south (Volgograd area and Krasnodar district) – the frosts were registered. As a result, in the most part of ETR and Urals the average monthly air temperatures became close to the norm. In Volga area and Urals, it was slightly colder than usual. The last April became warmer the norm in the west areas of Central and North-West Federal districts and in Crimea.

In China after the warmest March on the record, April became in the row of very warm months. In the most part of the country, the average monthly air temperature exceeded the norm by 2-4°. Approximately the same anomalies were in Korea and Japan. In the Land of the Rising Sun at the beginning of the month, the air was heated up to +25°, in China and Korea – up to 30° and higher. The new extremums of the maximum temperatures were noted. In Mongolia the anomalies are larger - +4-6°.
Colder than usual, although slightly, it was in the most part of South-East Asia. This cold anomaly was stretched to Bangladesh, Sri Lanka and east coast of India. However, in the most part of India, as well as in Pakistan, the month in general became noticeably warmer the norm. In Pakistan, the average monthly air temperature anomaly is +2…4°. In the last day of the month in Nawabshah, which is 200 km to the north-east of Karachi, the temperature crossed +50° mark. Now the value 50.2° is the new April absolute air temperature maximum of this country.
In Central Asia countries in April, the temperature conditions became close to the norm, mainly on the positive background, in some places – on the negative one. One can take to the negative trend the north areas of Kazakhstan and Turkmenia.
In the Middle East and most part of North Africa, it was warmer than usual approximately by 1-2° in the last April. Only in some areas of the west coast, the average monthly air temperature did not reached the norm. In the Mediterranean resorts of Turkey in the middle of March, the air temperature exceeded +30°.
In Europe, it was as in summer. It was not even one country, where the average monthly air temperature became lower the norm. From UK to Ukraine and Belarus and from Scandinavia to Italy and Balkans it was repeatedly informed on the new records of the maximum air temperature. Temperature higher than +25° in the second and third decades became routine phenomenon. To be honest, one can noted that in the beginning of the month in Scandinavia the new daily temperature minimums were registered. In the most part of the continent, the average monthly air temperatures exceeded the norm by 2° and more, in the Central Europe – by 4-8°. April of 2018 became the warmest on the continent record. Its average air temperature exceeded the previous record of 2011 by 0.3°.
On the other coast of Atlantic ocean the situation is opposite. In USA, the last April is one of the coldest on the record. Almost in all territory, except west states, average monthly air temperature is below the norm. In the Middle East and Great Lakes area, the anomalies have set -2…-5°. In states of Minnesota, Iowa, Wisconsin, Michigan one have never seen such cold month before, in states to the south of abovementioned, the month is the coldest on the record. Only in west coast states (California, Oregon, Washington) and in neighbouring Nevada, Utah, Arizona, Colorado, New-Mexico the air on average during the month was heated above the norm by 2-4°.
Approximately the same cold anomalies are in the most part of Canada. Here also it was warmer than usual only along Pacific coast and in polar region of the country by 1-2°. Positive anomalies are larger in the north areas of Mexico, bordering with USA.
Colder than usual in April there were substantial areas of Pacific, Atlantic and Indian oceans.
Average monthly air temperature in April in Northern Hemisphere takes a line in a margin between the first and second ten highest values in the ranged row since 1891. This April in the Hemisphere was noticeably colder their predecessors (Aprils of 2016 and 2017).
In Moscow the average monthly air temperature is +7.8°, anomaly is +2.0. On 10th of April the new daily temperature maximum was registered, the single in this month.

Ocean Surface Temperature.

Sea surface temperature anomalies (SST) in El-Niño – La Niña area approach to zero. However, the area of negative SST anomalies yet substantial, especially in South Hemisphere, it is obvious that continuing La Niña soon will come to neutral phase of Southern oscillation.
In Pacific ocean, the average SST anomaly in Northern Hemisphere have been kept at the previous month level and it is the same, as in last year April. Abnormally cold water is being kept in the west part of the ocean, but in general, the temperature of the most its part is above the norm. Especially it is apparent in tropical area, in warm stream Kuroshio and in Bering sea.
In Atlantic ocean, the average SST anomaly also corresponds to the March one, but it substantially higher than the same anomaly of the last year. In tropic zone and in the east of the ocean the temperature is below the norm. It is observed from West Africa to Norway coast. In the west of the ocean, the SST is above the norm, near the coast – by 1-2°.

Precipitation.

In ETR the main precipitations fell in the north, central region and in Volga area. Here they have set roughly the norm, in some places the exceeded the norm. Sometimes rains were protracted, for instance, in the end of the second decade, when in Moscow area the monthly precipitations norm fell over the day, in Volga area – about half the norm. The same cyclone brought to Stavropol and Krasnodar districts from 20 to 40mm of atmospheric precipitations over the day. However, they could not remove the spring drought in the south of Russia. Here the monthly precipitations quantity has set only 30% of the norm.
Precipitations norm is in Urals. In the beginning of the third decade, the snowfalls covered Sverdlovsk, Chelyabinsk, Kirov areas and Perm district. Daily growth of the fresh snow in some places reached 30-40cm. Local meteorological services assessed this event as the heaviest April snowfall in XXI century.
A lot of precipitation have fallen in Siberia and Yakutia. In the first half of the month, it was mainly snow. In the south of West Siberia and Krasnoyarsk district the monthly norms were exceeded in 2-3 times. Further to the east, the precipitations became lighter. In Transbaikalia and south of Far East, the weather was mainly dry. In some places the monthly precipitations sums have set here only several percent of the norm. The same situation is in the north-east of the country. In the beginning of the month, the heavy snow storm captured Magadan area. Snow storm was followed by the wind with 30m/s velocity and visibility less than two meters. Only northern areas of Khabarovsk district bordering with Okhotsk sea, have got in April the norm of precipitations and more.
In the central and east regions of China the atmospheric precipitations monthly sum reached the norm, in some areas they exceeded the norm, whereas in the west of the country there were the few of them. Abundance of rains was in Korea and Japan, where they exceeded the norm in 1.5 times and more. Cyclones brought 50-70mm of precipitations over the day.  
In South-East of Asia, it was norm and more of precipitations. Only in the south of Vietnam and Malaysia there were few.
Dry weather dominated in India and Pakistan. In the beginning of the month, the heavy sand storm covered the north-west of India. Wind with more than 30m/s velocity was transferring the sand so swiftly, that people did not have time to find the shelter. There were tens of suffocated people, hundreds of killed by ruined walls and trees.
Except the north territories of Kazakhstan, other Central Asia was dry. However, heavy rains sometimes took place. So, in Tashkent in the middle of the month it was one third of monthly precipitations norms over the day.
Precipitations norm in Iran was substantially exceeded in the vast territory in 1.5 times and more. In the end of the month, the heavy showers inundated Middle East. In Israel, the non-stop two days rains brought 90mm of precipitations. Water flooded the roads, cause the floods, mudflows and landslides.
Dry weather was in North Africa. Only in several countries of the Mediterranean coast (Algeria, Morocco, Egypt) and Gulf of Guinea (Côte d’Ivoire, Guinea) the monthly precipitations have set the norm. Heavy rains have been falling in Kenia for the second month. They caused floods, and hundreds of casualties. After catastrophic drought of 2017, the East Africa was overtaken by the new disaster. Landslides destroyed the water system and waste disposal, which caused the cholera and other diseases outbreaks.
In Central, East and South-East Europe almost all month the dry weather dominated. Precipitations sums did not exceeded here one third of monthly norm, and less. Only in the west and north of the continent it was cumulated the norm and more of rains. Quite sudden became the snow storm in the north-west of France in the last day of April.
In the most part of Canada, it was few precipitations. Only in the east along the Atlantic coast and in the polar area their monthly sums reached the norm or exceeded it, in some places in 2 times and more. In USA, east states have got the precipitations norm and slightly more. In the end of April, the strong cyclone crossed the Atlantic coast and brought up to 60mm of precipitations over the day. In the middle of the month, the snow storms covered Middle West and Great Plains. In the same areas of Michigan, Minnesota and Wisconsin 30cm of snow fell down. In Rocky Mountains and further to the west it was mainly dry. It was absence of rains in the vast territory from South Carolina to Texas. Only in the north-west (Oregon, Washington, Idaho) it was plenty of precipitations. In the north of Mexico, it was dry, whereas in the centre of the country precipitations norms were exceeded in 2-3 times.
In Moscow, it was 47mm of precipitations. This is approximately the norm.