The main weather and climate features of the northern hemisphere in May 2017

Air Temperature.

The last May of the European territory of Russia (ETR) will come to mind for the population for a long time as a cold and rainy. The often intrusions of the Arctic cold caused the record colds and even frosts during all month. The average monthly air temperature was below the norm in all federal districts. In Central Russia – approximately by 2°, in the Russian North – up to 4°. Almost daily somewhere the new minimum temperature records were registered. The negative temperature anomalies in May, similar to the present ones, were observed here the last time in 2008, and in general every decade in the Russian Plain was marked with at least one such cold May. Sometimes it has happened even more frequently. For instance, during the 90th of the last century it has happened triple times over the decade (in 1990, 1994 and 1999).
In Siberia and most part of Far East the warmth and cold swapped each other. Instead of the heat of 25-30° (Republic Tuva, Transbaikalia, Irkutsk district) frosts 
of -10° and colder came (south of West Siberia, Republic Tuva, Altai, south of Krasnoyarsk district). As a result, the average monthly air temperature in the most part of these areas was close to the norm, with small negative anomalies in Yakutia and with positive ones in the other territory. And only in Kemerovo region, in Altai and Tuva Republics and Chukchi Autonomous District and Jewish Autonomous Region the temperature norms were noticeably exceeded (by 2° and more).
The hot weather dominated in the east of Asia. In Beijing the air temperature reached +37°. In the north of the country, in Japan and Korean peninsula the average monthly air temperatures exceeded the norm by 2-3°, in Mongolia – by 3-5°. In China the last May is the third warmest one on the record after 2007 and 2012.

In the north of India and Pakistan, as in the last months, it was too hot. The average monthly air temperatures exceeded the norm by 3-4°.
The similar situation was in the Middle East. In Iran and Arabian Peninsula the anomalies were up to +4° and more.
In the north of Central Asia in Kazakhstan the air temperature roughly corresponded to the norm, with small negative anomalies in the west of the country, in the south of the Central Asia republics it exceeded the norm by 2-3°. Here the summer came with the temperatures 30-35°.
In North Africa it was the hottest May in the region history. Everywhere the average monthly air temperature exceeded the norm, in the north-west: Morocco, Algeria, Tunisia by 2-5°. Recently the May air in North Africa is warming up more and more. Among 10 highest average monthly air temperature values 8 correspond with XXI century.
In Europe in May the contrast took place between abnormally warm west and central part of the continent and relatively fresh and sometimes cold east part. In West Europe (Portugal, Spain, France) the air warmed up to +30…35°, in Central Europe (Germany, Luxemburg – more than +30°. At the same time in the east (Poland, Check, Slovakia, Baltic countries, Belarus, Ukraine) the new records of low air temperatures were registered. In the middle of the month it came to the frosts which caused the big damage to the harvest of the south Ukraine.
In North America the air temperature in the north of Canada and in Alaska became noticeably higher the norm by +2…+6°, and in the other territory of Canada, as well as in USA it approximately corresponded the norm.
Despite of the fact that air temperature in Arctic at that moment was far from the warm records and more corresponded to the norm, the Arctic shield continued to melt quickly. At this time the satellites fixed the early damage of the ice in Baffin sea and in north-west passage which separates Greenland from Canadian island of Ellesmere. By the end of spring 2017 the area of Arctic ice was noticeably less than the norm. 
Due to the fact that in Russia and East Europe, partially in North America and in the most parts of Atlantic and Pacific oceans the May air temperature became below the norm, the average monthly air temperature of the Northern Hemisphere is beyond the first three highest values, it is happening for the first time over the last 19 months.
May finished the spring of 2017. In the west and north of Russia it was quite different. In the European territory the extremely warm March was changed by fresh April and then by the cold May, at the same time in the Urals all spring was very warm and local average monthly air temperature anomalies reached here +4…+6°. In the north of Far East the last spring is the warmest on the region record, and in the south – and in Siberia it is in the first three warmest ones.
In Russia in general the average monthly air temperature of spring 2017 is in the headline of the highest values. The first place it shares with spring 2014.
The last spring in the north of China, in the Middle East, West Europe and north-west of Africa, south-west of USA and north of Mexico was the abnormally warm. Here the average season air temperature anomalies exceeded the norm by 2° and more.
The average monthly air temperature of the Northern Hemisphere in spring 2017 conceded to the same value of the last year.
In Moscow the average air temperature of May is +10.9°, it is below the norm by 2.2°. Such anomaly in XXI century is observed the first time in the capital. The last time it was the same on the threshold of centuries in 2000, and since 2009 the every May has been abnormally warm.

Ocean Surface Temperature.

The average anomaly of sea level temperature (SST) is 0.4°, i.e. in both cases it is less by 0.1° than in April.
In equatorial latitudes of Pacific ocean the neutral phase of Southern oscillation is being kept. Abnormally warm water is observing along the east coast of Asia from Taiwan to Chukchi Peninsula, and also in central part of tropic latitudes, but abnormally cold water – in the central part of the ocean, in middle latitudes.
All central part of Atlantic ocean is captured with negative anomalies of SST, penetrated far to the north along west and east coasts of Greenland. This cold water interrupted the transfer of the warm surface water along the North Atlantic Current, and in the abnormally warm condition it is observing only in south-west part of the ocean near the US coast and in the north-east of Greenland sea. Also the abnormally warm water takes place along west coast of North Africa.

Precipitation.

In the most part European territory of Russia it was the norm of precipitations and more, though there are regions with the less normal precipitations. There are some areas of North-West Federal Districts: Leningrad, Kaliningrad, Murmansk regions, also south regions of Central Federal District: Lipetsk, Kursk, Belgorod regions. At the same time in Volga area and in the south of ETR the monthly precipitation sums in some places exceeded the norm in 2 times and more: Samara, Saratov regions, Republic of Crimea, Ingush Republic. The rains inundated ETR south in the end of the month. So, in Stavropol and Krasnodar districts, in Adygei Republic and Crimea the daily precipitations reached 40-50mm. In Stavropol and Minvody the new records of monthly precipitations sums in May were registered. Rains, followed by floods, caused the residential communities impoundments in some areas of south of Russia. Cold weather in ETR promoted the snowfalls and temporary snow cover. Particularly, the new May snow cover appeared in Moscow area, which was observed the last time more than 20 years ago. 
The approximate norm and relatively more of precipitations were in the Urals. In the vast territory of Siberia and Far East there are regions with the surplus quantity of the precipitations, and some areas are with their deficiency. The first ones – Yakutia, Transbaikalia, some areas of south of West Siberia, the second ones are: Taimyr, Altai, Khakassia, Chukotka and Sakhalin. Sometimes it was the snowfall which resumed or, like in the north, deepened the snow cover. 
In China and neighbouring Mongolia and Korea it was in general dry weather. Heavy rains came only in the west, north-east and extreme south of the Celestial Empire. Guangzhou, which is situated in the South-China sea coast, was inundated with heaviest over the last several years rains, they caused massive floods. It was reported, that over the half-day the city has got up to 200mm of rain. 
Summer monsoon came to the south and south-east of Asia, with the heavy showers. In the most part of Indo-China monthly precipitations sums exceeded the norms, in some places of Thailand – in 2 times and more. In Sri Lanka local meteorologists reported precipitations of this year in the initial monsoon phase are the heaviest since 2003. They caused the large-scale floods, landslides and destructions. It was reported on hundreds of losses. In the end of the month over the three showers’ days more than 400mm precipitations was fallen. Tropical cyclone “Mora” brought heavy rains to the south-east of India and Bangladesh.
In the most part of Central Asia except some Kazakhstan areas it was predominantly dry. The same one can tell on Middle East, where rains came only to Iran and to Arabian Peninsula. 
In North Africa too wet south withstood to dry north. In Algeria, Morocco, Tunisia, Egypt it was almost absence of precipitations. At the same time to the south from Sahara in Senegal, Guinea, Burkina-Faso, Togo, Benin there were 2-4 norms of precipitations.
In Europe rains in May happened episodically. In the east of the continent (Ukraine, Belarus, Baltic countries) there were quite few, it was below the norm in Balkans and roughly the norm in the west. In the beginning of the month the precipitations in the east and north of the continent were as a kind of snow.
Central and east areas of USA and Canada in May were inundated by rains. The precipitations norms here were exceeded in 1.5-2.0 times. In Canadian provinces Ontario, Quebec over the day it was up to 20-30mm of rain, in New Brunswick at the Atlantic coast over the several days up to 150mm of precipitations have fallen. Showers caused floods. Population were forced to leave their houses. In USA at the east coast during 3 hours more than 70mm of rain fallen. Here also the floods took place, in some places the traffic collapse and temporary closing of airports. Monthly precipitations sum from New-Jersey to Man is in the first five highest values on the record. It was dry in the west of USA and north-west of Canada.
In Moscow the monthly precipitations sum has set 83mm or 163% of norm. The spring precipitations sum (March-May) in the capital was 217mm. This is forth result in ranged series since 1891. It was more spring precipitations only in 1976, 2013 and 1998. 
In the last but one day of May in Moscow was a storm. For the first time on the record the wind gust in Moscow was registered as 30m/s. The squall was followed by storm, rain and in some places by hail. It caused the losses and destructions.