Affected by the high altitude cold vortex and ground Mongolia cyclone, the rainfall processes were moderate to heavy rain and local heavy rain. Heavy rainfall periods mainly concentrated in June 15th to 16th, June 18th to 21st. The mainly rain belt located in the middle and upper reaches of the Nenjiang basin.
From June 14th to 22nd, on the 500hPa Eurasian high altitude map, the middle and high latitudes circulation situation was two ridge and one slot type; A high pressure center existed in the vicinity of the Ural mountain and Yakutsk to the Okhotsk Sea areas also had a blocking high. A wide and deep low pressure trough between the two heights. With the polar cold air from north to south, cool low pressure continuously separated from the trough of low pressureand became cold vortex. At 8 o'clock on the 15th, the cold vortex located above the Nenjiang River Basin. The high ridge existed near Okhotsk Sea which prevented the cold vortex moving eastward. However, the meridional circulation of the low pressure trough in the northwest of Lake Baikal was further enlarged, from which a small low pressure was split, accompanied by the invasion of cold air. At 8 o'clock on the 15th surface weather map, the northeast region was a mature Mongolia cyclone with the presence of cold and warm front. With the high-altitude cold vortex, there was also a cold front in the west of Lake Baikal with a small low pressure with a new split in the upper air. At this time, the entire northeast area had been completely under control of high-altitude cold vortex and ground Mongolia cyclone and began to rain in large areas.
In June 18th, the cold vortex moved out of the northeast regionand the low pressure of the western Lake Baikal began to move to the west of the northeast to become a deep cold vortex system whose meridional circulation of trough of low pressure of the northwestward was more obvious. Behind the trough of low pressure, cold advection power was very powerful, continuously conveying cold air to the Southeast. A cold vortex split from the trough bottom and a new round of rain began to increase.At 8 o'clock on June 19th, two cold vortex combined to become a strong coldcentrality with deep cold vortex center whose external forces had been extended to the northeast. However, near the Okhotsk Sea the warm anticyclone was cut off by the cold air to become a blocking anticyclone. The analysis chart of the high altitude weather situation at 8 June 20th. The cold eddy center had moved to the northern Inner Mongolia and became the Northeast Cold Vortex, cooperated with the cold center reached -20 C. The power of the Okhotsk Sea's blocking anticyclone was also very strong. At this time, on the ground weather map, the ground Mongolia cyclone had been occluded, the center of which was in the the northwest of the northeast region. Such situation had been maintained until 21. In June 24th, the cold vortex forces moved to NW and the rainfall process in the northeast was over.
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