Affected by high-altitude cold vortex, North China cyclone
moving to northward and Mongolia cyclone, the rain, heavy rain
and local rainstorm occurred in the rainfall process. But compared with
the previous one, the intensity was increased. The main rainy days were
in July 6th to 7th. The main rain belt located in the tributaries
of the middle reaches of the Nenjiang River Basin and the main stream
of the Songhua River.
On the 500hPa high altitude weather map of Eurasia, the general circulation
situation of the rainfall process was roughly still two ridge and
one trough type. In July 6th, the North China cyclone moved to north
to the south of northeast China. The high altitude cold vortex
near the Lake Baikal also generated disturbance. A weak vortex
was split from it and cooperated with the North China cyclone.
At this time, the subtropical anticyclone had a short northern jump
and the ridge line was located near 30 degrees north latitude.
Under the guidance of the subtropical anticyclone, the North China
cyclone continued moving northward and merged with the low pressure
from Mongolia, thus forming the northeast low pressure, which began to
affect the northeast and continue to strengthen. At a great height,
due to the cold air southward movement. At 8 o'clock on July 7th,
the sky over the Northeast was already a closed low pressure circulation
and the main part of the blocking high also moved to the vicinity of
Okhotsk Sea. At the same time, it showed a high pressure in the west
of Xinjiang. The isotherm and the circulation situation of the two ridge
and one trough were obvious. On the ground weather map
at 8 o'clock on July 7th, the Northeast China low located
in the central and western regions of Northeast China. The center
and the main rain area coincided and this situation continued until July 8th.
In July 9th, the northeastern low pressure began to weaken and
move to eastward. The high altitude closed gyre disappeared.
It was not until July 10th that the rainfall was over.