Synoptic situation in the Moscow region on May 9, 2020 was determined by sedentary high-altitude cyclone centered in the Kursk region. In the morning hours, the Moscow region was crossed from east to west by a cloud system of an occlusion front 100-120 km wide, consisting of layered rain clouds and cells of recessed convection with height up to 4 km, which shifted to Moscow with a course of 250-270 degrees at speed of about 20 km/h. At the background intensity of precipitation about 0,1- 0,5 mm/h intensity of convective precipitation in the East Moscow region was 3-5 mm/h (Fig.1).

Works on improving weather conditions began on may 9, 2020 at 04:00 MSK, when meteolaboratory aircraft An-26 (b/n 11) was raised from the Chkalovsky airfield and sent to the district at distance of 50 to 75 km in azimuth of 90 – 130 degree at altitude of 5400 m for measuring meteorological parameters of the atmosphere and clouds.

At 04:40 MSK, due to the fact that the cloud system giving precipitation with intensity up to 2 mm/ h, began to shift in the direction of Moscow, it was decided to send the aircraft to the east of the Moscow region at distances of 60-75 km, where work was started on clouds seeding with packages of coarse powder.

In the period from 06:30 to 8:00 MSK, six  more aircrafts (AN-12 (b/n 17), AN-26 (b/n 02), AN-12 (b/n 10), AN-26 (b/n 59), AN-26 (b/n 20) and AN-26 (b/n 34) were additionally lifted into the air and sent to the same area. Upon arrival in the area of work, the aircrafts carried out seeding of clouds, giving precipitation, with packages of coarse powder.

Owing to the massive seeding of the clouds that are coming to Moscow, it was possible to restrain precipitation in the city.

However, at 9:08 MSK, information was received from the aircraft commanders to the head of work at the Operational Control Center that they had received instructions from the shift supervisor of the Aviation Dispatch Center (Vnukovo) about the need to stop work: either to leave for landing, or to occupy an echelon of at least 230 (7000 m).

After receiving of this information four aircrafts were sent to the airfield, and one stopped the impact and occupied the 230th echelon.

As a result of the forced termination of work in the period from 9:40 to 10:40 MSK, precipitation with intensity up to 0,3 -1,0 mm/h was observed in the city.

Works on the impact on clouds and their monitoring was resumed at 11:36 MSK and continued until 22:28 MSK. There was no more precipitation in Moscow.

 A total of 14 flights were carried out on May 9, 2020.

 

Fig. 1. Digital maps of the heights of clouds and precipitation intensity at 03:40 UTC on May 09, 2020.