Characteristics of diving cyclones

Characteristics of diving cyclones

Characteristics of diving cyclones
© Met Office

Cyclones are associated with sudden changes in weather conditions, temperature fluctuations and various weather phenomena. Depending on the regions of origin and the trajectory of motion, they are of different types. Today we will talk about the so-called. “diving”.

Two days earlier, on December 19-20, an active cyclone “Neo” passed through the territory of Ukraine, which covered with snow most of the regions of the country, except the southern regions. Snowstorms, wet snow and gusts of up to 17-20 m / s were observed in places. And after the cyclone, an icy Arctic gas mass is gradually spreading from the north, due to which unusually cold weather is expected for the next 3 days. So this cyclone was a classic example of a “diver”, based on its characteristics and trajectory.

A “diving” cyclone is an exotropic low-pressure frontal gravity formation (cyclone) characterized by a special orbit, usually from north to south, an inverted hot field (located in the western and northwestern part of the cyclone) and high speed of movement..

The history of the term.

The very term “diving” is associated with the external perception of a geographical map: everything in the north is up, everything in the south is down. In any case, for the inhabitants of the Northern Hemisphere, this is the idea. A cyclone, at a fairly high speed (on average, 50 – 60 km / h), which erupts from the north to the south, is associated with something that has fallen from above or “dived”. Officially, in abbreviated meteorology, this term arose many years ago during the discussion or demonstration of meteorological forecasts for the territory of Eastern Europe. Meteorologists usually hung real-time and meteorological forecast cards on vertical projection bases. In those cases where a northwestern, or even northern, process was established in the atmosphere, cyclones appeared on the maps of Europe in the upper left corner and as the prediction was discussed, when moving from one map to another, bypassing the center quickly, they ended up on the leaves of the lower edge – “dipped”.

A logical question may arise here: why is the northwestern transport of gaseous masses into the atmosphere and how long can it continue? Meteorologists have a few more terms that journalists sometimes want to borrow, especially foreign ones, for example, “Rossby waves” and “jet streams”. These are the links of atmospheric circulation on a larger scale. Rossby waves, observed in the open air, cover the entire hemisphere, sometimes called planetary waves. In our case, such a large-scale wave, or rather its back, “hangs” above the ground of Eastern Europe, which determines the direction of movement of air masses from north-northwest to south-southeast. Well, the jet stream at the back of the hollow provides a high speed of “diving cyclones”. Schematically, a classic example of diving cyclones is shown on the map.

Phenomena and processes related to diving cyclones.

Weather conditions near the ground in such situations change very quickly. The high speed of the cyclone is usually accompanied by weather phenomena characteristic of the atmospheric fronts, on which the cyclone itself generally relies: rain, wind, frequent thunderstorms (if the season is warm), extensive areas with snowstorms and snowfall in winter. , as well as a sharp drop in atmospheric pressure. Even in the warm areas of diving cyclones, thaws are rare (compared to the hot areas of southern or Atlantic cyclones).

The vast majority of diving cyclones are formed in the cold semester (October to April), when conditions are in the atmosphere of the Arctic latitudes for the development of a strong cold center with its subsequent displacement to the south against the background of a well-defined altitude. cavity. During the summer, cyclonic activity in Europe is generally weakened and local brief conditions prevail.

For Eastern Europe, the orbits of “diving” cyclones most often follow the following orbits (see map below):

  • from the Barents Sea via Finland and west of the center of Russian territory to Lower Don;
  • from the tip of Cape Kanin through the Volga-Viatka region to Tatarstan and further down the Urals.
  • from the North Sea via the Skagerrak Strait and Poland down the Danube and further into Turkey.
  • from the Norwegian Sea via the Scandinavian Peninsula and further into Belarus and Ukraine.

The movement of such cyclones occurs mainly over the cold underlying surface; for this reason, they are rarely expressed in clouds and rainfall. As the “diving” cyclones are displaced from the northern latitudes, their passage is accompanied by a cold invasion and an increase in the northwest winds. In the case of a diving cyclone, all its parts are displaced by 90 ° in relation to the “classic” (moving from west to east) cyclone. The front and the warm front are on the south, the warm sector is on the west, the back is on the north and northeast. In some cases, a “diving” cyclone follows polar invasion (cold collapse from the northeast and exit of the arctic anticyclone or high pressure ridge from the north), which we are currently observing.

Thus, thanks to the development of northwestern and northern processes in the atmosphere, the classic winter weather with snow and frost has settled in most of the territory of Ukraine, which can not but rejoice especially on the eve of the coming new year.

Prepared by Igor Kibalchich, Candidate of Geographical Sciences, Meteorologist.

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