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 APPROVED FOR RELEASE: 2009/06/16: CIA-RDP01-00707R000200110023-8

3. Air (U/OU)

Except for the North and Baltic Seas in the north, the air approaches are over land. Weather conditions in all air approaches are most favorable in summer, when cloud cover, low ceiling, poor visibility, and frontal activity are at a minimum. Thunderstorms and their associated turbulence, however, are more frequent and widespread in summer than in other seasons. Thunderstorms occur on 3 to 7 days a month during May through August throughout all approaches except over the North and Baltic Seas, where they are less frequent. The mean height of the freezing level in summer ranges between 8,000 and 12,000 feet. Weather conditions in all approaches are least favorable in winter, when migratory storms and their accompanying frontal systems are most frequent. Common in all approaches during winter are extensive cloudiness (60% to 80%), frequently the multilayered stratiform type; low ceilings; poor visibility caused mostly by fog, snow, and haze; and severe icing conditions. However, short periods of bright, clear weather periodically appear, primarily over the eastern approaches, when high-pressure conditions push westward from the U.S.S.R. The average height of the freezing level is at or near the surface in winter. Upper winds are predominantly westerly, and means speeds are less than 50 knots in all seasons at all levels up to 55,000 feet.

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APPROVED FOR RELEASE: 2009/06/16: CIA-RDP01-00707R000200110023-8