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[[underlined]] c. [[/underlined]] Although disturbances in China follow one another at short intervals of time, rainfall at Kunming is less than half that found at Assan valley fields during the same months and visibilities caused by rain are not as low as these in the Brahmaputra valley.

[[underlined]] IV - FALL SEASON WEATHER [[/underlined]]

1. [[underlined]] THE HUMP. [[/underlined]] During the fall season, the "hump" weather is predominantly good. Clouds have begun to clear in early October and wind speeds have picked up to thirty and forty miles per hour from the west by the latter part of November. Occasional spells of bad weather during October give way to ideal conditions during November. Light to moderate rime icing conditions may exist. Up and down drafts are noted in the vicinity of Mount Tali and the main "hump". However, of the four seasons, the fall season is the most free of turbulence.

2. [[underlined]] BRAHMAPUTRA VALLEY. [[/underlined]] In the valley the monsoon rains have decreased to a minimum by the middle of October. By the latter part of November the ground fog season has set in. Clouds are caused by occasional outbreaks of moist air from the Bay of Bengal. The clouds usually form first on the hills and then spread back into the valley as a stratocumulus overcast. The rainfall is light. There may be heavy fog in November after the rain stops and the clouds clear away.

3. [[underlined]] CHINA TERMINALS.  [[/underlined]] There is no fall season in China at Kunming and Yunnanyi.

[[underlined]] V - WINTER SEASON WEATHER. [[/underlined]]

1. [[underlined]] THE HUMP [[/underlined]]

[[underlined]] a. [[/underlined]] The period including December and the first two or three weeks in January is usually the most cloudless of the year over the "hump". The up and down drafts increase in intensity and the prevailing west winds approach their heighest velocities. Average southwest winds of 100 miles per hour have been reported for the route. Over the Salween and Mekong Rivers and near Lake Tali pilots have reported losing and gaining altitude at the rate of 2,000 feet per minute, with the severity of up and down drafts only slightly less than during the spring months. It has been necessary to make fifteen to twenty-five degree drift corrections at levels above 17,000 feet to offset the southerly component of the wind. At other times there has been no drift at all at high levels when winds were almost due west. Clouds during this season are caused by cold fronts which move across India to the "hump" five or six times during the winter. These fronts hit the "hump" with a bang and clouds build up to 21,000 feet. During the latter part of January there may be clouds which cannot be topped at 30,000 feet, as tho spring season sets in. Icing in clouds is severe and may be accompanied by heavy snowfall and turbulence. When the cold fronts combine with a depression over Northern Bengal, there may be intense periods of icing in clouds over the "hump" and at the terminals. The icing level remains between 14,000 and 16,000 foott

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(Page 6, ICW-ATC Cir #18, 26 March, 1944)

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