Viewing page 276 of 349

This transcription has been completed. Contact us with corrections.

[[strikethrough]] RESTRICTED [[/strikethrough]]

to offset any effect of the weaker downdrafts over the valleys. One pilot reported gaining 8,000 feet in about a minute over the first ridge on March 13, 1943. March combines the strongest winds of the year with the highest cloud buildups. Thunderclouds which first appear during February, increase in intensity during March and frequently build up to 30,000 feet. Icing and turbulence may be severe in these clouds.

b. By the latter part of April the high winds over the "hump" have decreased to twenty to thirty miles per hour, still from the southwest. Turbulence and icing also decrease in intensity.

2. [[underlined]] BRAHMPAPUTRA VALLEY [[/underlined]]

a. Spring in the valley lasts from March through May. During these months there is considerable cumulus and thunderstorm activity between Jorhat and Lalmanirhat. A few thunderstorms occur during February and pilots have reported March thunderstorms to be the most severe of the year. However, the thunderstorm total for the month of May is the largest for the year with an average total of more than twelve thunderstorm days. These storms may cover a wide area between Jorhat and Lalmanirhat, making it difficult to avoid them. Tops of the clouds average between 17,000 and 18,000 feet, but it is frequently safe to fly below the bases of the clouds and there is little ice in the valley thunderclouds. There are two maxims for thunderstorm activity in the valley; the afternoon from 1400 to 1800 IST and the early morning between midnight and 0600 IST. A majority of the storms form in the afternoon, but the early morning thunderstorms are occasionally more severe.

b. Low overcasts also form early in the morning during the spring months and are accompanied by light rains and drizzle. During the early spring months the sky may become overcast any time of the day, but as the monsoon season approaches, the tendency is for overcasts to form during the morning and dissipate during the afternoon. Cloud formations occur irregularly, causing four to seven day spells of bad weather followed by a similar period of improved weather, free of overcast low ceilings and rain. After the layer clouds have cleared, usually by noon, cumulus clouds begin to form and there is thunderstorm activity during the afternoon. Thunderclouds clear in the evening and may reform during the early morning hours.*

3. [[underlined]] CHINA TERMINALS [[/underlined]]

   a. There is no definite spring season at Kunming and Yunnanyi. There, weather is broken into two season: winter and summer. May is the first summer month.

- 3 -

(Page 3, ICW-ATC Cir #18, 26 March, 1944)

[[strikethrough]] RESTRICTED [[/strikethrough]]

*Refer to training film MN 119 c.1 & c.2 for thunderstorm procedure.