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number representing true wind direction and coding the sum for symbol DD. Example: A wind direction of 260º and velocity of 94 miles per hour at 8000 feet is coded as "82694", but if the velocity if 104 miles per hour it is coded as "87604".

(c) For observed wind velocities of 200 miles per hour, or over, the actual velocity will be reduced by 200 and the remainder will be coded for symbol vv. The true velocity will be indicated by inserting a slant between the coded figures used for DD and vv. As in the case for velocities of 100 to 199 miles per hour 50 is aded to the number representing true wind direction and the sum coded for symbol DD. Examples: A true wind direction of 280º , with velocity at 214 miles per hour, occurring at 14,000 feet, is coded as 478/14.

2-908. Levels for which Data are Sent. -- Pilot balloon reports contain observed values for wind directions and velocities at the surface and at all standard levels. Wind directions and velocities for the levels which are not standard levels are never sent. Standard levels occur at 1000 foot intervals from sea-level up to and including 15,000 feet. Above 15,000 feet the standard levels occur at 5,000-foot intervals (20,000; 25,000; 30,000; 35,000; 40,000; 45,000, etc.)

When the altitude of a station is less than 200 feet below a particular standard level the wind data for that particular standard level will be omitted from the coded report, but data for all higher standard levels will be included. For example, where the elevation of the theodolite platform is 1,820 feet above sea level, it is less than 200 feet from the 2,000 foot standard level, and, accordingly, the first standard level above the surface for which wind data is coded in a report is the 3,000 foot level, and not the 2,000 foot level. However, if the elevation of the theodolite platform at a station is exactly 1,800 feet, (or below 1,800 feet), the observed wind data for the 2,000 foot standard level will be included in the coded report from that station.

2-909. Maximum Altitude Data.-- Obviously, a coded pilot balloon report should not have wind data for standard levels which are lower than the elevation of a station nor data for standard levels at elevations higher than the observed ascent of the balloon. However, whenever the maximum observed altitude of a balloon ascent is only a short and specified distance below a standard level the data observed at this maximum altitude, for coding purposes, are presumed to exist also at the next highest standard level, and are coded as though they actually were observed at the next highest standard level. Whenever the maximum observed altitude is three hundred feet or less below any standard level up to and including 15,000 feet, the data for such maximum altitude will be coded for the next higher standard level. Whenever the maximum observed altitude is 1,000 feet or less below any standard level above 15,000 feet the data for such maximum altitude will be coded for the next higher standard level.

Examples: When the maximum observed altitude of a balloon ascent is 7,750 feet (or 7,700 to 7,799 feet) and the wind direction and velocity are 260º and 15 miles per hour, the data would be coded for the next higher standard level, i.e., "82615". 

When the maximum observed altitude is 24,500 feet (or 24,000 to 24,999 feet) and the wind direction and velocity are 310º and 67 miles per hour, the data would be coded for the next higher standard level -- "53167".

When the maximum altitude observed is more than 300 feed below any standard level up to and including 15,000 feet, or is more than 1,000 feet below any standard level above 15,000 feet the final group in a message will be the

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