PREPARATION OF CHARTS B5-29 
15. Raob Messages. Raob messages will be coded and transmitted in 
accordance with the latest Federal Meteorological Handbook No. 4 
(Radiosonde Code). 
15.1 Entering Coded Message on WBAN-31(_). The coded message will 
be entered on WBAN-31( ) in the "Coded Message for Transmission" 
section. Data for the first transmission will be entered on WBAN-31A and 
data for the second transmission will be entered on WBAN-31B. Each 
group in the message will be entered on a segment of the broken lines 
provided for the entries. Corrections made after the data have been 
transmitted will be made in red without obliterating or erasing the data 
as they originally appeared in the transmitted message. 
15.2 Selecting Levels for Transmission. Levels will be selected for 
transmission purposes in accordance with instructions in the Federal 
Meteorological Handbook No. 4 (Radiosonde Code). 
15.3 Code Check. In the column headed ''Code Check'' on WBAN-31( ), 
number the transmitted significant levels as follows. The first signifi- 
cant level above the surface level and the first significant level above 
100 mb will be numbered '"'11,'' the second ''22."' etc. Code checks 00 will 
be used for the surface level only. If additional significant levels for 
transmission are discovered after the message has already been trans- 
mitted, the "Code Check" for these levels may consist of letters, "AA," 
"BB," etc. A correction message will be filedin accordance with instruc- 
tions contained in Federal Meteorological Handbook No. 4 (Radiosonde 
Code). 
15.4 Special Raobs. Messages based on special raobs willnotbe trans- 
mitted unless specifically authorized. 
15.5 Early Transmission of Specified Data. Data pertaining to desig- 
nated constant-pressure surfaces, freezing and icing levels, mean winds 
and the stability index will be computed in accordance with instructions 
in the following paragraphs as soonas they become available. These data 
are required for transmission before the regular transmission of the 
coded radiosonde report. 
15.6 Constant-Pressure Surfaces, Stability Index, and Mean Winds. 
These data will be coded for transmission as specified in the Federal 
Meteorological Handbook No. 4 (Radiosonde Code). 
15.7 Freezing-Level Data. Whenever, during an observation the tem- 
perature profile crosses the 0°C isotherm, the altitude and the relative 
S69 FMH#83 
