AEROGRAPHER'S MATE 3 & 2 



of radio silence; however the taking of radio- 

 sonde and other upper air observations involving 

 airborne electronic transmissions is governed 

 by the specific condition of radio silence in 

 effect at the time. 



Attention is invited to the instructions in 

 NWP 16 ( ) concerning transmission of weather 

 observations during periods of radio silence. 



VERIFICATION OF OBSERVATIONS. — Of the 

 several services provided by naval weather 

 units, the taking of observations is a basic and 

 most exacting one. Observational accuracy should 

 not be taken for granted. Constant vigilance 

 and care on the part of the observing personnel, 

 with close supervision by the weather officer, 

 are required to ensure that the weather ele- 

 ments are accurately observed, evaluated, and 

 correctly entered on recording and coding forms. 

 A recommended method for eliminating error 

 in the observational entries is to have them 

 checked by a second observer each watch or 

 each day. 



Other Entries on MF1-10 



The major elements such as pressure, wind, 

 temperature, precipitation, clouds, and visibility 

 and their entries on MF1-10 were discussed 

 in previous chapters of this manual. What re- 

 mains to be covered are heading, time (Col. 

 2) , weather elements and obstructions to vision 

 (Col. 5), supplementary data (Col. 13), observ- 

 er's initials (Col. 15), time (Col. 43) , and other 

 remarks, notes, and miscellaneous phenomena 

 (Col. 90). 



HEADING. — Enter in the spaces provided 

 across the top of MF1-10 the sunrise/sunset 

 times from monthly tabulations; station ele- 

 vation; time correction factor for LST to GMT; 

 degrees correction from magnetic to true; the 

 day, month and year; and the station number, 

 name, and state or country. 



TIME (COL. 2). — The actual time the last 

 element of the observation is observed and 

 evaluated for observations taken for an air- 

 craft mishap and for a Record observation. 

 On Specials and Locals, other than observa- 

 tions taken for an aircraft mishap, the actual 

 time of observation is the time the event re- 

 quiring the observation is observed. Entries are 

 in local standard time (LST) to the nearest 

 minute in terms of the 24-hour clock. Insofar 



as possible, elements having the greatest rate 

 of change should be evaluated last. When con- 

 ditions are stable, evaluate elements outdoors 

 first, then elements indoors with pressure last. 

 The individual elements should, as closely as 

 possible, reflect existing conditions at the actual 

 time of observation. Unless otherwise specified, 

 they must be within 15 minutes of the actual 

 time of observation for Special and Local ob- 

 servations or the standard time of observations 

 for Record and Record Special observations. 



WEATHER ELEMENTS AND OBSTRUCTIONS 

 TO VISION (COL. 5). — Atmospheric phenomena 

 considered as weather elements of an observa- 

 tion are tornadoes waterspouts, funnel clouds, 

 thunderstorms, and precipitation in any form. 

 Hydrometeors (other than precipitation) and 

 lithometeors are termed obstructions to vision. 

 Electrometeors and photometeors, such as 

 lightning, rainbows, halos, coronas, and auroras, 

 are also observed. Observations of these phe- 

 nomena, except for determining intensity of 

 precipitation, are taken without the use of in- 

 struments and from as many points as neces- 

 sary to view the entire horizon. 



A definition and an explanation of the above 

 elements are contained in chapter 15 of this 

 training manual. 



Enter weather and obstructions to vision in 

 column 5, using only authorized weather sym- 

 bols as shown in table 10-1. Determine the 

 intensity of precipitation, using tables 10-2 

 through 10-6 as applicable. Precipitation is 

 entered in this column only if actually occurring 

 at the time of the observation. 



The order of precedence for logging weather 

 and obstructions to vision in column 5 are as 

 follows: Tornado (funnel cloud or waterspout); 

 thunderstorm; liquid precipitation, in order of 

 decreasing intensity; freezing precipitation, in 

 order of decreasing intensity; frozen precipta- 

 tion, in order of decreasing intensity; and ob- 

 structions to vision, in order of decreasing 

 predominance, if discernible. 



Omit entry of obstructions to vision in col- 

 umn f vhenever the visibility recorded in col- 

 umn 4 Is 7 miles or more. If the visibility is 

 less than 7 miles, weather or obstructions to 

 vision must be reported either in column 5 

 if the phenomena are occurring at the station, 

 or in column 13 If the visibility Is reduced 

 by phenomena not occurring at the station. 



168 



