Chapter 10 — WATCH ROUTINES 



made is considered the completion time of the 

 observation). 



SEA WATER TEMPERATURE. — Entered to 

 tenths of a degree Celsius. 



WAVE ENTRIES. — Only one wave system will 

 be reported unless the height, direction, and 

 period of a second system are clearly defined. 

 Under normal circumstances, an experienced ob- 

 server may not be able to define more than 

 one wave train. In general, waves differing by 

 30° or more in direction or having a period 

 difference of 4 seconds or more will be 

 considered as separate wave trains. All wave 

 data will be with respect to large, well-formed 

 waves. The lower, poorly formed waves are 

 disregarded. 



Period. — Enter the time In whole seconds 

 between the passage of two successive crests 

 of well-formed waves past a fixed point. 



Height. — Average vertical distance in feet 

 between the wave crest and the adjacent trough 

 is wave height. Whenever possible, obtain this 

 distance by observing the waves near the side 

 of another ship, and estimate their height with 

 respect to known dimensions of the ship. For 

 example, if the height of the bridge above the 

 waterline is 28 feet and the wave crest reaches 

 a quarter of this distance, the wave height is 

 7 feet. If another ship is not available, take 

 the observations at a time when roll and pitch 

 are slight and from a point amidships and 

 near the centerline. 



Sea Waves. — Sea waves are generated by 

 local winds. Enter period and height of waves, 

 coded as a 4-figure group (P W P W H W H W ) ; period 

 to the nearest second as the first two figures, 

 e.g., 07 for 7 seconds; height to the nearest 

 foot as the last two figures, e.g., 03 for 3 feet. 



Swell Waves. — Swell waves are of two types: 



1. Waves generated at some great distance 

 from the ship. 



2. The remains of locally generated waves 

 after the local wind Is no longer in evidence. 



Swell wave information is entered in the 

 following order; direction from which the waves 

 are coming in tens of degrees with reference 

 to true north and period and height in the same 

 manner as sea waves. 



SYNOPTIC OBSERVATION. — Naval Weather 

 Service personnel utilize these columns to 

 record synoptic observations and to prepare 

 weather messages for transmission as required 

 by NAVvVEASERVCOMINST 3140.1( ). 



Entries made in these columns are made 

 in accordance with Instructions contained in 

 the latest revision to FMH No. 1. Coding in- 

 structions are contained in FMH No. 2, Syn- 

 optic Code. 



DRY, WET, AND ICE. — Data in these col- 

 umns are entered at synoptic times only, but 

 are not transmitted. 



Dry. — Enter the dry-bulb temperature to 

 the nearest l/lO of a degree Celsius. 



Wet. — Enter the wet-bulb temperature to 

 the nearest l/lO of a degree Celsius. 



Ice. — Enter a check in this column If ice 

 is on the wick of the wet-bulb thermometer. 



REMARKS, NOTES AND MISCELLANEOUS 

 PHENOMENA. — Enter the time of sunrise and 

 sunset, GMT, in the appropriate spaces. Other 

 pertinent data, such as significant cloud groups, 

 special phenomena groups, and other remarks 

 or notes should be entered in this column. 



WEATHER AND OBSTRUCTIONS TO VI- 

 SION.— Enter the times (in GMT) of beginning 

 and ending, the type and intensity, and the 

 latitude and longitude (to the nearest whole 

 degree) of weather and obstructions to vision. 

 The specifications for the entries are the same 

 as for the entries on MF1-10. 



Code Forms 



Other than the coded aviation hourlies, there 

 are various other code forms with which the 

 Aerographer's Mate must be familiar. The 

 following paragraphs will briefly describe some 

 of the more frequently encountered code forms. 

 For a more detailed description, refer to the 

 Codes Manual. 



SYNOP — SURFACE REPORT FROM LAND 

 STATION (FM ll.( )). — The word "synoptic" 

 means, in general, pertaining to or affording 

 an overall view. Synoptic observations are per- 

 iodio (3-hourly or 6-hourly) observations which 

 describe the overall weather conditions exist- 

 ing at the observing stations. The Implication 



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