Chapter 10 — WATCH ROUTINES 



Table 10-6. — Estimating the intensity of rain 



Light 



Moderate 



Heavy 



Scattered drops that do not completely wet an exposed 

 surface, regardless of duration to a condition where 

 individual drops are easily seen; slight spray is ob- 

 served over pavements; puddles form slowly; sound on 

 roofs ranges from slow pattering to gentle swishing; 

 steady small streams may flow in gutters and down- 

 spouts. 



Individual drops are not clearly identifiable; spray 

 is observable just above pavements and other hard 

 surfaces, puddles form rapidly; downspouts on build- 

 ings seen 1/4 to 1/2 full; sound on roofs ranges from 

 swishing to gentle roar. 



Rain seemingly falls in sheets; individual drops are 

 not identifiable; heavy spray to height of several 

 inches is observed over hard surfaces; downspouts 

 run more than 1/2 full; visibility is greatly re- 

 duced; sound on roofs resembles roll of drums or 

 distant roar. 



indicated in table 10-6. Determine the inten- 

 sity of drizzle or snow when neither is occur- 

 ring simultaneously with other atmospheric 

 obstruction to vision (smoke, fog, etc.) on the 

 basis of table 10-4. When either drizzle or 

 snow is occurring simultaneously with other 

 atmospheric obstructions to vision (except pre- 

 cipitation), estimate the intensity of drizzle on 

 the basis of criteria in table 10-3. Estimate 

 the intensity of snow on the basis of experience 

 with the relative apparent rate-of-fall or ac- 

 cumulation on a surface recently free of pre- 

 cipitation. 



It is well to remember that when precipita- 

 tion equals or exceeds 0.04 inch per hour, there 

 is a strong presumption that the precipitation 

 is rain. 



Intensities of ice pellets may be estimated 

 by using table 10-2, If recording or totalizing 

 gages are available; otherwise, estimate the 

 intensity in accordance with table 10-5. 



When more than one form of precipitation 

 is occurring simultaneously, the individual In- 

 tensities are estimated on the basis of experi- 

 ence; the use of tables 10-3 through 10-6 and 

 table 10-2 give the basis for estimating the 

 intensity of precipitation (other than drizzle) 

 on the rate of fall; and the apparent relative 



proportion of the precipitation forms, as ob- 

 served during their fall, or upon Impact upon 

 surfaces recently free from precipitation. 



REMARKS (COL. 13). — In column 13 are 

 entered mandatory and optional remarks which 

 may be warranted as a result of the occurrence 

 of weather or obstructions to vision. Some of 

 these phenomena may warrant a Special ob- 

 servation. 



Among the items requiring mandatory re- 

 marks are the times of beginning, ending, loca- 

 tion, and direction of motion of tornado, 

 waterspout, funnel cloud, thunderstorm; the fre- 

 quency, type, and direction of lightning. 



Obstructions to vision also require certain 

 mandatory remarks. For instance, when an ob- 

 struction to vision is increasing or decreasing 

 in intensity, or not occurring at the station, 

 it requires a mandatory remark. 



Enter remarks in symbols or abbreviations 

 whenever possible; otherwise, use plain lan- 

 guage. Use remarks to report any operationally 

 significant information not reported elsewhere. 

 Significant remarks are not limited only to 

 those specified elsewhere in the manual. It 

 is therefore important that the observer re- 

 port any condition which in his best judgment 



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