38 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS 



5200. WATERSPOUTS AND SQUALLS 



5201. Waterspouts occur when conditions are favorable for intense 

 thunderstorm activity. The distinguishing feature is the funnel-shaped ap- 

 pendage that hangs from the base of the cloud. The storm is described as 

 a tornado when it occurs over land. 



5202. A squall is a strong wind that increases suddenly in speed, main- 

 tains a peak speed over a period of minutes, and decreases in speed; similar 

 fluctuations will occur at succeeding intervals. 



5300. PRECIPITATION 



5310. GENERAL. Precipitation includes all forms of moisture that 

 fall to the earth's surface- -rain, drizzle, snow, hail, sleet, and ice crys- 

 tals. Precipitation is classified as to its character, intensity, and type. 



5320. CHARACTER OF PRECIPITATION. The classification of pre- 

 cipitation with respect to character is described below. 



5321. Continuous. Precipitation usually associated with stratiform 

 clouds. Any increase or decrease of intensity is gradual. 



5322. Intermittent. Intensity increases or decreases gradually, and 

 precipitation stops and recommences at least once within the hour preceding 

 the time of observation. 



5323. Showery . Precipitation associated with cumuliform clouds, es- 

 pecially swelling cumulus and cumulonimbus. Intensity varies rapidly. 

 Showers begin and end abruptly. 



5324. Combinations. . When showers occur with continuous or inter- 

 mittent precipitation, the precipitation does not always stop between showers. 

 Under these conditions, precipitation is marked by a sudden increase and de- 

 crease in intensity as the showers abruptly begin and end. 



5330. INTENSITY OF PRECIPITATION. The intensity of precipitation 

 may be determined by its rate of fall and by the amount it reduces the visi- 

 bility. The intensity is classified as light, moderate, or heavy. Tables 

 5-1 and 5-2 will be used as guides in determining the intensity of rain and 

 snow respectively. 



