26 THE METEOROLOGY OF JAMAICA 



**Tlie following will be recorded as upper clouds cirrus, 

 cirro-stratus, cirro-cumulus, and cumulus. 



*^ The following will be recorded as lower clouds cumulus, 

 stratus, cumulo-stratus, nimbus, and fog. 



"Cumulus maybe reported either as upper or lower clouds, 

 depending upon the position they occupy." 



It w^as soon found that the clearest months of the year 

 are January, February, and March, when on an average 

 three-tenths of the sky are obscured ; and that the cloudiest 

 months of the year are August, September, and October, when 

 on an average six-tenths of the sky are obscured. 



Also it was found that the upper clouds are for the most 

 part only seen from June to October inclusive, and during 

 those months only in the early morning, as a rule ; and that 

 the lower clouds are seen during midday all the year round. 



From January, 1896, onwards the clouds were divided 

 into upper, middle, and lower, following the primar}^ forms 

 of cirrus, cumulus, and stratus. This was necessary for the 

 following reasons : cumulus in Jamaica is often 6 miles 

 high, reaching from the rain falling on the ground to the 

 upper regions of cirrus ; and, during the hurricane months, 

 clouds of the cirrus class move from the east-north-east ; 

 clouds of the cumulus class move from the south-east ; and 

 clouds of the stratus class according to local circumstances 

 of sea-breeze, land-breeze, and mountain configuration ; and 

 for storm -warning purposes the importance of such generali- 

 zations cannot be over-estimated. 



Moreover, the nomenclature was brought into accordance 

 with the system adopted b}^ the International Committee; 

 and in Weather Ileport No. 193 a full account of these 

 changes was given. It will here be sufficient to describe the 

 different clouds as distinctly as possible. 



(1) Cirrus. This cloud consists of long fibrous threads, 

 often blown by the upper currents into such forms as feathers, 

 mares' tails, etc. When the threads or feathers point towards 

 the observer, they appear like w^isps of hay or straw. This 

 is the pure form of cirrus, and it is caused by the condensa- 

 tion of thin ascending streams of vapour, and b}^ the freezing 

 of the particles of water. These ice-clouds are often at great 

 elevations ; from the rate of decrease of temperature with the 



