32 THE METEOROLOGY OF JAMAICA 



over the northern hemisphere, and they are quite intelhgible ; 

 but when we come to details it would seem that there is much 

 we have yet to learn ; and it is here proposed to give the 

 result of twenty-five years' experience in Jamaica in connec- 

 tion chiefly with the Weather Service. 



(1) Depressions often pass near or over Jamaica at all 

 times of the year ; they often throw down immense quantities 

 of rain ; and all our flood-rains are due to such depressions, 

 or to cyclones proper, the latter being very few and far 

 between. From June to November their course is the same 

 as that of cyclones proper, namely, west-north-west ; from 

 December to May their course is in an opposite direction, 

 namely, east-south-east. Some of the former develop into 

 cyclones, as on October 15 and 16, 1897 ; some of them are 

 ''northers," which occur during the winter months, and get 

 mixed up with the effects of the anticyclone over the United 

 States ; and others throw down enormous quantities of rain. 

 The June floods of 1886 were due to a depression which passed 

 near Jamaica, where the fall of pressure could not have exceeded 

 0'15 inch ; and these rains were far in excess of those thrown 

 down by the more developed cyclones of 1880 and 1886, which 

 both crossed the island.* 



(2) When a cyclonic depression is generating it is station- 

 ary, or nearly so ; after a time it moves off, and may develop, or 

 diminish and disappear. The June depression, 1886, is a good 

 example. On the 5th and 6th it was generating south-east of 

 Kingston ; on the 7th it started on a course parallel to a line 

 joining Kingston and Montego Bay at the rate of 10 miles an 

 hour; so that, if instead of generating for two days and a half 

 it had been advancing towards Kingston, its diameter must 

 liave been 1200 miles, which is out of the question with such 

 a small fall at the centre. A better example occurred on 

 October 26, 27, and 28, 1899. The barometric pressure at the 

 Kemp shot observatory gradually fell, and the wind from the 

 south gradually increased in strength with torrents of rain, 



* The followinc: depressions give further examples : 



1885, December 1, 2. 1898, May 23, 27. 



December 26, 27. 1899, October 2(3, 27, 28. 



1888, May 8 to 15. November 8. 



September 3. 



