136 RAINFALL AT SARK, HERM AND ALDERNEY. 



islands quite unexpectedly. In Guernsey at any rate the 

 electrical disturbance was not particularly severe and here 

 too (Les Blanches) the rainfall, 0*64 in., was slightest. At 

 Herm the thunder shower yielded 0*72 in. of water, at 

 Alderney 0*77 in., but at Sark no less than 1*10 in. It is 

 rather curious to note in this connection that in spite of Sark 

 being recognized, and rightly so I think, as the driest of the 

 islands, it was, this distinction notwithstanding, the first 

 station to register an inch of rainfall in 1909. 



With the advent of May a sudden return to very dry 

 weather occurred, a return as sudden as that which developed 

 at the beginning of April, only on this occasion it lasted 

 without break until the 24th of the month when the passage 

 of a slight thunderstorm at night brought a 23 days' drought 

 to an abrupt end everywhere. Herm, for a change, had the 

 heaviest of the thunder rain this time, just over half-an- 

 inch (0'54 in.) being reported, while Alderney had the 

 comparatively small amount of 0*13 in. only. The month of 

 May was extremely dry at Alderney, the total measurement, 

 022 in., making it the driest month in that island during the 

 four years 1906—1909. 



June opened with an unusually wet week occasioned 

 principally by a depression which hung about in our neigh- 

 bourhood from the 1st to the 4th, and in addition to heavy 

 downpours gave intensely gloomy skies and a very low 

 temperature. The persistence with which the low pressure 

 area clung to us was, indeed, remarkable, and we know that 

 wretchedly unseasonable as our weather was far worse 

 conditions were experienced along the south coast of England. 

 At Les Blanches (Guernsey) the depression gave two falls of 

 over one inch each and a total for the four days of 2*87 in. ; 

 at Sark where as much as 1*38 in. was measured by Capt. 

 Henry on the 3rd, the total reached 2*39 in. Alderney had a 

 total of 2*12 in., and no inch fall, the heaviest being 0*93 in. 

 on the 1st. The deluge at Sark on the 3rd is the biggest 

 daily fall in that island since observations were begun in 

 January, 1906. On the night of the 21st a thunderstorm is 

 reported to have occurred at Alderney. 



Broken weather was our lot throughout July, but no 

 thunderstorms passed because the distribution of atmospheric 

 pressure was not favourable to their occurrence in the islands. 

 Easterly winds, with a high barometer over England, are the 

 ideal conditions for summer thunderstorms here, whereas 

 westerly winds, and consequently relatively low pressure over 

 England, was the prevailing distribution. 



