PRESIDENTIAL ADDRESS SECTION A. 



25 



If \vc apply these rules to some weather charts, we cannot 

 fail to remark that they certainly answer in many puzzling cases. 

 Abercromhy, among- the various weather types which he examines 

 in his book on the " Weather." mentions one which is the despair 

 of the forecaster in Western Euroije. It is the one in which 

 cyclones seem to hang over England, producing violent easterly 

 gales, and are finally dislocated or driven westwards. He gives 

 a series of weather charts for four consecutive davs to illustrate 

 this weather type. If we examine them in the light of these 

 rules, we see that the pressure sequence can be explained, and 

 that tlie stationary character of these cyclones or their drift west- 

 wards could be foreseen. In his maps a group of depressions 

 liangs over Western Europe extending from the Baltic to the 

 Azores. In front of this cyclonic area there is an anticyclone 

 over Scantlinavia in the rear, and an anticyclone over the Mid- 

 Atlantic. The winds in front of the cyclone are south-east; so 

 are also those in the rear of the Scandinavian anticyclone. The 

 c}clone is therefore in contact with a part of the anticyclone 

 where the winds are normal in direction in regard to cyclonic 

 circulation ; the cyclone finds, therefore, in that region a barrier 

 to further progress. This combination is likely to produce a 

 wind force larger than the normal. Abercromhy gives no indica- 

 tion about the force of the wind on his charts, but he mentions 

 that this type of weather gives very violent gales over the East 

 of England. If we put our back to the south-east wind over the 

 North Sea. we see that, according to Guilbert's rules, the 

 vScandinavian anticyclone is to encroach on the cyclone and drive 

 it westwards. A similar reasoning would show that the anti- 

 cyclone of the Azores would encroach from the south-west to 

 tiie north-west. The cyclone is. therefore, wedged in between 

 these two anticyclones, and obliged to be stationary and undergo 

 gradual compression^ — -a process which can be clearly followed 

 on the charts given by Abercromhy. 



Whatever may be the value of these rules for general fore- 

 casting, it seems certain that they may be used with great advan- 

 tage in countries which are subject to sudden storms that cannot 

 be forecasted owing to the lack of communication with the 

 regions where they originate. Mr. Guilbert has given many 

 instances of storms w'hich have burst upon Europe and caught 

 all the meteorological office-^ unawares. He had a little pre- 

 diction service of his own for the use of the members of the 

 meteorological society of which he is secretary. He has pro- 

 duced authentic documents to prove that in his forecasts he has 

 I)redicted storms, and even given to the millimeter the drop of 

 the barometer, in cases where official meteorology had been 

 altogether at fault. The sudden storm which burst upon Wes- 

 tern Europe on the 12th of March of this year gives a good illus- 

 tration of this. On the weather map of March 12th, at 9 a.m.. 

 we have two cyclones with feeble gradients, one .ofif the coast of 

 Scandinavia and one over the Bay of Biscay. The wind system 



