WEATHER FORECASTS. LECTURE BY MR CHEESEMAN.

Te Aroha News, Volume VII, Issue 408, 5 October 1889, Page 5

WEATHER FORECASTS. LECTURE BY MR CHEESEMAN.

1 Auckland, October 1. There are some believers and some disbelievers in the value of Captain Edwin's weather predictions, and ooth believers and unbelievers will probably be in-, toasted in a peep behind the scenes in order to obtain some inkling as to how this weather prophecy business is conducted. At a meeting of the Auckland Institute, 'held at the Museum meeting-room last . evening, Mr T. F. Cheeseman delivered a ' highly-interesting lecture on " Weather Forecasts and Storm Warnings," illustrated by a number of carefully-executed diagrams.

ANCIENT SUPERSTITION. In remote 'days, said the lecturer, disturbances of nature, of whatever kind and degree, were assumed to be personally : governed and directed by spirits or gods, which acted with much the same caprice and irregularity as human agents. Nearly all the tribes had a rain deity, which must > be propitiated with sacrifice and offering-* before the much-needed rain could be obtained, and this superstition is still common enough among rude and savage races.

WEATHER PROGNOSTICS, pure and simple, are mentioned in the earliest literature of all races, notably the Book of Job, and the Iliad of Homer, which contain many examples. Mr Cheeseman traced the weather prophecy from this stage, stated en passant that the science was mentioned in Virgil, and then proceeded to show that for several hundred years, indeed until quite close to our own times, it could hardly be said that meteorology made any advance at all.

WEATHER GLASSES. About 1600 the thermometer came into use, and a means was thereby obtained ot accurately measuring the temperatuie of the air, and, subsequently, ot obtaining some insight into its variations of heat and cold. Fifty years later, a still more important invention was made — the barometer— by which the pressure of the atmosphere at any particular locality could be obtained. It wa3 soon observed that as the barometer fell or the weight of the air became greater, bad weather approached, and that, conversely, as the barometer rose, or the weight of the air became less, the weather improved. From that time the barometer became the most important of meteoiological instruments so far as weather prediction was concerned. Later, means of measuring the amount of moisture, and ot determining whether it was increasing or decreasing, were secured, and a very important step was made towards ascertaining the approach of rain.

AIR CURRENTS. Then, through observations made by travellers, explanation of the trade-winds, anti-trades, and the monsoon, or periodic winde, a clue was obtained to the general system of atmospheric circulation. In the meantime, systematic observations of weather changes had been commenced at many places, and the height of the barometer and thermometer, amount of lainfall, the force and direction of the wind, etc., were recorded and tabulated, and those from one station sec against those of another. By these means the approach of bad or good weather, according to a low or high barometer, became more obvious, and.ib became possible to correlato these spells with the direction of the wind, temperature, etc. After it became clear that the weather at a particular locality, whether good or bad, did not belong to that locality alone, did not arise in it, and did not die out in it without atfecting other localities, but that, jusb as clouds drift across the sky, so areas of good or bad weather drift over the earth's surface, passing over one station and then over another.

THE ELECTRIC TELEGRAPH. The invention of the electric telegraph has made it possible to learn, in a few minutes, the weather that is being experienced at each station, and facilitates the prediction of particular storms, so that, given a large land suiface with a network of telegraph lines, it is now practicable to predict the weather within a day ov two in advance with considerable accuracy.

WEATHER DISTURBANCES. Mr Cheeseman went on to explain tha^ weather disturbances are due to movement 8 or disturbances in the atmosphere &ur" rounding the globe, heat moisture or elec tricity, and went on to refer at considerable length to the various currents of air. He explained that storms are nothing more than eddies or whirlwinds contained within these atmospheric currents, and which move along with them. Mr Cheeseman illustrated the movement of a .supposititious

CYCLONE OVER AUCKLAND, by means of a diagram. He said :At first the wind would be light, from the N.E., with a tolerably clear sky, and the barometer would stand materially high. After a while the sky would become hazy or black, and the wind would gradually freshen. The barometer slowly fall?, Then, after a period depending on the diameter of the cyclone and the- rate at which it was travelling, the sky would become covered with clouds, and rain commence to fall, the wind being almost a calm, and the barometer falling. If the .centre were to pasfa directly over Auckland, the force of the gale and the downpour of rain would gradually increase until suddenly tho wind drop, and a calm lasting about a quai'ter of an hour would follow, the barometer i - apidly sinking, and tho rain descending faster than ever. Then, all at once, the wind would shift to the S. W., the rain would cease, and the sky rapidly become clear, the barometer rising much taster than it fell. Usually, however, the centre passes to the south of Auckland, and the wind shifts gradually from N. to N.W. and S.W., and no central calm, or lall in the storm, is felt. Very rarely does the centre cross to the North of Auckland, but it it did the wind would shift by E., S.E., and S. to S.W., or, as it is usually called in common language, the wind would " back. J> Anticyolonep are the opposites of cyclones. If in Auckland we experience a epell of unusually bad weather, it is due to the visit of a cyclone of considerable intensity.

NO EASY TASK. Mr Cheeseman exhibited several charts , showing the weather experienced in Australia and New Zealand on particular dates to prove that predictions made had been actually verified. The task of weather prophecy, he went on to observe, was by no means an easy one, owing to the difficulty of interpreting slight chancres, and the fact that a cyclone was never the same for two' day 8.

NEW ZEALAND. " The geographical position of New Zealand," he said, "is almost as unfavourable as that of the United States is favourable for weather prediction. Placed in the mid«t of a vast) ocean, with no land nearer •than Tasmania, and that nearly 1,000 miles distant, it is, in many cases, impossible to kndvv what storms are nearing us utotil they* aotually < touch our western coast, and' then, owing 1 to the

narrowness of the territory, the time for warning is very small indeed. No doubt, many storms that pass over, or just to the south of Tasmania, also reach New Zealand, but a large proportion either die out in mid-ocean or pass far to the south, and of those that do live long enough to -cross the whole distance, their rate sof advance is so variable that the time of their arrival cannob be predicted with any approach to accuracy. It is also to be remembered that because the cyclone produces a serious storm on the coasts of Tasmania, it does not follow that it will bo felt with the same intensity in New Zealand. Practically, therefore, weather warnings from Australia are not of very great value to us, and our weather forecasts must rely, principally, on observations taken within our own coun*try."

CAPTAIN EDWIN. , " The weather forecasts of New Zealand," MrCheeseman said, "are periodically issued at Wellington by Captain Edwin. They are based upon weather telegrams forwarded to him at nine o'clock each morning, by certain of the chief telograph stations, I think twonty-two in number. In many places it is usual to ridicule his predictions because of their occasional failure, but I cannot find this feeling is entertained by those who are aware of their value as a whole. Certainly the masters of interprovincial steamers and of our local trading vessels usually take considerable notice of them, and their opinion should have some weight. New Zealand is a peculiarly difficult country for predictions, and a high percentage of accuracy cannot be expected trom a department with such an inefficient number of stations, and so poorly supplied with things for proper equipment. What is wanted is a full series of stations along the West Coast, especially of the South Island, which is usually the first to feel the impact of a coming disturbance ; they should report two or three times daily to the central office, and not onco a day, as under the present system."