WEATHER NEXT YEAR

Evening Post, Volume CXVI, Issue 105, 31 October 1933, Page 8

WEATHER NEXT YEAR

LOtfG EANGE FORECASTS

WILL THEY BE POSSIBLE ?

Will it ever be possible to form some idea of the general character of the weather for some months ahead, or perhaps even a year? Such an achievement is not possible yet N but meteorologists/are working hard with that end in view. It must bo remembered that meteorology as a science is. still very young, that new facts about the earth's atmosphere are .c'omirig to light with stiraulatingrfrequency, and that what; is;hot .possible today in tlie matter of weather, forecasting may be easy of achievement-in." the not too.•distant, future, . -7,:1V V'lrr^V :.:. ■■■./"■■' ,iV: -.'. ■'

v Writing." in/;" The ■; Listener",, on i( Wqitther Forecasting—How .Far Can Wo Go?" G, A. Clarke reviews the difficulties that■•e.ojifrpnt meteorologists in making'their-forecasts. They have to examine; ho;'points out, the corapleto at tho moment, to analyse as-;far^Bs'-i>6ssjble its structure, to estimate the-direction in which it is likely to move, and the velocity of that movement. 'That in itself is a task of no small magnitude, but docs not complete their work. In addition, they, have to, determine what is taking plage in the' moving: air masses as ,tirae elapses; and how the, weather system, may bo affected as- It moves from sea to land.-.. If within .'the weather' 'system there exist 'ariy shrirply-definod or. suddan changes!, of. .weather, the .time of tho urrivaVof those changes at-different places' must also bo estimated.

T,o do all this successfully calls naturally for a high degree of organisation. "From, a vast network of meteorological stations, not only in • our own country, but also all over Western Europe/and--even from such far-flung outposts of civilisation as Greenland, fepitsibergon, Jan Mayen; and Bear Island; and. also from numerous ships out-:,oji the Atlantic 'Ocean, tolographic reports are,sent in code to the Meteorological Qflico in London. These reports contain observations of all the meteorological; elements,, and of the state of weatjior at the.,varjous stations, and bocauso the observations Rrc made simultaneously 'everywhere, they, give,, when plotted on the chart, an instantaneous pioturo of the weather distribution over tho whole njca under.roviow.. Ini addition, from • certain observing stations, details of tho. state of matters in tho air at considerable heights above tho surface are obtained, such's3 the direction and volacity of the winds at various levels, tho movemont of the clouds, and the changes of tho tdmperature of the air with height, Theso latter observations aro very important as indicationsof. what development's Are likely to/take .placoin'tho weat^or systom.'' ;■. Th'd a,bo'yo.'is! a; skotcii.of the work at,< the - m'e\dorologi^t in tho British Isles. !';'; That of /the moteorologist in New Zealand.is similar, but moro difficult, perhaps; owing to tlio relative absences of stations from which to receive reports

ANTIOYCLONE3 AND ' DEPRESSIONS.

' "Listeners to woathor forecast's, remarks tlio writer, have heard much talk of anticyclones/ and depressions arid, haye gathered from tho remarks madd ,ttiat~ anticyclones are to be regarded ;as areas of good weather, while depressions are associated with rain, gales, or general,l?ad woathor. Both these systems arc characterised l)y certain states of ;\tho barometer,' the commonly ■ accepted '■ idea being that a high \#n<l' "stoady baromoter is associated witli an anticyclone, whereas tho depression isdistinguished by <a barometer which falls rapidly to a low level as the depression approaches and then rises when the centre of. the depression has passed over. The barometer; reading at any station -indicates . simply the pressure 'of the atmosphere' at'that place, and, because of the aforementioned association of pressure changes with weather changes, the barometric readings form a very convenient basis from whicji to draw .up a,weather map,.

' When the'barometric readings from all tho stations are plotted qu' the chart, lines are.drawn connecting':.those stations having' similar values' of 'pressure and;,tn'.o result resembles $hc^contour lines' on a, survey map,, the lines enclosing, areas of high aud-low;-.pres-sure: these, arfeas ar© respectively -the anticyclones and ; ..depressions'!'.;,which have just been1 ' referred to., ..Both these typos of pressure distribution, are' continually changing thoi'r position; and; shape, 'and, it is- these changes, whujh! our forecasters haye \to anticipate' or "forecast. 1' .It is 'obvioijs .therefore, that when.,the changes a>e slight and slow, a forecast • can bo made fora longer "period iu-'advanee than can be done- *when changes are yiolont and rapid, ' Anticyclones are on the' aver; ago more::enduring than depressions, 'they travel, more slowly; and often, remain nearly stationary over a.region for more'than,a. week. In such cases accurate forecasts can be. made for several days\in advance. , But with de-: pressions matters are different, for those weather systems have, a habit,of moving with considerable velocity, usually from 15 to 30 miles an hour. Depressions may therefore' opme, and go .very quickly, and, as their habit is of ten to follow oach other in. quick succession along, the same path, variable- and changeable weather is experienced and the forecast says "continuing, unsettled." , • '."'. ~ ... .

LONG-RANGE FORECASTS.

Discussing the possibility- of making forecasts for a season or even a year ahead, Mr,- Clarke says that meteorologists are studying the movements of air masses which follow a regular course There is, for instance* an average wind drift from south-westward across tho North Atlantic and this wind is warm arid moisture-laden;.it is met in its advance by ioy winds blowing, from off tho great ice-fielcl. of Greenland, afld down fttmi the polar seas. In sonic y«ars the .cold wands spread farther /south than ÜB,ual; the depression track also then-moves further south and lies niore over the British' Isles and in such years there is more . stormy Weather. "This fact .has > naturally encouraged meteorologists to seek , for some method whereby the weather of a season or a 1 year'ahead might be foretold—in other words to introduce a system of'long-range,, forecasting.'' In. India the character" of the monsoons can be predicted with considerable. success by taking into account' previous weather in other parts, of tho globe, and a great deal of work on similar lines lias been done for othcriparts of tho world. It has been found, for cx- p ample, that, if the north-oastcrly trade-' winds in the Atlantic arc weaker than normal ■in any year, then in: the following yoar the seasons in ;the British Islands tend to.bo wot. It.is obvious that in studying the. atmosphere, it must be taken as a whole, and certain events in some parts of it must naturally have their, repercussions in other places subsequently, so that, if we could once discover the factors which control these events and their subsequent effects, we should* be able to form some idea of the .'general character of the weather for some months or perhaps even a year ahead."