Page:Types of Australian weather.djvu/29

Rh At 9 a.m. on the 24th, (Chart 26) the cyclone was still in an active state, but it had passed to the south of Sydney and was receding from the coast; the barometers were rising rapidly on shore, and before noon a light northerly wind was blowing. On the 25th September, the day following the gale, the weather everywhere was generally fine, while all that remained of the energetic high and low pressure systems were parallel isobars lying over the southern areas of Australia with very shallow gradients. This gale was very destructive and did much damage to property in Sydney; in some instances houses were unroofed, and the wind and sea on the coast were very heavy.

TYPE XII. DEVELOPMENT OP A CYCLONE FROM A &Lambda; DEPRESSION.

The distinction between a &Lambda; depression and a monsoonal low pressure is not by any means well defined, and it is possible that this should be taken as a variation of Type 3; there are however, marked differences, not only in the shape of the isobars, but also in the wind; and the most decided distinction is perhaps the easterly wind circulating round the southern part of the monsoonal low pressure and the northerly and southerly winds about the &Lambda;; but in some cases, as in the one selected, the wind circulation is mixed, northerly, southerly and easterly winds being present, and these from their want of energy tend to throw the forecaster off his guard. The season is, however, some guide, as these storms are most frequent from September to April.

Their sphere of influence is very extensive, as may be noted in Chart 28, which shows rain over half Australia as the apparent result of this storm. Most of these storms take a direct easterly course over New South Wales and Victoria or through Bass' Straits. At times they move to north-east, the Polar winds being more energetic, and this feature intensifies all the storm and rain conditions. The winds in all these storms are violent, and in some very destructive.

The one selected for illustration appeared first on 27th May, 1893, (Chart 27). At 9 a.m. on that day, a dormant and irregular