In July, the lows are slightly further north than in June, and the preceding high covers Central and Eastern Australia. The winds are usually from the north drawn into the front of the low. Rains due to south-west winds in the rear of the low are also common, especially in the south-west corner.
In August.—In 1909 and 1910 the rains were generally due to northerly winds in front of a low. In 1911, they were nearly all due to south-west winds from the rear of the low, the high following close after. The lows appeared to have a somewhat more southern "habit" throughout the month of August in 1911.
In September, a tendency for the low to run up between the two highs is noticeable. If the latter are close together so that the gradient is steep there would seem to be better chances for rain. Thus in 1911 in this month there were six high-pressure systems in evidence, but only three with somewhat steeper gradients led to rain.
In October, rains are rare in the gold-fields region, and there seems to be no very favorable arrangement of the pressure conditions. Both south-west and north-east winds bring rain, chiefly to the south. Thunderstorms may occur over the fields.
In November, a low usually "broods" over Central Australia, sometimes forming a true "monsoonal" tongue from the north. Conditions are very unfavorable for rain over the gold-fields. Thunderstorms may, however, occur and give local rain.
In December, the same conditions obtain as in November. Thunderstorms are not uncommon.
Summary of Position of Eddies from July, 1909, to July, 1912.
| — | Highs. | Lows. | |||||||
| Summer. | Autumn. | Winter. | Spring. | Summer. | Autumn. | Winter. | Spring. | ||
| Off Perth and Cape Leeuwin | 9 | 8 | 9 | 6 | 1 | 5 | 15 | 1 | |
| S. of Esperance and in Bight | 6 | 3 | .. | 5 | .. | 12 | 16 | 8 | |
| Off N.W. Cape and Cossack | 2 | 5 | 5 | 7 | 13 | 1 | .. | 4 | |
| Over E. Australia | .. | 5 | 19 | 9 | .. | .. | .. | .. | |
| Others | 2 | 1 | 3 | .. | 1 | 2 | 3 | 7 | |
| tongues | |||||||||
Average figures for the monthly rainfall in the gold-fields have already been given in a preceding section.
X.(b).—FLOOD RAINS IN AUSTRALIA.
These phenomena occur at infrequent intervals in various regions of the continent, causing considerable damage to stock, bridges, roads, &c., in our sparsely-populated and pastoral territories. Brief summaries of the meteorological conditions accompanying the following occurrences will be of interest:—
- (1) 1909, August, floods in South-Eastern Australia.
- (2) 1910, January, floods on the Darling.
- (3) The heavy rains of Queensland.
- (4) The heavy rains of Northern West Australia.
