1919.] Pemberton.—Weather Forecasting in New Zealand. 171 
in force and variable, but with a westerly tendency in the north and 
an easterly in the southern districts. Some heavy seas were, however, 
reported along the eastern coast. Fogs and mists were much in evidence, 
and scattered places reported drizzling rain. These conditions are cha¬ 
racteristic of the approach of a cyclonic system centred due west of New 
Zealand. From the weather reports of the 10th and 11th this supposition 
was readily confirmable. On the latter date the centre was presumed to 
be about 800 miles due west of Farewell Spit, and on the following day 
some 250 miles west of the west coast of the South Island. On both the 
11th and 12th northerly winds were experienced northward of Cook Strait, 
and strong easterly winds mled in the southern districts. Rainfall was 
general, and foggy conditions were also prevalent. 
In the chart of the 13th August (fig. 8) the cyclone has wholly overspread 
the Dominion, but since the preceding day two centres have appeared, one 
off the east coast and the other off the west coast of the South Island. 
A range of mountains, such as the Southern Alps, at right angles to the track 
of a “ low ” or “ high ” system will sometimes delay its advance, and it is 
invariably noticeable that atmospheric pressure will remain relatively low 
or high, as the case may be, on the west coast when the greater part of the 
system has passed some time previously to the eastward of the mountain- 
range. It is possible that this is a factor in the development of many of 
our “ secondary lows,” and the second centre of this cyclone may have 
been thus developed. 
The effects of the division of the central region of the cyclone are shown 
in the decreased force of the wind south of a line joining the two centres 
and in the variability of the wind-direction. The latter, however, is quite 
in accord with the isobars. For instance, on the east coast of the South 
Island the direction is southerly in the rear of the first centre, while on 
the west coast of the same Island, from Farewell Spit to Westport, it is 
northerly in front of the second centre. Greymouth and Hokitika have 
a south-east direction, these stations being on the southern front of the 
second centre. 
At the time the chart refers to (9 a.m.) rain was falling in all that portion 
of the Dominion shaded in fig. 8, and in various districts throughout the 
country the heavy rains caused floods in the rivers. 
By the morning of the 14th August the first centre had moved farther 
eastward, while the second centre still remained on the west coast, but 
with a tendency to move northwards. Eventually the latter took a 
most unusual path, passing due north until the 15th, and then recurving 
about the northern extremity of the North Island. Fig. 9 shows the 
approximate paths of both the centres during the period they were under 
observation. 
It was not until the 16th that New Zealand was in the rear of the whole 
cyclonic system, and on that day high southerly winds were experienced. 
On the two following days cold and changeable conditions prevailed, with 
passing showers along the east coast. The actual effects of this disturb¬ 
ance, therefore, lasted from the 9th to the 18th August, with more or less 
stormy conditions during the whole of this period. 
Secondary “ Lows” 
In connection with cyclones and westerly areas of low pressure there 
often develops a smaller or “ secondary ” disturbance, sometimes merely 
