“N.Z. IN GRIP OF A COLD WAVE.”

Star (Christchurch), Issue 19255, 17 December 1930, Page 8

“N.Z. IN GRIP OF A COLD WAVE.”

HAS BEEN IN OPERATION SINCE JUNE LAST YEAR. By F. L. WOOLES. The present, spell of unseasonable weather is quite in keeping with the general conditions that have been a feature throughout the spring. An occasional cold storm is not an unusual occurrence during the spring and early summer in Canterbury, but this year the conditions have been distinctly abnormal. The cold spells have been more frequent and longer than during an average season, with the result that the mean monthly temperatures have been considerably below the normal for months past. In fact, records indicate that something like a cold wave has been in operation since June, 1929, affecting even the summer. The average mean temperature during the warmer months also has been markedly sub-normal. A reference to the nor’-westers will stress this point. In Canterbury this wind invariably produces the highest temperatures, but so far this season the nor’-wester on the average has not been as warm as in other years. On December 12 a maximum shade temperature of 81.7 deg., the highest to date since last summer, was recorded in the city. That was certainlj l - a fairly high reading, but shade readings of 80 deg. and over are not uncommon in October in a normal season. On October 10, 1914, a maximum shade temperature of 87 deg. was recorded in the city during a nor’-wester, while shade temperatures high as 91 deg. have been noted in November. The highest shade temperature ever officially recorded in Christchurch during a nor’wester was on January 29, 1908, the registration being 95.3 deg. Cause Unknown. There is insufficient data available to definitely account for the cause of periodical cold seasons, but they certainly do occur in a more or less irregular cycle. A periodical diminution in the sun’s heat may be the cause. If such were the case, it is quite understandable that with the immense preponderance of water over the land masses on the earth’s surface, the effect of any increase or decrease in the sun’s heat would result in a variation of ocean temperatures, which, because of the tendency of water to heat or cool much less readily than any land mass, would have a great controlling influence, especially on Oceanic and Insular climates.

The stormy weather that is at present affecting the east coast of New Zealand, though not directly, is indirectly connected with the conditions producing the floods in Victoria. The prevailing local conditions are part of an intense storm area centred near the Chatham Islands, while the Victorian visitation has resulted from a storm area centred near the south-east coast of Australia. The controlling factor is an intervening high pressure system centred in the Tasman Sea, producing in the one instance a deep gradient to the low pressure area centred near the Chatham Islands, thus causing the cold southerly gales along the east coast of New Zealand. The centre of the low pressure area near Victoria is so situated in relation to the high pressure system in the Tasman Sea that a gradient has been established for easterly winds with accompanying heavy rains, thus accounting for the floods in Victoria. The RainfalL The rainfall for the 24 hours ended at 3 p.m. to-day was 0.340, as against 0.850 for the preceding 24 hours. At noon, there was a little sunshine, and things were better, though heavy clouds were still hanging about in threatening patches.