2 MAY

THE NEW ZEALAND GAZETTE

885

CLIMATOLOGICAL TABLE—Summary of the Records of Temperature, Rainfall, and Sunshine for March 1974—continued

The "normal" refers to the present site of the instruments. Standard periods for normals are: Temperature 1931-60, Rainfall 1941-70, Sunshine 1935-60. No normals are available for stations with only short records.

*Indicates that the sunshine recorder is not located at the station but is in the near vicinity.

A rain day is a day with rainfall equal to or greater than 0.1 mm.

Where the extremes of temperature and rainfall have occurred more than once during the month, the date of the first occurrence is given.

NOTES ON THE WEATHER FOR MARCH 1974

General—A high frequency of south-easterly conditions during the month resulted in most of the country having below average temperature. Rainfall was inadequate to provide significant drought relief in some North Island areas though Gisborne, Hawke's Bay and parts of Wairarapa and Canterbury did receive above average rainfall. Apart from the dry areas of the North Island and the Nelson Province the month was a good one for pasture growth. A very cold period in the middle of the month did not seriously influence farming operations over most of the country.

Rainfall—The rainfall over the country varied from less than a quarter of the monthly average in Nelson and North Taranaki, to over twice the normal in parts of Central and Southern Hawke's Bay. In the west of Northland and in Bay of Plenty, Waikato, parts of Taranaki and most of Manawatu conditions were very dry. Most eastern areas from central Canterbury to Gisborne had above normal rainfall; generally up to fifty percent above normal.

Temperature—March was a cold month in most parts of the country. Over the eastern half of the country the mean temperature was 1°c to 2°c below normal. Over the western half it was about 1°c below normal. The predominant south-east winds were reflected in eastern areas being those with the lowest mean temperatures. Napier, Masterton, and Wellington had their lowest March mean temperatures since 1936. The cold spell from the 18th to 22nd was largely responsible for the low monthly mean temperatures. During this period the mean temperature was 6°c to 7°c below average in many eastern areas north of Christchurch.

Sunshine—Sunshine strongly reflected the general weather pattern over the country as did rainfall and temperature. In eastern districts, especially in the North Island, sunshine was below average by up to 15 percent while in western districts it was above average by up to 40 percent. On the West Coast, Greymouth recorded 233 hours of sunshine and this was the highest March total there since 1948.

Weather Sequence—The month began with a disturbed south-westerly airstream flowing over New Zealand. Cold fronts moving in this airstream brought some rain to many areas during the 1st, 2nd and 3rd. On the 2nd, falls of over 25 mm were recorded in parts of Marlborough and Westland. By the 4th the airstream had become westerly and a major frontal system crossing the country brought rain to western and southern parts.

A weak anticyclone moved steadily over New Zealand on the 5th, 6th and 7th and the weather was generally fine. A very shallow trough of low pressure which had moved slowly through the anticyclone produced some heavy rain in Hawke's Bay on the 8th, though conditions remained fine elsewhere.

The anticyclone intensified near the Chatham Islands on the 9th and by the 11th a very large anticyclone covered much of the Tasman Sea, New Zealand and ocean to the east. Some rain fell in Gisborne and Hawke's Bay from the 9th to the 13th but generally fine weather prevailed elsewhere. This fine spell, following a long period of little rain in the central North Island, resulted in Lake Taupo dropping to its lowest level so far during the summer.

A strong north-westerly flow became established over the South Island and south of the North Island on the 14th. Some heavy rain fell in western and southern parts of the South Island on the 14th and 15th. In South Westland there were 24-hour falls with return periods of once in five to ten years. South Island lakes rose sharply with this rainfall. Some rain spread to the North Island on the 15th and 16th but amounts were light.

On the 17th an unusual weather sequence began. A depression which had been over the Central Tasman Sea for some days moved quickly around the north of the North Island and at the same time a large intense anticyclone moved from near Tasmania to pass just south of New Zealand. A very strong and very cold southerly airstream became established over New Zealand and during the period 18th to 21st some very low temperatures were recorded. On the 17th and 18th rain fell over all the North Island and the north and east of the South Island with southerly gales in many places. Over 50 mm of rain were recorded near Taupo, but a heavy use of electricity with the very cold conditions caused a big draw on the lake.

On the 18th Auckland experienced its lowest daytime maximum temperature ever recorded in March. For the five days 18th to 22nd Wellington's mean temperature was 6.5°c below the March average.

The cold southerly airstream had moved away to the east of the country by the 22nd and a large anticyclone which had moved from the south of Tasmania was positioned over New Zealand. This anticyclone persisted until the 30th. The weather was predominantly fine during this time, though there were a few showers in the south of the South Island on the 24th and 25th, and some rain in Gisborne and Northland on the 23rd, 24th and 29th.

On the 30th the anticyclone began to move away to the east and rain spread into South Westland and the east of Northland and Auckland and also Gisborne. Fine weather persisted over the rest of the country to the end of the month.

(N.Z. Met. S. Pub. 107).

J. F. de LISLE, Director.