23 JULY THE NEW ZEALAND GAZETTE 2177

WEATHER NOTES FOR MAY 1980

General—May was considerably drier and milder than usual
throughout most of New Zealand. Mean monthly pressures were the
highest over the whole country since June 1979, and on the 9th,
Kelburn, Wellington recorded 1036.4 millibars, its highest May
9 a.m. pressure since 1934. There was a marked absence of strong
winds over the North Island, but westerly winds were stronger than
usual in southern areas of the South Island.

Mild drier conditions produced good grass growth in most districts,
and stock was reported to be in excellent condition. Some farmers
have experienced one of their best dairying seasons for many years.

Rainfall—The only areas that recorded above normal rainfall
totals for the month were parts of Westland and Southland. Even
here the excesses were less than 50 percent. The greatest departures
below normal occurred in Bay of Plenty, Hawke's Bay, Wairarapa,
and Canterbury. Many stations in these districts recorded less than
25 percent of their usual May rainfall, and on Banks Peninsula, Okuti
measured only 4 mm for the month, the lowest May total since 1927.
The station at Castle Point, Wairarapa, recorded 11 mm, the lowest
in May since observations began in 1902.

On the 21st, heavy rain in the Otira area caused a major washout
on the main railway line between Greymouth and Christchurch.
Three locomotives plunged into the Otira River, killing the driver of
the first. From 9 a.m. on the 20th to 9 a.m. on the 21st 152 mm of
rain were recorded at Otira, and the washout occurred during the
period of heaviest rain between 8 p.m. on the 20th and 7 a.m. on the
21st when nearly 130 mm of rain fell.

Invercargill city and surrounding areas suffered surface flooding on
the 24th when 36 mm were recorded between midnight and 7 a.m.
The total daily fall of 45 mm made this the highest May one-day fall
since the station at Invercargill Airport began in 1941. The town of
Kelso was flooded once again during this heavy rain.

Temperatures—Temperatures were warmer than usual throughout
New Zealand apart from some areas in Northland and Bay of Plenty.
In the North Island temperatures were above normal by 0.5°C and in
the South Island by more than 1.0°C. At Invercargill the highest May
mean temperature of 9.0°C since 1954 (also 9.0°C) was recorded. In
eastern districts daytime temperatures were colder than usual by 2.0°
to 4.0°C from the 28th to the 31st. During a warm spell from the 23rd
to the 25th maximum temperatures were generally above normal by
3.0°C.

Sunshine—Total sunshine hours for the month were near normal in
most districts. On the West Coast they were below average by about
10 to 20 hours, but in eastern districts of both islands they were above
by the same amount. Apart from 1975 (164 hours) Christchurch
Airport, with 163 hours, recorded it's sunniest May since the station
began in 1949.

WEATHER SEQUENCE FOR MAY 1980

The ridge of high pressure that extended onto New Zealand from
the Tasman Sea at the end of April moved slowly east, and by the
morning of the 3rd an anticyclone had become established over the
whole country. This anticyclone persisted until the morning of the
12th, with most of the country experiencing fine weather during this
period. Some districts in both islands had some showery conditions,
but they were of short duration. During the evening of the 12th a
trough of low pressure in the Tasman Sea began to move eastwards
towards the South Island, and by the morning of the 13th had reached
the West Coast. Heavy rain was reported in Fiordland and Westland,
and moderate falls in areas west of the main ranges in both islands.
More than 40 mm were recorded at Milford Sound in the 24 hours up
to 9 a.m. on the 14th, and 30 to 40 mm in some parts of Westland in
the same period. Temperatures were cooler than usual during the
first week of the month, but then became milder than average.

By the morning of the 15th the trough of low pressure had moved
to the east of New Zealand, and had been replaced by an anticyclone
moving from the Tasman Sea. During the morning of the 17th
depressions formed in the north and south Tasman Sea and began to
move east towards the country. One depression had moved onto
Northland, and the other onto Fiordland by the afternoon of the
18th. Heavy rain was recorded in Northland, Auckland, Taranaki,
Manawatu, Nelson, Westland, inland Canterbury, and Fiordland. At
Otira more than 70 mm were recorded in the 24 hours up to 9 a.m.
on the 19th, and many of the above districts had in excess of 50 mm.
Moderate rain was reported in all areas west of the main ranges and
lighter falls in the east. Temperatures remained warmer than usual
throughout the country.

On the morning of the 20th a cold front, associated with a
depression moving to the south of New Zealand, had moved onto the
South Island and this brought very heavy rain to western districts of
the South Island. Again at Otira the heaviest falls were recorded,
more than 150 mm in 24 hours. In other areas on the West Coast
100 mm were recorded in the same period. The only areas that did
not report rain were parts of Hawke's Bay and Wairarapa. From the
21st to the 24th a strong westerly airstream covered New Zealand,
and disturbances in this flow brought heavy rain to the West Coast
and Southland, and moderate rain to many areas west of the main
ranges. Most eastern districts had fine weather during this period.

A ridge of high pressure extended onto the South Island on the
25th, and two small depressions had formed within a trough of low
pressure, and were lying to the east and west of the North Island by
the morning of the 26th. As the depression to the west moved across
central districts of New Zealand during the 26th, heavy rain was
reported in Wellington and Poverty Bay, with moderate falls in
Wairarapa and Hawke's Bay. Some areas recorded 24 hour falls of
more than 40 mm. Temperatures were warmer than usual throughout
New Zealand from the 21st to the 25th, especially along the east
coasts of both islands. By the 27th an anticyclone in the Tasman Sea
had begun to move eastwards onto the country bringing fine weather
to most districts. Some areas east of the main ranges in the North
Island did report some showers.

From the 27th until the end of the month an anticyclone covered
the whole of New Zealand and most of the country experienced fine
weather. Showers were reported in Poverty Bay, Hawke's Bay, and
Wairarapa as small disturbances in the southerly airflow onto these
regions persisted for 2 days. By the 31st a depression that had formed
in the Tasman Sea was moving south-east towards the country.

J. S. HICKMAN, Director,
(N.Z. Met. S. Pub. 107)

Price 25c BY AUTHORITY: P. D. HASSELBERG, GOVERNMENT PRINTER, WELLINGTON, NEW ZEALAND—1980