National Climate Summary - The Big Dry Continues
TUESDAY 1 MAY 2001
NATIONAL CLIMATE SUMMARY – APRIL 2001
THE BIG DRY CONTINUES
- VERY DRY OVER MOST OF
THE SOUTH ISLAND, WELLINGTON AND WAIRARAPA
- EXTREMELY WET IN PARTS OF THE NORTH EAST
- WARM AND VERY SUNNY IN CANTERBURY AND OTAGO
Very low rainfall occurred in many South Island areas, especially in the east from the Marlborough coast to Otago, with most sites recording less than 25 percent of normal. Many sites in Canterbury and Otago measured rainfall totalling 15 mm or less for the second consecutive month. As a result severe soil moisture deficits continued in Canterbury, Otago, and parts of Marlborough. East coast rivers remained at abnormally low levels. Rainfall was also extremely low in Wellington where it was less than 20 percent of normal. Significant soil moisture deficits persisted in Wellington and extended into Wairarapa. Of special note, rainfall for the year to date is the lowest in more than 100 years in both Wellington (77 mm), and Christchurch (60 mm), and the lowest in more than 60 years throughout much of Nelson and Marlborough (Blenheim measured only 38 mm). At the same time as the east has been extremely dry, it has also been one of the driest in almost 40 years of measurement at Hokitika.
The remnants of tropical cyclone ‘Sose’ produced high rainfall and flooding in the Bay of Islands, Coromandel, and Bay of Plenty over the night of 12/13 April. This together with further unsettled weather resulted in extremely high April rainfall in these regions, with totals exceeding 300 percent of normal at some locations.
It was a sunny month over the South Island, especially in Canterbury and Otago. However, sunshine totals were below average in Gisborne.
April temperatures were near normal over much of the country. However, it was warmer than average in Canterbury and Otago. The national average temperature was 13.5°C, which was 0.1°C above the 1961-1990 normal.
April’s climate patterns were due to more frequent anticyclones often centred over and to the east of central New Zealand, bringing dry, settled conditions to most areas throughout much of the month. Lower than average pressures prevailed in the north Tasman Sea, and brought more prevalent northeasterlies over northern New Zealand.
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VERY DRY OVER MOST OF THE SOUTH ISLAND AND LOWER NORTH ISLAND
Rainfall was extremely low in many eastern South Island areas, from Marlborough to Otago, with totals much less than 25 percent of normal at most locations. Many Canterbury and Central Otago sites measured rainfall of 10 mm or less for the second consecutive month. Rainfall was also extremely low in Wellington where it was less than 20 percent of normal. Other rather dry regions, with less than 50 percent of normal rainfall, were southern Wairarapa, Nelson, and Westland.
Near or record low April rainfall was recorded at:
of normal Year
Records began Comments
Cape Palliser 5 6 1930 Lowest
Wellington, Kelburn 16 15 1862 Equal lowest
Wellington Airport 11 13 1960 2nd lowest
Westport Airport 53 28 1944 2nd lowest
Hanmer Forest 20 19 1905 3rd lowest
Kaikoura 7 8 1948 3rd lowest
Christchurch Airport 7 13 1944 Lowest
Christchurch Gardens 5 8 1864 2nd lowest
Lincoln 5 8 1881 Lowest
Akaroa, Rue Lavaud 12 14 1978 Lowest
Tara Hills 8 17 1950 3rd lowest
Dunedin, Musselburgh 21 32 1918 3rd lowest
Queenstown Airport 11 20 1969 Lowest
Rainfall was near average in Waikato, King Country, Wanganui, Manawatu, Gisborne, and Southland.
EXTREMELY WET IN SOME NORTHERN AREAS OF THE NORTH ISLAND
Extremely high April rainfall was recorded in the Bay of Islands and parts of Bay of Plenty, with totals exceeding 300 percent of normal at some locations. It was also very wet in eastern Coromandel with totals at least 200 percent of normal. Other wet regions, with at least 120 percent of normal rainfall, were eastern Northland, Auckland, and Hawke’s Bay.
Near or record high April rainfall was recorded at:
of normal Year
Records began Comments
Kerikeri 349 255 1982 2nd highest
Kerikeri Airport 383 320 1978 2nd highest
Tauranga Airport 348 359 1898 2nd highest
Whakatane 233 314 1992 Highest
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VERY SUNNY IN OTAGO AND SOUTHLAND
Sunshine and solar radiation totals were at least 120 percent of normal throughout much of Otago and Southland, and at least 110 percent of normal over the remainder of the South Island, as well as the south of the North Island. Sunshine totals were below average in Gisborne, with totals less than 90 percent of normal.
NEAR AVERAGE TEMPERATURES IN MANY REGIONS, BUT WARM IN CANTERBURY AND OTAGO
Mean temperatures were near normal in many regions. However, it was warmer than average in Canterbury and Otago where they were 0.5 to 1.0°C above average.
The highest air temperature for the month was 28.4oC, recorded in Rangiora on the 9th. The highest April air temperature on record for this location is 29.6°C.
The lowest air temperature for the month was –5.6oC, recorded at Middlemarch, Otago on the 25th; the lowest April air temperature on record for this area is -7.5°C.
High rainfall and flooding
The remnants of tropical cyclone ‘Sose’ produced high rainfall in the Bay of Islands, Coromandel, and Bay of Plenty over the night of 12/13 April. Significant surface flooding resulted in Keao where rainfall totalled 200 mm in less than 18 hours, and at Whitianga where 132 mm was measured in 24 hours.
For further information, please contact:
Dr Jim Renwick- Wellington
Tel (04) 386 0343 (Business)
or Stuart Burgess, NIWA - Wellington, Tel (04) 386 0569
© Copyright NIWA 2001. All rights
Acknowledgement of NIWA as the source is required. ENDS