NIWA February 2001 Climate Summary

NATIONAL CLIMATE SUMMARY – FEBRUARY 2001

A MONTH WITH DRAMATIC CONTRASTS
- INCREDIBLY DRY IN THE CENTRAL AREAS, UNUSUALLY WET IN THE NORTH

•{\f "Symbol" \s 10} SEVERE SOIL MOISTURE DEFICITS CONTINUE IN THE NORTH AND EAST OF THE SOUTH ISLAND AND LOWER NORTH ISLAND

EXTREMELY WET IN BAY OF PLENTY AND COROMANDEL

•{\f "Symbol" \s 10} WARM IN MANY REGIONS

•{\f "Symbol" \s 10} SUNNY IN CENTRAL NEW ZEALAND

A continuation of severe soil moisture deficits in Marlborough, Nelson, Canterbury and Wellington, with extreme or very high fire risk were features of climatic conditions in these regions during February. Severe soil moisture deficits now extend from Nelson through to North Otago in the South Island, and have spread to the Wairarapa in the North Island. In contrast, unusually high rainfall created significant runoff throughout Bay of Plenty, as well as parts of Gisborne and Waikato.

Marlborough, Nelson and Canterbury rainfalls were much less than 25 percent of normal in many areas. Blenheim’s 2-month rainfall total was only 8 mm; the 2nd lowest for any January through February period there in records going back to 1930. Only 1939 was drier. It was also very much drier than average in Buller, north Otago and Wellington, with rainfall 50 percent (half) or less than normal. Rainfall was below average over the entire South Island.

The wet unsettled weather throughout coastal Bay of Plenty and Coromandel, resulted in rainfall totals ranging from 200 to over than 400 percent of normal there. It was also unusually wet for the Chatham Islands. Other wetter than average regions were Auckland, Waikato, King Country, Tongariro, Gisborne and Hawke’s Bay.

February was a warm month in many areas, with mean temperatures between 0.5 and 1.5°C above normal over much of the North Island, as well as northern and inland South Island areas, including the Kaikoura and Canterbury coasts. In contrast, mean temperatures were between 0.5 and 1.0°C below average on the west coast of the South Island. The national average temperature was 17.7°C, which was 0.6°C above the 1961 – 1990 normal. Sunshine totals were above average throughout in central New Zealand, but below average totals occurred in Bay of Plenty, Gisborne and Hawke’s Bay.

February’s climate patterns were due to more frequent anticyclones (‘highs’) centred in the Tasman Sea and the east of New Zealand, maintaining ridges across central New Zealand. These caused the very dry conditions over the middle of the country. Lower than average pressures prevailed north of the North Island giving more prevalent easterlies in northern North Island regions, drawing in warm and humid air masses from the tropics at times and producing rather wet conditions.

EXTREMELY DRY IN MARLBOROUGH, NELSON AND CANTERBURY

Rainfall was extremely low in Marlborough, Nelson, Canterbury and Buller, with totals much less than 25 percent of normal in many areas. It was also very much drier than average in Buller, north Otago and Wellington, with rainfall 50 percent (half) or less than normal. Other drier regions, with less than 75 percent of normal rainfall, were southern Wairarapa, parts of Taranaki, Westland, Fiordland, Central and eastern Otago and much of Southland.

Near or record low February rainfall was recorded at

Westport 39 mm , 28% of normal, lowest on record which began in 1945

Lake Rotoiti 7 mm, 7% of normal, lowest in record, which began in 1934

Motueka. 2 mm, 3% of normal, 2nd lowest, records began in 1943

Nelson Airport 6 mm, 11% of noraml, 3rd lowest of records back to 1941

Blenheim Airport, 3 mm, 9% of normal. 4th lowest in records back to 1941

Hanmer Forest 7 mm, 10% of normal, 2nd lowest in records back to 1905

Christchurch Airport, 4 mm, 10% of normal. Lowest in records back to 1944

Christchurch Gardens 4 mm, 10% of normal, 3rd lowest in records back to 1864

Timaru Airport 9 mm, 19% of normal, lowest in records back to 1957

Waimate 10 mm, 20% of normal, lowest in records back to 1898

Manapouri 15 mm, 19% of normal, 3rd lowest in records back to 1914

EXTREMELY WET AND UNSETTLED IN BAY OF PLENTY AND COROMANDEL

February’s rainfall was unusually high throughout coastal Bay of Plenty and Coromandel, with totals ranging from 200 to more than 400 percent of normal. In Coromandel, some locations had seven more rain days than the February normal. It was also unusually wet for the Chatham Islands. Other wetter than average regions were Auckland, Waikato, King Country, Tongariro, Gisborne and Hawke’s Bay, all having at least 125 percent of normal rainfall.

Extremely high February rainfall was recorded at:

Great Barrier Island, 212 mm, 277% of normal, 2nd highest on records back to 1977

Whitianga, 270 mm, 281% of normal,, 2nd highest on record back to 1942

Tauranga Airport 268 mm, 325% of normal, 2nd highest on record back to 1898

Te Puke 263 mm, 228% of normal, 3rd highest on record back to 1973

Whakatane 310 mm, 426% of normal, highest on record

Chatham Islands 115 mm, 207% of normal, 3rd highest on record back to 1957

WARMER IN THE NORTH ISLAND AND NORTHERN AND INLAND SOUTH ISLAND

Mean temperatures ranged from 0.5 to 1.5°C above normal over much of the North Island, as well as northern and inland South Island areas, including the Kaikoura and Canterbury coasts.

Extremely high February mean temperatures were recorded at

Tauranga Airport 20.7°C, +1.6 above normal, 2nd highest

Taupo Airport 18.5°C, +1.8 above normal, 3rd highest

It was much cooler than average, with mean temperatures between 0.5 and 1.0°C below normal, on the west coast of the South Island.

SUNNY IN CENTRAL NEW ZEALAND

Sunshine and solar radiation totals were at least 110 percent of normal in Wellington, Marlborough and Nelson. Sunshine totals were well below average in Bay of Plenty, Gisborne and Hawke’s Bay with totals less than 80 percent of normal. Near normal sunshine occurred elsewhere.

HIGHLIGHTS

Extreme temperatures

The highest air temperature for the month was 35.3oC, recorded at Timaru Airport on the 4th. The highest February air temperature on record for this location is 39.8°C.

The lowest air temperature for the month was –2.8oC, recorded at Ranfurly on the 7th after a clearance from cold southerly conditions. The lowest February air temperature on record for this location is -3.1°C.

High rainfall

High rainfall occurred in Coromandel on the 11th, with totals as high as 120 mm recorded at Whitianga, and at least 50 mm throughout much of eastern Northland, Bay of Plenty, Waikato and Wanganui. Further high rainfall occurred in Bay of Plenty and Gisborne on the 17th, Whakatane recording 130 mm.

For further information, please contact:

Dr Jim Salinger, NIWA - Auckland,

Tel (09) 375 2053 (Business) or (09) 527 3939 (after hours)

© Copyright NIWA 2001. All rights reserved.

ENDS

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