Seasonal Climate Outlook: June - August 2011
La Niña gone, but a mild winter still likely.
The strong La Niña event which has dominated the tropical Pacific for several months has faded out, according to the NIWA National Climate Centre.
The Centre’s latest outlook, for winter (June to August), indicates that temperatures are likely to continue above average in many regions of the country, but near average in the west and south of the South Island, and average or above average for the northern North Island. Despite the overall pattern of mild conditions, cold snaps typical of winter will still occur from time to time through the period.
Seasonal rainfall and seasonal river flows are likely to be near normal in the north and east of both Islands, and normal or below normal over western regions of both Islands. Soil moisture levels are likely to be near normal in all regions.
The outlook states that mean sea-level pressures are likely to be above normal to the south and east of the country, and below normal north of New Zealand, with weaker westerlies and more frequent than normal easterly flow over the country.
Overall Picture
Temperature:
For the June-July-August period as a whole, temperatures are likely to be average or above average for the northern North Island, near average for the west and south of the South Island, and above average in all other regions. Sea surface temperatures near New Zealand are expected to be average or above average.
Rainfall, soil moisture, and river flows:
The National Climate Centre says that seasonal rainfall is likely to be near normal in the north and east of both Islands, and normal or below normal over western areas of both Islands. Seasonal river flows are likely to follow the same pattern as rainfalls, while soil moisture levels are likely to be near normal in all regions.
Regional predictions for the next three months:
Northland, Auckland, Waikato, Bay of Plenty:
Temperatures are equally likely to be near average or above average for the time of year. Winter rainfall totals, soil moisture levels and river flows are all likely to be in the normal range.
Probabilities are assigned in three categories; above average, near average, and below average. The full probability breakdown is:
| Temperature | Rainfall | Soil moisture | River flows | |
|---|---|---|---|---|
| Above average | 40% | 30% | 35% | 25% |
| Near average | 40% | 50% | 45% | 50% |
| Below average | 20% | 20% | 20% | 25% |
Click these links to view the historic rainfall and temperature ranges for this region
Central North Island, Taranaki, Wanganui, Manawatu and Wellington:
Temperatures are likely to be above average. Seasonal rainfall totals and river flows are equally likely to be near normal or below normal during the winter, while soil moisture levels are likely to be near normal.
Probabilities are assigned in three categories; above average, near average, and below average. The full probability breakdown is:
| Temperature | Rainfall | Soil moisture | River flows | |
|---|---|---|---|---|
| Above average | 50% | 20% | 30% | 20% |
| Near average | 30% | 40% | 40% | 40% |
| Below average | 20% | 40% | 30% | 40% |
Click these links to view the historic rainfall and temperature ranges for this region
Gisborne, Hawke’s Bay, Wairarapa:
Temperatures are likely to be above average. Seasonal rainfall totals, soil moisture levels and river flows are all likely to be in the near normal range.
Probabilities are assigned in three categories; above normal, near normal, and below normal. The full probability breakdown is:
| Temperature | Rainfall | Soil moisture | River flows | |
|---|---|---|---|---|
| Above average | 50% | 30% | 35% | 25% |
| Near average | 30% | 50% | 45% | 50% |
| Below average | 20% | 20% | 20% | 25% |
Click these links to view the historic rainfall and temperature ranges for this region
Nelson, Marlborough, Buller:
Temperatures are likely to be in the above average range. Seasonal rainfall, soil moisture levels and river flows are all likely to be in the near normal range.
Probabilities are assigned in three categories; above average, near average, and below average. The full probability breakdown is:
| Temperature | Rainfall | Soil moisture | River flows | |
|---|---|---|---|---|
| Above average | 50% | 20% | 25% | 15% |
| Near average | 30% | 50% | 45% | 50% |
| Below average | 20% | 30% | 30% | 35% |
Click these links to view the historic rainfall and temperature ranges for this region
West Coast, Alps and Foothills, Inland Otago, Southland:
Temperatures are likely to be near average, for the three winter months as a whole. Seasonal rainfall and river flows are both equally likely to be in the near normal or below normal range. Soil moisture levels are likely to be near normal.
Probabilities are assigned in three categories; above average, near average, and below average. The full probability breakdown is:
| Temperature | Rainfall | Soil moisture | River flows | |
|---|---|---|---|---|
| Above average | 30% | 20% | 20% | 20% |
| Near average | 50% | 40% | 45% | 40% |
| Below average | 20% | 40% | 35% | 40% |
Click these links to view the historic rainfall and temperature ranges for this region
Coastal Canterbury, East Otago:
Temperatures are likely to be in the above average range. Seasonal rainfall is likely to be in the normal range, for the 3-month period as a whole. Soil moisture levels and river flows are also likely to be near normal.
Probabilities are assigned in three categories; above average, near average, and below average. The full probability breakdown is:
| Temperature | Rainfall | Soil moisture | River flows | |
|---|---|---|---|---|
| Above average | 50% | 30% | 40% | 35% |
| Near average | 30% | 50% | 45% | 50% |
| Below average | 20% | 20% | 15% | 15% |
Click these links to view the historic rainfall and temperature ranges for this region
Background
The tropical Pacific is now in a neutral state, with the previously strong La Niña event having dissipated. In the longer-term through winter and the rest of 2011, the majority of the international forecast models maintain neutral conditions in the Pacific, although the development of an El Niño, or another La Niña, cannot be ruled out for later in 2011.
For comment, please contact:
Dr James Renwick, NIWA Principal Scientist, Climate Variability & Change
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