Seasonal Climate Outlook: July - September 2013

28 June 2013

Mild conditions likely to continue over late winter.

Late winter (July–September) temperatures are very likely to be above average in North Island regions, and likely to be average or above average in all South Island regions. Nevertheless, cold snaps, frost and snow conditions will of course still occur in many areas from time to time, as is typical of this time of year. Sea surface temperatures around New Zealand’s coasts are likely to be above the climatological average for the coming three months near the coast and to the east and south of the country, with conditions near average further to the west in the Tasman Sea.

Rainfall for the July–September period as a whole is likely to be normal or above normal in the east of the North Island, normal or below normal in the west and south of the South Island, and in the near normal range for all other regions. Soil moisture levels are likely to be normal or above normal in the east of the South Island, and near normal in other regions. River flows are likely to be normal or above normal in the southwest of the North Island, normal or below normal in the west and south of the South Island, and near normal in other regions.

The equatorial Pacific Ocean remains in a neutral state (neither El Niño nor La Niña). International guidance indicates that these neutral conditions are likely to persist for at least the coming three months. For the New Zealand region, higher pressures than normal are forecast south of the country, with slightly lower pressures than normal in the north Tasman Sea. This circulation pattern is likely to produce a weak easterly flow anomaly over the country.

Overall picture

Rainfall, soil moisture and river flows

Rainfall, soil moisture and river flows for the July–September period as a whole are likely to be in the normal ranges for many regions of the country. Exceptions are as follows: in the southwest of the North Island, river flows are likely to be near normal or above normal; in the east of the North Island, rainfall is likely to be near normal or above normal; in the west and south of the South Island, both rainfall and river flows are likely to be near normal or below normal; and in the east of the South Island, soil moisture levels are likely to be near normal or above normal.

Temperature

July to September temperatures as a whole are very likely to be above average in all North Island regions, and likely to be average or above average in all South Island regions, for this time of year. Sea surface temperatures around New Zealand are also forecast to remain above average near to and southeast of the country, whereas sea temperatures west of New Zealand are likely to return to near average.

Regional predictions for the next three months

Northland, Auckland, Waikato, Bay of Plenty

Temperatures for the July – September period as a whole are very likely to be above average. Rainfall totals, soil moisture levels and river flows during this period are all likely to be in their near normal ranges.