NIWA Outlook: April-June 2015
NIWA Outlook: April-June 2015
Overview
Sea surface temperature anomalies in the tropical Pacific intensified significantly around the international Dateline during March 2015 and are currently showing a pattern consistent with weak El Niño conditions. Atmospheric patterns across the region were also generally consistent with weak El Niño anomalies.
International guidance indicates that the probability for conventional El Niño thresholds being crossed over the next three months (April – June 2015) is about 60%.
During April - June 2015, lower than normal mean sea level pressures are expected to the east and northeast of New Zealand with positive mean sea level pressure anomalies west of New Zealand. This circulation pattern is likely to produce anomalous westerly quarter wind flows.
Coastal waters are forecast to be in the near average or above average temperature range for the April – June 2015 period.
Outlook Summary
April – June 2015 temperatures are most likely (50% chance) to be in the above average range in the east and north of the North Island. For all remaining regions of New Zealand temperatures are about equally likely (35-45%) to be in the near average or above average range. As autumn progresses, cold snaps and frosts can still be expected from time to time in some parts of the country.
April – June 2015 rainfall is about equally likely (35-40% chance) to be in the near normal or above normal range in the west of the North Island. Rainfall totals for the season are about equally likely (35-40% chance) to be in the near normal or below normal range for the north and east of the North Island and the east of the South Island. In the north and west of the South Island, rainfall is most likely (45% chance) to be in the near normal range.
April – June 2015 soil moisture levels and river flows are most likely (55-60% chance) to be below normal in the east of the South Island. Soil moisture levels and river flows are most likely (45% chance) to be in the near normal range in the west of the North Island and west of the South Island. In the north and east of the North Island, soil moisture levels are about equally likely (40-45% chance) to be in the near normal or below normal range, while river flows are most likely (45-50% chance) to be in the below normal range. Soil moisture levels and river flows are equally likely (40% chance) to be in the near normal or below normal range for the north of the South Island.
Full document:
SCO_Apr2015.pdf