Seasonal climate outlook - April – June 2019

Seasonal climate outlook - April – June 2019

28 March 2019

Outlook Summary

• A central Pacific El Niño event continued during March as the ocean and atmosphere remained weakly coupled. Sea surface temperatures warmed across the equatorial Pacific during March and El Niño is expected to continue during the upcoming three-month period.

• While April – June 2019 is expected to start off with mixed air flows, higher pressure than normal is forecast to develop in the northern Tasman Sea along with lower pressure than normal south of New Zealand. This is expected to result in more westerly quarter winds than normal, particularly during the second half of the coming season.

• Air temperatures are forecast to be above average in the north and east of the North Island and east of the South Island and about equally likely to be above average or near average in all remaining regions of New Zealand for April – June 2019.

• Rainfall is about equally likely to be above normal or near normal in the west and north of the South Island and about equally likely to be below normal or near normal for all remaining regions of New Zealand.

• Well above average coastal and Tasman Sea surface temperatures, including marine heatwave conditions, are forecast to have a strong influence on regional temperatures and may contribute to significant rain events.

• For the current tropical cyclone season (November 2018 to April 2019), NIWA’s Southwest Pacific Tropical Cyclone Outlookindicates that the risk for New Zealand is near normal. On average, at least one ex-tropical cyclone passes within 550 km of New Zealand each year. Significant rainfall, damaging winds, and coastal damage can occur during these events.

April – June 2019 temperatures are forecast to be above average in the north and east of the North Island and east of the South Island (50% chance) and about equally likely to be above average (45% chance) or near average (40% chance) in all remaining regions of New Zealand. However, cold snaps and frosts are likely to occur, particularly in colder locations, as the season progresses.

April – June 2019 rainfall is about equally likely to be above normal (35-40% chance) or near normal (35-40% chance) in the west and north of the South Island and about equally likely to be below normal (35-40% chance) or near normal (35-40% chance) for all remaining regions of New Zealand.

April – June 2019 soil moisture levels and river flows are most likely to be below normal (50-55% chance) in the north of the North Island and east of the South Island. For the west of the South Island, soil moisture levels and river flows are most likely to be above normal (50% chance). In the north of the South Island, soil moisture levels and river flows are most likely to be in the near normal range (40% chance). For the west and east of the North Island, soil moisture levels and river flows are about equally likely to be below normal (40% chance) or near normal (35% chance).

Full climate outlook: SCO_April_2019_final.pdf

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