NIWA Outlook: May – July 2020

Outlook Summary

• ENSO-neutral conditions continued in April. The Southern Oscillation Index (SOI) was neutral and central Pacific sea surface temperatures (SSTs) were on the El Niño side of neutral.
• Oceanic ENSO-neutral conditions will very likely persist (76% chance) over the next three months.
• Rainfall and thunderstorm patterns in the global tropics are expected to be associated with more westerly-quarter winds than normal (from southwest to northwest) around New Zealand.
• Sharp cold snaps are possible during the month of May as fronts move onto the country from the Tasman Sea and Southern Ocean.
• May – July 2020 air pressure is forecast to be higher than normal north and lower than normal south of New Zealand. This is expected to be associated with a westerly quarter air flow anomaly.
• Air temperatures are about equally likely to be near average or above average in north and east of both islands. Near average temperatures are most likely in the west of both islands. Cold snaps and frosts can be expected in typically colder locations through the three-month period.
• Rainfall is about equally likely to be near normal or below normal in the north and east of both islands. Near normal rainfall is most likely in the west of both islands.

May – July 2020 air temperatures are about equally likely to be near average (40% chance) or above average (40-45% chance) in the north and east of both islands. Near average temperatures are most likely (45% chance) in the west of both islands.

May – July 2020 rainfall is about equally likely to be near normal (35-40% chance) or below normal (35-40% chance) in the north and east of both islands. Near normal rainfall is most likely in the west of both islands (45% chance).
May – July 2020 soil moisture and river flows are most likely to be below normal (45% chance) in the north of the North Island and most likely to be near normal in the west of the South Island (40% chance). For the east of the North Island and north and east of the South Island, soil moisture levels and river flows are about equally likely to be near normal (40-45% chance) or below normal (35-40% chance). For the west of the North Island, soil moisture is most likely to be near normal (45% chance) while river flows are about equally likely to be normal (45% chance) or below normal (40% chance).

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