It’s almost a year since I last reported that the region had below normal rainfall for the month, so it’s a real novelty and, let’s face it, a relief to say March rainfall was well below normal – about 60% of the long-term average. Totals on the Ruataniwha Plains and the region’s south coast were particularly low, both receiving less than half of usual March rainfall, while the Heretaunga Plains had roughly three quarters. It allowed soil moisture levels and river flows to ease a little but they remain very high for early autumn. Groundwater levels continue to break records for the time of year.
Air temperatures, both daytime and overnight, were near normal during March. Soil temperatures on the Ruataniwha and Heretaunga Plains finished the month in the mid-teens and about 12⁰C in the ranges.
The El Niño-Southern Oscillation is in neutral mode but El Niño conditions could develop by the end of winter. Chances are that we’ll also have a positive Indian Ocean Dipole. Both raise the potential for drier than normal weather and a big change to the weather we’ve had for the past so many months. Already the seasonal forecast models are hinting at a change in the sea level pressure pattern. Higher than normal pressure is expected to the west of the country and lower than normal to the northeast, which may give winds a southerly tilt. However, with warm seas around us, temperatures are expected to stay near or above normal over the next three months. Rainfall too might hover near normal but forecasts that extend beyond three months suggest drier weather is to come.
Percentage of Normal Rainfall
Dr Kathleen Kozyniak
Principal Scientist Air
Hawke’s Bay Regional Council
