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La Niña is on the doorstep…

Posted By Jo Pentreath | November 16, 2021

Dr Kathleen Kozyniak
Pri
ncipal Scientist Air
Hawke’s Bay Regional Council

Spring has treated the region generously so far.  We had above normal rainfall in September, followed by near normal rainfall in October, then November kicked off in style with much of the region hitting November averages already. The one worrying aspect of October’s rain was that a few areas, namely the Ruahine and Kaweka Ranges and northern Hawke’s Bay, got just two thirds of their month’s usual total. Early November rain made up for the lost ground in northern Hawke’s Bay and the Kaweka Range, but the Ruahine Range wasn’t so fortunate and still needs 60-100 mm to hit the November average.

The lack of rain in the ranges meant October’s river flows were below normal while soil moisture levels across the region were looking good for the time of year.  October’s groundwater levels appeared to improve on the previous month but the majority of our sites remained below normal – it’s just that the majority has slimmed a little.  Temperatures were warmer than usual, the overnight temperatures in particular, and soil temperatures ended the month on about 18°C on the Plains.

A La Niña event is most likely with us for the summer.  Warmer than usual sea and air temperatures are expected over the next three months, along with higher than normal sea level pressure over central and southern New Zealand and lower to the north.  That should bring us more easterlies than normal and the onshore flow helps our chances of getting decent rain.  So near normal rainfall over the period is the pick but it’s possible, with the forecast pressure pattern, that the rain favours the north rather than the south.

Percentage of Normal Rainfall


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