Dr Kathleen Kozyniak says La Niña events bring more northeast winds than usual. Those onshore winds can bring with them moisture picked up from travelling over warm seas, giving us more cloud and rainfall than normal. Photo / Ian Cooper
Dr Kathleen Kozyniak says La Niña events bring more northeast winds than usual. Those onshore winds can bring with them moisture picked up from travelling over warm seas, giving us more cloud and rainfall than normal. Photo / Ian Cooper
It seems reasonable to say Hawke’s Bay had lousy weather in 2022.
This summer – can it really be called summer? - gumboots have been more common than jandals.
The Hawke’s Bay Regional Council has rain gauges dotted across the region, most of them installed in the 1980s and 1990s. The majority recorded their highest annual total in 2022.
Our observations were consistent with MetService which, as reported in Hawke’s Bay Today, saw Napier Airport record its highest rainfall since 1971. One thing the two years, 1971 and 2022, had in common was a La Niña event that spanned the entire year.
The El Niño and La Niña phases of the El Niño-Southern Oscillation (ENSO) are associated with different weather patterns in Hawke’s Bay.
During an El Niño event, west or southwest winds typically dominate. The westerly angle of the wind brings into play a rain-shadow effect from the Ruahine and Kaweka Ranges so we link El Niño phases to drier than normal weather.
Dr Kathleen Kozyniak is the team leader Marine, Air and Land Science at the Hawke's Bay Regional Council. Photo / Supplied
During La Niña events we expect more northeast winds than usual. Those onshore winds can bring with them moisture picked up from travelling over warm seas, giving us more cloud and rainfall than normal. There are no guarantees the different ENSO phases will bring the conditions described, but they raise the likelihood of getting them.
Last year’s La Niña, which continued into this summer, ran true to form. The saturated ground throughout the year made it difficult to grow and harvest the produce that Hawke’s Bay is renowned for.
We’re pretty well versed in the region on the devastating impact drought can have. We lived it in the summer and autumn of 2019-20 and again in 2020-21. The past 12 months taught us that a lengthy spell of wet weather is problematic too.
The amplitude and frequency of ENSO events – the La Niña and El Niño events - are higher since 1950 than over the past 500 years.
Under climate change scenarios it is assumed that ENSO will continue behaving and influencing our weather as it has in the recent past.
It is likely though that rainfall variability associated with ENSO will intensify as temperatures increase. The weather patterns that bring us rain, will bring more of it.
Those that bring us sunshine will increasingly dry out our soils because of hotter temperatures. We only need to look to the spring and summer of 2020-21 to see how that can play out.
In November 2020 Napier suffered a terrible flood that had a return period exceeding 100 years. Then followed six months of dry weather culminating in a drought. It looks like the future is a rollercoaster with all the fun taken out of it.
