{"id":255139,"date":"2026-01-28T02:34:13","date_gmt":"2026-01-28T02:34:13","guid":{"rendered":"https:\/\/www.newsbeep.com\/nz\/255139\/"},"modified":"2026-01-28T02:34:13","modified_gmt":"2026-01-28T02:34:13","slug":"whats-driven-this-months-big-wet","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/nz\/255139\/","title":{"rendered":"what\u2019s driven this month\u2019s big wet?"},"content":{"rendered":"

It has been a month of umbrellas rather than sunscreen across much of New Zealand, with persistent rain, low sunshine and deadly storms dominating headlines<\/a> and daily life.<\/p>\n

For many people, it has felt like midsummer never really arrived. Is it simply bad luck, or is there something more going on?<\/p>\n

As with most aspects of our climate and weather, the answer isn\u2019t straightforward. It reflects the interplay between New Zealand\u2019s geography, warmer-than-average ocean temperatures<\/a>, large-scale regional climate patterns and long-term global warming.<\/p>\n

What the data shows \u2013 and why it\u2019s been so wet<\/p>\n

Climate observations back up what many New Zealanders have been feeling this month. Across northern regions in particular, sunshine hours have been well below average, while rainfall totals have been far above normal<\/a>.<\/p>\n

In central Auckland, a weather station in Albert Park had recorded around 244mm by January 27 \u2013 nearly three times the (1981\u20132010) average for the month. <\/p>\n

At Mount Maunganui<\/a>, the month-to-date total had climbed to roughly 385mm, more than four times the norm.<\/p>\n

Similar patterns have been seen in many parts of the upper North Island, with repeated heavy rain events<\/a>, high humidity and prolonged cloudy spells. The result has often been soggy soils, swollen rivers and increased risks of flooding and landslides.<\/p>\n

While each storm that affects New Zealand is different, many of the systems visiting the country this summer share some common features. <\/p>\n

Several have originated in the tropics, subtropics or the north Tasman Sea before drifting south toward New Zealand. These systems typically carry warm, moisture-laden air \u2013 and the potential for intense rainfall.<\/p>\n

When these moist air masses interact with cooler air from the south, or encounter New Zealand\u2019s rugged topography, conditions become ripe for heavy rain.<\/p>\n

As air is forced upwards over hills and mountain ranges \u2013 particularly along the Coromandel Peninsula, Bay of Plenty, East Cape and Gisborne regions \u2013 moisture condenses rapidly, producing very high rainfall totals. <\/p>\n

This is why northern and eastern parts of the country so often bear the brunt of these subtropical events.<\/p>\n

The regional patterns loading the dice<\/p>\n

\"Damage<\/p>\n

Damage in Te Araroa on the East Coast. (Source: Huia Ngatai)<\/p>\n

One background factor this summer has been the lingering influence of La Ni\u00f1a, part of the El Ni\u00f1o\u2013Southern Oscillation (ENSO) system that dominates climate variability across the Pacific.<\/p>\n

During La Ni\u00f1a, atmospheric pressure tends to be lower than normal over Australia and the north Tasman Sea, and higher than normal to the south and east of New Zealand. <\/p>\n

This effectively flips our usual weather pattern on its head, reducing westerly winds and increasing the frequency of easterly and northeasterly flows.<\/p>\n

Those northeasterly winds draw warm, humid air from the subtropics toward New Zealand. Because our temperatures are highly sensitive to wind direction, even small shifts can have large effects.<\/p>\n

La Ni\u00f1a also tends to be associated with warmer-than-average sea surface temperatures, which have again been observed around New Zealand. So, when northeasterly winds blow across these warmer waters, they pick up additional heat and moisture, further fuelling heavy rainfall potential.<\/p>\n

Another background driver that constantly shapes New Zealand\u2019s weather and climate is the Southern Annular Mode (SAM), which describes the north\u2013south movement of the westerly wind belt that circles Antarctica.<\/p>\n

A positive SAM phase, which has dominated much of this summer, tends to bring higher pressures over the South Island and southern New Zealand. This allows storms from the subtropics more room to drift south and linger near the North Island.<\/p>\n

Climate change as an intensifier<\/p>\n

\"Karangahake<\/p>\n

Karangahake Gorge slip and flooding (Source: NZTA)<\/p>\n

Overlaying these regional drivers is the broader influence of climate change, which is steadily warming both the atmosphere and the oceans surrounding New Zealand.<\/p>\n

As the planet heats, the atmosphere can hold more moisture \u2013 about 7% more water vapour for every 1\u00b0C of warming. This means that when storms do develop, they have more fuel available, increasing the potential for heavier rainfall and stronger winds.<\/p>\n

Climate change does not cause individual weather systems, nor does it directly control large-scale climate patterns like ENSO or the SAM. But it acts as a powerful intensifier.<\/p>\n

Event-attribution studies in New Zealand to date have shown climate change can increase the total rainfall from intense storms by around 10\u201320%.<\/p>\n

But for the most intense downpours \u2013 when the atmospheric \u201csponge\u201d is wrung out most vigorously \u2013 rainfall intensities can increase by as much as 30%, depending on the frame of time being looked at. These short, extreme bursts of rain are often what cause the greatest damage.<\/p>\n

There are still important uncertainties. Scientists are actively researching whether climate change will alter the frequency or strength of La Ni\u00f1a and El Ni\u00f1o events, but so far there is no clear answer. The same is true for long-term trends in the Southern Annular Mode.<\/p>\n

What we can say with confidence is that background warming is shifting the risk profile.<\/p>\n

As global temperatures continue to rise, the kinds of extremes we\u2019ve experienced this season are likely to become more common. The biggest unanswered question is how quickly we can reduce greenhouse gas emissions to limit how severe these impacts ultimately become.<\/p>\n

James Renwick is a professor of physical geography (climate science) at Te Herenga Waka \u2014 Victoria University of Wellington.<\/p>\n

This article is republished from The Conversation<\/a> under a Creative Commons licence.<\/p>\n

The morning’s headlines in 90 seconds, including Police appeal for help over spate of robberies, Melania speaks about Minneapolis protests, and a tennis star\u2019s meltdown caught on camera. (Source: 1News)<\/p>\n","protected":false},"excerpt":{"rendered":"It has been a month of umbrellas rather than sunscreen across much of New Zealand, with persistent rain,…\n","protected":false},"author":2,"featured_media":255140,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[390,42,43,147,40,38,41,39,3393],"class_list":{"0":"post-255139","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-headlines","8":"tag-climate-change","9":"tag-headlines","10":"tag-news","11":"tag-science","12":"tag-top-news","13":"tag-top-stories","14":"tag-topnews","15":"tag-topstories","16":"tag-weather-news"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/255139","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=255139"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/255139\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/255140"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=255139"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=255139"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=255139"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}