At the mercy of the elements

Many southerners will be shrugging their shoulders and expressing incredulity at the huge change in weather across Otago over the past couple of days.

From scorching heat igniting large and worrying scrub fires, to torrential rain and flooding. It brings to mind singer-songwriter James Taylor’s song Fire and Rain, in which he says "I’ve seen fire and I’ve seen rain, I’ve seen sunny days that I thought would never end."

Many might have been thinking the same on Wednesday. But look what has happened since.

The transformation is almost too hard to believe. Yet, somewhat paradoxically, these extremes of nature are pretty closely related. Without the warmth, we probably would not have had this intensity of rain.

Residents of Burnside in Dunedin had to flee an inferno on Wednesday evening and were fortunate the outcome was not worse. Temperatures in the low to mid-thirties, very low humidity and gusty northwesterly winds combined to provide perfect fire conditions, coming after a prolonged spell of dryness and heat that has left much of the South desiccated.

Wednesday’s fires — not just in Dunedin but also near Palmerston, Papatowai and Invercargill — were probably inevitable, given the tinder dry state of the South. An extreme fire risk is not communicated without just cause and reflects the fact the slightest spark is likely to cause a conflagration.

Yesterday, it was the turn of former Tropical Cyclone Fehi to make trouble. The storm system carved a rapid path southeast across the South Island and pretty much directly over Dunedin in the afternoon, bearing its dangerous cargo of heavy rain and, in some locations, high winds. The very low air pressure at its centre also played a role in allowing the sea to rise higher than normal which, combined with wind-generated waves and high tides, caused coastal inundation in places.

The consequences of a direct hit from even such a rapidly moving, decaying storm shows just how much punch a  former tropical cyclone can carry.

This is a reminder, if ever it was needed, that, even after an incredibly settled summer, the weather here can still change suddenly and dangerously. So while some are reading news that January was likely New Zealand’s hottest month in 150 years of records, others are handing out the sandbags in South Dunedin, picking up children from school and heading home early from work as floods threaten.

It is no wonder fires have been breaking out in recent weeks. Early calculations by climate scientist Dr Jim Salinger show the country’s average January temperature was 20.2degC, 3degC above normal.

A lack of cold outbreaks into the Tasman Sea over the past three months has allowed an unusual marine heatwave to develop. This in turn has heated up New Zealand even more and brought the amazing summer weather. But as a consequence of having sea-surface temperatures 5degC or more above average, and a hotter atmosphere, it has long been on the cards that, when a rain-bearing system arrived, the rain was going to be more extreme than it might otherwise be. That has come to pass.

This week began with Niwa warning temperatures could hit 40degC in some parts of the South Island. They did not, peaking a few degrees short.

Fortunately, warnings were already being issued of the probable impact of ex-Fehi at this end of the week. As a result, the need to be prepared in many parts of the South Island was not lost behind the hyperbole accompanying the 40degC prediction.

One day it is fire, the next rain. Both are frightening; both can have huge effects on the everyday lives of those in the South.

The rains may have put out the fires threatening many parts of the South. They may also relieve the drought. But they have brought their own problems.

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