Summer of discontent

Ask anyone and they will tell you Otago's had a lousy summer - even the experts. With the official summer season ending yesterday, Rebecca Fox seeks the truth behind the perceptions.

Dave Stewart
Dave Stewart
It all started positively. For once, it was fine for an international cricket test match in Dunedin. People left the University Oval with suntans and peeling noses.

Inland, Clyde had four consecutive days of maximum temperatures reaching at least 29.9degC and recorded the nation's highest - 34.2degC - on December 5.

Only it was not to last.

By the end of the test the rain had arrived and the unsettled weather had begun.

It hit Dunedin on December 16 with a short thunderstorm causing flooding through the central city. Heavy rain fell on Ranfurly later in the month, when 44mm on December 21 contributed to the town's third-highest December rainfall of 135mm.

As Christmas holidays approached people were optimistic the weather would improve.

They packed their tents and loaded their caravans and cars and headed to the region's favourite holiday spots along the coast and inland.

Everyone was disappointed.

In Alexandra alone, it rained nearly double the number of days it normally does over the Christmas-New Year period, and temperatures were nearly 3degC below average.

And it continued for weeks, so it was not surprising when Niwa's January figures showed well below average temperatures - Dunedin's 1.4degC below, Balclutha's 1.9degC and Cromwell's 2.5degC.

Everyone was hanging on for school to go back and for the good weather to begin, as February is traditionally Otago's most settled month.

But it began with a high of only 15degC and Dunedin experienced nearly a week of rain from the 11th. Temperatures did increase in Central Otago, Wanaka reaching 32degC on the 20th.

So many will expect a pretty grim summer picture to be painted by Niwa's summer climate wrap, due out next week.

A preview of those figures for Otago shows an average summer so far.

The general consensus is of an unsettled season. Temperatures were slightly below average. Some parts were wetter, some drier. But what made it different from most years was more westerlies.

A pedestrian runs across George St in heavy Monday-afternoon rain in mid-December. Photo by Craig...
A pedestrian runs across George St in heavy Monday-afternoon rain in mid-December. Photo by Craig Baxter.
In Dunedin the winds have come from a southwesterly or westerly direction on 14 days out of the past 30.

Climate scientist Jim Salinger said the westerly winds made coastal Otago summers much more unreliable.

''The trend towards more westerlies or southwesterlies in summer has increased. That does not bode well for coastal Otago.''

Niwa's January climate summary recorded a strong southwesterly flow anomaly across New Zealand, which caused significantly lower than normal temperatures for the time of year, especially in the south and west, resulting in temperatures well-below average for the South Island.

MetService meteorologist John Law said the weather had been different in Central Otago compared with the coast in recent weeks.

''Through January the south of the country had its fair share of southerly winds, bringing cooler and moist air across the country,'' Mr Law said.

During January the highest temperature recorded at Dunedin Airport was only 28degC, compared with 34degC the year before.

''One of the most noticeable southerly pushes occurred on the 17th of the month when the 1pm temperature at the airport was a mere 8degC.''

As well as bringing cooler air, the southwesterly winds brought ''a fair scattering'' of showers about the eastern parts of the region.

In January there were about 18 days when Dunedin city reported some rainfall, while Wanaka reported just a little more than average rainfall for the time of year, although most fell at the start of the month.

February was working out to be a little warmer and drier than the previous month, Mr Law said.

The rainfall total at the time of writing this month in Dunedin is 45.8mm compared with 72.4mm in January.

''The difference inland is even larger, with Wanaka only reporting 4mm of rainfall so far in the month. An average month's rainfall in Wanaka is around 35mm for this time of year.''

Dunedin hydrologist Dave Stewart said the unsettled summer should come as no surprise as Otago's driest month historically was September, followed by April, while the wettest month was December, then January.

The two summer months were also some of the most unsettled, with thunderstorms and heavy rainfalls often causing flooding, especially inland.

February was traditionally the most settled of the summer months with 15% less rainfall than December, although at an average of 67.8mm it was still well above September's average of 48.3mm, Mr Stewart said.

''Usually there are more high-pressure systems, which bring long settled dry spells.''

While it was not as dry, it was warmer, averaging 15degC, compared with September's 9.5degC.

February was often when droughts began and last summer it was the beginning of a long warm dry spell.

''It came right and we hoped it would do the same this year, but no, it has just carried on raining.''

September could also bring heavy rainfalls. The highest recorded volume for the spring month is 225mm, compared with February's 128mm.

''We can also get those lamb-killing winds.''

- rebecca.fox@odt.co.nz

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