Cool March ending with welcome rain

IT'S RAINING, IT'S POURING: A deserted Gladstone Road this morning as rain drenched the city. Pictures by Paul Rickard

A rumbling of thunder, a heavy rain warning and the threat of flooding this morning heralded the start of Gisborne's second week of the coronavirus lockdown.

Overnight MetService upgraded a heavy rain watch to a full warning, with computer-predictions of some of the heaviest hourly rainfall figures for some time.

The first downpours early this morning dumped 25mm on Makaraka, with another 20mm by 9am.

The East Cape Lighthouse gauge measured 57mm by 7.30am while Pouawa received over 45mm by 7am including a downpour of 20mm between 6am and 7am.

MetService warned a slow-moving front with the weather driving in from the north-east could deliver hail, thunderstorms and rainfall accumulations of 90 to 120mm, especially south of Tokomaru Bay, with possible intensities of up to 25 to 40 mm an hour.

The warning was for surface flooding, slips and bad driving conditions. However, by mid-morning conditions had eased, and the weather had moved further south to Wairoa, the Hawke's Bay and Wairarapa.

Until this morning, the district had been experiencing ongoing drier-than-normal weather, with a persistent soil moisture deficit which stood at 118mm yesterday.

All the signs pointed to a colder, dry autumn, with sunshine hours and rainfall totals well short of normal.

March in this region has been dominated by colder winds from the south and east.

Sixteen days of winds from the southerly quarter and four of easterlies far outweighed the nine days of warmer winds from the north-west and west.

Overcast weather has also had a cooling effect, without delivering much rain.

By the weekend, the mean daily temperature was around 16.65 degrees — almost a whole degree below the 30-year (1981-2010) average.

Gisborne's daytime temperatures have been hit the hardest, averaging 21 degrees to date, against a 30-year average of 22.6 for March.

Overnight temperatures have averaged just under 12.3 degrees — below the 30-year mean of almost 12.6.

The chill of some nights has hinted at the approach of frost weather, despite the night of the 22nd-23rd recording a warm 18.1 degrees.

There have been six nights with temperatures below 10 degrees, the coolest in the early morning of the 26th with an air temperature of just 6.6 degrees and frost-approaching grass minimum of 1.1 degrees.

Until this morning it had been a dry March, with just over 46mm of rain — less than half the 30-year average rainfall of 91.4mm.

The first three months of the year had totalled just 108mm — half of the 30-year average of 219mm for the first quarter.

Regarding the possibility of an El Nino developing, the World Meteorological Organisation's El Nino/Southern Oscillation (ENSO) update says there is a 60 percent chance of ongoing neutral conditions continuing during March to May.

The chances for an El Nino or La Nina are 35 percent and 5 percent respectively.

For the June to August period, the chance for ENSO-neutral is 55 percent, that for El Nino is 20-25 percent and that for La Nina is also 20-25 percent.