Spring equinox brings high tides: Warmer and sunnier than normal so far this month

Warmer and sunnier than normal so far this month
Climate Update by Roger Handford

Despite the spring tug o' war between the warmth of the north and the chill of the south, September in the Gisborne region is about a degree warmer than usual.

The lack of rain might be another indicator to watch.

Warm northwesters have gained the upper hand with 15 days of winds from the west and north quarter against 8 days from the south.

As of September 23, the mean daily temperature was running at over 13.3 degrees Celsius - just over a degree warmer than the 30-year mean (1991-2020).

Daytime temperatures have been averaging 18.5C - almost a degree-and-a-half above the 30-year mean.

Night temperatures have been around 8.25C - still warmer than the 30-year average for September of 7.3C.

It has been sunnier than usual, with 155 hours to date, against the September average of just under 190 hours.

Daily climate maps from the National Institute of Water and Atmospheric Research (Niwa) show the daily hours of sunshine are around 10% more than the norm.

Rainfall is the major aspect to watch, with only three real rainy days and just 40mm of rain to date against the September average of 71mm.

Nonetheless after four wet months - and a record soaking last year - the district’s soils are still wetter than usual for the time of year.

Signs of the predicted La Nina are yet to appear, according to the latest reports from the major overseas climate agencies such as the Climate Centre of the US National Oceanic and Atmospheric Administration.

The latest data indicates a neutral position in the El Nino/Southern Oscillation (ENSO).

The US Climate Centre gives the chance of a La Nina developing from now to November at about 71%.

If one does develop, the forecast is for it to last through January to March of 2025.

For beachgoers, the water is still cool - “fresh” in some people’s terms - with the temperature off the beach yesterday at 13.5C, or about 0.7C colder than usual for the time of year.

Spring equinox brings high tides

With the spring equinox on Monday, the journey towards summer is under way.

The exact moment, astronomically speaking, when day and night were equal, was at 43 minutes after midnight, on Monday morning.

The return to the warmer months began with the solstice in late June — the point at which night time reached its greatest extent, and when daytime started to lengthen.

The September equinox is also when the Gisborne coast experiences its longest run of highest tides, starting on the 16th and ending on the 25th.

The high tides have been over 2 metres since the September 18, peaking at 2.2m on September 20 and 21.

At the same time the Moon on September 19 was at its second closest approach to Earth for the year, at a distance of 357,286km.

It will be slightly closer on October 17, at 357,175km.

Locally, an early start to spring has been signposted by early flowering of trees such as the kōwhai, tī kōuka (cabbage tree) and kōhūhū, releasing their distinctive scents.