It’s one thing to declare the global El Niño has come to an end; it’s another thing saying farewell to the El Niño weather pattern in our part of the world.
Like trying to turn a cargo ship around in the Suez canal, it’s difficult to do and you might get stuck.
New Zealand now has a backlog of rain orders. Many parts of eastern NZ look like we’re still in the thick of El Niño and this is due to the stubborn and lingering highs.
At the time of writing this column, a high pressure zone well into the 1040 Hectopascal range (hPa) was lying just south of Adelaide. It stretched south to the Antarctic ice shelf and as far north as 80% of Australia. This giant high pressure belt is now going to affect NZ for the first half of May,
Yes, half of the month.
The high will spend a full week centred near Tasmania. Usually in this position it’s just a matter of days before it reaches NZ, but this high is so enormous and in such a way that it may even drift backwards (westwards) to go from being centred over Tasmania to being centred back south of South Australia again.
This continues the southwesterly flow into NZ. It’s a little cooler, but it’s also a fairly dry setup – with true southerlies barely coming into NZ. It may not be until Monday (May 13) that finally it slides over to the NZ area. Half a month from now.
It doesn’t end there either. Once this high pressure zone spreads across NZ a new high will likely re-form back over Tasmania and south of Adelaide. This means the first two, and maybe even three, weeks of May are dominated by high pressure rather than low pressure.
It’s not to say there will be no lows, fronts or rain makers; it just means that any that do form will be controlled by this specific high pressure belt. The high pressure zone will be the deciding factor whether you get more rain or not.
One wild card is that since El Niño officially ended last month, we have seen a slight (and it is only slight) uptick in sub-tropical low pressure zones – and some modelling says more of that may be trying to bubble up in the weeks ahead. If you need rain, this is what we call a “silver lining”!
So for now, that long kiss goodbye means dry areas will linger – and despite some recent rain relief we may see some dry areas drying out further again before more real rain finally arrives.
We tell you this as NZ mainstream news outlets obsess over La Niña already, which global modelling is still conflicted about.
Upcoming highlights:
• A southerly flow kicks off the first Monday of May
• High pressure expands over southern NZ
• A few showers for eastern areas
• An offshore sub-tropical depression to NZ’s northeast worth monitoring
