Monday, January 23, 2023

MetService Weekly Forecast

High pressure may give way to a sub-tropical low


Covering period of Monday 23 - Friday 27 January.

A large area of high pressure moves onto New Zealand today from the Tasman Sea, bringing fine, settled weather to most places this week, before drifting slowly eastwards.  However, MetService is keeping an eye on the sky to the north of the country, where a sub-tropical low is expected to develop.  This low is preceded by humid easterly winds, and could bring wet weather to Northland on Friday, and possibly into the weekend.

MetService Meteorologist Peter Little comments, “Computer weather models are all developing a low to the north of New Zealand on Wednesday, then moving it slowly southwards, possibly bringing heavy rain to Northland on Friday.  The models currently differ as to how far south they spread the sub-tropical moisture and rain associated with this low, so there will probably be some fine-tuning of forecasts for northern New Zealand later in the week as models come to a consensus.”

(Continued below)

Severe Weather Outlook.  Issued Monday 23 Jan 2023.

A weak ridge covers central New Zealand on Wednesday, moving slowly eastwards, while an easterly flow affects northern New Zealand. Northerlies develop over southern New Zealand on Thursday, and a trough may bring localised rain to Westland which has the potential to be heavy for a time. However, there is currently a large amount of uncertainty associated with this feature. On Friday, a sub-tropical low is likely to approach the country from the north, with the potential for heavy easterly rain to affect Northland from Friday onwards. There is low confidence that warning amounts of rainfall may eventuate. Meanwhile, a weak front should move onto the southwest of the South Island from the Tasman Sea, bringing a brief period of northwesterly rain to Fiordland and South Westland, and a change to cooler southerly winds over southern New Zealand.

Covering period of Monday 23 - Friday 27 January continued:

With high pressure dominating for most of the week the weather will be mainly fine in many regions, including today in Wellington where locals are celebrating the region’s Anniversary Day.  There will be showers in the mix for some though, and daytime cloud buildups might even produce a few heavier showers in some inland places.  As the high drifts slowly eastwards, a weak trough is forecast to bring an increase in cloud and showers to the West Coast on Wednesday.

Finally, a front is expected to bring a brief burst of rain to southern New Zealand on Friday, preceded by warm northwesterlies in the east of the South Island.

“The front that is forecast to move over southern New Zealand on Friday is expected to weaken rapidly as it moves northwards, so only a few millimetres of rain are likely in most places.  The warm northwest winds ahead of the front are expected to push daytime temperatures in the east of the South Island towards 30°C, which will be around 10°C warmer than the start of the week,” adds Little.

MetService  23 Jan 2023

Pigeon Post News, Richmond.

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