Two options for Anzac Day weather

A large high over New Zealand - or a deep and nasty looking sub-tropical low. These are the two options for Anzac Day weather this Saturday...and it's the reason I sound like a politician when answering the question "What's the weekend gonna be like?". For some areas - namely the northern half of the North Island - it's too 50/50...and I can hardly say "Anzac Day will be sunny with the risk of a sub-tropical storm"!

At the time of writing this MetService has issued a severe weather watch for northern New Zealand - with low to moderate risks for places like Northland, Auckland, Coromandel Peninsula, Bay of Plenty and East Cape receiving heavy rain this Saturday.

However computer models are showing other possible outcomes. According to long range weather maps the low could track into the central Tasman Sea and maybe cross the lower South Island on Sunday or Monday. Weather data from Weather.com says there's a 30 to 40 per cent chance of rain for northern New Zealand late on Saturday and perhaps Sunday too.

The issue with a tough cookie like this forecast is a large high just to the east of New Zealand and a deep low north-west of us. The high isn't anchored over us - it's centred east of the country and that makes NZ vulnerable from lows moving in from the west. But if the high strengthens, as predicted by the weather maps, then that will push the low into the Tasman. Think of the high as a bump in the ground and the low as water flowing towards it...the water will move around it not over it. If the high is over us then we're protected from the severe stuff.

So there's a fine balance at play here - if the high moves to the east (or weakens) then that flattens out the air pressure and allows the low to easily follow in behind it. If the high strengthens then the low slides down around the western side of it - taking it close to NZ but offshore out in the Tasman Sea.

Definitely something to watch closely if you live in northern and western NZ. To give credit to MetService they know our severe weather better than weather.com or the international weather charts. Then again, it's 2 against 1.

For the rest of New Zealand I think most of the main centres are pretty safe at having a dry Anzac morning - possibly a mild start too with winds coming from the north almost everywhere...however the rain clouds may roll in later. WeatherWatch.co.nz is issuing a detailed Anzac Day forecast around noon Wednesday. I'll also have a detailed weekend forecast in my Friday blog right here.

POLL - Should the North Island and South Island be renamed?

New Zealand, Aotearoa - "Land of the long white cloud" - and now the Geographic Board is reviewing the official names of our North and South Islands.

Some people (including me) think "North Island" and "South Island" are pretty unimaginative names, especially on the international stage. I understand the strong feelings people will have about not wanting to change it - look at the uproar over Wanganui and that was only adding one letter. I also wouldn't be quick to change anything...I'd want a new name that reflects each islander appropriately. We're all proud of being a "North" or "South" Islander...in sport we love being North against South....but surely there are more imaginative names that reflect us as a people and not just simply 'a direction'.

The weather plays a part in naming places - we have an official Maori weather name for New Zealand, "Aotearoa". Also, Mt Cook's Maori name is also related to the weather - "Aoraki" which means "Cloud Piercer".

So have your say in our Weather Watch Poll or simply post a comment below this blog.

Philip Duncan

The Auckland War Memorial Museum's offical Book of Remembrance can be read online. It alllows people to send their messages and memories of loved ones who have served in past wars or to people currently serving in the armed forces.

Rain clouds with sunshine oner Devonport. Photo / Brett Phibbs