Yesterday’s relatively small low compared to the predictions of tomorrow’s giant pool of low pressure.
A low pressure system developing in the southern Tasman Sea and across New Zealand continues to keep forecasters on their toes today. The low, which is expected to grow to the size of Australia, is set to bring rough weather to both islands from Thursday night and last several days, through until Wednesday next week. The storm is going to bring heavy rain, gales and thunder to some regions and end with a blast of cold air right off the polar caps.
Head weather analyst Philip Duncan says the storm has 4 main characteristics – rain, wind, snow and wind-chill.
“Strong winds are expected to build over the North Island later tomorrow and will rise to gale force in exposed places south of Auckland. Then, western areas especially, are in for several showery, windy days”.
Saturday morning sport may well be cancelled again this weekend as the wintry storms sets in.
Mr Duncan says the low is certainly a complicated one. “It’s so big and so unstable our weather models are changing regularly. Our 3:30pm update today shows a mixture of snow flurries and rain across coastal Canterbury on Monday night and Tuesday next week however the wind direction appears to contradict this – coming from the south west which is usually a drier direction”.
“Due to the size of the low pressure and its unstable characteristics we feel it’s best to share this information early and update regularly if the system changes direction, weakens, or strengthens. This is not an ‘out of the box’ low”.
Mr Duncan says while the low is extreme in size but shouldn’t be a repeat of previous storms. “Yes it’s large but that helps spread the energy over a much wider area – in other words, it can dull the impact of wind and rain”.
The Weather Watch Centre is expecting snow flurries to low levels across Southland during Friday night but easing on Saturday as winds shift from southerly to warmer westerly. The coldest air looks likely to move over the South Island later on Monday and during Tuesday. “If it’s not snowing it’ll certainly be close to it. The wind chill will be bitterly cold by Tuesday and this will be the biggest concern for farmers with new born animals”.
This image sent in by a weatherwatch.co.nz reader shows an impressive rain cloud over Auckland’s Northern Motorway this morning creating a large rainbow over the city.
on 13/08/2008 2:41am
Great site ! I check it several times a day 🙂 Can you tell me, at this point, what the forthcoming storm front is likely to mean for the Whangarei region ? Many thanks.
on 13/08/2008 2:50am
Being at the far end of this system Whangarei shouldn’t see the worst of the weather…which I’m sure will be a relief to many. Strong winds, maybe up to gale force at times, and plenty of those big heavy showers marching through.
Thanks for the feedback on the site – be sure to tell everyone you know about us! The more visitors we get the more resources we can put in to it.
The Weather Watch Team
on 12/08/2008 11:17pm
what a great website – very informative! and love the rainbow photo!
on 12/08/2008 10:43pm
I’m yet to see any evidence that the Canterbury region needs to be worried about anything unusual. Latest models look westerly, all the action will be in the mountains
on 12/08/2008 11:27pm
Yes our latest update (after 11am) reflects that shift in the wind. We’ll be the first to update if any forecasts weaken. Last night the models we use all pointed towards snow for Canterbury…but 18 hours later and it’s not looking so strong. I think that’s the great thing about this site – the frequent updates ensure good coverage of approaching systems.
And Im sure the lambs will appreciate a little heads up on some cold wet weather!
on 13/08/2008 5:44am
“We’ll be the first to update if any forecasts weaken. Last night the models we use all pointed towards snow for Canterbury…but 18 hours later and it’s not looking so strong. I think that’s the great thing about this site – the frequent updates ensure good coverage of approaching systems.”
I don’t see anything good about this. It’s dangerously reactionary and a bit of “knee-jerk” forecasting.
The latest model is not always the best. Just because a new model run changes a situation does not mean that is what will happen. On the next run it may well see-saw back to where it came from.
It’s important to have some understanding of the physical and mathematical processes behind these models, otherwise you risk being a slave to the computer, regardless of how much “instinct” you use in forecasting.
It’s better to wait for strong convergence of model solutions from several sources, rather than report every weakening. It’s in everyone’s best interests, you don’t want to sow confusion amongst the public.
on 13/08/2008 6:06am
Hi Douglas – thanks for your feedback and suggestions, they are appreciated. I should probably make it clear that we don’t ‘react’ to every model change. I agree with you completely that one run may ‘see-saw’ from the last one, so we need to be consistent otherwise we’ll confuse the public.
At the end of the day we are a Weather News site and while we offer our opinions on the weather forecasts, the news stories are why people come in here. In America, where weather news sites are a dime a dozen, they are all about reporting the evolution of a system. Rather than just saying "this is what will happen" they report what current predictions are and how they’ve changed over the past 24 hours etc.
Thanks again for your comments,
on 12/08/2008 9:24pm
Last Saturday I went to our Saturday market. A regular weekly trip usually however this was the first time in 9 weeks that it wasn’t washed out…looks like this weekend will be a washout.
Are our architects, entrepreneurs and city fathers taking NZs rather unstable weather into account?
The newer type of malls I find are open air weather prone developments often without even the luxury of a verandah. Ideal for the med.
When are they going to realise in our climate we need to still be building completely covered, temperature controlled weather proof malls like the older ones of the 1980s.