DEVELOPING STORY — WeatherWatch.co.nz forecasters have high confidence that a significant and rapidly deepening low this weekend will reach “weather bomb” criteria – where the air pressure plummets 24hPa in 24 hours. This is much faster than the usual rate for a storm to develop.
Head weather analyst Philip Duncan says the storm will be timed to rapidly develop on Saturday while it actually crosses the North Island. “It will go from a non-existent mark on our weather maps today to a nasty storm by Saturday morning – with the bulk of the deepening happening in a 24 hour time frame”.
The weather bomb is expected to bring gales force winds to many parts of the North Island and in extreme cases those winds will be destructive.
With the centre of the deep low crossing through the heart of the North Island residents can expect winds to come from all directions over the next few days, along with a period of heavy rain at the beginning of the low.
Winds will build from the northerly quarter and peak from
“The bulk of the rain will move across the North Island overnight Friday and through Saturday, clearing in the west during the afternoon. The rain will then linger along the eastern side of the North Island, especially around Gisborne and Hawkes Bay”.
Mr Duncan says winds will build over Saturday with gales – possibly severe – which may cause some problems. “This is an unusual low due to it’s tracking and rapid deepening – it could push south east gales into regions that don’t often get them, like Kapiti, Horowhenua and Manawatu”.
Mr Duncan says trees and infrastructure in the lower western North Island is geared up for the frequent westerlies, which cause the trees to grow on a noticeable angle. “So when the winds are gale force from the opposite direction it can sometimes cause unexpected damage”.
“But really much of the North Island and north eastern South Island will be exposed to a period of heavy rain and gales this Saturday”.
By Sunday the low will be east of Hawkes Bay and Wairarapa and will be churning out big seas and hurricane force winds offshore. On land the skies will likely clear and dry out on Sunday for most regions, apart from eastern areas where the low will still be dragging in cloud, rain and showers. Gales are still likely onland in the east too, but conditions will ease as we head towards Monday.
WeatherWatch.co.nz believes the storm will impact travel plans this weekend – and if you’re driving, flying or going by Cook Strait ferry we advise travellers to keep in touch with their travel providers.
WeatherWatch.co.nz will have extra updates this weekend as we track the incoming low – this has the possibility of being a significant severe weather event and all North Islanders and those in the upper South Island are advised to remain up to date with the latest weather news and MetService warnings.
on 1/03/2012 7:51pm
Ironman NZ is due to start at 7am on Saturday with a 3.8km swim in Lake Taupo followed by 1&0km of cycling to Reporoa and back (twice) and then a marathon. It sounds like this storm could cause problems. Are we likely to see significant weather hitting the Taupo area and if so from when (roughly). Thanks
on 1/03/2012 7:54pm
Hi there – yes rough weather for Taupo – early heavy rain will ease during the morning to showers and gale force sou’westers – which will strengthen during the entire day. Will be a tough one if it goes ahead!
on 1/03/2012 9:34am
Hi Phil, at last a good storm to hit the horowhenua, any chance this will produce small tornados or even thunder? I know from previous easterly storms they do a lot of damage in the way of trees being uprooted, but am glad its a weekend so we can all get a good look at it, bring it on! Love the weather and its ability to bring us the unexpected. Cheers, Phil Smith
on 1/03/2012 9:22am
Lets hope there is not too much damage from this system. Many have had a lousy summer already and do not need more weather related woes.
We were lucky, had lovely weather sailing to Sydney and pretty good once we got there with only some late afternoon showers 1 day and a lightning show the night before we left. The only hiccup was a three hour “engineering delay” at Sydney Airport and home after midnight to yet more rain. Last weekend was pretty good and I thought the weather may be starting to improve but no mother natures throwing it at us again.
My chillies have not even grown enough to flower, let alone fruit, and they were planted in November. Need more heat and sun.
on 1/03/2012 9:08am
Well this one could possibly dredge up the scallops out here at Army Bay and conveniently dump them on the shore as weather of this kind can often do. Its actually quite stunning out here when the weather whips up too – I greatly admire the raw power of nature – so a few positives in it all. Cheers for the heads up Phil and safe days to all.
on 1/03/2012 7:14am
What is the main power source for such a storm as by your comment earlier to Roly, the Tasman storms have a cold heart?
Thanks in anticipation.
on 1/03/2012 10:37am
The main source of energy for mid latitude storms like this incoming one is a difference in temperature between 2 air masses, the air mass on the equator-ward side of the storm being significantly warmer than the airmass on the pole-ward side. This is why much of the ‘action’ happens along the fronts – either warm, cold or occluded – which define exactly where the boundary between these air masses is.
If you have been watching the sattelite loops for the last 2-3 days, you will see that the front that passed over NZ on Wednesday morning did not make much northward progress in the Tasman Sea – in fact it appears to have stalled on a line between NSW and Northland. Which happens to be exactly where this disturbance coming out of Australia (which has already created plenty of rain and flooding in central and eastern Australia) is going to track.
I would expect that at times, the behaviour of the jet stream will also play a part – if the winds aloft are ‘divergent’ or spreading apart from a particular spot, then that will create a vacuum effect for the air at the surface to fill at that location, thereby enhancing the rate of air pressure drop and the increase in winds to fill this vacuum.
on 1/03/2012 6:37am
I’m glad you mentioned kapiti in your predictions, as the met service haven’t mentioned us specifically yet, I suppose we won’t get any warnings until this system develop’s futher.
The south east gales are as you say, more unusual here in Kapiti and in my experience are often damaging for us.
I have ‘battened down the hatches’ so to speak. as I know “a weather bomb’ has the potential to be a significant weather event.
Would love to hear a bit more about the term “weather bomb”
on 1/03/2012 6:32am
…this is just another of our normal bog-standard fortnightly storm-of-the-century weather bombs!!