NZ Weather Forum

I would love to know why so often the nor' wester across the Canterbury Plains seems to run out of puff near Yaldhurst just west of Christchurch and the city remains NE.

Inland areas such as Kirwee, Darfield and West Melton also seem to see the fohn wind hit fairly often in spring but yet Christchurch and other coastal areas see the nor' easter remain at work until the nor' wester has enough grunt to reach the coastline.

Forecaster's nightmare?

the NEer undercuts it...as its colder/moister and so denser...forcing the NWer to go over the top of the NEer
The Port hills though upset those layers, ie create turbulance and so places out the end of the BP get strong NW winds coming down off the hills (e.g Le Bons Bay)

Good answer there, Brian
The NW tends to 'bounce' because of the onshore NE wind.
This has happened quite often this spring.

Yeah and its bloody horrible today in Rangiora with a screaming gale all afternoon gusting 70-80kph.
Sick to death of the bloody thing

Yes ,its been same here as well,so pleased i planted lot of trees 13 years ago where we dont get blown inside out like we once did.

The other interesting thing is, the NEr is often actually the NWer going through cook straight and then bending around and running down the coastline, past Kaikoura (and influencing the NWer at times there too) to hit CHCH

Also inland heating in the warmer months will help create onshore flow especially given the cool sea temps along the SI east coast, same for coastal Otago.

Manukau heads obs wrote:The other interesting thing is, the NEr is often actually the NWer going through cook straight and then bending around and running down the coastline, past Kaikoura (and influencing the NWer at times there too) to hit CHCH

Alex Neale, retired forecaster (I think it was him) put out a paper years ago describing 3 kinds of Plains Nor'Easter - you're describing the "return flow" one here.

yup,because I remember the paper

Interesting how the NWer was a tad cooler today cant be the snow on the mountains as thats nearly melted, so its either cooler upper air or its a more W-NW coming up the alps slightly rather than straight over in a typical fohn affect.

re feeling cooler...the NWer currently over eastern SI only originates as a westerly over the south tasman that was then a cooler SW ..i.e is not picking up any heating off australia

The Canterbury NW is hottest when there is subtropical moisture being advected onto the West Coast. That scenario returns Thursday.

RWood wrote:

Manukau heads obs wrote:
Alex Neale, retired forecaster (I think it was him) put out a paper years ago describing 3 kinds of Plains Nor'Easter - you're describing the "return flow" one here.

Interesting. I was reading his 1987 book Weather forecasting in New Zealand yesterday.
what I find interesting when a NW blows is that in some situations there is the famous "NW Arch" and on other days when the Nor'wester blows, there is no cloud at all.

Took a helicopter ride yesterday from ohoka 5pm, very blustery NW at the time, to the Port levy Heads (unsure the offfical title) were it was almost dead calm. By 6pm when we left the NW had caught up and was blowing an absolute gale. Could see the white caps forming on its approach out to sea.

Slightly O.T., and not exactly new news, but perhaps worth a mention anyway…

'Many people think Canterbury's nor'west winds make them grumpy' - Voxy

Thanks for all your useful comments.

I read this story and didn't they do a study on this many years ago on the NW's impact?? Personally I like the nor' wester as long as the house stays in one piece!

Yeah...thats not new news about the effects
negative ions...

My wife suffers hunches, I mean headaches during periods of prolonged NW-sters.
It has something to do with the negative ions in the atmos.

Think you mean 'positive ions'?

I think the theory was that positive ions from static electricity in the dry air creates an electromagnetic field, which may in turn alter people's seratonin/melatonin ratios. Hence the term, mad-dog nor'wester. This might also mean that people closer to the coast can predict the nor'wester long before it arrives.

Nev wrote:Think you mean 'positive ions'?

I think the theory was that positive ions from static electricity in the dry air creates an electromagnetic field, which may in turn alter people's seratonin/melatonin ratios. Hence the term, mad-dog nor'wester. This might also mean that people closer to the coast can predict the nor'wester long before it arrives.

Probably positive ions. just like, occasionally I get my La Nina's and El Nino's mixed up??

Several days of NW, she can be stressed out

NZ Thunderstorm Soc wrote:

Nev wrote:Think you mean 'positive ions'?

I think the theory was that positive ions from static electricity in the dry air creates an electromagnetic field, which may in turn alter people's seratonin/melatonin ratios. Hence the term, mad-dog nor'wester. This might also mean that people closer to the coast can predict the nor'wester long before it arrives.

Yes, Nev , it is probably positive ions. just like, occasionally I get my La Nina's and El Nino's mixed up??

Several days of NW, she can be stressed out

I get hayfever

From my experience of NW-ers, I liked it when the arch cloud was absent or at least not obscuring the sun - otherwise a bit more equivocal. I recall being in Southland (briefly) and Central Otago in the days leading up to Tuesday 7 February 1973. Over the weekend 4th-5th it was warmish in Lumsden but with persistent high cloud, and it felt rather oppressive - I got a headache. In Alexandra on the Monday things were much brighter, and hot - max about 35.5C I think. I enjoyed it and felt no real heat stress.