Ex-TC Ita affecting NZ - April 17-19 (Thu-Sat)

[Nev]

Check out this video
http://i.stuff.co.nz/national/9965952/B ... d-off-roof

Wow! Some incredible winds down there all right!

For 60 houses to lose roofing, gusts must've been more than the 141 km/h recorded at Greymouth Aero on Thursday evening. NIWA'S Mt Philistine site also recorded gusts to 165 km/h around that time, but that's about 1660m asl and about 50 km inland from Hokitika.

There's also some amazing aftermath footage in this earlier video, although I'm a bit dubious about the gusts to 300 km/h?

'1000 still without power after West Coast storm' - TV3

[NZstorm]

300km/h would likely blow the houses away completely in my opinion!

[einzack]

Cliflo shows the following for the max gusts recorded on the 17th:
Greymouth Aero Ews 140.8 km/hr (5m asl)
Pigeon Creek Cws 94.5 km/hr (105m asl)
Mahanga Ews 146.4 km/hr (1995m asl)
Mt Philistine Ews 164.9 km/hr (1655m asl)
Hokitika Aws 72.3 km/hr (38m asl)
Reefton Ews 38.9 km/hr (198m asl)
Westport Aero Aws 126.0 km/hr (126m asl)

Though I believe that Westport lost power for significant periods - would that affect the recording?
Regardless, some impressive winds, and it's also relevant that Greymouth airport is not in the area that was subjected to the worst winds. That belonged to areas closer to the river where the wind is funneled through the small gap where the Grey River flows.
From reports I have heard, 5km inland there was very little wind - it was very concentrated right on the coast.
In Reefton, as you can see, we had nothing.

[NZ Thunderstorm Soc]

No wonder Cobden Bridge was closed. Imagine the wind blowing through there
Worse than the "Barber" which is known for it's coldness, this wind must have a West Coast name for it's strength.

PS. off topic. Could Willougby update the smiles as some of these ones are useless

[Richard]

On TV1 news tonight they used the term 'five days of storms' on the West Coast,ive been away and haven't kept up with what's happening in the outside world but wasn't the wind just on the Thursday?

[einzack]

The winds were still quite strong on the Friday, but nothing like Thursday.
Apart from that it's been pretty regular West Coast weather.
The rain hasn't helped the cleanup efforts, but to call the other days 'storms' is stretching it.

[David]

Interesting footage on 3 News tonight showing damage on the West Coast http://www.3news.co.nz/Ita-leaves-more- ... fault.aspx
Must be over 150 km/h to flatten such large areas of forest. Maybe gusts up to 180 km/h?

[jamie]

Far out that's impressive destruction on the native forests that have stood for so long.

[Manukau heads obs]

When u get hardie coasters saying they have never seen
Anything like it...(i.e on another level)..wow. .
I Gotta say...another example of extremes caused by unusual jet streams
Of late and stronger high pressures etc

[Richard]

It was interesting how the shoots they showed on TV of flattened forest showed how much it was in patches,like to know how wide spread it was though.

[Manukau heads obs]

I would assume the damage to the trees would have
Been in swathes /lines near gullies
/gorges

[NZstorm]

.
I Gotta say...another example of extremes caused by unusual jet streams
Of late and stronger high pressures etc

I thinks its more a function of the time of year than anything else. When ex tropical cyclones come into the Tasman in Jan/Feb they are unlikely to find a jet stream but in April the risk of a polar jet is a lot higher as happened in this case.

[Manukau heads obs]

True that..e.g wahine storm interacting
With cold front in April
That was an intense high that wad positioned
A bit further south than you would expect
I suggest that there was a bit of cry wolf after Luci
I myself was like. .let's see what happens instead of saying. ..jet
Right over the top...This could deepen rapidly alright
(Which is what I was thinking on the wednesday)

[iomkiwi]

Can't believe the pics/video linked to in this thread, have just arrived back from a trip around the SI. Drove down the West Coast on 14th-16th, a day later and it could have been me in that overturned motorhome
We had rain and strong winds but nothing extreme.
Hope the treetop walk south of Hokitika escaped damage - well worth seeing for anyone going that way.

[Manukau heads obs]

I suspect the damaging winds were running
Down the gullies/rivers
So you could easily miss them...

[Storm Struck]

You will recall me saying earlier in this topic that winds could potentially reach 140-150kmh for the likes of Westport and Greymouth, what caught my eye especially was not only the present upper level jet influence but also on the METVUW site the wind socks were showing not three lines but several black flags which I have never seen on these maps before.
I don't know whether its a new feature on the site, for when winds could potentially reach hurricane force.
I also knew it had a similar positioning to that of the low which caused high winds to 150kmh through Westport back in 2008.

To me I am seeing an increase in not only wind related events due to the upper jet, but also everything else to do with the weather.
We had 3 days in Canterbury this storm season where severe storms of supercell like or mesocyclonic nature occurred, on average we should see these kind of storms once every 5-6 years.
These days were once again influenced but the upper jet.

[Nev]

...on the METVUW site the wind socks were showing not three lines but several black flags which I have never seen on these maps before.
I don't know whether its a new feature on the site, for when winds could potentially reach hurricane force.

Don't have archives of MetVUW's forecast charts, but below are couple of their 3-hourly wind-map obs for Apr 17 based on MetService sites.

Interestingly, Westport's mean winds were 45 kts (83 km/h) at 3pm, 40 kts at 6pm and only 20 kts at 9pm, while Greymouth's winds (not shown) peaked around 6-7pm.

[Manukau heads obs]

That fits with the low and associated front moving
Slowly south...and increasing the squash
Zone up against the high

[NZ Thunderstorm Soc]

...plus the fact of the Southern Alps

[Dale]

Yeah Nev is right, around 6pm onwards all hell was breaking loose here in Cobden.

Evening all, it's been a while since my last post but life & times have been extremely busy.. not so busy enough tonight to scroll through this thread & simply say in all my years of chasing storms & amateur forecasting.. I have been through some storms in my time but this one has taken it to a new level. People living next door & nearby have also said this was as bad if not worse than 2008. Gusts, I personally estimate were in excess of 150km/h for the duration of the storm, some peaking higher, others lower.. but at the end of the day I was sitting here watching 4x2s, pink batts, roofing iron & the occasional garden chair & wheelie bin flying past my window.. when it wasn't being pounded by foliage & loose chip from the roads surrounding. The most interesting part of it all was not just watching the roof of the old hall here in Cobden peel off before my eyes, but the neighbours garage door blowing into his shed, and clean out the back wall covering our front lawn in gyprock & debris. We came out unscathed so to speak, had a huge tree completely uprooted which pieces of it are now currently inside the firebox keeping me warm but so many others were not so lucky. Cobden bridge was closed all day, it was simply because the winds were too strong.. you could get back into Cobden if you went the long way through Stillwater & Taylorville but even then as the evening wore on, cops were stopping people from coming in here unless you were local & coming home. Massive trees down, swathes of trees down, concrete powerpoles snapped clean in half.. not going to forget this baby in a hurry!

[Orion]

A memorable event, Dale!

[Dale]

Truly.. no shortage of firewood around the place right now.. even today 1 month later, the sounds of chainsaws, hammering of rooves, rebuilding of tarpaulined houses (which haven't been condemned) is still ongoing.. from my bedroom window I can still see a good 3 or so houses which were just walked away from completely destroyed.

Einzack was talking about the winds being funneled through the Grey Valley & into town itself.. it wasn't quite the case. We had a eneral SE flow there which whipped around & ran parallel to the hills backing onto Grey.. the coastal areas copped the worst yes, Cobden, Blaketown espescially.. very destructive damage recorded there, they looked to have been hit the hardest.
Runanga was spared the worst of it all.. but they didn't escape. Iron was peeled off the Miners Hall & across the road from my old place, ol mate lost his roof.. as well as a few others in the Runanga / Dunollie area. But yes, topographical influences were a big part of who came through unscathed, and who didn't.

Filled so many pages of writing on this as it is something I not only don't want to forget, but would like to learn a lot more about.

[Dale]

Should also add too.. for Brian.
Had a gentleman across the road staying overnight for a lawnbowls comp.. he was down from Wellington & went through the Wahine storm... his comparision was almost identical, it bought back memories of that night/day.

[NZ Thunderstorm Soc]

Yes, sad about the old Rununga Miners Hall. We had a Morris Dancers convention in that hall in 2010, and even though it was in it's neglected state, had a good time there.
Amazing Façade.
Maybe David Cunliffe should use it to launch his campaign for Labour in this years national election?