Complex low Oct 1 & 2

Cyclone Tracy · Unread post by **Cyclone Tracy** » Fri 29/09/2017 15:12

This is lining up to a very windy direct hit to the top half of the North Island. A surface low will spawn and deepen from a polar trough early Sunday morning. The finer details will be a little clearer in the next 24 hours but its certainly an unstable cold shot from the Antarctic as the surface temperature leak is currently underway.

TonyT · Unread post by **TonyT** » Fri 29/09/2017 17:55

There is no "unstable cold shot from the Antarctic" feeding this system. Its a wave in the westerly flow. The air in the system originated south of Australia, well north of sub Antarctic waters.

127156_trj001.gif

Cyclone Tracy · Unread post by **Cyclone Tracy** » Fri 29/09/2017 19:10

TonyT wrote: ↑Fri 29/09/2017 17:55 There is no "unstable cold shot from the Antarctic" feeding this system. Its a wave in the westerly flow. The air in the system originated south of Australia, well north of sub Antarctic waters.127156_trj001.gif

Hi Tony, nice input but the latest EC & GFS runs don’t entirely agree with you. They think there is a polar air injection into the base of the trough from around 65 to 70 degrees south. If they are right, it looks like the convergence is spring cold shot to me, which would be a tad unstable and quite windy through the north island from the latest runs. I won’t be hanging out the washing on Sunday up here

NZstorm · Unread post by **NZstorm** » Sat 30/09/2017 08:14

Yes, tomorrows trough is a polar trough. Tony's output from the Hyspilt model is not measuring the set up well as the source selected is at the 500m level. The cold air advection is higher up in the atmosphere.

Looking like squally thunder on the cards for Sunday for the west of the North Island. Front coming in tomorrow morning after dawn.

Cyclone Tracy · Unread post by **Cyclone Tracy** » Sat 30/09/2017 13:42

MetService now starting to crank up the outlook on the North Island. Gales and thunderstorms for Sunday into Monday.

Latest Access R (18z) shows the cold core gyre drop to around 979 hPa Sunday morning off the west coast of the south Island and then develop a 2nd core around the south Taranaki bight Sunday night. It's going to have a nice wrap around south westerly attack late Sunday into Auckland.

NZ Thunderstorm Soc · Sat 30/09/2017 20:37

Cyclone Tracy wrote: ↑Sat 30/09/2017 13:42 MetService now starting to crank up the outlook on the North Island. Gales and thunderstorms for Sunday into Monday.

Yes, well I wish they wouldn't go to bloody Auckland all the time, and come down this way instead

spwill · Unread post by **spwill** » Sun 01/10/2017 10:12

The better upper level cooling moving in this afternoon, best chance to hear thunder looks like later in the day in the west.

Cyclone Tracy · Unread post by **Cyclone Tracy** » Sun 01/10/2017 10:46

spwill wrote: ↑Sun 01/10/2017 10:12 The better upper level cooling moving in this afternoon, best chance to hear thunder looks like later in the day in the west.

Spot on - Latest GFS 3 hour snap shot showing around -29 to -30c @500 hPa west of the North Island. Sustained winds over 100 km/h @850 hPa, it's going to get a little breezy and unstable.

David · Unread post by **David** » Sun 01/10/2017 11:32

Feeling more like July here today rather than October. 12C with rain most of the morning. Was quite heavy between 9 and 10am.

Cyclone Tracy · Unread post by **Cyclone Tracy** » Sun 01/10/2017 15:14

10mm so far here. Baro currently 993 hPa and highest wind gust so far of 52km/h

RODALCO · Unread post by **RODALCO** » Sun 01/10/2017 15:32

Vector has issued a storm warning for us field staff when we are called out to attend faults.
Do it safe and don't take any risks out there. Main risk is tonight and tomorrow morning at this stage.

GraemeWi · Unread post by **GraemeWi** » Sun 01/10/2017 16:02

Just had a very sharp squall hit here is Swanson with very strong wind and hail

NZstorm · Unread post by **NZstorm** » Sun 01/10/2017 18:16

GFS has the wind threat aimed at Northland and North Auckland overnight.

Cyclone Tracy · Unread post by **Cyclone Tracy** » Sun 01/10/2017 19:48

Gusting to around 70 km/h here with hail in that last squall. Some private stations on the north shore are 80 km/h to 90 km/h now with the latest batch of squalls coming through.

Simon Culling · Unread post by **Simon Culling** » Mon 02/10/2017 03:15

Looks like it was a bit windy at the NZ Women's Open Golf Tournament at the aptly named Windross Farm golf course on Sunday afternoon:

http://www.bbc.co.uk/sport/golf/41460869

I believe the course is a little inland from Auckland.

NZstorm · Unread post by **NZstorm** » Mon 02/10/2017 06:29

Quite a decent system on the charts but the max gust at the airport was only 40 knots. But I reckon Northland must have got some decent gusts this morning.

There was a couple of flashes and distant thunder about 3.30am here.

Cyclone Tracy · Unread post by **Cyclone Tracy** » Mon 02/10/2017 07:27

18mm, top gust of 88 km/h, hail, thunder during the night.

I see a private weather station west of Whangarei was gusting over 120 km/h during the night.

A few inches of snow in central north island overnight.

David · Unread post by **David** » Mon 02/10/2017 08:22

Max gusts only 52 km/h here, nothing particularly unusual. 29mm rain since early yesterday.

spwill · Unread post by **spwill** » Mon 02/10/2017 08:34

I was expecting more in the way of wind and thunder from this system, no strong winds at my place.

Nev · Unread post by **Nev** » Tue 03/10/2017 07:30

Re the LPGA golf tournament video at Windross Farm, Ardmore Aero right next door recorded gusts to 65 km/h on Sunday afternoon (and up to 78 km/h yesterday), although it looked more squally at Ground Zero. Media reports also say gusts were close to 100 km/h on the Harbour Bridge and around 110 km/h in the Hauraki Gulf. While further south, Aurora Energy said gusts of more than 100 km/h caused outages to 900 Otago Peninsula customers yesterday.

Here's some of the higher gusts MS recorded over the last 2 days…

Code: Select all

Oct 1-2 Gusts km/h

Cape Reinga         135  
Manukau Heads       125  
Golden Valley       109  
Mamaku Radar        109  
Hokianga            107  
Stratford Mount     106  
Kaikohe             104 
Okahu Island        104  
Nugget Point        104  
Mokohinau Islands   102  
Whangaparaoa         94  
Invercargill Aero    93  
Takapau Plains       91  
Tutukaka Harbour     89
Auckland Aero        89  
Dunedin Aero         89  
Whenuapai            87  
Port Taharoa         85  
Hicks Bay            85  
Mahia                83  
Le Bons Bay          83

GraemeWi · Unread post by **GraemeWi** » Tue 03/10/2017 08:59

I checked my weather station last night to see what the peak gust was for us, 91kph just after midnight / early am Monday morning.

Plenty of tree debris on the roads too

Cyclone Tracy · Unread post by **Cyclone Tracy** » Tue 03/10/2017 13:07

A few trees down around here yesterday as well.

Nice stats Nev. 100 km/h on the Harbour bridge lines up pretty close to my 88 km/h not far from there.

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Complex low Oct 1 & 2

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