Low pressure sequence June 2 to 9

Razor · Unread post by **Razor** » Thu 31/05/2018 14:15

Yes looks a wet weekend for a number of places. And GFS suggests a wee snowmaker for the Canterbury ski fields mid next week?

Bradley · Unread post by **Bradley** » Thu 31/05/2018 14:56

[attachment=0]63315242_metgram.gif

Razor wrote: ↑Thu 31/05/2018 14:15 Yes looks a wet weekend for a number of places. And GFS suggests a wee snowmaker for the Canterbury ski fields mid next week?

Yes going by GFS this could actually be a fairly decent low level snow event for Canterbury with snow down to 300-400m but EC is going for much milder conditions with snow only down to about 700m, will be interesting to see which model wins out...

Bradley · Unread post by **Bradley** » Sat 02/06/2018 08:10

A significant upgrade in the latest model run with EC for the system next week for Canterbury with widespread rainfall totals of 80-100mm and snow now down to 300-400m, could be a very interesting period of weather ahead with almost certainly some road closures coming up...

Cyclone Tracy · Unread post by **Cyclone Tracy** » Sat 02/06/2018 09:23

I think this might deserve it's own thread, as it's a fairly complex chain of events coming up. An initial small brief with plenty of details to unfold as it goes I'm sure.

A Tasman cut off low from 5th polar upper low in the last fortnight is circulating to the NW of the North Island and is moving in a south easterly direction. Models are fairly aligned on its movement with rainfall intensity potentially heavy around parts of the NI from late tonight into tomorrow. The cut off low will keep the ridge west while moving SE across the NI allowing a 6th strong polar low to move up into the SI. The 2 systems will spin under a fujiwhara effect briefly powering a vigorous southerly into parts of the SI. A secondary upper effect from these 2 systems will create a disturbance in the tropics, which could possibly move south into the NZ region late next week but this is still quite uncertain.

edit: Date changed to finish 5th June with other thread in progress

Cyclone Tracy · Unread post by **Cyclone Tracy** » Sat 02/06/2018 15:35

Water vapor 3pm image detecting substantial amounts of moisture advecting in from the sub tropics. Near saturation at -50c to -70c. Plenty of moisture at high levels. This might go very big somewhere on the NI overnight.

TonyT · Unread post by **TonyT** » Sat 02/06/2018 15:55

It will be interesting to see what the 0Z models deliver us. The 12Z EC was pretty wild for central and northern parts of the South Island mid-week, probably an outlier at this stage but both GFS and UKmet have hinted at similar in recent runs.

spwill · Unread post by **spwill** » Sat 02/06/2018 16:46

Looking interesting for some Winter weather over the SI, snow developing in Central Otago later Tuesday spreading north through inland areas of the South Island Wednesday.

We might get some thunder up here Wednesday from the cold trough

NZstorm · Unread post by **NZstorm** » Sat 02/06/2018 18:36

Looking at latest thickness charts on gfs, snow for all inland areas and possibly to near sea level on coast.

1000mb to 700mb thickness chart for Wednesday morn. Just model output rather than a forecast at this stage.

Razor · Unread post by **Razor** » Sat 02/06/2018 18:41

Only 3-4 days out looking significant now that's for sure

NZstorm · Unread post by **NZstorm** » Sat 02/06/2018 18:54

That model output above is for South Island. Looks like Central NI won't miss out with snow to below 800m. And 850mb-2C reaching Auckland so chilly this far north again.

Bradley · Unread post by **Bradley** » Sat 02/06/2018 20:15

Latest run of EC a few minutes ago supports even more strongly that this will be a significant inland snow event for inland Canterbury with 10-20 cms down to 200m, 20-30cm down to 300m and 30-60cm from 400-800m, not exactly as major a system as the one exactly 6 years ago with not as quite as much snow at elevation and no snow sea level snow but still, this will cause alot of disruption for farmers and people travelling over to the west coast...

TonyT · Unread post by **TonyT** » Sat 02/06/2018 20:54

Bradley wrote: ↑Sat 02/06/2018 20:15 Latest run of EC a few minutes ago supports even more strongly that this will be a significant inland snow event for inland Canterbury with 10-20 cms down to 200m, 20-30cm down to 300m and 30-60cm from 400-800m, not exactly as major a system as the one exactly 6 years ago with not as quite as much snow at elevation and no snow sea level snow but still, this will cause alot of disruption for farmers and people travelling over to the west coast...

0Z EC has 8cm of snow on the ground in Kaikoura on Wednesday and 2cm in Christchurch. Not sure I believe that yet, but still...

snowykiwi · Unread post by **snowykiwi** » Sat 02/06/2018 21:24

Bradley wrote: ↑Sat 02/06/2018 20:15 Latest run of EC a few minutes ago supports even more strongly that this will be a significant inland snow event for inland Canterbury with 10-20 cms down to 200m, 20-30cm down to 300m and 30-60cm from 400-800m, not exactly as major a system as the one exactly 6 years ago with not as quite as much snow at elevation and no snow sea level snow but still, this will cause alot of disruption for farmers and people travelling over to the west coast...

Will be interesting getting to work in the middle stages of the week if this latest model run holds

. We travel between Rakaia and our business in Methven week days.

mikestormchaser · Unread post by **mikestormchaser** » Sat 02/06/2018 22:03

I have been watching this system since about wensday.
It had kind of backed away but has since come back significantly. In my eyes I see snow to near sea level on coast.

Nev · Unread post by **Nev** » Sun 03/06/2018 09:11

Fairly strong blustery winds here overnight. I see Whangaparaoa recorded gusts to 49 knots before 8pm yesterday, while the Mokohinau Islands in the outer Gulf were up to 60 knots before 11pm, but possibly higher earlier this morning. 13mm here since about 5am this morn.

June 02 Highest Gusts ℅ MS
111 km/h .. Mokohinau Islands
109 km/h .. Okahu Island
107 km/h .. Tutukaka Harbour
94 km/h ... Cape Reinga
93 km/h ... Hokianga
91 km/h ... Whangaparaoa
89 km/h ... White Island

Cyclone Tracy · Unread post by **Cyclone Tracy** » Sun 03/06/2018 09:22

Noticing that wind obs north of Auckland are now more N to NE with Auckland maintaining easterlies. A nice little squeeze zone may develop soon. 15mm here so far, current rainfall rate is 15mm/h

Bradley · Unread post by **Bradley** » Sun 03/06/2018 09:33

Significant downgrade on all models for both snow and rain for mid Canterbury this morning for mid next week however this is a tricky, complex system so I’m thinking the models will struggle with this one right up to the event...

TonyT · Unread post by **TonyT** » Sun 03/06/2018 10:03

Bradley wrote: ↑Sun 03/06/2018 09:33 Significant downgrade on all models for both snow and rain for mid Canterbury this morning for mid next week however this is a tricky, complex system so I’m thinking the models will struggle with this one right up to the event...

Agreed. The 12Z EC run shows snow over the coast and ocean from Dunedin to Banks Peninsula, but less of it for the rest of the South Island.

Cyclone Tracy · Unread post by **Cyclone Tracy** » Sun 03/06/2018 10:09

Significant moisture at mid to high levels to the north of Auckland. Water vapour sat pic at 9.40am suggesting some heavy downpours around the gulf coming up. Now on 22mm here

Edit: Not surprisingly the MS warning has now been issued

Issued by MetService at 10:10am Sunday 03-Jun-2018
Heavy rain for Auckland, Coromandel Peninsula, Bay of Plenty about and west of Te Puke, and the Kaimai Range during today(Sunday).

http://www.metservice.com/warnings/seve ... r-warnings

spwill · Unread post by **spwill** » Sun 03/06/2018 10:50

I notice Maungawhai Heads has had 96mm today, some big showers through there last two hrs going by the radar.
Heavy rain here.

David · Unread post by **David** » Sun 03/06/2018 11:05

spwill wrote: ↑Sun 03/06/2018 10:50 I notice Maungawhai Heads has had 96mm today, some big showers through there last two hrs going by the radar.
Heavy rain here.

PWS at Matakana showing 86mm today also.

David · Unread post by **David** » Sun 03/06/2018 11:29

Rain has suddenly become really heavy in Howick. Looking like that heavy band to the north might be going to slide down this way...

David · Unread post by **David** » Sun 03/06/2018 11:53

Incredible amount of surface water here now.

Cyclone Tracy · Unread post by **Cyclone Tracy** » Sun 03/06/2018 11:56

David wrote: ↑Sun 03/06/2018 11:53 Incredible amount of surface water here now.

40mm here now with moderate surface flooding. I'm on the western side of the convergence zone, so still receiving intermittent downpours. You are in the sweet spot David

spwill · Unread post by **spwill** » Sun 03/06/2018 12:01

Maraetai could be the spot for a deluge.

Howick up to 28mm last hr

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