Trough 4-5 April

NZstorm · Unread post by **NZstorm** » Sat 02/04/2011 12:02

Looks like quite a sharp trough will cross the country early week.

There looks to be good thunderstorm chances over the North Island on Monday particularly upper NI Monday pm when a front looks to trigger convection over Auckland/Waikato/BOP.

The cold pool crosses central NZ on Tuesday with wintry style cbs with hail and thunder possible in a few spots over the lower half of the NI/upper SI. Hopefully the colder air ends up coming a bit further north but the lastest GFS run has it well south of Auckland. Still 3 days out.

Chart of 500mb heights/winds Monday. Also MSL pressure.

Storm Struck · Unread post by **Storm Struck** » Sat 02/04/2011 12:43

A few thunderstorm shots for canterbury too monday more so, and other days perhaps wintry CB'S of the thundery type.
Could well be seeing our first snow to low levels for the season too.

NZstorm · Unread post by **NZstorm** » Sun 03/04/2011 07:41

Front in the Tasman has some lightning on it currently but it is modeled to weaken a bit as it reaches the NI tonight. Looks to be a F1 tornado risk for Taranaki with that front later tonight given some low level directional shear there. Will depend on how much instability can make it to Taranaki.

NZstorm · Unread post by **NZstorm** » Mon 04/04/2011 06:56

BOP looks the spot for thunderstorms today, the front is modeled to stall as a convergence zone over BOP. Have to see what happens there today. Cb tops to 11000m. I can't see much happening over Auckland today due to a lack of convergence here.

Tomorrows cold pool will bring widespread hail to the North Island with the odd clap of thunder in places. Waitomo to Auckland look best placed to catch the coldies coming in off the sea. Will be interesting to see a winter style cold pool again, when was the last time we saw one?

East of the South Island should catch a few coldie cbs as well.

Forecast 500mb temps for midday tomorrow.

Tornado Tim · Unread post by **Tornado Tim** » Mon 04/04/2011 08:16

Lightning Detected from the NE and E now, up to 5/min at one stage.

Looking forward to this cold pool

spwill · Unread post by **spwill** » Mon 04/04/2011 08:56

Line of distant Cb tops with the front can be seen north and east of Auckland this morning.

03Stormchaser · Unread post by **03Stormchaser** » Mon 04/04/2011 09:00

NZstorm wrote:BOP looks the spot for thunderstorms today, the front is modeled to stall as a convergence zone over BOP. Have to see what happens there today. Cb tops to 11000m. I can't see much happening over Auckland today due to a lack of convergence here.

Tomorrows cold pool will bring widespread hail to the North Island with the odd clap of thunder in places. Waitomo to Auckland look best placed to catch the coldies coming in off the sea. Will be interesting to see a winter style cold pool again, when was the last time we saw one?

East of the South Island should catch a few coldie cbs as well.

Forecast 500mb temps for midday tomorrow.

and from Metservice:

Valid to: 12:00am Tuesday 5 April 2011
Issued at: 8:09am Monday 4 April 2011

An unstable showery north to northwest flow should cover the North Island today..
A trough of low pressure is expected to move slowly east over the Coromandel
Peninsula and Bay of Plenty during the afternoon and evening.
Heavy showers already affecting these regions are expected to turn thundery from
about midday. The most likely area for thunderstorms is Bay of Plenty and the
far northern parts of Gisborne, where rainfall intensities of 25mm per hour are
possible. A low risk also covers the area from Auckland south to Taranaki and
Tongariro.

A front moving north of Westland and Buller this morning is bringing heavy rain (see details on heavy rain warning). This front may contain a few thunderstorms.
A low risk continues following the front through the afternoon and evening with
heavy showers.

A southerly change is expected to move north over North Otago and Canterbury during the afternoon and early evening. Heavy showers are expected to trigger as this southerly works its way northwards and inland. A moderate risk is indicated for North Otago and South Canterbury (mostly near the foothills).Small hail is possible in these heavy showers.

If things look good from CHCH im free to chase today.

Chris Raine · Unread post by **Chris Raine** » Mon 04/04/2011 09:02

I'm heading to Chch from Oamaru this morning and back tonight. So will see if anything develops during the drive

spwill · Unread post by **spwill** » Mon 04/04/2011 14:34

A warm day for Auckland, up to 25C at Greylynn, some towering Cu around, distant Cb line ( Thunderstorms) visible beyond the Coromandel .

GFS showing some very upper cold air from Auckland to the south tomorrow, suggests isolated thunder risk .

spwill · Unread post by **spwill** » Mon 04/04/2011 14:46

This shower cloud has just developed over SE Auckland

spwill · Unread post by **spwill** » Mon 04/04/2011 15:33

Shower line starting to develop just east of Auckland, photo from Mt Eden.

spwill · Unread post by **spwill** » Mon 04/04/2011 16:08

Cb east of Auckland just now.

CHCH Weather Chaser · Mon 04/04/2011 16:26

Heavy rain most the day in Westport. Eased back in last couple of hours to light rain but 20mm in an hour and 33mm in 2 hours at one point. 47mm of rain today. 35 from yesterday afternoon so 83mm all up so far.

Tornado Tim · Unread post by **Tornado Tim** » Mon 04/04/2011 16:28

Storm over North Western Mangakino atm, got my ranging nearly perfect with the boltek on it

Big Heavy shower line to my NE, not surprised if lightning comes out of it soon

NZstorm · Unread post by **NZstorm** » Mon 04/04/2011 16:36

Pic here of some t/cu out to NE.

jamie · Unread post by **jamie** » Mon 04/04/2011 16:38

Tim I just txt u. I'm keen for chase. Can be ague house or lookout very soon. NE looks worthy of a better look

snowstormwatcher · Unread post by **snowstormwatcher** » Mon 04/04/2011 16:44

Moderate rain here with some heavier falls early on 16mm so far. Currently 7.9 degrees so it will be snowing on the mountians.

spwill · Unread post by **spwill** » Mon 04/04/2011 17:07

This cell out to the SE looks like it has produced some lightning, shower clouds are moving quickly down a convergence line running from Nothland down into Waikato ( east of Auckland), some isolated thunderstorm activity along the line.

NZ Thunderstorm Soc · Mon 04/04/2011 17:28

What a magnificent photo

Don't see thunderstorms down here like that.

JohnGaul
NZThS

David · Unread post by **David** » Mon 04/04/2011 17:28

What a brilliant fine day in Auckland! Warm too, a high of 23C in Howick, with dewpoints up to 19C (plummeted to 14C between 4pm and 5pm). Metservice seems to think the hail showers tomorrow will be south of Auckland, but we might catch a little bit I hope?

Tornado Tim · Unread post by **Tornado Tim** » Mon 04/04/2011 18:18

A nice CB developed off the Henua Ranges and drifted SE'wrds gave some good structure b4 it became obscured

Hardly any lightning (if at all) with it.

Vertigo · Unread post by **Vertigo** » Mon 04/04/2011 19:11

the incoming front looks quite good indeed at this stage, if a bit short lived once it gets here..

it was refreshing to see some cells around auckland this afternoon with some great structure to them, but as is often the case, the best stuff was miles away all day

spwill · Unread post by **spwill** » Mon 04/04/2011 19:19

Nice pool of Cb in the Tasman but I see latest GFS has pushed the colder air further south of Ak tomorrow so perhaps the thunder chance will be south of Hamilton.

Tend to be more in the firing line up here from May, roll on Winter.

NZstorm · Unread post by **NZstorm** » Mon 04/04/2011 19:26

Nice pool of Cb in the Tasman but I see latest GFS has pushed the colder air further south of Ak tomorrow so perhaps the thunder chance will be south of Hamilton.

Yes, we may still get some small hail in Auckland though to remind us winter is on the way.

Tornado Tim · Unread post by **Tornado Tim** » Mon 04/04/2011 20:00

I cant believe M/S has no risk for Waikato tomorrow, the forecast soundings are blindingly obvious yet no risk at all?!

Lapse rates will be higher than today, upper air temps very cold and with favorable TT Index's and K index's not mention LI and CAPE.

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