Cold trough crosses North Island 5-6th November

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NZstorm
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Cold trough crosses North Island 5-6th November

Unread post by NZstorm »

Tomorrows storm chances over the North Island looking mediocre with the cold pool very slow to come in. 00Z gfs for 4pm tomorrow below. Ukmet looks the same. Area of interest for storms tomorrow will be Waitomo provided there is good surface heating down there.
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Re: General November Weather

Unread post by Nev »

Here's this evening's updated MS T-Storm Outlook for tomorrow arvo…
MetService - Thunderstorm Outlook

Valid to: Midnight Wednesday 5 Nov 2014
Issued at: 8:31pm Tuesday 4 Nov 2014

Updated at 8:25pm - Low and moderate risk areas expanded over the central North Island. Minor changes to South Island areas.

Unstable conditions are expected again on Wednesday afternoon, with daytime heating and cold air aloft combining to produce scattered heavy showers and a risk of thunderstorms over the upper South Island and central North Island.

The highest risk of thunderstorms is anticipated for inland parts of Nelson,tending to a moderate risk for Buller, the ranges of northern Westland and inland Marlborough. Any thunderstorms in these areas will bring localised heavy rain and hail, but should clear at night. There is a lower risk of thunderstorms extending farther south through Kaikoura, the Canterbury High Country and Mackenzie Basin.

Over the North Island, there is a moderate risk of thunderstorms developing inland about Bay of Plenty/Rotorua, Taupo, Taumarunui, Taranaki, Gisborne and northern Hawkes Bay, with a surrouding lower risk from Auckland and Coromandel to Taihape and central Hawkes Bay. Any thunderstorms in these areas will also bring localised heavy rain and hail, and should ease into the evening, but heavy showers are likely to continue overnight.

No other thunderstorms or significant convection expected on Wednesday afternoon or evening.
MetService T-storm Outlook Map update - Oct 5, pm.png
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Cold trough crosses North Island 5-6th November

Unread post by NZstorm »

700mb temperature chart indicates chilly air widespread over NI today so showers could pop up anywhere today. Some lightning/small hail possibilities as well, more likely from Taranaki to Central North Island.

But colder 500mb air coming into west of North Island tonight (Waikato) with Isolated thunderstorms/hail overnight in the west.


500mb chart for midnight tonight.
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Re: Cold trough crosses North Island 5-6th November

Unread post by Nev »

Thanks NZstorm. I've moved last night's posts over to this thread. :-)
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Re: Cold trough crosses North Island 5-6th November

Unread post by Manukau heads obs »

Had a heavy shower here in the wee small hours
and more showerd out to west
sunny looking over waikato way
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Re: Cold trough crosses North Island 5-6th November

Unread post by NZstorm »

There has been a little bit of lightning this morning out to sea west of here.

For storm chase prospects today I will target the colder 500mb air tonight. Could be a lightning photo op.
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Re: Cold trough crosses North Island 5-6th November

Unread post by Nev »

MS T-Storm update for today…
MetService - Thunderstorm Outlook

Valid to: Midnight Wednesday 5 Nov 2014
Issued at: 8:57am Wednesday 5 Nov 2014

One or two thunderstorms have occurred west of Auckland over the sea this morning, with heavy showers and small hail moving onto western coasts of Northland, Auckland and Waikato. Heavy showers are likely to continue in these areas this morning, but any further thunderstorms should remain offshore.

Conditions remain unstable today across the central North Island and upper South Island in the presence of a significant cold pool aloft. Daytime heating and onshore winds will trigger showers from late morning into the afternoon about many areas from Auckland to Taihape, also in the northwest of the South Island.Some of these showers are likely to be heavy with small hail and a general low risk of one or two thunderstorms (including inland Marlborough and Canterbury).However, there is an elevated risk of thunderstorms this afternoon and early evening for inland areas from Bay of Plenty to the Hawkes Bay ranges and across to Taranaki, also in northwest Nelson, Buller and northern Westland.Any thunderstorms that occur will bring locally heavy rain (with rates 10-20mm/hr)and hail (reaching 10-15mm in diameter).

Finally, there is a moderate risk of thunderstorms over the sea just west of Auckland and Waikato tonight associated with a trough and shallow low just offshore. While thunderstorms will probably remain over the sea, heavy showers with hail may drift onto western coasts.

Elsewhere, no thunderstorms expected.
MetService T-storm Outlook Map - Oct 5.png
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Re: Cold trough crosses North Island 5-6th November

Unread post by David »

Have a sea breeze here, that will be good for some heavy showers to develop this afternoon
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Re: Cold trough crosses North Island 5-6th November

Unread post by Manukau heads obs »

Saw a brief funnel cloud :)
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Re: Cold trough crosses North Island 5-6th November

Unread post by NZstorm »

A dry sunny afternoon in Auckland with cool 18C Max.

I see there has been isolated weak storms west of Taupo this afternoon.
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Re: Cold trough crosses North Island 5-6th November

Unread post by Nev »

Noticed Blitzortung showing a lot of activity around Brian's place, and yet there's nothing on the Boltek or the rain-radar? Just wondering, as it's not the first time I've noticed this recently?
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Re: Cold trough crosses North Island 5-6th November

Unread post by Manukau heads obs »

Sunny here
must be some interference
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Re: Cold trough crosses North Island 5-6th November

Unread post by Nev »

Ah, thanks for clarifying that. :smile:

Yes, has been mostly sunny here this arvo, but some good build-ups and dark clouds around. Had the odd shower this arvo and this morn (not to mention a brief little downpour around 9:30pm last night).
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Re: Cold trough crosses North Island 5-6th November

Unread post by Nev »

Some great pics of the hail-storm in New Plymouth this arvo, including a funnel-cloud…

'Torrential rain and hail hits New Plymouth' - Taranaki Daily News
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Re: Cold trough crosses North Island 5-6th November

Unread post by treetop »

Only 1 rumble here east of the Kaimais, no height to the showers, more like glaciated statocumulas. The air had a real hail feel to it though . Some snow virga down to 1000m which is unusual for here in Nov.Hope for better tomorrow but will need a S air flow[ SW will kill any development.]E BOP may cop a storm regardless.
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Re: Cold trough crosses North Island 5-6th November

Unread post by Nev »

Now looking more promising before dawn for Akld, the Gulf and coastal Waikato...
MetService - Thunderstorm Outlook

Valid to: Noon Thursday 6 Nov 2014
Issued at: 8:32pm Wednesday 5 Nov 2014

Updated at 8:30pm Wednesday - Moderate risk area expanded across Auckland,moderate risk area removed from eastern Bay of Plenty, minor changes elsewhere.

A shallow low and trough are forecast to cross the upper North Island during the morning, with unstable conditions under cold air aloft.

There is a moderate risk of isolated thunderstorms about Auckland and the Hauraki Gulf during the morning, and about coastal Waikato/Waitomo before dawn.

A lower risk covers other northern areas from Waikato and Bay of Plenty northwards during the morning as the low crosses over, and also about coastal Hawkes Bay before dawn as southerlies freshen through the area with an accompanying rainband.

Localised heavy rain and small hail will accompany any thunderstorms that do develop.

No other thunderstorms or significant convection expected over New Zealand on Thursday morning.
MetService T-storm Outlook Map - Oct 6, am.png
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Re: Cold trough crosses North Island 5-6th November

Unread post by David »

Nev wrote:Now looking more promising before dawn for Akld, the Gulf and coastal Waikato...
Where does it say before dawn for Auckland? Sounds more like mid-morning to me, reading the outlook :-k
(I have to travel to the city late morning, so am interested in the timing)
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Re: Cold trough crosses North Island 5-6th November

Unread post by Nev »

Sorry, misread that - 'before dawn' seems to only refer to 'coastal Waikato/Waitomo'. #-o
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Re: Cold trough crosses North Island 5-6th November

Unread post by Manukau heads obs »

Surprisingly windy here
When its only a shallow small low
but it took lool like it has deepened a bit
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Re: Cold trough crosses North Island 5-6th November

Unread post by tgsnoopy »

treetop wrote:The air had a real hail feel to it though.
I was working in Hamilton/Ngaruwahia area yesterday, took a call around 4pm from Gary (Kaimaikid) advising of a heavy hail shower in Katikati that might be heading towards Tauranga.

Driving back about 5pm drove through a very dark cloud, some tiny hail component in the heavy drops. Only saw one flash, but it was embedded intercloud.

I'm back over in the Waikato again this afternoon.
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Re: Cold trough crosses North Island 5-6th November

Unread post by Nev »

Seems to have been a bit of a fizzer for Akld so far. :-(

Here's this morn's update for later today…
MetService - Thunderstorm Outlook

Valid to: Midnight Thursday 6 Nov 2014
Issued at: 9:13am Thursday 6 Nov 2014

An upper level cold pool is forecast to remain over the upper South Island this afternoon, then move onto the North Island during the evening. This brings a contined threat of thunderstorms and hail, especially to the northwest of the South Island.

The main risk of thunderstorms is about Nelson, Marlborough and Buller this afternoon and evening where they will be fairly slow moving, and also Bay of Plenty and Gisborne where they will be a little more mobile. A lower risk covers other northern and western South Island areas,and Coromandel,Waikato,Taupo and inland Hawkes Bay,as indicated on the chart.

These thunderstorms will produce localised heavy rain and hail, which could cause damage to crops and orchards in these areas, as well as make driving conditions hazardous. The slow movement of the storms in the northwest of the South Island once again brings a risk of significant hail accumulations.

Finally, there is also low risk of a few thunderstorms about Taranaki and coastal Waitomo from late evening.

No other thunderstorms or significant convection expected over New Zealand during this period.
MetService T-storm Outlook Map - Oct 7.png
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Re: Cold trough crosses North Island 5-6th November

Unread post by Manukau heads obs »

Can see CB's down in Waikto
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Re: Cold trough crosses North Island 5-6th November

Unread post by Tornado Tim »

A bit of Lightning coming this cell just SE of Tauranga atm....
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Re: Cold trough crosses North Island 5-6th November

Unread post by NZstorm »

The timing was out for Auckland with two fine afternoons out of this trough (bit windy today though). Taranaki caught the onset yesterday and BOP getting the departure. Atleast the gfs had picked up on that quite well.

Could see the cb tops to SE this afternoon, a real summer sight!
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Re: Cold trough crosses North Island 5-6th November

Unread post by Tornado Tim »

Yikes Big radar returns on that cell off Tauranga! 70dbz! Warrants a warning I think!
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