Thunderstorms - 14th - 18th December, 2013

[NZstorm]

Easy forecast today for the North Island, thunderstorms over the ranges and possibly few elsewhere.

The big question is will any convection develop near Auckland? I would say a good chance of a thunderstorm on the sea breeze convergence zone late this afternoon.

[spwill]

I noticed the Hawkes Bay storms yesterday evening were still going after sunset.

Current weather here, fine 18C, dewpoint 17C

[NZstorm]

We need a temperature 25C + for a cb on the Auckland convergence zone today. Same deal tomorrow.

[Nev]

I see MS have extended their low-risk to cover much more of the N.I. in this morn's update…

MetService - Severe Thunderstorm Outlook

Valid to: Midnight Saturday 14 Dec 2013
Issued at: 8:21am Saturday 14 Dec 2013

Afternoon sea breezes and cold temperatures in the upper atmosphere are expected to produce scattered heavy showers about central and northern parts of the North Island today. The most unstable area is from inland Bay of Plenty to Taihape,across the to Tararua District then northwards to the ranges of Hawkes Bay and Gisborne. In this area, there is a moderate risk of slow moving SEVERE THUNDERSTORMS, producing localised downpours of 25 to 40mm/hr and small hail. A lesser risk of thunderstorms extends over northern and remaining central parts of the North Island as depicted on the chart.

Also of note, afternoon convergence zones are expected to produce showers across eastern parts of Southland, Otago and the South Canterbury foothills. In these areas, there is a low risk of a few of these showers becoming thundery.

No thunderstorms expected over the rest of New Zealand.

MetService T-Storm Outlook Map - Is. Dec 14, 8.21am.png

[NZstorm]

Todays 500mb chart showing the cool upper air mass across NZ, reason for the storms.

[Tornado Tim]

The GFS shows the instability and lift goes a bit further north to north Waikato, so I would tend to ignore the outlooks high risk area.

Instability is fairly deep, but the mid to upper level flow is slack to say the least.
So slow moving Isolated to scattered storms possible today over the Kaimai ranges, eastern central Waikato, Hawkes Bay and Gisborne Ranges.
If temps remain high over late afternoon, storms should continue popping to mid evening.

[Tornado Tim]

Some GFS Charts for reference:
GFS Charts Courtesy of [url=http://bsch.au.com"]BSCH[/url]

[jamie]

Tomorrow looks better for us and MS have indicated that on their chart.

I tend to agree with you Tim. To me today has more potential than a low risk for up this way.

[Storm Struck]

I cant agree at all with their low risk over the south island tomorrow would love to know what they are looking at , to me its a moderate/high risk in some areas when you have -3C LI's and up to 700 cape.
Its also clear from the surface maps its not just an inland ranges set up but on the plains too, so the forecast for fine with light winds is very lazy and ridiculous.
Rant over.. North Island looks like some good chances look forward to the photos.
Monday and Wednesday look like potential days for us too.

[spwill]

18C dewpoint here, 24C.

[Tornado Tim]

Storms already on the Gisborne Ranges I see, quite a quick initiation!

[Manukau heads obs]

sea breeze getting going here now
some towering CU inland and even over the waitakeres

[NZstorm]

Can see cb rapidly forming out to east of here, will be over the Coromandel.

[spwill]

Yes, nice cell developing out east, blowing up over Thames.
http://www.metservice.com/towns-cities/ ... nd-central

[Tornado Tim]

I see they updated the outlook to cover the coromandel, and I bet as soon as stuff gets going just east of here they will expand the outlook a 3rd time.

[Tornado Tim]

Cumulus Congestus now forming to the north of me.

[Tornado Tim]

Oh man heaps of towers going up now..... Anvils to east over Kaimais. Hauaraki Plains lots of activity starting there!

[NZstorm]

Decent towers over the Hunua ranges, east Auckland. Will be thunder there before too long.

[Tornado Tim]

A fair few of early developing potential cells in Northern Waikato now

[NZstorm]

Over Bombay. Very glaciated cloud. Heavy showers down there now.

[spwill]

At Bombay , very heavy showers and thunder here

[NZstorm]

CB building up out to NW of Auckland.

[Tornado Tim]

I see they updated the outlook to cover the coromandel, and I bet as soon as stuff gets going just east of here they will expand the outlook a 3rd time.

And what do you know......

Updated at 3pm to increase risk of thunderstorms over Northland and Auckland to moderate, and extend Severe Thunderstorm risk into Waikato.

Daytime cloud buildups are producing scattered heavy showers about northern and central parts of the North Island today. There is now a moderate risk of thunderstorms about Northland and Auckland, and a high risk from Coromandel Peninsula and Waikato southwards to Gisborne and Hawkes Bay. These thunderstorms will be slow-moving and therefore have the potential to be SEVERE producing localised downpours of 25 to 40mm/hr and hail. A lesser risk of thunderstorms extends over northern and remaining central parts of the North Island as depicted on the chart.

Also of note, afternoon convergence zones are expected to produce showers across eastern parts of Southland, Otago and the South Canterbury foothills. In these areas, there is a low risk of a few of these showers becoming thundery.

No thunderstorms expected over the rest of New Zealand.

[03Stormchaser]

Dammit looks good for storms down here tomorrow. Although upper air isnt very cold. I'm busy tomorrow and Monday so both days should storms form I cant get out. Mind you my car is out of action anyway, rear wheel bearings booked in to be replaced next week.

[NZstorm]

Can see lightning from central Auckland off the Bombay cb!