Storm Risk Central Upper North Island - 21st-23rd October

[Tornado Tim]

Convergent showers with low risk of one or turn turning into Thundershowers in the afternoon tomorrow in the Waikato down into Taupo.

[NZstorm]

I would included Auckland in the low thunder risk area. Cloud layers look like being a big issue today.

[spwill]

Yes, comes down to heating today to how heavy/widespread those late showers will be.
Reasonable moisture showing at the Airport, 12C dp.

[Razor]

Keep it away from the cricket at Mt Maunganui

[spwill]

Yes, hopefully a dry day at Mt Maunganui http://www.takeabreak.co.nz/accommodation/tauranga.asp

[jamie]

I would included Auckland in the low thunder risk area. Cloud layers look like being a big issue today.

Metsrvice have in their outlook today.

It's a fine day here in Hamilton. I will be keeping an eye on things from the airport today. Looks a decent setup to me.

[Tornado Tim]

The Outlook today for reference:

A combination of afternoon sea breeze convergences, daytime cloud buildups and cooling temperatures aloft are expected to produce scattered afternoon and evening showers about many parts of the northern and central North Island today.

In general, there is a low risk of isolated afternoon and evening thunderstorms from Northland to northern Taranaki and Taihape, however this risk of thunderstorms is considered closer to moderate about Waikato in the late afternoon and early evening (as indicated on the chart).

If any thunderstorms do develop they will be slow-moving and therefore have the potential to produce localised heavy rain (possibly as high as 20-25mm/hr) and small hail. Small funnel clouds are also a possibility about Waikato.

Tonight, a weak front associated with a low west of the northern North Island will move onto Northland and there is a further low risk of one or two thunderstorms in this area tonight.

No other thunderstorms or significant convection expected over New Zealand today.

[David]

Very grey and gloomy here, doesn't seem to be any rain around though. Maybe not enough sunshine today to get things going.

[NZstorm]

Very grey and gloomy here, doesn't seem to be any rain around though. Maybe not enough sunshine today to get things going.

Yes, we needed the spring sunshine. Layered cloud dominated our skies.

Tomorrow is another day and we will still have the polar vortex over the upper North Island.

500mb chart for tomorrow Wednesday midday.

[jamie]

But of a bust really. Looks to have all had a lid put on it at the mid to lower level

[spwill]

Looked like an inversion there which helped create the cloudy layer.
Calm overcaste conditions at my place this afternoon.

[Tornado Tim]

A pity about the mid level cloud today stopping decent convection.....

Well the Outlook from Metservice looks quite promising tommorow

I will probably go out for a drive/chase if the convection is good enough...

Valid to: Midnight Wednesday 22 Oct 2014

Issued at: 8:33pm Tuesday 21 Oct 2014

Strong sea breeze convergence and instability associated with relatively cool temperatures aloft are likely to trigger showers over much of the upper North Island in the afternoon.

In the area with the strongest convergence, Waikato, Waitomo and Taumarunui,there is a high risk of thunderstorms in the afternoon. These storms could be accompanied by localised heavy rain up to 25mm/hr (or possibly higher) and hail.

A moderate risk encompasses a larger area including the south of Auckland,inland Bay of Plenty and Taupo as indicated on the map. Those storms could be accompanied by heavy rain, 10 to 25mm/hr and small hail.

A slow moving front is expected to affect the far north. This is likely to bring frequent showers or periods of rain and there is a moderate risk of some thundery falls with heavy rain as indicated on the map.

No other thunderstorms or significant convection expected over New Zealand during this period.

[Tornado Tim]

Forecast sounding wise the atmosphere looking much better, with overall cooler upper level temps.

I have attached a forecast sound in central North Waikato tomorrow from BSCH with some re-initializing of the Temp and DP at SFC.
The close temp and DP's in the upper air means there is good potential latent heat give off. Wouldnt surprise me if MU CAPE exceeds 800-1000j/kg accounting for latent release.
Karipiro is looking like a good place for storms, as it usually is. Ricky and Jamie what you up to tomorrow?

[Manukau heads obs]

spotty rain here at the moment

[jamie]

I'm stuck at air port again today then I play sport tonight. So I'm out sorry.

[NZstorm]

Its not a big instability/big storm day but there will be surface convergence and cold air at 700mb.
I see the DP in Auckland is 12C so enough moisture for pm heat showers and a chance of thunder Waikato/Auckland.

[Tornado Tim]

Moderate Risk of Severe Storms according to Metservice:

A combination of sea breeze convergence, daytime cloud buildups and cool temperatures aloft are expected to produce scattered afternoon and evening showers and/or thunderstorms about the northern and central North Island today.

The most likely area for thunderstorms is about southern and western Auckland,Waikato, Waitomo and Taumarunui during the afternoon and early evening, but a low risk covers other northern and central areas from western Northland to the central high country as indicated on the chart.

These thunderstorms will be slow moving and therefore have the potential to produce localised heavy rain with hail. Rainfall rates will most likely be in the 10-20mm range, however a few of the storms could be severe with localised downpours as high as 30mm/hr (particularly in Waikato). Rainfall rates of this intensity can cause surface and/or flash flooding and make driving conditions very hazardous.

Further north, a few thunderstorms associated with a narrow frontal band are also expected in the Far North from afternoon. These thunderstorms should move offshore tonight, but could also produce localised heavy rain and small hail.

No other thunderstorms or significant convection expected over New Zealand today

Had a look at the next lot of forecast soundings, they look even better than last night. Trop at around 350hPa, so convection could get quite tall.

[spwill]

Some sunshine arriving here now which is nice after yesterdays gloom

[jamie]

Not sunny here.... yet. Shouldn't be too fat away though.

If there is something decent around 5pm I'll skip sport I think and do a chase.

[Manukau heads obs]

looking good here
NE breeze currently and sunshine

I will be in the Pukekohe/Waiuku area this arfternoon

[Tornado Tim]

Not sunny here.... yet. Shouldn't be too fat away though.

If there is something decent around 5pm I'll skip sport I think and do a chase.

Very good!
Clearance should be coming in from the west according to the latest sat image:

[Tornado Tim]

Severe T-storm Watch issued.

Issued by MetService at 08:40 am Wednesday 22 October 2014
Valid until 09:00 pm Wednesday 22 October 2014
This watch affects people in the following weather forecast districts:
Auckland
Waikato
Waitomo
Taumarunui

Daytime cloud buildups are expected to produce scattered heavy showers and thunderstorms about western and southern Auckland (south and west of the CBD), Waikato, Waitomo and Taumarunui this afternoon and early evening.

These thunderstorms will be accompanied by localised heavy rain and hail.

A few of the thunderstorms (particularly in Waikato) may be severe producing localised downpours of 20-30mm/hr.

Rainfall of this intensity can cause flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys. Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain.

Note: A Severe Thunderstorm Watch means conditions are favourable for severe thunderstorms in and close to the watch area. People in these areas should be on the lookout for threatening weather conditions and listen for possible Severe Thunderstorm Warnings.

Issued by: John Crouch

This watch will be updated by: 02:00 pm Wednesday 22 October 2014

[jamie]

Still cloudy. Doesn't look good

[Tornado Tim]

Still cloudy. Doesn't look good

I agree, the Moderate Severe risk is going down the toilet. Wont even be worth a low risk of thundershowers with this going on.

[Manukau heads obs]

its looking good here
sea breeze starting to develop here now
and we have had some good land heating this morning with some good sunshine
(19C here now)
already some good cloud build ups around)