Unstable air to start the year?/Canterbury Thunderstorm

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NZstorm
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Unstable air to start the year?/Canterbury Thunderstorm

Unread post by NZstorm »

The convection in the north Tasman Sea on this mornings satellite pic marks some very moist air and that moisture is headed our way. Looks like 18-20C dewpoints should move onto the west/upper North island tomorrow (Friday). This will certainly increase the risk of Saturdays front being a thundery one for the North Island. GFS also indicates some low level convergence tomorrow afternoon NE versus NW from Northland to Waikato, so maybe a convection risk later tomorrow.

Strong upper trough crossing the South Island Saturday with low level onshore flow developing in the afternoon produces a thunderstorm/hail risk for east of South Island, North Otago to mid Canterbury.
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Re: Unstable air to start the year?

Unread post by NZstorm »

The upper flow over the South Island tomorrow will be particularly strong. For example forecast 06Z 500mb wind for Hokitika is 77kts and 300mb 108kts. With that kind of shear West Coast thunderstorms will go nuts. The forecast 500mb winds for the North Island on Saturday are in region of 60kts.
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Re: Unstable air to start the year?

Unread post by David »

Certainly very hot air to start the year! Edging 29ºC in Howick...
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Re: Unstable air to start the year?

Unread post by Nev »

WOW 29°C and 27.8°C at Grey Lynn! 8-o Just 26.4°C here not long ago (DP 16°). A few brief rouge showers here last night btw (3.5mm). I've noticed that your T-maxs are usually quite similar to ours David, although T-mins are generally a little lower, so presumably you're quite a bit more inland?

Off for a dip to cool down... 8)
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Re: Unstable air to start the year?

Unread post by David »

Not too far inland, but I am going to alter my thermometer set-up for this year slightly. Am thinking of taking weather station off the roof and put it in the backyard, as to obtain better temp. readings than the last few years. Am looking at a wireless wind meter to substitute onto the roof (so I still have decent wind data). This one looks OK:
http://www.scientificsales.co.nz/wirele ... ature.html
The station on the roof today said 29.8°C but I suspect the roof tiles contributed that extra degree...
That 28.9°C was recorded in my backyard in the shade, this afternoon. :cool:
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Re: Unstable air to start the year?

Unread post by Manukau heads obs »

not as hot here, being closer to the ocean breezes I guess
25.4C max today
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Re: Unstable air to start the year?

Unread post by spwill »

A weak southwest seabreeze here from about 3pm so a hot day under that sun.

Auckland dewpoints aorund 15C today, 12C at Wellington and 0C at Christchurch. Very dry air over the eastern SI.
Last edited by spwill on Thu 01/01/2009 19:55, edited 1 time in total.
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Re: Unstable air to start the year?

Unread post by NZstorm »

I can believe the 28-29C readings away from the coast. Very little wind today. Tomorrow should be another hot one.
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Re: Unstable air to start the year?

Unread post by NZstorm »

The bad news is that the cricket on Saturday in Christchurch may get washed out by a thunderstorm.
500mb temps and MSL pressure chart here. Classic thunderstorm set up for Canterbury.
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Re: Unstable air to start the year?

Unread post by carrot »

Good to see the possibility of a storm for the first w/e of the year.
Some nice flashes too last night coming from the west. was pretty
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Re: Unstable air to start the year?

Unread post by Tornado Tim »

Update: Deleted the wrong soundings.
Last edited by Tornado Tim on Thu 01/01/2009 21:38, edited 1 time in total.
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Re: Unstable air to start the year?

Unread post by NZstorm »

Tim, those charts are for 1500hrs GMT on the 3rd which is 4am Sunday 4th local time. You need to look at 0300hrsGMT.
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Re: Unstable air to start the year?

Unread post by Tornado Tim »

Opps man I h8 going on foreign time zones they cock everything up.
:mad:
Thanks for pulling that up NZStorm.
Update: Ah that looks a whole lot better.
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Re: Unstable air to start the year?

Unread post by David »

And with metservice going for 27C (Auckland) on Saturday, there looks to be strong surface heating as well. With a NW forecast, it could be very warm here again. Gentle W-NW breezes today dragged offshore air across us, and with quite a lot of land between here and the west coast I suspect that's why it was particularly warm out here today.
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Re: Unstable air to start the year?

Unread post by NZ Thunderstorm Soc »

spwill wrote:
Auckland dewpoints aorund 15C today, 12C at Wellington and 0C at Christchurch. Very dry air over the eastern SI.
It was a much pleasanter day here today with the low dewpoints rather than the previous 2 days. :smile:

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Re: Unstable air to start the year?

Unread post by GraemeWi »

There were a couple of anvils at sunset, way to the north of Auckland on the west coast. Looking at the satellite and radar images, maybe somewhere up near Dargaville.
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Re: Unstable air to start the year?

Unread post by spwill »

The afternoon showers have arrived.
Showery along the west coast of Auckland / Northland currently. Warm rain with 20C with 18C dewpoints
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Re: Unstable air to start the year?

Unread post by NZstorm »

If we can get some convergence going today we may see a thunderstorm or two develop in the north. We are relying on the low level NW flow augmenting into a NE. Also need daytime heating too with temperatures above 25C. The GFS is forecasting CAPE values 800j/kg for northern Waikato/Coromandel.

Chart 12Z GFS Lifted Index values for 0600Z, also low level winds.
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Re: Unstable air to start the year?

Unread post by Tornado Tim »

Looks like the area of intreats will be out east on Sunday.....The East side of Auckland might get a thunderstorm.
Greymouth and Hokitika looks promising as well....basically any town out East in the NI.
Hopefully This overcast weather will burn and get some daytime heating going for today...
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Re: Unstable air to start the year?

Unread post by Nev »

Just some very light drizzle here in the last hour or so, which is hardly surprising given those rising DPs this morn. Had a little last night also (0.3m). Just a little patchy I guess. Those 2 minor fronts are still well to the NW.

Could also be the possibility of the odd tornado around the South Island's Westcoast today?
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Re: Unstable air to start the year?

Unread post by David »

What's happened to our 'hot' day? No sun at all??
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Re: Unstable air to start the year?

Unread post by spwill »

What's happened to our 'hot' day? No sun at all??
Yes, solid overcaste but our dewpoints are now 21C, highest for the summer so far, very muggy.
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Re: Unstable air to start the year?

Unread post by CHCH Weather Chaser »

Beautiflly fine yet again here. 26 degrees currently with a nice NW. Tomorrow metservice now Forecasting a good chance of hail and of golf ball size!!
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Re: Unstable air to start the year?

Unread post by jamie »

Looks like alot of NZ is in for some interesting weather finally. Good luck all, and hope some good storms fire up at least somewhere.
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Re: Unstable air to start the year?

Unread post by borris89 »

Just about to pass thru 30 degrees here and the westerlies are just startn to pick up now, only 19% humidity. Gisbourne looks to be a bit warmer than here tho
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