Major Low Pressure system - 8th to 12th May

[tidd66]

Wind has changed to the south down here, steady rain and cooling off. Better light the fire.

[DT-NZ]

took this pic approx 30 mins ago... the sun's gone behind cloud's... the temperature has dropped... and... it's grey and bleak out there again... rain's stopped though... nothing too exciting to report yet...

07052009_0.jpg

[DT-NZ]

great looking instability today! i happened to lock my keys in the house, so i was treated to a delightful walk to work amongst the Cb's. the overcast seems to be creeping in now.

Hi Vertigo sorry to hear you locked your keys in your house... though... thank's for the smile & chuckle...
hope you beat the rain home... take care.

[Manukau heads obs]

squally hail shower and thunder through here, heading towards auckland

[David]

Here's that CB Brian

EDIT: We seem to have the situation where the showers weaken as they head inland again...just a brief rain shower even though that CB went right overhead!

[spwill]

One or two nice Cb clouds around Auckland today . yes, the weather action is on the Coastal fringe (west), cool land temps today.

[Manukau heads obs]

more thunder
(passing just to the south of me)

[Michael]

Thunder here now,sky black as the Jack of Clubs.14°

[gllitz]

Nice wee little "hook" on the Invercargill radar at 1600....

[Michael]

Thats it 3 minutes of Gale Force SW with Rain.

[Myself]

Remember that MetVuw is exclusively GFS. So the worst model of the lot.

I don't think the gfs is any worse than any other model. UKmet and ECMRF are not any better. And GFS is more comprehensive in its forecast period and output.

...well I think this is just wrong.

"UKMet and ECMWF are not any better" -

The ECMWF is way ahead of the game in terms of both its model and the scale of ensemble forecasting they go into. The equivalent resolution of their model is 25km. The GFS is something approaching 80km, and the UKMO is 60km.
The ECMWF have the most sophisticated means of integrating current observations into their model.

The UKMO and ECMWF have one huge factor in their favour over the GFS in New Zealand: Orographic fields. The GFS understanding of our terrain is rubbish. You can pretty much guarantee they will have their orographic troughs and ridges all over the shop, and the pressure field looks far, far too smooth to be realistic.
Any model will have trouble with NZ's mountains, but the GFS is notable for being persistently weak in this regard.

"And GFS is more comprehensive in its forecast period and output" -

"Comprehensive"? GFS runs 4 times a day, but there are question marks over whether it's worthwhile. Oh, another model run, oh looks it's crap again. When you produce oddball output like the GFS, then running 4 times a day is not worthwhile.
And as for output...there is far more output for the ECMWF and UKMO models, it's just not accessible to us in the public. The GFS makes everything free because it has to (something to do with the constitution I think). So all GFS output is freely available, but it is not for the other two main models. Doesn't make it a better model by any means.

[NZstorm]

Heard that thunder here in Grey Lynn too about 30mins ago. .

[NZstorm]

Bear in mind Myself we are discussing the models that are avialable to the public, rather than what the Met Service buys with its tax payer funding.

[spwill]

I like ECMWF( free version ) less these days and are looking more at the GFS.
Photo, Michaels thunderstorm, one distant clap of thunder here.

[Razor]

Great pics up there! Lovely day in ChCh today. Calm before the storm as I head off to Te Anau tomorrow....

[jamie]

have not heard any thunder today but i was inside for most of it. I have seen some awesome CB's today though.. will be watching the sky tower tonight for sure though.

off topic did anyone see that jet flying around the city 15mins ago... was very low and noisy as hell. looked like it flew right over towers in the city at one point.. i think it was a fighter jet but didnt thnk NZ had any????

[Myself]

Bear in mind Myself we are discussing the models that are avialable to the public, rather than what the Met Service buys with its tax payer funding.

Yeah fair play, it's a good point. I still think that the limited output available from the UK model is more useful than the abundance of GFS fields if it's a case where the GFS is really not onto it.
I wonder how much it costs to get all the output from something like the ECMWF?

[Myself]

Great pics up there! Lovely day in ChCh today. Calm before the storm as I head off to Te Anau tomorrow....

Fiordland probably not the worst place to be with this system...but Te Anau might cop it a bit. Should be a sparkling day in Milford Sound though!

[Razor]

From metservice:

Fiordland National Park Thu May 7 Issued at 11:59 am 7 May 2009 NZST
Rain this afternoon, with a few heavy falls and isolated thunderstorms. Rain easing to showers this evening, and clearing and becoming fine about the fiords. Snow level lowering to 8000 metres.

Haha its a heatwave!

[Vertigo]

off topic did anyone see that jet flying around the city 15mins ago... was very low and noisy as hell. looked like it flew right over towers in the city at one point.. i think it was a fighter jet but didnt thnk NZ had any????

if it was the one i saw, it was a passenger jet, and it flew strait into a monster Cb!

[Philip Duncan]

I heard that before - it was incredibly loud! Speaking of jets and CBs, I saw a 777 do a sharp turn to avoid a CB over Auckland today...have never seen anything like it!

[Tornado Tim]

Yea, Pilots do a course to identify clouds and which 1s to avoid. Usually all planes have a doppler radar in the cockpit so they can take evasive action.
If i remember correctly they avoid any thing with CB in it esp when it has a Pileus cap, and even a Cu congestus because of the turbulence involved.
But as you all know they can never avoid clear air turbulence which is the invisible cirrus kelvin helmholtz or another form with similar characteristics.
Now back on the subject of today,
Clear conditions now with Not 1 clap of thunder here, but heaps of CBs,
I think the low DPs made the CB's die, Max here was 12°C.

[David]

Looks like pressures could dip down to 984hPa early next week in Auckland!

[Manukau heads obs]

yes, great day for watching passing CB's, and thunder heard here on 4 occasions

[Nev]

lol, think you mean the doppler is mounted in the nose Tim. Yes, what they're primarily looking for are microburts. The doppler should give them just enough time to take evasive action, which sounds like what Phil described.