Depressing Depressions!

tich · Unread post by **tich** » Sat 27/09/2003 14:53

I can usually tell when we're in a westerly rather than a northwesterly flow - the clouds are different. In a northwesterly, there is usually high northwest arch style cloud, while in a westerly (like today) there is scattered cumulus. I guess that's an indication we're in a colder airmass, even though it might still be mild in Chch.

NZstorm · Unread post by **NZstorm** » Sat 27/09/2003 15:12

Alot of lightning about today Brian. 419 strikes is impressive. That would be composed of both CG and CC.

And I saw the cb boilup over North Auckland on the 2pm satellite. I notice the cb activity has even got into the BOP today.

Over the last two days the upper air over Auckland has progressively become more unstable(off the surface), while surface dewpoint temperatures have stayed relatively high(around 15C). A weak frontal zone over the region has provided the extra instability and forcing to trigger the convection. With all the low cloud about I cannot see the cb buildups. Pity.

I am hoping this ts activity is still about tonight. Still crackling on the am band.

Manukau heads obs · Sat 27/09/2003 15:27

this new low developing in the tasman looks like it will be a real good one
we should get some good gales here!

NZstorm · Unread post by **NZstorm** » Sat 27/09/2003 15:32

Looks like the low will be a clash of the airmasses. Bitterly cold southern air with a low freezing level mixing with warm humid northern air.
This low will be very nasty for some parts of the country.

Thunder · Unread post by **Thunder** » Sat 27/09/2003 15:36

Something might be floating round here to in Chch.

Photo is of Cu clouds near me today.

Cheers
Aaron Wilkinson

NZstorm · Unread post by **NZstorm** » Sat 27/09/2003 17:22

Looks to be some cb's off the coast of Banks P as you suggest Aaron.
But given the dewpiont in Christchurch is currently minus1C, I don't see them coming to much. Must be a bit of an easterly shift off the coast.

I like the cumulus photo.

Cb's have cleared Auckland. I expect to see more thundery weather with the front tomorrow. Ingredients are there for quite an active front.

NZ Thunderstorm Soc · Sat 27/09/2003 18:02

Yes, you are right Steven. I saw those clouds too and wasn't interested in them. Westerly blowing and a low dew-point.
I think tomorrow will also be disappointing here in ChCh, just a bit of drizzle now as the barometer is rising now with higher air pressure coming in to cradle the low moving onto central NZ.
The weather event will occur much north of ChCh
JohnGaul
NZTS

Thunder · Unread post by **Thunder** » Sat 27/09/2003 18:37

4:54pm sat pic from Graham W's site

Somethings out there!

Did you get any static John?

Cheers
Aaron Wilkinson

Manukau heads obs · Sat 27/09/2003 19:02

i think it will be mainly all upper level cloud sheet,......which you can still get rain from (which shows on the rain radar), as some of it made riught over mt cook intact and was not greatly affected by the souther alps./...
my thouhtgs,,,

NZ Thunderstorm Soc · Sat 27/09/2003 19:40

Sorry Aaron, high cloud. Toooooooooo westerlieish. I did notice high cloud forming here about then but it looked boring and flat

JohnGaul
NZTS

As far as the Ranfurly shield goes, I think they should saw it in half and give half to Wellington. They did do a good job to try and win it.

NZ Thunderstorm Soc · Sat 27/09/2003 23:34

Some distant sferics on the AM band late tonight. Not continuous but could be from that bright blob way out to the east of Auckland on the 9pm satpic.

Nothing much here at the moment to herald the arrival of the cold SE deluge and Depressing Depression scenario that mooted the posting of this topic. Light Sw. I notice the 9pm Met Service map had a trough line over south Canterbury but there was nothing on the 9pm Rakaia radar.

JohnGaul
NZTS

Thunder · Unread post by **Thunder** » Sun 28/09/2003 00:23

High cloud!! Oh well....

Yes John I notice that trough line to. I'll litsten to the radio in bed till 1:00am but if nothing happens (in terms of static / scferix) buy then I'm going to sleep.

Cheers
Aaron Wilkinson

Dean. · Unread post by **Dean.** » Sun 28/09/2003 07:37

Looks to me that this storm might move further south than forecast by Metservice,Canterbury might feel the brunt of it not Marlborough.
Heavy rain developing on the Rakaia radar.
Might be a few overnight campers on Mt Hutt today hehe.
Cheers.

NZstorm · Unread post by **NZstorm** » Sun 28/09/2003 07:52

Deano, there is potential for a heavy snowfall to low levels in Canterbury later today. Met Service say 500m but I suspect the snow level will be well below that. But it all depends on how much of the 'bitterly cold air' over southern NZ advects northward into Canterbury and how much of that warm advective rain to the north comes south. A situation worth watching closely.

NZstorm · Unread post by **NZstorm** » Sun 28/09/2003 08:01

and its a fine morning in Auckland, all that awful drizzle has gone.
Temp 16C.

looks to be a squall line on that front out to west of North island. Good chance of thunder/hail in western parts of NI today.

TonyT · Unread post by **TonyT** » Sun 28/09/2003 08:28

We have been predicting snow to 3-400m in inland South Canty since about Thursday and I still feel that is likely. Probably 5-600m further north. I also feel totals will be quite high in North Canterbury, perhaps 50-100mm rain, 50-70cm snow above 700m, and 20-50mm in Mid and South Canty, perhaps 30-40cm snow. Falls on Banks Peninsula and the Kaikoura Coast could be even heavier. Also, look for serious gales around dawn Monday, especially on the Peniunsula and Kaikoura, followed by a period of heavy damaging swells along the coast.

Dean. · Unread post by **Dean.** » Sun 28/09/2003 08:55

Looks like a great day to go for a drive,will post some photos later of snow hopefully!.
Steady rain here now,temp slowly dropping.
I have been keeping an eye on Tony's forecasts all week,they always seem a bit more accurate.
Cheers.

TonyT · Unread post by **TonyT** » Sun 28/09/2003 08:59

Head out Tekapo way Dean, but dont get stuck!

Raining steadily in Amberley since 6am, quite hard now but not yet at the point I would call it heavy. Easterly breeze 15-20 knots, 7 degrees.

This is going to be a major weather system for many parts of the country methinks, and it may be the wind speeds which are the biggest problem rather than the rain.

tich · Unread post by **tich** » Sun 28/09/2003 09:00

I think we should remember this is a southeasterly rather than a southerly flow, and probably a warm advection rain/snow event. The latest MetService severe warning warning is for heavy rain to affect areas north of the Waimakiriri River and the Kaikoura Coast. The foothills tend to be more exposed to such airstreams, plus snow should fall to lower levels. Banks Peninsula is more affected by direct southerly flows, so I doubt rainfall totals will be as nearly as high there, plus snow levels should be higher. Chch gets a bit of a rainshadow from BP, so should get quite a lot less rain.

So my guess (I might be wrong) is that snow will fall to low levels inland, with some heavy accumulations, and heavy rain will affect the Kaikoura Coast and North Canterbury. (hill country north of Amberley and foothills north of the Waimakiriri) Watch out for possible snow to low levels in Otago as well - Dunedin was only 0.5C at 6AM.

Michael · Unread post by **Michael** » Sun 28/09/2003 09:37

[quote="NZstorm"]and its a fine morning in Auckland, all that awful drizzle has gone.
Temp 16C.

Make a change for once but it will be raining again in another hour and will go on and on for the next three months

TonyT · Unread post by **TonyT** » Sun 28/09/2003 09:54

At present its an easterly flow event Ben, expected to veer through SE and then S overnight, tending SW tomorrow as it dies away. Strongest winds for Canty look likely around dawn Monday with a SSW direction, not so different to the October 2001 storm

NZstorm · Unread post by **NZstorm** » Sun 28/09/2003 10:00

am band is really crackling here now...almost continuous lightning coming through on it. The static will be from that front to our west.

Weather here quite fine with 2/8 cloud, temperature 19C dewpiont 17C.

Dean. · Unread post by **Dean.** » Sun 28/09/2003 10:12

The Rakaia radar on Sky digital at 9.45am shows very heavy rain inland from Springfield in the north down to around Fairlie in the south.
At this stage anyway the heaviest precipation is falling further south than the severe warning that was forecast.
Driving rain here now.
Cheers.

tich · Unread post by **tich** » Sun 28/09/2003 10:36

The radar seems to show heavy rain (and probably snow to quite low levels - chains now essential on Porter's Pass) in inland Canterbury, with lighter falls on Banks Peninsula, what you'd expect from an easterly/southeasterly flow. Steady, but not heavy rain in central Chch.

TonyT · Unread post by **TonyT** » Sun 28/09/2003 10:45

I'd call it heavy in Amberley now. And the wind has picked up too.