Thunderstorms in West 6th to 8th October

[David]

It's raining here now, unexpected.

Wow, it really must be a dry climate down there for you to be shocked at unexpected rain. Probably happens in Auckland about once a week

[NZ Thunderstorm Soc]

It is quite dry compared to an Auckland climate.
We have things down here called the Southern Alps which stop a lot of the westerly rains from coming through.
That is why is can be quite thunderstormic in western regions of New Zealand.

JohnGaul
NZTS

[Inny Binny]

Yes, this rain was a bit unexpected.

[Storm Struck]

Yes raining here too quite steady didnt expect it either, looks like the trough is backing up against the warm front over Kaikoura directing the rain back down from the north.
Much needed rain anyway .
Cheers
Jason.

[mikestormchaser]

raining here aswel, and i notice on the storm tracker there is a thunderstorm north of Christchurch aswel. hmmm
Look at the latest rain radar at 11 pm, and there is some red there, that is unusual

[Willoughby]

Man! is that a great line of thunderstorms out there or what? still sparking.

Paraparaumu 10z sounding shows a wet ascent to 700mb... for once this morning the reporting dewpoint is higher in Wellington (15C) than Auckland (14C).

It's 14/14 here now with low cloud and a bit of haze like yesterday.

[Razor]

Still raining here in ChCh, most unexpected! Steady rain all night, continuing...gold for the farmers I would say!

[spwill]

Warming up here, 19C, dewpoints are 14 C.

Active Thundery weather moving onto Taranaki now I see

[Shepherds Valley WX]

Significant rain even here in Upper Hutt captured by my WX Station here:
http://home.clear.net.nz/pages/andrew.c ... e/SVWX.htm

Also, intersperesed with rumblings of thunder. Its actually been quite an interesting week in Upper Hutt, with quite a lot of TS activity, strong wind and rain.... I think I asked in another thread why we don't get many TS in the Wellington/Hutt region, I'd be interested to know why, if any of you know!

Still raining heavily here and very windy.

[Wildland]

No further thunderstorm activity noted here at Tawa since about 8 last night.
Northern windows sparkling clean after this morning's squalls which briefly raised hopes of thunder.
21 mm of rain since 4 a.m.
Windspeed indicator passed through the Grey Havens at 10 last night (worked to death by recent gales?)
Will retrieve ladder and check connections when I can get to the garage without drowning. Where did I leave my water-wings????

[Shepherds Valley WX]

Hi Wildland...interesting local variation there between your location and Upper Hutt...I recorded 24.8mm on my WX Station, which was backed up by a 25.0mm in the manual rain guage since 9am this morning....I can't confirm, but I think the max rain rate may be a new record for the station at 1.77 mm per hr...

Edit: Not a record rain rate, but a new record for rain in 1hr at 15mm.

Now raining again after a short respite, 13.7C, dark and overcast.

[GreggWard]

Just had a very intense CG bolt hit somewhere in the southern part of Palmerston North. Apart from that it has just been rather overcast and we have just had a short period of heavy rain. It looks like it's already clearing a bit to the SW, already.

[Paul Mallinson]

Significant rain even here in Upper Hutt captured by my WX Station here:
http://home.clear.net.nz/pages/andrew.c ... e/SVWX.htm

... I think I asked in another thread why we don't get many TS in the Wellington/Hutt region, I'd be interested to know why, if any of you know!

Still raining heavily here and very windy.

Hi,
To get thunderstorms over the Wellington City area you need wind convergence happening right over the city along with it being unstable ofcourse.

There are two setups that come to mind...

1. Like today and maybe yesterday - an area of wind convergence sets up in a very strong northwest flow with a slightly more westerly flow to the southwest of the convergence line. This provides the trigger. Often it is the top of the Marlborough Sounds that creates the first part of the convergence (a bit like the way you see a long ropy length of shower cloud that comes off Banks Peninsula in a southerly flow and streams all the way along the Kaikoura coast to slam sometimes quite heavy showers either into Wellington or Wairarapa.) Sometimes (often) the convergence sets up so that the line of showers (or thunderstorms) travels over the Upper Hutt area or generally further north over the Kaitoke area. But if the flow has sufficient northerly in it, then the action can come down into the Wellington City area.

2. When a strong southerly flow blasts through Cook Strait and meets a moist northwesterly (given an unstable environment).

So to get TS over Wellington City, the convergence has to occur over the city, and for a relatively small target, it doesn't happen all that frequently.

In summer time, the heating inland creates quite a good southerly flow (15kts or so) up the Hutt Valley and showers or thunderstorms often trigger up over the Kaitoke area. The southerly gets squeezed by the narrowing of the Hutt Valley but it also gets lifted the further inland it penetrates. Even in regular showery southerly flow, the Hutt Valley is the last to clear for these reasons (the city may be dry for half a day or more in this dying southerly situation).

Hope this helps.

Paul

[RWood]

Paul's comment about the southerly flow "squeeze" up the Hutt Valley, together with proximity of hills and reduced westerly protection help explain why average cloudiness increases significantly as you leave Wellington City and head up the Hutt.

[NZstorm]

The models were picking the front to start to fizzle today and thats what has happened. It has fizzled a bit more than I thought though.

The trough in the Tasman looks like being the next big thing with models now firm on the idea of low deepening and crossing the country on thursday or there abouts.

[David]

still waiting for this period of rain which is expected to come through and hopefully dampen the ground again

[spwill]

A warm night ahead, still 17C here and on the humid side, dp15C.

[Shepherds Valley WX]

Thanks Paul for the excellent and detailed response to my question. Much appreciated!

Much more settled here today, with a mild 8.8C and a gentle breeze. Makes a change from the gale sof recent days.

[spwill]

why we don't get many TS in the Wellington/Hutt region

Wellington is quite well sheltered from deep shower cloud off the Tasman Sea also developing land convection showers in the warmer months will be generally moving away ( upper westerlies) unlike say Dunedin which can catch heavy showers that develop inland.