Thunder possible Waitomo/Waikato Saturday/Sunday pm

NZstorm · Unread post by **NZstorm** » Fri 07/02/2014 07:32

A moist subtropical airmass over the North Island tomorrow may be sufficiently heated to release some CAPE/thunder over western North Island.

An upper level trough will be in transit across the North Island. Sea breeze convergence also needed.

Warm 500mb temps about -10C/-11C so the heating is important.

GFS moisture for 00Z tomorrow.

Nev · Unread post by **Nev** » Fri 07/02/2014 13:05

Here's this morn's Severe T-Storm Outlook for tomorrow (not overly encouraging)…

MetService - Thunderstorm Outlook

Valid to: Noon Saturday 8 Feb 2014
Issued at: 10:48am Friday 7 Feb 2014

An area of low pressure and associated fronts are forecast to spread over the central North Island during the morning, bringing rain or showers to many parts of the North Island and northern South Island. There is a low risk of a few elevated thunderstorms from Waikato and Bay of Plenty down to Manawatu and northern Wairarapa and also about Golden Bay during this time.

No thunderstorms or significant convection expected elsewhere.

MetService T-Storm Outlook Map to Noon, Feb 8.png
Valid to: Midnight Saturday 8 Feb 2014
Issued at: 10:49am Friday 7 Feb 2014

The area of low pressure over the central North Island mentioned above is forecast to move away to the east during the evening. There is a low risk of isolated thunderstorms from Waikato and Bay of Plenty down to Manawatu and northern Wairarapa during the afternoon and early evening. However, this risk of thunderstorms is considered nearer moderate from Taupo and inland Waitomo down to the eastern hills of Taranaki and the Wanganui hill country, as indicated on the chart. Any thunderstorms that eventuate are likely to produce localised heavy rain of 15 to 25mm per hour.

There is also a moderate risk of isolated thunderstorms over the western ranges of Nelson down to the Nelson Lakes area during the afternoon and early evening. Any thunderstorms that eventuate here are also likely to produce localised heavy rain of 15 to 25mm per hour.

No thunderstorms or significant convection expected elsewhere.

MetService T-Storm Outlook Map to Midnight, Feb 8.png

spwill · Unread post by **spwill** » Fri 07/02/2014 13:35

keep an eye on Sunday for Auckland, need the moisture to hang in there, heating and west coast seabreeze convergence.

Tornado Tim · Unread post by **Tornado Tim** » Fri 07/02/2014 22:54

Hmm tomorrow is very borderline setup for the Waikato, GFS is indicating the instability is right on the Saturated Adiabatic Lapse Rate. i.e.: it won't take much for the scales to tip the wrong way and have a complete flop. I agree with Metservices outlook for the Waikato Region, however I don't think the risk extends south west.
Further south inland to southeast looks better with higher daytime temps being reached (that be it depending on cloud cover).

NZstorm · Unread post by **NZstorm** » Sat 08/02/2014 08:26

My thinking for today was to chase south of Tirau but likely not worth it now. Instability looks to be tracking off to the east.
But will keep an eye on it.

GFS has a convective risk for Sunday over Waikato but with the flow SE, moisture could mix out a bit. But this thread can cover Sunday as well.

GreggWard · Unread post by **GreggWard** » Sat 08/02/2014 09:12

The Weatherzone website (http://www.weatherzone.com.au/satellite ... d/infrared) showed some good thunderstorms in Northern Taranaki/Southern Waitomo and Central Plateau, betwen 3am and 5am. Based on the Metservice's Severe Thunderstorm Outlook, these would have been elevated.

Nev · Unread post by **Nev** » Sat 08/02/2014 09:45

The goal-posts have shifted a little further east in this morn's MS update for today...

MetService - Thunderstorm Outlook

Valid to: Midnight Saturday 8 Feb 2014
Issued at: 8:34am Saturday 8 Feb 2014

An area of low pressure and associated fronts are forecast to cross the central North Island today, bringing rain or showers to many areas. There is a low risk of isolated thunderstorms from southern Waikato and Bay of Plenty down to Manawatu and Wairarapa during the afternoon and early evening. However, this risk of thunderstorms is considered nearer moderate about the ranges of Bay of Plenty, Gisborne, Hawkes Bay, Taupo and eastern Taihape, as indicated on the chart. Any thunderstorms that eventuate here are likely to produce localised heavy rain of 15 to 25mm per hour.

There is also a moderate risk of isolated thunderstorms over the western ranges of Nelson down to the Nelson Lakes area during the afternoon and early evening.Any thunderstorms that eventuate here are also likely to produce localised heavy rain of 15 to 25mm per hour.

No thunderstorms or significant convection expected elsewhere.

MetService T-Storm Outlook Map to Midnight, Feb 8.png

Nev · Unread post by **Nev** » Sat 08/02/2014 09:53

And the outlook for tomorrow arvo…

MetService - Thunderstorm Outlook

Valid to: Midnight Sunday 9 Feb 2014
Issued at: 9:46am Saturday 8 Feb 2014

Afternoon heating and wind convergences are expected to produce isolated showers about southern Auckland, Waikato, Coromandel Peninsula and the Kaimai Ranges,with a low risk of one or two thunderstorms late afternoon or early evening.

Similarly, afternoon heating and wind convergences are also expected to produce a few showers about western Nelson and Buller, with a low risk of isolated thunderstorms about the ranges, as indicated on the chart.

Rain or showers are forecast about eastern parts of the North Island from Gisborne to Wairarapa and Wellington in a strong, cool southerly flow, but thunderstorms are not expected here.

No thunderstorms or significant convection expected elsewhere.

MetService T-Storm Outlook Map to Midnight, Feb 9.png

Tornado Tim · Unread post by **Tornado Tim** » Sat 08/02/2014 10:13

Nev wrote:And the outlook for tomorrow arvo…

Ignore it for the moment, the GFS has been sticking with a north Waikato, South Auckland Setup. The 00z will be the verifying round.
I like the forecast sounding, have a look at the wind vectors, some veering with height (however the flow isnt strong).
The Trop is quite high, so any strong associated convection should get quite tall enhancing charge differentiation.

NZstorm · Unread post by **NZstorm** » Sat 08/02/2014 16:49

A scattering of cb's/isolated thunder has developed over the central North Island.

NZstorm · Unread post by **NZstorm** » Sat 08/02/2014 18:19

For Sundays set up,

00Z GFS suggests a storm very possible while 00Z UKmet has too much of a warm nose at 600mb making convection unlikely.

NZstorm · Unread post by **NZstorm** » Sun 09/02/2014 07:51

Checking out the models this morning it still like that warm nob of air in the middle atmosphere will choke off any storm that tries to develop. However, if temps can get as high as 29C over north Waikato then a cb could develop.

jamie · Unread post by **jamie** » Sun 09/02/2014 08:03

29 does look on the cards in pockets around the area today

Manukau heads obs · Sun 09/02/2014 12:21

can see some CU in the north waikato..
I see the waikato has high temps now, with the southerly wind there....
only 21C here with a SSW wind...

jamie · Unread post by **jamie** » Sun 09/02/2014 12:33

yup i can see the start of the convergence line from here. Looks good for this time of the day. Its close to me. Im on the SE side of it (southerly here).

Manukau heads obs · Sun 09/02/2014 12:39

hummm...a chase could be on the cards?

spwill · Unread post by **spwill** » Sun 09/02/2014 13:06

Can see a cumulus convergence line east of Auckland,small Cu at this stage. I will go for a drive when I see towers.
Hunua on 26C, 24C here, dewpoint 18-19C, fine conditions

Tornado Tim · Unread post by **Tornado Tim** » Sun 09/02/2014 13:10

GFS forecasting 1200j/kg of CAPE, in North Waikato. As NZstorm said there is an area around 500mb that's warmer than the lapse rate, hopefully the SFC temps can get high enough to offset this.

NZstorm · Unread post by **NZstorm** » Sun 09/02/2014 13:14

Yes, the moisture looking good with dps 18-20C.

I can see cumulus line there although no turkey towers yet.

Tornado Tim · Unread post by **Tornado Tim** » Sun 09/02/2014 13:42

28 degrees now in Matangi and at Hamilton Airport, looks like a more likely setup is brewing. Some nice Cumulus pushes see going up.

jamie · Unread post by **jamie** » Sun 09/02/2014 15:01

been up to 28.4 here in the last few mins with the DP at 19.3. Clouds are really starting to build now. I wont chase unless something really goes. Happy watching from here for now. Its in my back yard.

jamie · Unread post by **jamie** » Sun 09/02/2014 15:31

Nice base near me

ImageUploadedByTapatalk1391913076.520600.jpg

Manukau heads obs · Sun 09/02/2014 15:43

always nice when its in your backyard

Have seen one tower...but did not last...
22C here...thats out max only due to the coastal cooler SSW wind

Tornado Tim · Unread post by **Tornado Tim** » Sun 09/02/2014 15:56

Got to 29°C here, Some towers going up..... GFS has most moisture/CAPE getting developed after 6 PM.....

Cross finger, convection at CAP level, hopefully it will break soon..... 29°C-27°C won't be held long....

Manukau heads obs · Sun 09/02/2014 16:12

looks like something trying to get going hamilton/huntly way?
also north waikato looking better now too

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