Air Mass Storms Possible Waikato - 3rd Jan

Tornado Tim · Unread post by **Tornado Tim** » Fri 02/01/2015 01:09

Looks like a weak surface low is expected to develop over the Northern Central North Island on Saturday.
Indications in the models suggest some deepening caused by expected warm surface conditions.

Moisture being dragged in by a SW to W flow overnight to a weak westerly during the day and combining with an easterly sea-breeze late afternoon means a good chance of convergence and convection.
Due to the favourable theta-e temps of around 48-50*C (DP's of 16-17*C) and upper level temps being sufficiently cold, there should be a fair to good chance of some Sea-breeze convergence induced Airmass Thunderstorms.

SFC Convergence needs to be strong for a sea-breeze induced storm on Sat, as upper levels are quite dry and there is a possibility of mixing out.

I will keep an eye on the models as this could be one that's worthwhile going for a drive for.

jamie · Unread post by **jamie** » Fri 02/01/2015 06:31

I saw this last night. Thought I'd wait for thismornings update. Will see what that says but I'm pretty keen for a chase.

tgsnoopy · Unread post by **tgsnoopy** » Fri 02/01/2015 07:33

Fingers crossed, about time I had another chase.

jamie · Unread post by **jamie** » Fri 02/01/2015 07:54

I'll be free from about 2pm. I'm happy to drive (company car) so if anyone wants to team up let me know.

NZstorm · Unread post by **NZstorm** » Fri 02/01/2015 07:58

A possible big problem with tomorrows set up is the speed of the shortwave, its over the North Island at 1pm but moved off by 7pm. If it could slow down a bit then that would certainly be favourable to the chances of convection. This is not a set up like Monday 29th where there was a lazy upper trough and a pile of low level moisture. Will watch with interest anyway.

Nev · Unread post by **Nev** » Fri 02/01/2015 10:14

Here's MS's outlook for tomorrow arvo...

MetService - Thunderstorm Outlook

Valid to: Midnight Saturday 3 Jan 2015
Issued at: 10:08am Friday 2 Jan 2015

Abundant moisture, low level convergence and cooling at upper levels is expected to provide a good environment for showers over the northeast of the North Island Saturday afternoon and evening. There is a high risk of thunderstorms in the east of Rotorua and Bay of Plenty, inland Gisborne and parts of Taupo and Hawkes Bay as indicated on the map. These storms are expected to be slow moving and could bring localised heavy rain. There is a low risk of SEVERE storms with 25 to 35mm per hour which could make driving conditions hazardous and lead to flash flooding.

There is a moderate risk of thunderstorms over a broader area over the central North Island as indicated on the map. These storms could be accompanied by heavy rain, 10 to 25mm per hour.

Showers are also expected inland over the upper South Island. There is a low risk that a few of these could be thundery with heavy rain.

No other thunderstorms or significant convection expected over New Zealand Saturday afternoon and evening.

MetService T-storm Outlook Map - Dec 3, pm.png

Nev · Unread post by **Nev** » Fri 02/01/2015 21:00

I see MS have maintained tomorrow arvo's moderate to high risk for eastern BoP, Taupo, Gisborne ranges and northern Hawkes Bay, but now only have a low, albeit extended, risk for the rest of the central North Island.

MetService - Thunderstorm Outlook

Valid to: Midnight Saturday 3 Jan 2015
Issued at: 8:37pm Friday 2 Jan 2015

Reviewed and updated at 8:30pm Friday - changes to thunderstorm risk about the central and western North Island.

A combination of good atmospheric moisture, low level wind convergences and cooling at upper levels are expected to provide a good environment for daytime cloud buildups to produce scattered afternoon and evening showers about the central and eastern North Island, and also about the northern South Island.

There is a moderate to high risk of isolated thunderstorms about eastern parts of Bay of Plenty and Taupo, and about the ranges of Gisborne and northern Hawkes Bay as indicated on the chart.

These thunderstorms are expected to be slow moving and therefore have the potential to produce localised heavy rain.

Rainfall rates should be generally in the 10-25mm/hr range, however there is a low risk one or two of the storms could be severe producing localised downpours of 25-35mm/hr. Rainfall rates of this intensisty can cause surface flooding and make driving conditions hazardous.

Elsewhere about the central North Island from Waikato to inland Taranaki and Taihape, and also about inland parts of Nelson and Marlborough, there is a low risk of a few showers developing into thunderstorms for a time in the afternoon and evening.

No other thunderstorms or significant convection expected over New Zealand on Saturday afternoon and evening.

MetService T-storm Outlook Map - Dec 3, pm update.png

jamie · Unread post by **jamie** » Fri 02/01/2015 21:32

Yea that's a bummer!

bpo · Unread post by **bpo** » Sat 03/01/2015 10:04

Looking good for today.

http://www.metservice.com/IcePics/fc/75 ... 5d89.0.png

Tornado Tim · Unread post by **Tornado Tim** » Sat 03/01/2015 11:45

I might go to Karipiro this arvo, that place always seems to do well storm wise.
Jamie if your keen, meet up?

spwill · Unread post by **spwill** » Sat 03/01/2015 11:48

Shame the best of upper cold air moves through a little early. I could travel south later but it all looks a bit too far south for me to chase, will keep a watch from the beach.

jamie · Unread post by **jamie** » Sat 03/01/2015 13:20

Yep what do you think of the chances Tim?

Tornado Tim · Unread post by **Tornado Tim** » Sat 03/01/2015 14:30

jamie wrote:Yep what do you think of the chances Tim?

If we chase 30-40ks south and push perhaps a bit east, I think Moderate. The 18Z GFS has the upper level air stabilizing a bit quicker, but I dont trust GFS runs other than the 00Z much, due to the model having less data to ingest and initialize itself.

A clearing should come in soon and bump the temps up a bit. Southerly to SSE SFC flow atm with a Dp at 16*C atm.
Hoping the NE is strong enough to overcome the west. Tauranga I see hasnt even got a sea-breeze yet....

Tornado Tim · Unread post by **Tornado Tim** » Sat 03/01/2015 16:15

Me and Jamie, In Karipiro atm, heading south, convection flaring to the west of Taupo.

Tornado Tim · Unread post by **Tornado Tim** » Sat 03/01/2015 17:32

Convergence line developing in East Tokoroa atm.

jamie · Unread post by **jamie** » Sat 03/01/2015 17:36

To the south east (down by taupo city)

ImageUploadedByTapatalk1420259599.519390.jpg

And to our east which is what we are keeping a close eye on

ImageUploadedByTapatalk1420259567.919815.jpg

spwill · Unread post by **spwill** » Sat 03/01/2015 18:43

Isolated thunderstorms down there now, developed quickly.

NZstorm · Unread post by **NZstorm** » Sat 03/01/2015 21:16

18mm early evening at Wharekiri in Waitomo on the EW site.

jamie · Unread post by **jamie** » Sat 03/01/2015 21:40

Tough chase today. Saw some nice storms but difficult to get close to them due to the roads and forestry. Clocked up 350kms and a feed of macas. Felt just like America lol.

tgsnoopy · Unread post by **tgsnoopy** » Sat 03/01/2015 22:06

Was in Hamilton till about 3.30pm (I was working on something), then headed South, left Rotovegas about 5pm and returned home. Didn't think I'd be able to get to anything worth chasing.

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