More Thunderstorms & possible Tornadoes? - May 18

NZstorm · Unread post by **NZstorm** » Tue 17/05/2016 07:17

Another low cape, high shear thunderstorm set up tomorrow for the west of the North Island.
Front due in the morning and largely south of Auckland.
A good set up for squalls and thunder. Not really a tornado set up.

I am still in Auckland tomorrow and may chase if decent lightning eventuates for north Waikato.

500mb jet stream chart.

Lunar2 · Unread post by **Lunar2** » Tue 17/05/2016 14:42

What's your thoughts on tomorrow? Much the same as yesterday?

Nev · Unread post by **Nev** » Tue 17/05/2016 19:09

Thought another thread for tomorrow's active front might be in order…

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jamie · Unread post by **jamie** » Tue 17/05/2016 19:44

I'm stuck inside at the Hamilton airport tomorrow. Bummer!!!

NZstorm · Unread post by **NZstorm** » Tue 17/05/2016 20:02

Latest models indicating Auckland also in the high risk zone now for lightning strikes and chance of damaging gusts. Could be some tree damage in Auckland tomorrow.

melja · Unread post by **melja** » Tue 17/05/2016 20:16

Great I'm flying in from Niue tomorrow then on to Chch.

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Tornado Tim · Unread post by **Tornado Tim** » Tue 17/05/2016 21:03

One very promising thing about this setup is that a good portion of the instability is within the entrance/exit region of the upper level jet. With a good NW flow ahead of the front with a warm sea SFC temps, the front should be quite active as it comes towards the country.
This type of setup is very good for creating significant divergence and much more powerfull resultant updrafts.
Squally characteristics are major feature of the storms coming in tomorrow.

I presume Metservice will be looking at this setup quite carefully as they have already issued a Severe Thunderstorm Watch since midday today for tomorrow.
They mention the risk of a Tornado, which I would tend to agree esp on the west coast of the South Island where the air can start to bank up due to the topography and veer creating enhanced helicity (which often is not modelled due to coarser resolution of domain grids for the GFS and EC etc).- Classic case was the Supercells and resultant Tornadoes that occurred around Greymouth and Hokitika.

Watch for reference:

Metservice wrote: Issued by MetService at 12:08 pm Tuesday 17 May 2016
Valid until 06:00 pm Wednesday 18 May 2016
This watch affects people in the following weather forecast districts:
Waikato
Waitomo
Taumarunui
Taranaki
Taihape
Wanganui
Manawatu
Kapiti-Horowhenua
Marlborough
Nelson
Buller
Westland

A very active front should move quickly across New Zealand during Wednesday and is expected to bring a period of thunderstorms to western areas of the country.

In western areas of central New Zealand from Waikato, to the Kapiti Coast, including western Taihape, and also about the Marlborough Sounds, western Nelson, Buller and Westland north of Greymouth, there is a moderate risk these thunderstorms could become SEVERE for a time from mid-morning to mid-afternoon. These SEVERE THUNDERSTORMS have the potential to produce squally thunderstorms with gusts greater than 110 km/hr, brief downpours with intensities of 25 to 35 mm/hr and the possibility of a tornado.

Wind gusts greater than 110 km/hr can cause some structural damage, including trees and power lines, and may make driving hazardous. If any tornados occur, they will only affect very localised areas.

Downpours can cause flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips. Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain.

Note: A Severe Thunderstorm Watch means conditions are favourable for severe thunderstorms in and close to the watch area. People in these areas should be on the lookout for threatening weather conditions and listen for possible Severe Thunderstorm Warnings.

Issued by: Gerard Barrow

This watch will be updated by: 09:00 pm Tuesday 17 May 2016

jamie · Unread post by **jamie** » Tue 17/05/2016 21:06

Yea I like the looks of tomorrow. Shame I'm inside. Oh well......

Lunar2 · Unread post by **Lunar2** » Tue 17/05/2016 21:10

Sounds like an exciting set up.

You mentioned the tornado risk for west coast south Island? Any kind of risk for lower north?

Might keep the cat inside tomorrow

Manukau heads obs · Tue 17/05/2016 21:26

already a couple of very lightning active cells, and right in line with Auckland too

watch area now extends into northland
http://www.metservice.com/warnings/seve ... torm-watch

Nev · Unread post by **Nev** » Tue 17/05/2016 21:53

Tonight's T-storm Outlook update from MS also looking good for northern areas tomorrow arvo…

MetService - Thunderstorm Outlook

Valid to: Noon Wednesday 18 May 2016
Issued at: 9:37pm Tuesday 17 May 2016

Chart reviewed at 9:35pm Tuesday and only minor changes made (mainly removing risk of downpours in SEVERE THUNDERSTORMS).

A very active front is expected to move onto the South Island just before dawn on Wednesday and reach western areas of the North Island later in the morning.

For Western areas of New Zealand from Southern Auckland to central Westland there is a high risk of thunderstorms developing during the morning, with a moderate risk that the thunderstorms could become SEVERE. A SEVERE THUNDERSTORM WATCH has been issued. For western Northland, the remainder of Auckland and areas to the west of the high risk area and for the remainder of Westland and Fiordland there is a moderate risk of thunderstorms developing, with a low risk that the thunderstorms could become SEVERE. These thunderstorms have the potential to bring squally winds with gusts 90 to 110 km/h, heavy rain with intensities of 10 to 25 mm/hr and hail. However with SEVERE THUNDERSTORMS squally gusts greater greater 110 km/h are possible and there is the possibility of damaging tornadoes.

A low risk of thunderstorms extends further east from the previous areas and also includes most of Southland.

MetService T-storm Outlook Map for May 18, am.gif
Valid to: Midnight Wednesday 18 May 2016
Issued at: 9:43pm Tuesday 17 May 2016

Chart reviewed at 9:40pm Tuesday and high risk area in the North Island altered to remover Taranaki and add Northland, Auckland, Coromandel Peninsula, Rotorua,Bay of Plenty and northern Gisborne.

The active front moves quickly across the country during the afternoon.

A high risk of thunderstorms with a moderate risk of SEVERE THUNDERSTORMS continues into the afternoon from Northland to northern Wellington and across to Bay of Plenty, with a moderate risk of thunderstorms and a low risk of SEVERE THUNDERSTORMS further east. These thunderstorms have the potential to bring squally winds with gusts 90 to 110 km/h, heavy rain with intensities of 10 to 25 mm/hr and hail. However with SEVERE THUNDERSTORMS squally gusts greater 110 km/h and damaging tornadoes are possible.

The risk of thunderstorms decreases to moderate in Buller, northwest Nelson and Taranaki for the afternoon. There is also an afternoon moderate risk of thunderstorms in Fiordland and coastal Southland.

A low risk of thunderstorms continues in the western and southern areas of the South Island during the afternoon and evening.

MetService T-storm Outlook Map for May 18, pm.gif

03Stormchaser · Unread post by **03Stormchaser** » Wed 18/05/2016 05:47

About to fly out to US via SYD, looks like it may be a bumpy flight thru the thunderstorms on the WC.

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NZstorm · Unread post by **NZstorm** » Wed 18/05/2016 06:36

Have a good flight Steve.

Manukau heads obs · Wed 18/05/2016 06:36

nice cell on its own heading towards the Auckland area

Manukau heads obs · Wed 18/05/2016 06:53

I think I just jinxed it , lol

NZstorm · Unread post by **NZstorm** » Wed 18/05/2016 06:57

Front is due around the middle of the day.

Nev · Unread post by **Nev** » Wed 18/05/2016 08:53

This morn's T-storm Outlook update for today…
Edit: Update Amended

MetService - Thunderstorm Outlook

Valid to: Midnight Wednesday 18 May 2016
Issued at: 8:35am Wednesday 18 May 2016

An active front with frequent thunderstorms is expected to move east over the upper South Island and onto the west of the North Island this morning and then east across the North Island this afternoon.

There is a high risk of thunderstorms with a moderate risk of SEVERE THUNDERSTORMS from Northland to northern Wellington and across to Bay of Plenty as indicated on the chart, with a moderate risk of thunderstorms and a low risk of SEVERE THUNDERSTORMS further east. These thunderstorms have the potential to bring squally winds with gusts 90 to 110 km/h, heavy rain with intensities of 10 to 25 mm/hr and hail. However with SEVERE THUNDERSTORMS squally gusts greater 110 km/h and damaging tornadoes are possible.

The risk of thunderstorms decreases this afternoon, first in the west and the storms should move east off the North Island this evening.

There is also an afternoon moderate risk of thunderstorms in Fiordland and Stewart Island with strong wind gusts, 90 to 110 km/h and hail.

There is a low risk of thunderstorms continues in the western and southern areas of the South Island during the afternoon and evening.

No thunderstorms expected elsewhere in New Zealand during this period.

MetService T-storm Outlook Map for May 18.gif

Manukau heads obs · Wed 18/05/2016 09:13

doesn't look very impressive on the rain radar currently
and Blitzortung shows the lightning activity has decreased, except for south Taranaki....they getting a good thunderstorm currently

Manukau heads obs · Wed 18/05/2016 09:24

I suspect these are elevated thunderstorms?

David · Unread post by **David** » Wed 18/05/2016 10:25

Manukau heads obs wrote:doesn't look very impressive on the rain radar currently

agreed, just looks like a standard rainy front moving in

spwill · Unread post by **spwill** » Wed 18/05/2016 10:30

I see a nice line of Thunderstorms there, will be random who catches a storm, I think north Waikato looks good.

Manukau heads obs · Wed 18/05/2016 10:38

temperature jumped up here with the first shower line through..so that was a warm front
with a wind change from N to NW
yes, north waikato getting it again

jamie · Unread post by **jamie** » Wed 18/05/2016 10:39

Yea elevated storms I think. Heavy rain at the airport but bland sky and half expecting to hear a rumble but that's about it.

Manukau heads obs · Wed 18/05/2016 10:51

I can see that cold frontal line to my SW now, as its clearing here a bit now
Punchy CB tops (no anvils but glaciated)

jamie · Unread post by **jamie** » Wed 18/05/2016 10:53

Thunder over head at Hamilton air port.

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