Possible Thunderstorms/Heavy Rain -North Island 1st-3rd June

NZstorm · Unread post by **NZstorm** » Mon 01/06/2015 08:46

June starts with a couple of days in which we may get thunder over the upper North Island. While the chance of thunder occurring somewhere on Tuesday is 100%, not sure what we will get in Auckland. I suggest the top of Northland and BOP have the best chances tomorrow with a non zero risk of a small tornado. Wednesday sees the colder upper air scenario. Maybe some hail Wednesday.

500mb chart for tomorrow night..

Tornado Tim · Unread post by **Tornado Tim** » Mon 01/06/2015 17:22

OK - Time for a Thread relating to the Risk of Thunderstorms/Heavy Rain with developing low pressure system that's developing:
The latest AQUA Modis Image shows what a Dynamic system we have got coming towards us.

Will be Interesting next few days thats for sure

Manukau heads obs · Mon 01/06/2015 19:22

yes, the front will get even more active as low in the western tasman gets closer and adds some energy to it

Tornado Tim · Unread post by **Tornado Tim** » Mon 01/06/2015 19:39

A good revision needs to take place in regards to the Metservice Thunderstorm Outlook contained below:

Metservice wrote:The active front continues eastwards across Coromandel Peninsula, Bay of Plenty and northern Gisborne during the afternoon and early evening, bringing a burst of heavy rain as detailed in the latest SEVERE WEATHER BULLETINS. The moderate risk of thunderstorms continues with this front as it moves through these areas,which may produce localised rainfall rates of 10 to 25mm/hr.

Later in the afternoon and early evening, a trough should move out of the Tasman Sea and over central and northern parts of New Zealand. At the same time,temperatures in the upper atmosphere rapidly cool. There is a moderate risk of thunderstorms with this trough over Waitomo, Taranaki, Nelson and northern parts of Marlborough. These thunderstorms may produce brief heavy rain, hail of 5 to 15mm diameter, strong wind gusts of 100 km/h, and the chance of a small coastal tornado. This trough brings a low risk of thunderstorms from Taupo up to Auckland and Northland, as depicted on the chart.

No thunderstorms or severe convection expected over the remainder of New Zealand.

756c-14dadb48b00-14db4247e00-14dac0a1860.0.png

Models have had the frontal system moving in on Tuesday Pm as a good risk of a Storm, and this has been occurring for the most part of last week, its only recently that it flipped, but its now back in.
The upper level jet will really kick things off tommorow, with a good surface northerly flow containing a decent amount of moisture, theta-e's being elevated which should result in a good release of latent heat.

Winds are somewhat veering in height, from NW to N, SFC winds being the most strongest from Eastern Northland down to central Waikato.

It wouldnt really surprise me if there was some Tornadoes on that frontal change.

NZstorm · Unread post by **NZstorm** » Mon 01/06/2015 20:27

I now think tomorrow's 500mb could be a bit warm for lightning until the colder air comes in later in the day. The lapse rates will be 7.2C down the west of the North Island at 12Z tomorrow night.

Tornado Tim · Unread post by **Tornado Tim** » Mon 01/06/2015 20:42

NZstorm wrote:I now think tomorrow's 500mb could be a bit warm for lightning until the colder air comes in later in the day. The lapse rates will be 7.2C down the west of the North Island at 12Z tomorrow night.

If tomorrows temps remain fairly good... 16-17 and Dps sit around 14-15 there should be enough latent heat released to compensate if upper levels are indeed a little too warm. Forecast Theta-e values are positive around mid 50*C.

Manukau heads obs · Tue 02/06/2015 07:08

well things look different re the current frontal band over the NI this morning...heavy rain in some areas, nothing in others...
looks like a new frontal line is developing out to the west though

jamie · Unread post by **jamie** » Tue 02/06/2015 07:58

Yea only a couple mm. Last night metservice forecast was for about 40mm right now.

David · Unread post by **David** » Tue 02/06/2015 08:26

Yeah the heavy rain failed to eventuate here. Just 3mm light rain overnight.

Nev · Unread post by **Nev** » Tue 02/06/2015 08:35

Looks like it kinda just missed most of Akld - got about 7mm here.

spwill · Unread post by **spwill** » Tue 02/06/2015 09:21

Only 1mm at Greylynn since midnight.

Looks like upper level temps really cool off by this evening so best chance for some thunder is later in the day.

Nev · Unread post by **Nev** » Tue 02/06/2015 10:48

This morn's T-storm Outlook update for the later today also looks a little different to yesterday's…

MetService - Thunderstorm Outlook

Valid to: Midnight Tuesday 2 Jun 2015
Issued at: 8:28am Tuesday 2 Jun 2015

A cold unstable airmass is expected to move east onto the country today. The strongest instability is likely to affect the upper South Island and much of the North Island.

There is a high risk of thunderstorms in Waikato, Waitomo, Taumarunui, Taranaki and the far west of Nelson as indicated on the chart. These storms could be accompanied by heavy rain, 10 to 25 mm/hr, 5 to 15mm hail and strong wind gusts,90 to 110 km/h.

There is a moderate risk of thunderstorms in Northland, Auckland, Coromanel, the far west of the Bay of Plenty and for the west of the central North Island high country. These storms could be accompanied by heavy rain, 10 to 20 mm/hr, 5 to 15mm hail and strong wind gusts, 90 to 110 km/h.

There is a moderate risk of thunderstorms in the north of Buller, the remainder of Nelson and for the north of Marlborough as indicated on the map. These storms could be accompanied by heavy rain, 10 to 20 mm/hr.

The unstable airmass is expected to affect the remainder of the Bay of Plenty this evening and there is then a moderate risk of thunderstorms there as indicated on the chart. These storms could be accompanied by heavy rain, 10 to 25 mm/hr, 5 to 15mm hail and strong wind gusts, 90 to 110 km/h.

A low risk encompasses a broader area as indicated on the map. This applies for the entire period.

No thunderstorms or severe convection expected over the remainder of New Zealand.

MetService T-storm Outlook Map for June 2.png

Tornado Tim · Unread post by **Tornado Tim** » Tue 02/06/2015 10:59

Good they took my advice

LOL

Nev wrote:This morn's T-storm Outlook update for the later today also looks a little different to yesterday's…

spwill · Unread post by **spwill** » Tue 02/06/2015 12:40

Looking active west of the NI currently, a thundery Cb line out there

SnwAddct · Unread post by **SnwAddct** » Tue 02/06/2015 13:36

Look rather active out to the west indeed..

http://www.weatherwatch.co.nz/lightning

Tornado Tim · Unread post by **Tornado Tim** » Tue 02/06/2015 13:57

SnwAddct wrote:Look rather active out to the west indeed..

http://www.weatherwatch.co.nz/lightning

Dont use WeatherWatch.co.nz -> use Blitzortung.org, Lightningmaps.org or Nzapstrike.net.
Support websites that actually have a right to use the data.

Manukau heads obs · Tue 02/06/2015 14:09

lots of heating here with sunshine
20C

Tornado Tim · Unread post by **Tornado Tim** » Tue 02/06/2015 14:14

Severe Thunderstorm Watch Issued:

Issued by MetService at 02:02 pm Tuesday 02 June 2015
Valid until 09:00 pm Tuesday 02 June 2015
This watch affects people in the following weather forecast districts:
Northland
Auckland
Great Barrier Island
Coromandel Peninsula
Waikato
Waitomo
Taumarunui
Taranaki

This is an alert to the potential development of severe thunderstorms with damaging winds. A line of fast moving thunderstorms is moving east towards the upper North Island. These storms could be accompanied by damaging wind gusts of around 130 km/h. The storms are expected to move away to the east this evening.

Wind gusts of this strength can cause some structural damage, including trees and power lines, and may make driving hazardous.

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: Hordur Thordarson

This watch will be updated by: 09:00 pm Tuesday 02 June 2015

Looks like they are taking this thing more seriously now, It looked good in models for sure!
That SFC temp is certainly going to help with all this sun we are getting atm....

Exciting

spwill · Unread post by **spwill** » Tue 02/06/2015 14:34

The incoming Cb line still looks active. Its been a balmy afternoon, dewpoint up to 17C/temp 20C.

David · Unread post by **David** » Tue 02/06/2015 14:35

Had a humid max of 18.9C here this afternoon, just 0.4C below my record high for June. Beautiful sunny afternoon so far.

David · Unread post by **David** » Tue 02/06/2015 15:58

I see the thunderstorm outlook has been updated to include a risk of a small tornado

spwill · Unread post by **spwill** » Tue 02/06/2015 16:21

Cg lightning observed in the west.

Manukau heads obs · Tue 02/06/2015 16:26

coming in fast
thunder here now

Happy Feet · Unread post by **Happy Feet** » Tue 02/06/2015 16:28

Just had some thunder here near Kaikohe and a sudden "cloudburst" of very heavy rain for a few minutes. Now steady rain.

NZstorm · Unread post by **NZstorm** » Tue 02/06/2015 16:41

Can see lightning out to west.

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