Nth Island convective period 27 Feb - 2nd March

spwill · Unread post by **spwill** » Fri 24/02/2017 12:35

The current GFS points to isolated thunderstorms Waikato-Taranaki on Monday and Tuesday afternoon/evening.

NZstorm · Unread post by **NZstorm** » Sun 26/02/2017 08:05

Looking like scattered pm heat showers for the central and upper North Island this week.
A big high dominates but converging airstreams and dewpoints 18C favour shower development. Deep layer lapse rates of around 6C should allow isolated thunderstorms/locally heavy falls in central areas Taupo/Waitomo/southern Waikato.

NZstorm · Unread post by **NZstorm** » Mon 27/02/2017 07:20

Air stream convergence over the central North Island today.

Western Waikato could catch a thundery cb later today but the potential looks mainly around Taupo region.

spwill · Unread post by **spwill** » Mon 27/02/2017 11:20

Expecting a dry finish to the month here, we were lucky to have the moist trough mid month.
Current weather here is sunny,24C, dewpoint 17.5C, a light easterly
Will keep a watch for anything interesting south of Auckland next couple of days.

jamie · Unread post by **jamie** » Mon 27/02/2017 12:40

Making anew topic for this. Each day looks different but the over all trend is converging winds in the afternoon. Looks like potential is there for some decent storms.

Can Mods move posts from general feb weather to here in relation to this topic.

I will be chasing this afternoon and tomorrow afternoon if things fire within about an hours drive from home.

Nev · Unread post by **Nev** » Mon 27/02/2017 13:52

jamie wrote:Can Mods move posts from general feb weather to here in relation to this topic.

Ok, have moved a few posts from the General Feb thread to here.

Also here's MS's T-Storm outlooks for this arvo and tomorrow arvo…

MetService - Thunderstorm Outlook

Valid to: Midnight Monday 27 Feb 2017
Issued at: 8:32am Monday 27 Feb 2017

The combination of a warm humid afternoon, light winds, and coolish temperatures aloft are again expected to allow daytime cloud buildups to produce scattered showers or thunderstorms about the northern and central North Island this afternoon and evening.

The main risk of thunderstorms is about the ranges of Gisborne and northern Hawkes Bay, and also Taupo, Taumarunui, Taihape (including Tongariro National Park), and inland areas of Waitomo and Waikato during the afternoon and evening.A lower surrounding risk extends from southern Auckland and Bay of Plenty to the Whanganui hill country and northern Manawatu, and also about western parts of Northland, as indicated on the chart.

Any thunderstorms that occur will be accompanied by localised heavy rain.Rainfall rates should generally be in the 10-25mm/hr range, however as the storms will be slow-moving it is possible rainfall rates could be 25-30mm/hr in one or two places.

No other thunderstorms or significant convection expected over New Zealand during this period.

MetService T-storm Outlook Map for Feb 27.png

MetService - Thunderstorm Outlook

Valid to: Midnight Tuesday 28 Feb 2017
Issued at: 11:22am Monday 27 Feb 2017

Afternoon heating and light winds are again expected to lead to the development of scattered showers or thunderstorms about the central North Island during Tuesday afternoon.

From Waikato to Taranaki and across the central North Island from Bay of Plenty to Taihape and to the ranges of Gisborne and Hawkes Bay, there is a moderate risk of thunderstorms during the afternoon and evening, producing localised heavy rain with intensities of 10 to 25mm/hr. Additionally in Waikato, Waitomo,Taumarunui (including Tongariro National Park), Taupo and inland Bay of Plenty,there is also a moderate risk that any slow moving thunderstorms in these areas could become SEVERE and bring downpours with intensisites of 25 to 40mm/hr to one or two places.

A lower risk of thunderstorms extends north into southern Auckland and south to Manawatu.

No thunderstorms or significant convection expected over the remainder of New Zealand during this period.

MetService T-storm Outlook Map for Feb 28, pm.png

dogmelon · Unread post by **dogmelon** » Mon 27/02/2017 15:39

Neat. I'd like to experience these no wind, afternoon shower type days again one day. I miss it.

Manukau heads obs · Mon 27/02/2017 16:18

Heavy hear shower on Waiuku

spwill · Unread post by **spwill** » Mon 27/02/2017 17:58

Some TCu/isolated Cb visible SE -SW of here, has remained fine here.

spwill · Unread post by **spwill** » Mon 27/02/2017 20:05

Looks like isolated TS activity around Taupo this evening

Manukau heads obs · Mon 27/02/2017 22:46

photo of the CB heat showers that passed through the Waiuku Area

NZstorm · Unread post by **NZstorm** » Tue 28/02/2017 06:54

A few weak thunderstorms over the central NI yesterday.

The mid level lapse rates are weaker today (5.8C) so that suggests less chance of lightning than yesterday.

Nev · Unread post by **Nev** » Tue 28/02/2017 08:52

Here's this morn's MS T-storm update for today…

MetService - Thunderstorm Outlook

Valid to: Midnight Tuesday 28 Feb 2017
Issued at: 8:36am Tuesday 28 Feb 2017

The combination of a warm humid afternoon and light winds are again expected to lead to the development of scattered heavy showers and thunderstorms about the central North Island this afternoon and evening.

There is a moderate risk of thunderstorms this afternoon and evening extending from southern Auckland (south of the Manukau Harbour) through Waikato and Bay of Plenty/Rotorua to inland North Taranaki and northern Taihape including Tongariro National Park. A broader low risk covers the area from about the Waitakere ranges (Auckland) to northern Manawatu as indicated on the chart.

These thunderstorms will be slow-moving and accompanied by heavy rain with intensities of 15 to 25mm/hr and possibly small hail. However some of the thunderstorms within this area may be severe, producing localised downpours of 25-40mm/hr. Rainfall of this intensity can cause surface or flash flooding, and make driving conditions extremely hazardous. A SEVERE THUNDERSTORMS WATCH has been issued.

No other thunderstorms or significant convection expected over New Zealand during the period.

MetService T-storm Outlook Map for Feb 28.png

Nev · Unread post by **Nev** » Tue 28/02/2017 09:36

I see MS have also issued a Severe T-Storm Watch this morning for this arvo…

MetService Severe T-storm Watch Map for Feb 28.png

Manukau heads obs · Tue 28/02/2017 17:00

More heat showers in the Waiuku area

spwill · Unread post by **spwill** » Tue 28/02/2017 17:20

Thunderstrorms showing up around Taupo /Rotorua

jamie · Unread post by **jamie** » Tue 28/02/2017 17:54

Severe thunderstorm warning on one heading towards putaruru. I have family here that I forgot about so can't be chasing sadly. Will be watching the night time lightning if these hold into the night.

jamie · Unread post by **jamie** » Tue 28/02/2017 17:57

View from my back door

jamie · Unread post by **jamie** » Tue 28/02/2017 18:01

In these setups in the past I have seen central Waikato (Hamilton area) develop very quickly around 7 - 9pm. I think it's often triggered from the outflow of the south Waikato storms earlier in the arvo/evening

NZstorm · Unread post by **NZstorm** » Tue 28/02/2017 20:08

The IR satellite on weatherzone showing the best convection to occur over the North Island since spring.

The forecast sounding on GFS for central North Island shows the temperature at the tops of the cloud -55C, 10km. Tall skinny CAPE.

Nev · Unread post by **Nev** » Wed 01/03/2017 08:59

Just for posterity, here's the Blitzortung CG's picked up over the N.I. between 4.40pm and 8.40pm yesterday…

Blitzortung NZ GG's - Feb 28, 1pm-9pm.png

Nev · Unread post by **Nev** » Wed 01/03/2017 09:00

I see this morn's MS T-storm outlook includes Akld in their medium risk this arvo/evening…

MetService - Thunderstorm Outlook

Valid to: Midnight Wednesday 1 Mar 2017
Issued at: 8:08am Wednesday 1 Mar 2017

The combination of a warm humid afternoon and light winds are expected to lead to the development of scattered showers and thunderstorms about the central North Island during this afternoon and evening.

There is a moderate risk of isolated thunderstorms during the afternoon and evening from Auckland and Coromandel Peninsula down to inland North Taranaki and Tongariro National Park. A broader low risk extends from western Northland to northern Manawatu as indicated on the chart.

These thunderstorms will be accompanied by localised heavy rain and possibly small hail. Rainfall rates should generally be in the 10-25mm/hr range, but may be a little higher in one or two places.

No other thunderstorms or significant convection expected elsewhere.

MetService T-storm Outlook Map for Mar 1.png

Manukau heads obs · Wed 01/03/2017 09:11

we actually got a sprinkle of rain here this morning, from the remains of those south waikato showers that drifted north overnight

Tornado Tim · Unread post by **Tornado Tim** » Wed 01/03/2017 09:51

Today's forecast convergence zone around the redline from Hamilton down to along Karipiro southwards to eastern Tokoroa.

Nev · Unread post by **Nev** » Wed 01/03/2017 10:09

Nev wrote:I see this morn's MS T-storm outlook includes Akld in their medium risk this arvo/evening…

Hmm… I see MS's 9:05am update now says moderate risk 'from South Auckland…' ...

MetService T-storm Outlook Map for Mar 1 (updated).png

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