Nth Tasman Low - Dec 16-18

NZstorm · Unread post by **NZstorm** » Tue 16/12/2014 07:16

Looking forward to warmer weather coming in tomorrow, I think 25C should be on the cards for the afternoon for Auckland. Dewpints rising to 18C.

The warm front tomorrow should produce some elevated thunderstorms over Northland in the morning, these may reach Auckland. Also the risk of west coast convergence thunder in the afternoon from Northland to Waikato. Something to keep an eye on tomorrow!

littleheaven · Unread post by **littleheaven** » Tue 16/12/2014 09:51

I hope you're right, Steven. Jolly chilly walking the boy to school this morning. Sitting on about 15.5C at 9am, but the wind felt a few degrees cooler than that. Really hoping this pattern breaks soon. I'm starting to have flashbacks to the horrid overcast summer we had a few years back!

spwill · Unread post by **spwill** » Tue 16/12/2014 12:04

Auckland has been on the cool cloudy side of a sub tropical system for a few days now due to a blocking high out east but a change moves through tomorrow with a warmer humid airmass , the afternoon dewpoint in Auckland will be around 20C.
The humid weather hangs around until atleast the weekend and will bring some thunder risk with any frontal activity and perhaps a few afternoon heat showers.

David · Unread post by **David** » Tue 16/12/2014 12:09

Windy day today. Here is a video I took at Eastern Beach about 11.20am. Best viewed in HD

https://plus.google.com/u/0/10685371658 ... 5182427394

Vertigo · Unread post by **Vertigo** » Tue 16/12/2014 14:23

The low system coming in from the north west has a very tropical look to it on the sat loop, but waters not warm enough for it to go full cyclone.

Looks like its being energized by the jetstream it just encountered in the past 6 hours, and has taken a nose dive south.

Nev · Unread post by **Nev** » Tue 16/12/2014 19:08

Quite an interesting low this one, so thought it was probably worthy of another thread.

Looks like it's going to affect much of the country over the next day or two, with heavy rain and gale Warnings and Watches out for northern areas (and Nelson) tonight and tomorrow, and the risk of the odd T-storm.

David · Unread post by **David** » Tue 16/12/2014 21:04

Very gusty out there this evening, my station recorded a gust of 67 km/h about 10 minutes ago.

Nev · Unread post by **Nev** » Tue 16/12/2014 21:17

Here's tonight's T-storm Outlook for tomorrow…

MetService - Thunderstorm Outlook

Valid to: Noon Wednesday 17 Dec 2014

Issued at: 8:55pm Tuesday 16 Dec 2014
Updated at 8:55pm Tuesday

A warm front is expected to move slowly southwards over Northland during the morning to lie near Auckland at midday. Associated rain and strong easterly winds south of the front will spread over much of northern and central New Zealand - see latest Severe Weather Watch and Warning for more detail regarding areas of heavy rain and gales.

There is a moderate risk of elevated thunderstorms both with and ahead of the front over Northland, Auckland (including the Hauraki Gulf and Great Barrier Island), Coromandel Peninsula and western Bay of Plenty during the morning. A lower risk of thunderstorms extends from Waikato down to Taranaki later in the morning, as indicated on the chart.

These thunderstorms will be embedded within broader areas of rain and will boost localised rates to 10-25mm/hr and possibly more about the ranges. This may cause areas of surface flooding and make driving conditions hazardous.

No other thunderstorms of significant conveciton expected over New Zealand on Wednesday morning.

MetService T-storm Outlook Map - Dec 17, am.png
Valid to: Midnight Wednesday 17 Dec 2014

Issued at: 9:01pm Tuesday 16 Dec 2014
Updated at 9:00pm Tuesday

The frontal rainband will move southwards over the North Island during Wednesday afternoon and evening, with a very warm and humid northerly flow following it.

There is a moderate risk of elevated thunderstorms embedded within broader areas of rain about Coromandel Peninsula in the early afternoon, and about Bay of Plenty and the far north of Gisborne during the afternoon and early evening. These thunderstorms will boost localised rainfall to 10-25mm/hr and possibly more about the ranges (see latest Severe Weather Warning for more detail regarding heavy rain in these areas).

Behind the front, afternoon cloud buildups are likely to produce isolated heavy showers and a few thunderstorms about western areas from Northland through Auckland to Waitomo in the afternoon and early evening. These thunderstorms will also produce localised heavy rain in the 10-25mm/hr range. There is also a low risk of one or two SEVERE THUNDERSTORMS in these areas producing downpours of 25-40mm/hr. Rainfall of this intensity can cause surface and/or flash flooding and make driving conditions hazardous.

Finally, there is a broad low risk of thunderstorms over remaining parts of the northern and central North Island, Nelson, Buller, Westland and northern Fiordland as indicated on the chart. If any thunderstorms do devleop in these areas, they will also produce localised heavy rain.

MetService T-storm Outlook Map - Dec 17, pm.png

NZstorm · Unread post by **NZstorm** » Wed 17/12/2014 07:18

Been some elevated thunder over Northland this morning.

Slight risk of a tornado in the west today if optimal conditions develop. (heating/convergence)

David · Unread post by **David** » Wed 17/12/2014 07:23

Doesn't look like much rain heading this way, initially the models were showing 40+ mm for today!

spwill · Unread post by **spwill** » Wed 17/12/2014 07:45

NW Auckland might catch some thunder shortly

Nev · Unread post by **Nev** » Wed 17/12/2014 08:42

MS have extended today's BoP risk further inland for later today...

MetService - Thunderstorm Outlook

Valid to: Midnight Wednesday 17 Dec 2014
Issued at: 8:31am Wednesday 17 Dec 2014

A warm frontal band with rain and embedded thunderstorms is spreading southwards over the Auckland area this morning and will continue spreading southwards over the remainder of the North Island today. Heavy falls are expected in eastern areas and about parts of Nelson - see latest Severe Weather Watch and Warning for more detail.

There is a moderate risk of a few elevated thunderstorms embedded within broader areas of rain over southern Northland and Auckland this morning, about Coromandel Peninsula late morning and early afternoon, and about Bay of Plenty and the far north of Gisborne this afternoon and evening. These thunderstorms will boost localised rainfall rates into the 10-25m/hr (or possibly higher)range.

Behind this front, isolated thunderstorms are expected to develop again about western areas from Northland through Auckland to Taumarunui in the late afternoon and early evening. These thunderstorms will produce further localised heavy rain, and it is quite likely a few of them will be SEVERE (especially south of Auckland) producing localised downpours of 20-40mm/hr. Rainfall rates of this intensity can cause surface and/or flash flooding, and make driving conditions extremely hazardous.

A low risk of thunderstorms covers much of the remaining North Island this afternoon and evening as indicated on the chart.

In the South Island, a low risk of thunderstorms covers northern and western area from Marlborough to Westland this afternoon and evening, but the risk of storms is considered closer to moderate about Golden Bay and Northwest Nelson. A low risk of isolated thunderstorms also affects Southland this afternoon. Any thunderstorms that do develop in these areas will produce localised heavy rain.

MetService T-storm Outlook Map - Dec 17.png

jamie · Unread post by **jamie** » Wed 17/12/2014 08:45

They haven't dropped it Nev. it's increased to moderate.

I'll be chasing if something develops

Nev · Unread post by **Nev** » Wed 17/12/2014 09:09

jamie wrote:They haven't dropped it Nev. it's increased to moderate.

Opps, changed that comment before I saw your post. But yes, the low risk of severe T-storms has been increased to moderate.

littleheaven · Unread post by **littleheaven** » Wed 17/12/2014 09:51

Steady, heavy rain here in Glenfield. 17.3 currently, humidity 85%, dew point 14.7. Very gloomy out there. Looking forward to some decent thunderstorms later, hopefully. Should liven up the staff Christmas party.

Edited to add: Thunder heard just now.

NZstorm · Unread post by **NZstorm** » Wed 17/12/2014 09:54

Hearing thunder here in Grey Lynn to NW.

ben g · Unread post by **ben g** » Wed 17/12/2014 09:54

3 or 4 claps of thunder in west Akl, moderate rain

Manukau heads obs · Wed 17/12/2014 10:08

I will b at orewa this arvo...often a good spot for thunder on nw wind changes

SnwAddct · Unread post by **SnwAddct** » Wed 17/12/2014 10:11

Moderate rain in Auckland CBD now..

NZstorm · Unread post by **NZstorm** » Wed 17/12/2014 10:21

Very heavy rain here now.

Nev · Unread post by **Nev** » Wed 17/12/2014 10:56

Some heavy little downpours here also - not as much as the city though.

Also looked like quite a nice wee fare-up for Akld earlier…

Nev · Unread post by **Nev** » Wed 17/12/2014 10:59

Looks like inland South Island's turn tomorrow arvo, particularly around Canterbury and Otago…

MetService - Thunderstorm Outlook

Valid to: Midnight Thursday 18 Dec 2014
Issued at: 10:33am Wednesday 17 Dec 2014

The South Island is expected to be fairly unstable on Thursday afternoon and evening due to the combination of a warm moist airmass and weak pressure gradients associated with a decaying low pressure system.

Daytime cloud buildups are expected to produce scattered heavy showers and thunderstorms about the inland South Island from midday. The main risk of thunderstorms is about the inland ranges of Canterbury and Otago during the afternoon and evening, with a lower risk covering much of the remaining South Island as indicated on the chart.

These thunderstorms will be slow-moving and therefore have the potential to produce localised heavy rain and/or downpours. Rainfall rates of 10-25mm/hr are likely, and there is a low risk of a few severe thunderstorms producing more intense rainfall. (Note, it is possible the risk of severe thunderstorms may be increased tomorrow, so people within this area are advised to keep up to date with the latest forecasts).

No thunderstorms or significant convection expected over the North Island on Thursday afternoon or evening.

MetService T-storm Outlook Map - Dec 18, am.png

Nev · Unread post by **Nev** » Wed 17/12/2014 11:12

Power out in Pt Chevalier and earlier in Langholm…

'Strong winds in Auckland down power lines, cut power' - NZ Herald

spwill · Unread post by **spwill** » Wed 17/12/2014 12:26

Looks like more heavy rain/ thunder moving into our area in about an hr

David · Unread post by **David** » Wed 17/12/2014 13:14

Red blob on the rain radar heading this way. Think I just heard very distant thunder too

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