Troughs and Possible Storms- Sep 25-30

[NZstorm]

An upper trough is moving onto the upper North Island Wednesday so perhaps isolated thunderstorms occuring.
The 700mb temps look 2-3C cooler over Auckland tomorrow (gfs) which could lead to a funnel cloud if there was some decent heating.

[Tornado Tim]

Yes the 700hpa temps cooling is good sign, however from 400hpa the parcel traversal is quite iffy despite being saturated comparing to the sat adab lapse rate, in which case we will most probably see CB's form on sfc convergence zones but contain little to no lightning.

Will need the Sun to come out to get decent temps to get the more steeper lapse rates, but looking at the profile this is looking like a limiting factor with 4-6/8 octas forecast.

So we will most probably see CB's form (and get the resulting heavy showers), its just if they will start to spark off.

Metservices latest Outlook this evening is interesting:

Updated at 8:35pm Tuesday - Moderate risk area redefined. Low risk added to Fiordland.

A moist east to northeast flow will continue to cover most of New Zealand on Wednesday afternoon and evening, with rain or showers affecting many areas.

Over the North Island, the combination of this moist northeasterly flow and west coast sea breezes should produce enhanced cloud buildups, scattered heavy showers and a few thunderstorms over many northern and western areas from about northern Manawatu northwards. The main risk of thunderstorms is about Northland,Auckland, and western parts of Waikato, Waitomo and northern Taranaki, with a broader low risk covering other areas as indicated on the chart. Any thunderstorms that develop will be slow-moving and accompanied by localised heavy rain of 15-25mm/hr.

In the South Island, daytime cloud buildups are also expected to produce scattered afternoon and evening showers about Fiordland, and there is a low risk of one or two of these developing into thunderstorms.

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

[spwill]

GFS pointing to quite a cloudy day today, brighter conditions tomorrow.

[Tornado Tim]

GFS pointing to quite a cloudy day today

Yea but despite that, convection is already starting to pulse over the higher ranges.

I see Coromandel is directly underneath a trough and is getting dumped even more rain with the assoc heavy showers contained on it than what it received last night!

[jamie]

I'm up awhitu at the moment and there are some juicy cloud bases around. Half expecting a funnel to appear. Lots of skud.

[Manukau heads obs]

dang, I am not at home..
but my weather cam video does look interesting

[Tornado Tim]

The suns come out, 18.8°C and increasing.......
Some very heavy showers down south with hail signatures in some.

[spwill]

Overcast/some light showers here keeping the temp down, 15C but dewpoint is 14C, light winds
There has been Isolated thunderstorm development over Northland.

[Tornado Tim]

Isolated Thunderstorms over central south Waikato, inland Taranaki and BOP over the past hour. The Lightning is Low-mid amplitude which is means lapse rates are somewhat somber, but just enough to spark.

[NZstorm]

Thunder observed over Auckland just now.

[spwill]

Bright lightning closely followed by very loud thunder here just now

[NZstorm]

2 seconds between lightning thunder!

[Demchy]

Spotted some lightning pop out of the cloud base a few km to my south from the top of Dominion Road. Couldn't see if it hit the ground or not. The ensuing thunder rattled the windows somewhat.

[spwill]

Cell moved way to the southwest, a few rumbles heard here.

[Rogue]

Rumble of thunder heard from a small cell over Kapiti. Drove through heavy rain about half an hour earlier, very beefy buildups.

[David]

Thunder observed over Auckland just now.

While I was driving home there was some torrential rain with lightning over Tamaki Drive at 4.50pm.

[Nev]

Looks quite active over the North Island this arvo. Here's Blitzortung's CG's over the last 6 hrs…

Blitzortung NZ - Sep 28, 12pm to 6pm.png

MetService T-storm Watch map - Sep 28, 3.42pm.png

[NZ Thunderstorm Soc]

No thunder here, that's why I'm considering of closing down the NZ Thunderstorm Society, or possibly renaming it the Auckland Thunderstorm Society as most of the thunderstorms occur up there. ?
Maybe the Upper NI and West Coast Thunderstorm Society?
The Whatever Thunderstorm Society, maybe a good name

[NZstorm]

No thunder here, that's why I'm considering of closing down the NZ Thunderstorm Society, or possibly remaining it the Auckland Thunderstorm Society as most of the thunderstorms occur up there. ?
Maybe the Upper NI and West Coast Thunderstorm Society?
The Whatever Thunderstorm Society, maybe a good name

Canterbury has a higher chance of storms in December/January than Auckland.

[NZstorm]

Good to finally see some lightning occurring today!

The steeper lapse rates are still there tomorrow, maybe more rumbles for Auckland. Sun will be out tomorrow as well.

[shovelopikis]

thunder and lightning since 2pm this arvo, faded two hours ago but a great afternoon here

[NZstorm]

Tomorrows set up looks potentially more convective over the South Island than the North Island. Thunder for inland Canterbury also.
Lapse rates are starting to weaken over the North Island tomorrow despite upper trough.

[spwill]

Bright conditions today, currently 19C, dp 15C.

The best chance for a shower around Auckland today will be in the west.

[mikestormchaser]

Tomorrow has some daytime heating and a moist NE flow with convergances that should produce localized heavy showers and possibly some thunder in Canterbury

[David]

Been great getting the sunshine today, temperatures up to 20C too