Thunderstorms possible 20-22 Sept upper North Island

[NZstorm]

Moist unstable airmass over the North Island today, we need convergence to fire up the cb's! In these types of set ups the N/NE coming in from the Hauraki Gulf can run into a NW. Have to see what can develop.

There have been some good blow ups out to NW of Northland this morn.

The upper trough becomes more amplified over the Tasman tomorrow (Saturday) and an associated front moves across the NI overnight Saturday/Sunday am. I notice the upper air does warm a bit which weakens the instability. But thunder activity still looks possible especially over Northland down to Coromandel with a risk of a tornado. Taranaki could also have a tornado risk.

[jamie]

We have been getting heavy on off showers. The sort you expect when there is instability.

Very decent lightning activity to the west of 90 mile beach ATM

[Manukau heads obs]

oh...yes..nice looking blow up to the NW of upper NI

[David]

dunno what happened with the activity expected today but nothing much on the radar. Not too bad a day really! Muggy though with 16C dewpoint.

[spwill]

Plenty of storms in the Tasman but yes, a nice afternoon here after a few morning showers, our first humid day of the season

[ben g]

Suns out now, beautiful day, see how that effects things..

[Manukau heads obs]

these NW stalled fronts often are fickle things and hard to predict

blue skies out to my west now
19C max here today

[NZstorm]

I notice a cb has developed over the west of Waikato. Can see it from here.

[jamie]

Just saw a flash to my NW. Radar shows a cell closing in.

[spwill]

Saw that Cb to the southwest, some late day towering Cu showers here but nothing much.

[jamie]

Heavy rain here. Pushing 200mm/hr rain rate at one point.

[NZstorm]

Bay of plenty have caught some heavy showers overnight with 55mm in one spot west of Rotorua.

Radar shows a mass of frontal rain to our west. The front is modeled to reactivate later today so we'll have to see how much thunderstorm activity can develop. Upper Northland and top of the South Island look the best spots for lightning overnight.

[jamie]

I'm trying to calculate if we will get that big blob of heavy rain moving in from the west. I think it's about 50/50 for us. If we get it we will be right on the northern edge.

[NZstorm]

Some weak storms over the south Waikato/Waitomo this afternoon associated with that blob of rain down there.

[NZstorm]

Starting to reactivate now with more lightning showing up.

[Manukau heads obs]

distant lightning out to sea from here

[jamie]

Thunder just heard here to my NW

[Tornado Tim]

Thunder just heard here to my NW

Just heard that too!

[Tornado Tim]

Owhh lovely

Issued at: 8:15pm Saturday 21 Sep 2013

An active front is expected to move east onto the North Island and the upper South Island during the morning, bringing a burst of heavy thundery rain to many areas.

From Northland through Auckland to the west of Waikato there is a high risk of thunderstorms before dawn with heavy rain, strong wind gusts and small hail.There could also be isolated tornadoes, especially in coastal areas. In this area there is a moderate risk of severe storms with downpours, 25 to 35 mm per hour. These could cause surface flooding and could make driving hazardous.

From Taranaki to Waitomo and across the Bay of Plenty northwards there is a high risk of thunderstorms with heavy rain, strong wind gusts and one or two small tornadoes. This risk accompanies the front so the storms should ease in the west but develop in the east as the morning progresses.

In the north of Marlborough, Nelson, Buller and the north of Westland there is a moderate risk of thunderstorms with heavy rain, strong wind gusts and small hail.

A low risk of thunderstorms covers a broader area as indicated on the map.

No thunderstorms expected over the remainder of New Zealand.

[NZstorm]

I see Met Service have a watch up now.

[jamie]

Nice!

[Tornado Tim]

More thunder to the west just now......

[iomkiwi]

thunder and lightning just north of me, nothing to see though as it's pouring with rain too

[ben g]

Have roused flat mate for a chase, good looking storm heading our way !

[NZstorm]

I went up to Silverdale and watched activity up there. Big flashes/rumbles overhead but hard to get lightning pics due to low visibility.