Storms Possible - 24 September

Tornado Tim · Unread post by **Tornado Tim** » Wed 23/09/2015 21:17

Interesting how the Metservice increased the risk of a Storm over Auckland in this evenings update:

Updated withe the target area for thunderstorms moved over Auckland and northern Waikato...

Cold temperatures aloft and afternoon heating are expected to produce showers over the North Island on Thursday afternoon and evening. There is a moderate risk of thunderstorms developing over northern Waikato and Auckland tomorrow afternoon, clearing in the evening. These thunderstorms have the potential to produce hail in the 10 to 20mm range and rainfall rates of 10 to 25+mm/hr. The highest rainfall intensities are most likely over the Auckland area due to slow storm motions. In addition, there is also a risk of significant localised hail accumulations. These conditions would make driving difficult and may cause localised flash flooding.

The risk of thunderstorms is lower in a surrounding area including Waitomo to Bay of Plenty and eastern parts of Northland.

Elsewhere, no thunderstorms or significant convection expected.

Most like due the sfc trough forecast to be further north and SFC dps being a bit higher than more inland.

NZstorm · Unread post by **NZstorm** » Wed 23/09/2015 21:39

The last couple of runs of the gfs has pushed the moisture convergence northward to lie over the Auckland region.

Overall looking like a borderline set up but hoping for an improved outlook in the overnight modelling.

spwill · Unread post by **spwill** » Wed 23/09/2015 21:56

See what the cloud cover is like tomorrow, our weather has been underperforming for sunshine lately.

NZstorm · Unread post by **NZstorm** » Thu 24/09/2015 07:21

The moisture is right today with moist air at the surface and dry aloft. Big tick there. GFS indicates convergence still on the cards for the Waikato and also around Auckland up to Whangarei. There is good upper easterly flow over the Waikato so any development will quickly move into the west. Auckland north should see slow motions with lighter winds aloft. Localised heavy falls/small hail possible.

Manukau heads obs · Thu 24/09/2015 07:35

wind has died here again...this morning..from the SW
so a bit of a repeat setup to Tuesday in that regard

Manukau heads obs · Thu 24/09/2015 08:12

wind shifted SE here now...good sign

Tornado Tim · Unread post by **Tornado Tim** » Thu 24/09/2015 08:42

The 12Z run of the GFS has moisture back in further South over central Waikato. Today could be interesting. Will watch the radar with interest

Would like to see the Whenuapai Sounding......

Tornado Tim · Unread post by **Tornado Tim** » Thu 24/09/2015 08:44

This Morning's T-storm Outlook, even more north:

Metservice wrote:Cold temperatures aloft and daytime heating are expected to produce showers over northern parts of the North Island, with a broad low risk of isolated thunderstorms from Waitomo and Bay of Plenty northwards, as indicated on the chart. However, this risk of thunderstorms is considered nearer moderate over northern Waikato and Auckland this afternoon and early evening. Any thunderstorms that eventuate have the potential to produce localised heavy rain of 10 to 25mm per hour and hail of 5 to 15mm in diameter.

Elsewhere, no thunderstorms or significant convection expected.

Manukau heads obs · Thu 24/09/2015 09:02

temperature climbing with some sunshine here

jamie · Unread post by **jamie** » Thu 24/09/2015 09:25

Not great here with light shower at the moment

Tornado Tim · Unread post by **Tornado Tim** » Thu 24/09/2015 09:37

jamie wrote:Not great here with light shower at the moment

Yea Looking at the Radar, a few more will have come through yet. Hopefully they fizzle fast, otherwise we will get Tuesday occurring again.
Need that temp to climb.....

David · Unread post by **David** » Thu 24/09/2015 10:17

Unfortunately it's a rather dull cloudy day here in central Auckland

shovelopikis · Unread post by **shovelopikis** » Thu 24/09/2015 12:31

Activity will be more south I reckon, judging by current outdoor obs it's 17c with on off cool showers, hot sun....we had hail showers the other day, this one might produce something......I hope.

treetop · Unread post by **treetop** » Thu 24/09/2015 12:34

Thunderstorms over Mamakus heading Hamilton way intensifying now . Looks good for West Waikato. Will be hail too. Happy chasing !

Manukau heads obs · Thu 24/09/2015 12:39

that early warming caused early cloud build ups (was impressive bases on them)...and it cooled down again...sunny spells again now here...so it might have another go at it

Tornado Tim · Unread post by **Tornado Tim** » Thu 24/09/2015 12:40

Yup fair bit of Lightning going on in central Waikato atm

Heading west

Tornado Tim · Unread post by **Tornado Tim** » Thu 24/09/2015 12:46

Up to 18 so far in Matangi, nice

Initiated very early.......

David · Unread post by **David** » Thu 24/09/2015 12:47

Weather has fined up nicely now, I see it's currently 18C with dewpoint 13C in Howick.

Manukau heads obs · Thu 24/09/2015 12:51

we actually have a light sea breeze here...so things could get interesting later...or not...

Tornado Tim · Unread post by **Tornado Tim** » Thu 24/09/2015 13:10

Manukau heads obs wrote:we actually have a light sea breeze here...so things could get interesting later...or not...

I love how pessimistic we have become

......... LOL

shovelopikis · Unread post by **shovelopikis** » Thu 24/09/2015 13:56

Few rumbles here's, dark cloud bases with heaps of Sun in between on a balmy 18c now.

NZstorm · Unread post by **NZstorm** » Thu 24/09/2015 14:20

3pm convergence chart from gfs. The southern Waikato convergence shows up well.
Perhaps some convergence over Auckland as well but the NZWP midday sounding shows some CIN aloft.

NZstorm · Unread post by **NZstorm** » Thu 24/09/2015 14:23

NZWP sounding from today. A warm nose at 700mb.

Tornado Tim · Unread post by **Tornado Tim** » Thu 24/09/2015 14:37

Some Thunder to the North of Raglan

Nev · Unread post by **Nev** » Thu 24/09/2015 15:10

Pic of a funnel-cloud over Hamilton airport this arvo posted on Civil Defence Waikato's Facebook-page…

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