Thunder chances Saturday 13th September

NZstorm · Unread post by **NZstorm** » Fri 12/09/2014 06:41

Have to say tomorrow looks good considering the trough is timed well with daytime heating.
The instability is over a large area from lower North Island to about Auckland!
Daytime heating will be a key player. Looks like this should occur with not much high cloud in the gfs model.

I may chase this set up but be driving south. Have to see how it looks tomorrow.

Nev · Unread post by **Nev** » Fri 12/09/2014 06:57

Looks like there may be some tornado potential there?

jamie · Unread post by **jamie** » Fri 12/09/2014 09:00

When did you grab that picture steven? Currently it looks like their site is down, for NZ and Aus.

jamie · Unread post by **jamie** » Fri 12/09/2014 11:20

Working again now.

Metersevice only going for moderate risk. I had a good look and it does look promising. Ill keep an eye out while im out fencing. Might have to drop tools and chace.

Nev · Unread post by **Nev** » Fri 12/09/2014 11:40

Probably 'Glitch' again?

MS's moderate risk tomorrow arvo is for the Hauraki Gulf

to BoP and the Wairarapa/Manawatu area, although that may change...

MetService - Thunderstorm Outlook

Valid to: Midnight Saturday 13 Sep 2014
Issued at: 10:37am Friday 12 Sep 2014

As the surface low and pool of cold air aloft spreads eastwards across the upper North Island, rain and showers with heavy falls are forecast for many places. From the Hauraki Gulf to western Bay of Plenty there is a moderate risk of thunderstorms during the afternoon, and this extends into the eastern Bay of Plenty in the evening. Any thunderstorms that do develop could boost rainfall rates to 25mm/hr.

A larger area of low risk extends to Western Auckland, and southwards to Waitomo, Taumarunui and Taupo.

Over the lower South Island [sic], daytime heating and afternoon sea breezes are expected to produce showers in many places, and there is a moderate risk of thunderstorms in Wairarapa, central Hawkes Bay and Manawatu. Thunderstorms here could be relatively slow-moving, and rainfall rates could locally reach 10-25mm. A larger area of low risk extends to inland Taranaki, Wanganui and the Central Plateau.

MetService Sep 13 pm T-Storm Outlook Map - Is. Sep 12.png

NZstorm · Unread post by **NZstorm** » Fri 12/09/2014 11:47

In the latest model run the set up for Auckland/Waikato has weakened a lot. Looks like we get NW developing too early. I was hoping for a surface N/NE into the afternoon.

jamie · Unread post by **jamie** » Fri 12/09/2014 21:00

It's not looking too bad tomorrow. Nothing amazing but at least it's something.

NZstorm · Unread post by **NZstorm** » Fri 12/09/2014 21:14

Potentially a good set up. Midday run of gfs has swung back in our favour. See how it looks in the morning.

Nev · Unread post by **Nev** » Fri 12/09/2014 21:47

Yes, tonight's MS update looks more promising for tomorrow arvo…

MetService - Thunderstorm Outlook

Valid to: Midnight Saturday 13 Sep 2014
Issued at: 9:32pm Friday 12 Sep 2014

A low and pool of cold air aloft is expected to spread organised bands of showers over much of the North Island Saturday afternoon and evening. This together with afternoon heating (which is now getting stronger), will lead to additional areas of shower activity.

There is a moderate risk of thunderstorms developing Saturday afternoon over a fairly wide area from southern parts of Auckland to central Bay of Plenty and then southwest to Taranaki and Taumarunui and then down over the lower North Island through Wanganui, Manawatu and Wairarapa. Some of these have the potential to deliver rainfall rates in the 10-25mm/hr range along with some small hail. This activity is expected to ease during the evening hours, but last longest over southern areas.

The risk is lower during the same period for remaining areas of the North Island except for eastern Bay of Plenty and Gisborne and the far south of the North Island as depicted on the chart.

Over parts of Marlborough during the afternoon, there is a low risk of a thunderstorm associated with a southerly change as it moves over central and eastern Marlborough.

Elsewhere, no thunderstorms or significant convection expected

MetService Sep 13 pm T-Storm Outlook Map - pm Is. Sep 12 pm.png

Tornado Tim · Unread post by **Tornado Tim** » Fri 12/09/2014 22:52

A nice 15 C outside atm, scattered showers coming in from the Hauraki Gulf. More beefy ones just off the coast.
Fairly Unstable forecast sounding for Tommorow afternoon in the Waikato. With High SWEAT index's, suggesting the potential for some very heavy rain in any assoc storm.

Forecasted SFC flow NNE to NE, with the upper flow being North, might be interesting structure wise to storms. Particularly if a Sea Breeze occurs.

spwill · Unread post by **spwill** » Fri 12/09/2014 23:56

Tropical like showers here tonight, 15C, 15C dewpoint.
I see Greylynn got a quick 10mm within the last hr

Will watch for a possible Tstorm tomorrow.

jamie · Unread post by **jamie** » Sat 13/09/2014 04:46

Had 20mm in 2 hours here. So a decent fall. Got woken by a very heavy burst of rain.

Nev · Unread post by **Nev** » Sat 13/09/2014 06:31

Great view of distant lightning around the outer Gulf earlier this morn - every few minutes around 5am, although mostly IC not picked up by Blitzortung by the looks…

David · Unread post by **David** » Sat 13/09/2014 06:32

Only 7 mm here since 9pm, we missed the heavy falls overnight.

NZstorm · Unread post by **NZstorm** » Sat 13/09/2014 06:56

23mm here last night. Very heavy precip just before midnight.

Fog this morning temp 14C.

jamie · Unread post by **jamie** » Sat 13/09/2014 07:04

Thick low cloud here. Hopefully it clears soon.

NZstorm · Unread post by **NZstorm** » Sat 13/09/2014 07:23

Yes, not sure how much heating we'll get though. If we can get 18C-19C that'll be good enough.

David · Unread post by **David** » Sat 13/09/2014 08:00

Fog has just descended on Howick now, even though there is an ENE breeze blowing

spwill · Unread post by **spwill** » Sat 13/09/2014 08:04

Some blue sky here now however I think any heating today will quickly lead to showers, dewpoint is 14C

Nev · Unread post by **Nev** » Sat 13/09/2014 08:31

Yeah, fog came in around 6am here - started clearing around 8am.

This morn's update from MS for today looks interesting…

MetService - Thunderstorm Outlook

Valid to: Midnight Saturday 13 Sep 2014
Issued at: 8:25am Saturday 13 Sep 2014

A warm and unstable airmass covers the North Island today, with cold temperatures in the upper atmosphere. A trough is moving eastwards across eastern Bay of Plenty and northern Gisborne this morning and early afternoon,with a moderate risk of embedded thunderstorms. A low pressure system is moving onto the upper North Island this afternoon and early evening, bringing a moderate risk of thunderstorms across much of Northland, Auckland, Coromandel Peninsula, Waikato and western Bay of Plenty. These thunderstorms may produce localised rainfall rates of 10 to 25mm/hr and small hail.

Afternoon sea breezes are likely to develop heavy showers across the central and lower North Island this afternoon, with a low risk of thunderstorms, as depicted on the chart. However, there is a high risk of thunderstorms this afternoon and early evening from Waitomo to Taranaki, and across to Wairarapa and the Tararua District. These thunderstorms may produce localised rainfall rates of 15 to 25mm/hr and small hail. In addition, there is a low risk of these thunderstorms becoming SEVERE, with downpours of 25 to 40mm/hr.

Finally, afternoon convergences may produce a few heavy showers in the ranges of Nelson and Marlborough, with a low risk of a few thunderstorms there.

No thunderstorms expected over the remainder of New Zealand.

MetService Sep 13 T-Storm Outlook Map - Is. am Sep 13.png

NZstorm · Unread post by **NZstorm** » Sat 13/09/2014 08:57

Rickys lightning counter has picked up 5200 discharges, so a lot of electrical activity has occurred on that front out east.

ben g · Unread post by **ben g** » Sat 13/09/2014 13:14

Suns trying to come out, a few nice cb out towards the west

ImageUploadedByTapatalk1410570867.653022.jpg

spwill · Unread post by **spwill** » Sat 13/09/2014 13:49

Lots of cloud today but it is quite humid, next shower line is worth watching, isolated storm activity showing up with it.

NZstorm · Unread post by **NZstorm** » Sat 13/09/2014 13:58

Can see t/cu to west. Temp 17C dp15C. Unfortunately still lots of low cloud over Auckland.

David · Unread post by **David** » Sat 13/09/2014 13:59

Lovely and sunny here. Dewpoint 15 - 16C. Looks like we'll miss out on the action here, NE is too breezy and is pushing the activity down over western parts

NZ Weather Forum