Thunderstorms upper North Island Saturday May 4

NZstorm · Unread post by **NZstorm** » Thu 02/05/2013 07:24

Models are consistent with a robust upper trough crossing the upper North Island on Saturday.
Deep layer lapse rates along the trough line are fairly steep at 6.5C and reasonable low level moisture with dewpoints 15C.
Given the low level flow will be northeast, localised heavy falls could occur Northland to Auckland and Bay of Plenty.
Both gfs and ukmet vary a bit on timing. GFS brings the precip/thunder risk into the north late Friday.
An isolated tornado can not be ruled out.

NZstorm · Unread post by **NZstorm** » Fri 03/05/2013 07:38

I am less enthusiastic about tomorrows set up now with the upper system looking weaker and the main forcing being offshore.
Bay of Island looks the most likely spot for a storm with Auckland's chances possibly low but still worth keeping an eye on. The air mass will be unstable, its just decent forcing that could be missing.

With the evolving low out to the west of the country Sunday in the models, we may see unstable squally conditions coming our way Sunday pm.

Nev · Unread post by **Nev** » Fri 03/05/2013 12:54

MS currently going for a more Northland, Nth Akld, Hauraki Gulf and Coromandel event tomorrow arvo/evening.

Their morning outlook (not incl. below) also mentions squally gusts and the risk of the odd tornado for the Far North.

MetService - Severe Thunderstorm Outlook

Valid to: Midnight Saturday 4 May 2013
Issued at: 10:47am Friday 3 May 2013

The northern North Island remains very unstable through Saturday afternoon and evening, with a band of rain and thunderstorms moving over Northland in the afternoon, and northern Auckland, the Hauraki Gulf and Coromandel Peninsula in the evening.

There is a high risk of thunderstorms about Northland in the afternoon and early evening, and about the Hauraki Gulf and northern Coromandel Peninsula towards evening and at night. A moderate risk of thunderstorms extends into northern Auckland and southern Coromandel Peninsula, with a lower risk of storms extending into southern Auckland, and parts of Waikato and Bay of Plenty late in the day as indicated on the chart.

These thunderstorms will bring localised heavy rain of 15-25mm/hr (or possibly higher) and small hail.

In the South Island, there is a moderate risk of thunderstorms associated with a slow-moving front about southern Westland, northern Fiordland and the Otago Alps from late afternoon, and a low risk of a few lightning strikes occurring over the remainder of Otago and possibly eastern Southland from Saturday evening as indicated on the chart. Localised heavy rain will accompany these storms.

No other thunderstorms or severe convection expected over New Zealand on Saturday afternoon and evening.

MetService TS Outlook - Is. May 3, 1047am.png

DTNZ · Unread post by **DTNZ** » Fri 03/05/2013 13:11

by Nev on Fri 03/05/2013 12:54

MS currently going for a more Northland, Nth Akld, Hauraki Gulf and Coromandel event tomorrow arvo/evening.

Yay

Their morning outlook (not incl. below) also mentions squally gusts and the risk of the odd tornado for the Far North.

Tornado... tarn pity I dont live in the Far North.

iomkiwi · Unread post by **iomkiwi** » Fri 03/05/2013 19:38

by Nev on Fri 03/05/2013 12:54

MS currently going for a more Northland, Nth Akld, Hauraki Gulf and Coromandel event tomorrow arvo/evening.

Their morning outlook (not incl. below) also mentions squally gusts and the risk of the odd tornado for the Far North.

Given these two statements, and the fact I took delivery of my new 60D only a couple of days ago and don't have a lot of time to 'learn' it - can someone give me a heads up on what settings to use should I happen to go chasing

TIA

Skywatcher · Unread post by **Skywatcher** » Fri 03/05/2013 21:46

iomkiwi wrote:Given these two statements, and the fact I took delivery of my new 60D only a couple of days ago and don't have a lot of time to 'learn' it - can someone give me a heads up on what settings to use should I happen to go chasing

Here are some settings to get started with...

Long term you should shoot RAW images which allow more post-processing but you could start off with JPEGs. Set ISO to 100 to increase exposure time and reduce noise.

Switch the lens to Manual focus and then use magnified Live View to accurately set it on a distant object during the day or a light/bright star at night. (Remember to switch back to Auto for normal use !)

Daytime - you really need a trigger to have the best chance of capturing lightning but can sometimes fluke it by half-pressing the shutter then fully pressing it when you see the flash. Use Av mode and a smaller aperture (high f-number) of e.g. 8 to increase exposure. Too high an f-number and the lightning will lose contrast.

Twilight/Night - easier, especially if you have a locking remote shutter cable. First method for twilight or bright location at night - Av mode and adjust the f-number until the exposure is more than 2" (seconds) but not above 8, drive mode to continuous, press and hold the shutter down - this will keep taking shots with no gaps.

Second method for a dark site - B mode (if there is one) otherwise M mode and set exposure to Bulb, set f-number to 5.6 or less, drive mode single shot, press and hold shutter until you see some lightning then release and start again. I'd usually release it after about a minute if there hasn't been any lightning. You can also keep the shutter pressed for multiple lightning strikes if they're reasonably frequent...

It's worth occasionally checking the results as you go and reducing f-number to increase brightness if required. When f-number is at its minimum you can then increase ISO.

iomkiwi · Unread post by **iomkiwi** » Fri 03/05/2013 22:47

Thanks - hopefully I may get a chance to try it out tomorrow

NZstorm · Unread post by **NZstorm** » Sat 04/05/2013 07:20

The front will come south slowly today, reaching Auckland this afternoon. Just have to see whether thunderstorms can get energised on it! Isolated very heavy falls on the cards, particularly in the BOP later today.

GFS Lifted index chart for 3pm, good instability!

Manukau heads obs · Sat 04/05/2013 07:22

does not look very flash on the sat image today and looks like its going to roll over the top?

Nev · Unread post by **Nev** » Sat 04/05/2013 08:30

Hi DT, yes I see you've moved. Nice to hear from you again and hope you're well.

I see last night's and this morn's MS outlook for this arvo now includes a low risk of the odd tornado for eastern Northland, the Hauraki Gulf and eastern Coromandel, so you might be lucky (or unlucky depending on one's perspective). Some waterspouts would be nice...

MetService - Severe Thunderstorm Outlook

Valid to: Midnight Saturday 4 May 2013
Issued at: 8:16am Saturday 4 May 2013

Bands of rain and thunderstorms are expected to spread over the northern North Island today.

There is a high risk of thunderstorms about northern and eastern Northland this morning and afternoon, and about the Hauraki Gulf and northern Coromandel Peninsula in the afternoon and evening. A moderate risk area extends over the remainder of Northland through until afternoon, and about Auckland, Coromandel Peninsula, western Bay of Plenty, and possibly northern and eastern Waikato from this evening. A lower risk covers the area down to northern Gisborne, Taupo and northern Taranaki from evening as indicated on the chart.

Localised heavy rain of 15-25mm/hr (or possibly more in one or two eastern places), hail, and squally winds up to 70-80km/hr will accompany these thunderstorms. One or two small tornadoes are also possible about the east coast, but this risk is now considered quite low.

In the South Island, a slow-moving front on the west coast is expected to become more unstable during the day, with a moderate risk of embedded thunderstorms about southern Westland, northern Fiordland and the Otago Lakes from late afternoon or evening. There is also a low risk of a few lightning strikes over the remainder of Otago and possibly eastern Southland from evening as indicated on the chart.

No other thunderstorms or severe convection expected over New Zealand today.

MetService TS Outlook Map - Is. May 4, 0811am.png

Manukau heads obs · Sat 04/05/2013 08:46

the front currently moving onto northland does look more active now....

spwill · Unread post by **spwill** » Sat 04/05/2013 08:56

A few thunderstorms over the very far north overnight and some developing there now.

littleheaven · Unread post by **littleheaven** » Sat 04/05/2013 10:36

MetService have a severe weather watch in place for Northland to BOP. I'm supposed to be going to Gulf Harbour for a baby shower this afternoon but not sure I want to drive up there in that kind of weather.

iomkiwi · Unread post by **iomkiwi** » Sat 04/05/2013 11:13

We have had thunder around here since around 8am, but we are smothered in low cloud as well so no chance of photos yet

Have also had 20mm of rain in the 3 hours since 8am

ben g · Unread post by **ben g** » Sat 04/05/2013 11:20

Just had 10 mm in ten min here.

spwill · Unread post by **spwill** » Sat 04/05/2013 12:01

Just had a heavy shower here, I see Greylynn got 8.2mm from it.

DTNZ · Unread post by **DTNZ** » Sat 04/05/2013 12:15

12:12 hrs Heard thunder rolling thru Kamo...

nice, likes... pretty dark and bleak out there at moment, my son's playing rugby in this weather.

littleheaven · Unread post by **littleheaven** » Sat 04/05/2013 12:38

Several torrential showers in Glenfield. Having one right now.

Brassnz · Unread post by **Brassnz** » Sat 04/05/2013 13:25

Torrential rain in Laingholm also. Rather spectacular.

Manukau heads obs · Sat 04/05/2013 14:19

Shower lines developing real fast around Auckland!

Looks like we might get a hum dinga nw gale later tomorrow

DTNZ · Unread post by **DTNZ** » Sat 04/05/2013 14:25

Nev wrote:Hi DT, yes I see you've moved. Nice to hear from you again and hope you're well.

Hi Nev

The front has moved on now & the skies are beginning to clear in Kamo. Since noon today had moderate to light rain with the odd heavy down pour, nothing too dramatic to talk about, still my son enjoyed their rugby game today, but his team lost.

David · Unread post by **David** » Sat 04/05/2013 14:29

Not much going on out in east Auckland yet today, apart from a few brief showers

DTNZ · Unread post by **DTNZ** » Sat 04/05/2013 14:30

iomkiwi wrote:
Given these two statements, and the fact I took delivery of my new 60D only a couple of days ago and don't have a lot of time to 'learn' it - can someone give me a heads up on what settings to use should I happen to go chasing

TIA

Hi Alan

Enjoy your new 60D

Take care

littleheaven · Unread post by **littleheaven** » Sat 04/05/2013 14:53

Thunder audible in Glenfield, about every minute, but not particularly close by.

Nev · Unread post by **Nev** » Sat 04/05/2013 15:08

Woo Hoo!

Lightning and thunder near here. Windy but the rain's not that heavy.

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