Deep Subtropical Low 12-18th May!!!

[Manukau heads obs]

video showing the sharp trough axis (upper level flows) (end of video sequence (you should be able to use the slider to control the video playback)
http://www.weather-display.com/downloadfiles/cbs2.mp4

[Dean.]

Wow that ECL looks mean on the latest GFS and EC models,imagine that moving towards NZ and combining with a cold mass from the south.

[David]

Wow that ECL looks mean on the latest GFS and EC models,imagine that moving towards NZ and combining with a cold mass from the south.

That may just be the thing we need for some proper rain! (this low hasn't given much at all here)
Although I'm not convinced yet - it's too far out at this stage.

[tgsnoopy]

I'm trying very hard to teach myself how to use my new camera tonight. Sadly the off shore storms were a long way off before I was in a position to get out and have a crack. Fingers crossed I'll get someyhing for my efforts though.

[DT-NZ]

Fingers crossed I'll get someyhing for my efforts though.

Ok -

Well a few more pics taken yesterday - also great storm photo's Drew.

The first photo was taken yesterday morning looking NE - a brief shower heavy of rain passed over - so I sat and waited for the shower to pass and snapped this - a natural water colour.

The last 2 are CB's looking NE - photogenic day yesterday - great forms - lines - light - shadows... great day for photographing CB's.

[DT-NZ]

The base of those huge towering black ominous CB lines that pulled through here from the west 30mins ago most diffinately had a green tinge

Known to sailors as 'The Devil's Beacon'!!

Ominous - anyway I did a little vid clip of the actual low-level CB line as it moved over head in front of me - Im looking west at the time I took this clip unfortunately the camera did not pick up the green tinge, however, I know what observed

http://www.youtube.com/watch?v=FYeJjWddLO4

[tgsnoopy]

Well my newer camera definitely is broken in. Sadly I was way too late to get any decent photo's as the storm was far too far away. But I did get a couple of shots.

1.JPG

2.JPG

Now I've worked out there is a special night shot mode that's not so easy to find and I can keep the shutter open up to 15 seconds, next time I hope to have better luck.

[Nev]

Follow-up story to that tornado in Taranaki on Friday night. One extremely lucky lady! ...

Woman clings on for her life as tornado hits
By FELICITY ROSS - Taranaki Daily News
Last updated 05:00 17/05/2010

A Taranaki woman clung to a farm gate fearing for her life as a tornado hurtled towards her near Oakura. Melva Benton was walking home from milking just on dark when she saw debris swirling in the sky heading her way. "I just closed my eyes and held on," the Koru Rd farmer said. "I was terrified."

The Friday night twister had come from nearby Plymouth Rd where it dropped a tree and demolished a hayshed. "I just heard this noise and saw all the debris coming from the neighbours. I started to walk down the middle of the road but there was nothing to hang on to so I went for the gate," Mrs Benton said.

She was struck in the back by debris and pushed against the gate by the force for the wind. "I just stopped there holding on tight until it was all over." She clung to the top pipe railing as a sheet of iron came flying towards her. "I was thinking which way to go when it stopped about six metres away. I was lucky." "I was watching it [the tornado] and was terrified. I tried to be brave."

The tornado flattened a large pine shelter belt on the Benton farm, took the roof off a wood shed and destroyed a tractor shed. "I could hear the noise of the trees but I closed my eyes because I didn't know what was going to happen to me. There were a lot of trees over the other side of the road and they have all been mowed down." Before the twister appeared, heavy rain, thunder and lightning hit the area and she was keen to finish milking and get home. "I couldn't get out of the shed quick enough but I came up to that."

Mrs Benton suffered a bruised back but reckons she was pretty lucky. "I can count my lucky stars. It wasn't my time, my number couldn't have been up," she said. ...

(more...)

There was also a reported tornado in the Kaipara Flats (west of Warkworth) on Saturday, which apparently took out a few trees.

[Manukau heads obs]

good photos Tgsnoopy
amazing story from Naki!

Canty has a better looking rain band heading towards them this morning

very foggy here this morning with a SE breeze...(but clouds are from the west)

[Nev]

Also, an interesting first-hand account of the flooding in Nelson/Tasman area...

'Families evacuated as deluge hits homes'

[Manukau heads obs]

I wonder if the problem was not so much the amount or rate of the rain but the fact that the ground was so dry before hand and ran off?
(as 150mm in 24 hours for those mountain areas SW of Nelson would not be unusual I would think?)

[Tim S]

Regarding that flooding in Tapawera, I drove around the headwaters of the Motueka River about 10-15km upstream from Tapawera and was amazed at how much of the plantation forest had been cleared. I am not sure if this would have been a major contributing factor but I imagine it would have had an influence as if this rain fell with the forests intact upstream this would have delayed the rainfall reaching the river and possibly avoided the amount of water coming down the river at Tapawera in the main flood surge.

The first of the photos is of the eastern slopes of the valley, the second is looking north up the valley towards Tapawera (its out of view to the top right of the photo). It seemed that in the 5-10km down stream of this location around 80% of the Eastern side of the valley had been recently cleared (probably in the last 6 months). Quite unbelievable that they would log such large areas of the forest at a time, although I am sure there's a good reason.

Upstream from Tapawera.jpg

Upstream from Tapawera2.jpg

Report of the flooding from the civil defence page: http://nelsontasmancivildefence.co.nz/

As far as how Nelson faired, looking at that civil defence site yesterday it sounded like they were worried the Maitai river was getting close to flood watch level and were closely monitoring it but was a long way off being a concern by the sounds of it, no doubt due to the dry conditions leading up to this event. According to metservice stats we looked to have received around 100mm over the last 96 hours or so, although the total may be higher as the Nelson Mail reported the 24 hrs to sat rainfall as 58mm and the metservice reported it as 44.8mm. The only flooding I saw was at the botanical gardens in Nelson with the lake there bursting its tiny banks. There were a few very happy ducks and a few very amused tourists and locals.

Nelson flooding.jpg

Nelson flooding2.jpg

[Michael]

For us here in Auckland its a very tame low ie had little NE/SW orientation flows,the next one looks different.

[RWood]

One of the least attractive things to be seen in Nelson/Tasman (which has many lovely areas) are the very large tracts of exotic forest, with substantial cleared areas generally on show as well. The same applies to parts of the Marlborough Sounds.

[Nev]

Great report Tim S.

...According to metservice stats we looked to have received around 100mm over the last 96 hours or so, although the total may be higher as the Nelson Mail reported the 24 hrs to sat rainfall as 58mm and the metservice reported it as 44.8mm.

From what I gather, there are 2 WS's at Nelson Aero. The MetService one is mounted over grass near the runway, while the other (a DSE WS I think) is mounted on the Control Tower. It appears that in the 24 hrs to 9am on the Saturday, the tower recorded about half as much again as the MetService one less than a km away. NIWA also have a WS about 11km to the west in Appleby.

Below is a few stats c/o NIWA...

Code: Select all

May Rainfall (mm) to 9am    13th   14th   15th   16th   17th

Nelson Aero Aws (M/S)        8.0    0.2   41.8   25.0   22.6
Nelson Aero Ews (Tower)     14.7    2.1   58.1   25.1   22.2
Appleby 2 Ews (NIWA)        14.2    1.2   32.8   24.6   16.0

[Nev]

A 'small tornado' has also apparently been blamed for blowing a shed roof through power lines in the Tasman District on Friday or Saturday?

'Tornado cuts power' - Nelson Mail

[Manukau heads obs]

that makes 3 , so well done to M/S for sticking their necks out and forecasting small tornadoes

[Manukau heads obs]

this next lof of CB's approaching the upper NI look good on the sat image, and I can see some of them already way to the west and they look impressive: temperature's have cooled again in that cold pool
and with the slower movement, more potential for bigger rain totals

[RWood]

Great report Tim S.


From what I gather, there are 2 WS's at Nelson Aero. The MetService one is mounted over grass near the runway, while the other (a DSE WS I think) is mounted on the Control Tower. It appears that in the 24 hrs to 9am on the Saturday, the tower recorded about half as much again as the MetService one less than a km away. NIWA also have a WS about 11km to the west in Appleby.

Below is a few stats c/o NIWA...

Code: Select all

May Rainfall (mm) to 9am    13th   14th   15th   16th   17th

Nelson Aero Aws (M/S)        8.0    0.2   41.8   25.0   22.6
Nelson Aero Ews (Tower)     14.7    2.1   58.1   25.1   22.2
Appleby 2 Ews (NIWA)        14.2    1.2   32.8   24.6   16.0

From NIWA's CliFlo, the EWS (Tower) above is "Nelson Aero" (G13222), with all manual equipment removed except for the sunshine recording, by 1996. Originally there was an enclosure.

The AWS is "Nelson AWS" (G13322). The rainfall histories of the 2 sites (from my recollection) showed the M/S tower getting consistently higher monthly totals than those from the AWS.

[Tim S]

Thanks for that info on the two Nelson sites Nev and RWood, strange that one would record so much more than the other and on a consistent basis. If anything I would have thought the control tower would record less as it would most likely be more exposed to stronger winds (unless its on the lee side of the tower). Even more interesting is the posibility it would be a DSE one (I take it by that you mean Dick Smith Electronics?), as I'd imagine although these would be fairly accurate they would definitely not be accurate enough for any scientific basis.

Anyway it seems as if I need to go for a walk around the airport to see what I can see, I'll make sure I am wearing my 'I am not a terrorist t-shirt'

Also from what I heard the 'small tornado' was somewhere in Golden Bay, not sure of its exact location though.

[Nev]

Hi RWood. Yes, NIWA refer to the EWS as "Nelson Aero", which, based on coordinates, is at the Tower. However, MetService also refer to their AWS (or used to) as "Nelson Airport", which appears to be at the S'ern end of the runway (not the tower). Yes, annual totals over last decade show that the MetService AWS site has consistently read lower than the EWS Tower site. Note that last Jan, the MetService screen was re-sited over grass, facing N; the previous year it was mounted on a pole, over concrete, facing W.

Hi Tim, the DSE WS (yes, Dick Smith Electronics) may have just been used as a temporary comparison, for the existing site. I'm not too sure. Maybe they were just as perplexed.

[David]

this next lof of CB's approaching the upper NI look good on the sat image, and I can see some of them already way to the west and they look impressive

Yes I could see those way in the distance on the way home this evening, silhouetted against the dusk colours of the horizon

[Tornado Tim]

Some very very impressive CB's out to the west coast.

I can see them all the way from here and the sat image shows where they are:

That means they are at a very considerable height!

I can also see the thunderstorm to the north of Auckland as well, perhaps Auckland will get a visit from it?

It has currently got Purple on the radar, probably some hail in it as well

[Tornado Tim]

Severe thunderstorm warning has now been issued from m/s:

ssued by MetService at 06:23 pm Monday 17 May 2010.
Valid until 07:15 pm Monday 17 May 2010.

This warning affects people in the following local government areas:
KAIPARA, WHANGAREI and RODNEY.

At 06:15 pm, MetService weather radar detected severe thunderstorms near PAPAROA
,
MATAKOHE, MAUNGATUROTO, BRYNDERWYN and TAIPUHA.

These severe thunderstorms are expected to lie near MAUNGATUROTO, PAPAROA,
TINOPAI, KAIWAKA and BRYNDERWYN at 06:45 pm and near KAIWAKA, OKAHUKURA
PENINSULA, PORT ALBERT, MAUNGATUROTO, MANGAWHAI, BRYNDERWYN and TE ARAI at 07:15
pm.

These thunderstorms are expected to be accompanied by very heavy rain.

Very heavy rain can cause surface and/or flash flooding about streams, gullies
and urban areas, and make driving conditions extremely hazardous.

The Ministry of Civil Defence and Emergency Management advises that as storms
approach you should:
- Take shelter, preferably indoors away from windows;
- Avoid sheltering under trees, if outside;
- Move cars under cover or away from trees;
- Secure any loose objects around your property;
- Check that drains and gutters are clear;
- Be ready to slow down or stop, if driving.
During and after the storm, you should also:
- Beware of fallen trees and power lines;
- Avoid streams and drains as you may be swept away in flash flooding.

This warning is due to be updated or lifted by 07:15 pm Monday 17 May 2010.

[Tornado Tim]

I can see the lightning from it all the way from here, some anvil crawlers apparent as it flashes up on the horizon.