Low #3, yet more Thunderstorms

Storm Struck · Unread post by **Storm Struck** » Tue 02/05/2006 21:33

03Stormchaser wrote:
NZ Thunderstorm Soc wrote:Interesting skies around Christchurch today but nothing much to photograph.
Looking really heavy especially in the afternoon when the weak convergence when through around 12:30pm.
Not much wind.
JohnGaul
NZTS
Was interesting, had a decent heavyish shower come thru around 12.15pm. My home rain gauge didnt record anything other than a few spits, and I like a mere 2 minutes away!! So was very localised.

Also seen that weak CU this afternoon some heavyish light rain showers came over around 12pm and 3pm if that makes any sense

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I photographed it John

may as well not much to photo at the moment and for some time to come yet

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Cheers
Jason.

Flutterbye · Unread post by **Flutterbye** » Tue 02/05/2006 21:38

I don't know if John should read this thread - he will only get depressed. Actually some thunderstorms & wind would make a change down here.

Manukau heads obs · Tue 02/05/2006 21:39

well paul when you see so many Cb's by pass the auckland area its easy to loose faith, but sometimes its out turn

thinking about it, you can hear thunder up to 10 or even 12 seconds after seeing lightning...from inside a house....but you have to be listening for the thunder, and being in a quite rural area would help too

ps, we have a SE wind here....
and the rain radar shows its a warm front being caught up and getting ocluded by a cold front...(the fronts moving onto the auckland area)

Paul Mallinson · Unread post by **Paul Mallinson** » Tue 02/05/2006 21:50

I know what you mean Brian.

We are dealing with structures that are only a few miles or tens of miles across and these are heavily influenced by wind flows and distortions by the land etc and so it can be pretty hard to guarantee that a given spot will get a thunderstorm.

I guess folks should remember that the threat charts are basically saying that conditions are likely to be such that there is a certain risk (low, moderate or high) that a thunderstorm or thunderstorms will develop somewhere within the area drawn - but not everywhere. Depending upon the trigger, they often occur in similar places, due to the influence of the land either due to wind convergence by the topography or heating/sea breeze convergence etc etc. And so the places that often miss out do so due to their local circumstances.

I think you are right with your comment about the limit to hearing thunder. I seem to remember it is about 10 miles. It is due to the loss of higher frequency sounds over this distance.

Paul

Manukau heads observer wrote:well paul when you see so many Cb's by pass the auckland area its easy to loose faith, but sometimes its out turn
thinking about it, you can hear thunder up to 10 or even 12 seconds after seeing lightning...from inside a house....but you have to be listening for the thunder, and being in a quite rural area would help too

Cameo1 · Unread post by **Cameo1** » Tue 02/05/2006 21:50

rain getting heavy now

Manukau heads obs · Tue 02/05/2006 21:53

the rain radar also seems to suggest there is a small low where the warm and cold fronts occlude, currently west of Helensville

those cbs lines way out to the NE show up well on the rain radar....and on the lighthing tracker....there are some real hot spots out there....to the NE of Gt barrier island....maybe some warm patches of water out there?

ps. we have had great electrical storms at night time in this area in the past....just not for a while!

TonyT · Unread post by **TonyT** » Tue 02/05/2006 22:11

Paul Mallinson wrote:Ooh all yea of little faith!

Paul

To which I might also add, "Patience is a virtue".

Cameo1 · Unread post by **Cameo1** » Tue 02/05/2006 22:38

Bay of Plenty and coromandel are getting hammered now... again

tgsnoopy · Unread post by **tgsnoopy** » Tue 02/05/2006 23:00

Cameo1 wrote:Bay of Plenty and coromandel are getting hammered now... again

We are?

Willoughby · Unread post by **Willoughby** » Tue 02/05/2006 23:06

Those thunderstorms have sparingly slid east of Coromandel/BoP.

NZstorm · Unread post by **NZstorm** » Wed 03/05/2006 00:08

Intense rain in Grey Lynn at the moment. 16mm in the last 10minutes!

Edit, Rain eased. 31.8mm is 25minutes!

Thats the heaviest rain I've seen for a while.

spwill · Unread post by **spwill** » Wed 03/05/2006 00:23

Woken by big downpour here, heaviest rain I can remember.

Willoughby · Unread post by **Willoughby** » Wed 03/05/2006 00:27

That's heavy!

Looking at the RR images.. looked like the rain 'held back' over the ithmus thanks to the warm Manukau/Waitemate harbours rather than over the cooler land mass.

Convection very nice for this time of day!

NZstorm · Unread post by **NZstorm** » Wed 03/05/2006 00:28

Yes, 26mm of it fell in about 15minutes here.

Willoughby · Unread post by **Willoughby** » Wed 03/05/2006 00:34

Looking at MML.. http://www.portunus.net.nz/weather/mml.html
there seemed to be quite a bit of surface convergance too. I noticed Brian had an odd SW'er against the other easterlies in the AK region. Northerly now on the North Shore against the Grey Lynn's southerly. Interesting.

NZstorm · Unread post by **NZstorm** » Wed 03/05/2006 06:58

Yes I agree Foggy, some local convergence going on there interacting with a frontal boundary.

Doesn't look like Coromandal got much rain overnight. Lucky for them, a bit of a fizzer.

Paul Mallinson · Unread post by **Paul Mallinson** » Wed 03/05/2006 07:00

Good observation Foggy. This sort of wind shift (and therefore convergence) is exactly what is expected across a front - clearer in some cases than in others. On this larger scale (rather than the small local scale), this acts to trigger embedded thunderstorms on the front if the airmass is unstable. Then, if the front (convergence line) is slow moving, rainfall rates can be very high as NZStorm reported (31.8mm in 25mins!)

Paul

Foggy Hamilton wrote:Looking at MML.. http://www.portunus.net.nz/weather/mml.html
there seemed to be quite a bit of surface convergance too. I noticed Brian had an odd SW'er against the other easterlies in the AK region. Northerly now on the North Shore against the Grey Lynn's southerly. Interesting.

tgsnoopy · Unread post by **tgsnoopy** » Wed 03/05/2006 07:06

I never heard any thunder overnight, never was woken by rain. The event seems yo have completely missed us. Pleased there was no flooding down here, but disapointed there was no display.

Sounds like Auckland was hammered with flooding reported etc.

Manukau heads obs · Wed 03/05/2006 07:08

again the city gets some big rain dumps!

still unstable at first light, with towering cumulus around, under older decayed CB tops
more cb's and thunder today I would expect
wind NE here at the moment

ricky · Unread post by **ricky** » Wed 03/05/2006 07:56

Rainfall peaked at 6mm per minute here! definately a record for me

Manukau heads obs · Wed 03/05/2006 08:12

wow!

that is heavy
I have only recorded rain rate that high here before a few times only in the past

Manukau heads obs · Wed 03/05/2006 08:53

the inlaws, who are staying, said they watched lots of lightning out to east around midnight time...for nearly an hour...but no thunder heard...
and they did not wake me up!

spwill · Unread post by **spwill** » Wed 03/05/2006 11:26

Cloudy 19C,Dp16C.
Cu and Cb in our skies this morn.

Willoughby · Unread post by **Willoughby** » Wed 03/05/2006 11:47

Overcast with rain this morning and cold. Looks as though a clearance is on the way soon. Would be good to get some heating for convection like you guys are getting!

Manukau heads obs · Wed 03/05/2006 12:26

realy beafy CB showers moving through the area at the moment