Another Low Pressure system for the weekend 2-3 August

[Philip Duncan]

Severe Thunderstorm warning is a bit OTT?

Its a Severe Thunderstorm Watch Philip, not a warning. Two entirely different things. A watch indicates the chance of severe weather occuring, a warning means the severe weather is happening.

yes I realise that - was a typo. I've actually done some work with MetService to help them with a "Warning" system for the media.

[NZstorm]

I have never been a huge fan of the instability on this front. The warming aloft that has occured today means the lower level environment really needs to moisten up to yield CAPE. The dewpoint at Cape Reinga of 14C is a good sign but we need to see that type of moisture comin south. Whether a watch is required or not is just a matter of opinion. If storms develop there is certainly a good chance of damaging wind gusts.

[Manukau heads obs]

M/S have updated .....they think things are still on track:
http://www.metservice.co.nz/default/ind ... ormoutlook
I guess we will find out in 3 hours from now!
(I cant see anything other than a garden variety cold front crossing at this stage, but, the way the winter has been so far and with the strong jet stream .....you never know!)

[jamie]

ETA on the cold front?

Anyone care to throw in an educated guess?

[Manukau heads obs]

6pmish it has looked like looked all day long...for the active part of the front...
final clearence around 7:30pm, in time for the big game

[Manukau heads obs]

I have to go and milk some cows (relief milking) now...
certainly nothing serious showing on the rain radar at the moment out to the west....

[Myself]

I don't usually gloat

Yes you do.

[Weathermad]

Please can we stop the ' digs ' and ' jibes ' towards some members.

I want to be here to learn,observe and discuss the weather

[Cameo2]

Hear hear, it's getting irritating

Please can we stop the ' digs ' and ' jibes ' towards some members.

I want to be here to learn,observe and discuss the weather

[spike_01]

Steady rain here right now.. We have had enough this week already with wind.. Lots of damage.. 1st time I have seen the CBD shut on a work day.. Trees, roofs, fences damaged..

Power was off here for 14 hours, and some outlying areas wont have it on till Tuesday..

[Manukau heads obs]

I'm back.....
there are some cb's that look half decent on the rain radar on the back edge of the front....
the cb's associated with the low center look to have more potential me thinks...

one thing I think to watch is that this front could fire up alot more in the hauraki gulf and BOP....

ps, i wondered how you got on spike in levin!

[Philip Duncan]

Im with you on that second lot...have just updated my site to say thats where the thunder will be.

[David]

This front seems quite weak, in my opinion. Looking at the rain radar it looks like we won't have lots of rain as I originally though, perhaps only a few millimetres? Not sure why the thunderstorm outlook was so dramatic!

[Philip Duncan]

Is it just me or is that second band moving at over 120km/h towards us?

[Nev]

Interesting! Less than 1mm here so far but getting fairly blustery.

Thanks for the report Spike - didn't realise it was that bad down that way.

[NZ Thunderstorm Soc]

Will there be lightning flashing away overhead at the match at Eden Park this evening?
Might be worth watching, just in case


JohnGaul
NZTS

[Michael]

Aside from the score,Auckland can put on its usual expected show of bad weather

[Philip Duncan]

Will there be lightning flashing away overhead at the match at Eden Park this evening?
Might be worth watching, just in case


JohnGaul
NZTS

I am certain that it was this exact game last year that saw lightning during the Haka...was VERY cool

[Manukau heads obs]

front through here now
heavy rain with it ,(1.68mm/min)intensifying as it goes through.. (had that rain throttling up and down type, just when you thought it was finished it would get heavy again (good sign of instability!) ,wind gusty now.....
watch out Pukekohe...
looks to be another narrow squall line that will be through eden park around kick off time...

[Paul Mallinson]

This front seems quite weak, in my opinion. Looking at the rain radar it looks like we won't have lots of rain as I originally though, perhaps only a few millimetres? Not sure why the thunderstorm outlook was so dramatic!

Well, it's like this... You have a bunch of forecast fields from many models to evaluate. Today, there were many parameters that coincided (such as low level and upper level instability, storm motions and very strong wind shears across the front) and so one has to have the discipline to stick to the guidance and have some faith that things will work out based on theory. At midday today, what was happening out to our west fit some new 6am model guidance very well...

The most important factor today from thunderstorms was their potential to deliver damaging gusts. You get this possibility when you add the potential convective gust from the CB to their likely storm motions (which was 40 to 46kts). Having said that, I would rather not see anyone get hammered by the big gusts or a tornado, but when the forecast components point to that situation, you have to react to it. Now that it is dark, we could get a tornado somewhere and never get any confirmation.

Paul

[Manukau heads obs]

Paul, we got an active part of the front here....it was squally with heavy rain , and had a real unstable feel to the whole thing (rain changing in intensity all the time)
I see other intense rain narrow squall lines just to the SW of waiuku too in the last hour...so the back end of the front has become more active suddenly....
also, yes, the upper level winds were much stronger than the low level wind, and there was windsheer, with the upper level being NNW and the low level being NNE
just before it got dark I watched good updrafts occuring, with the strong winds above creating great venting...to me, the incoming squall line did look tornadic

[Philip Duncan]

Well, it's like this... You have a bunch of forecast fields from many models to evaluate. Today, there were many parameters that coincided (such as low level and upper level instability, storm motions and very strong wind shears across the front) and so one has to have the discipline to stick to the guidance and have some faith that things will work out based on theory. At midday today, what was happening out to our west fit some new 6am model guidance very well...

Paul

Do you use gut instinct a lot in an area like this? For example, all the science seemed to point towards severe storms...but the gut instinct this afternoon just "felt" like that was wrong. As a scientist do you have inner arguments when science goes against your gut?

Phil.

[waterboy]

Is any of this going to hit us in the south island?

[Nev]

Here's MetService's 6pm mean-wind obs for the Hauraki Gulf / Waitemata Harbour

Channel Island - 87 km/h
Tiritiri Lighthouse - 61 km/h
Bean Rock - 46 km/h
Passage Rock - 52 km/h

[NZ Thunderstorm Soc]

Is any of this going to hit us in the south island?

No, sadly

...but as the people of Marlborough and North Canterbury would say...
... thank goodness

JohnGaul
NZTS