Paul Mallinson wrote:
Those are my thoughts for now. It really comes down to instability and windshear.
Paul
Thanks for those comments Paul, I guess what I was driving at was to what extent you think the strength of the surface flow (and hence its tublulence) might negate the ability of the instability and windshear to form tornadoes in the first place, and whether in fact conditions like this might be more prone to produce microburst type destructive winds rather than tightly rotating "twisters"?
Tony,
I'm not sure that I really am expert enough to fully answer your question. What I would say 'though is that given the setup previously discussed (instability, strong shears etc, etc) occurring over the land, then there will be interactions with the terrain that will enhance the conditions for tornado formation and there will be areas that negate it. I think it is fair to say that microbursts and strong straight line outflow winds (gust fronts etc) will all occur with thunderstorms given the right conditions (i.e. dry layers aloft for microbursts and well developed rain shafts for gust fronts) whether tornadoes form or not.
Just been speaking to my counterpart in Dunedin...they are apparently getting pummeled down there by the cold snap.
Still sunny, breezy and mild in ChCh but I'm expecting big action later on!
I can see cloud building up to the southwest and 2pm radar shows precipitation just to south of Timaru.
I recall Paul mentioned a situation in Canterbury when, after a cold southerly change has replaced a northwesterly, undercutting can occur leading to intensification of rain and developing a freezing layer which reduces snow level often to below what is forecast. Happened several times last year (the big snow of June being an extreme example); could it happen tonight?
Just been speaking to my counterpart in Dunedin...they are apparently getting pummeled down there by the cold snap.
Still sunny, breezy and mild in ChCh but I'm expecting big action later on!
I can see cloud building up to the southwest and 2pm radar shows precipitation just to south of Timaru.
I recall Paul mentioned a situation in Canterbury when, after a cold southerly change has replaced a northwesterly, undercutting can occur leading to intensification of rain and developing a freezing layer which reduces snow level often to below what is forecast. Happened several times last year (the big snow of June being an extreme example); could it happen tonight?
Have a look at the run for the 12 pm - 2 pm radars...is that the effect you are seeing?...and yes, the clouds off to the south and southwest look a bit menacing...bubbling up nicely, and yet only like 23% humidity outside??? ...and they are coming in quick...will be interesting to see the next set of radar/sat loops...
Last edited by gllitz on Wed 17/10/2007 15:06, edited 1 time in total.
Well I'm struggling to see any activity near Auckland or any significant rain this evening for that matter. Hopefully I'm wrong about this? Been very warm this afternoon.
Paul Mallinson wrote:Tony,
I'm not sure that I really am expert enough to fully answer your question. What I would say 'though is that given the setup previously discussed (instability, strong shears etc, etc) occurring over the land, then there will be interactions with the terrain that will enhance the conditions for tornado formation and there will be areas that negate it. I think it is fair to say that microbursts and strong straight line outflow winds (gust fronts etc) will all occur with thunderstorms given the right conditions (i.e. dry layers aloft for microbursts and well developed rain shafts for gust fronts) whether tornadoes form or not.
Oh yes it loaded - looking good if thats whats on the way this evening
Strange - I never really thought NW had much effect on Auckland temperature because it comes off the sea, but the last 2 northwest days this month have been around 22C.
First wave came through about 3:30. Quite gusty winds, but not much action.. "Apparently" thunder heard in Lyttelton, but nothing showing on tracker. Photo below.. lovely AMI stadium at bottom, formerly Jade stadium, formerly Lancaster park... with the empty trophy cabinet <sigh>!
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Last edited by Andrew Massie on Wed 17/10/2007 16:42, edited 1 time in total.
front came through here at around 1.30 with some pretty heavy rain and a 5-6c drop. some more rain coming in no so i took some photo's just for the sake of it lol. no thunder here today unfortunatly
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this just came through the area. shame it didnt produce anything interesting.
But wet further south in Hawkes Bay - flooding near Dannevirke. Seems suprising considering the airflow is west/northwest up there today. (Ruahines should provide shelter)
Cloudy in Chch, though no rain yet. But probably not far off, looking at 7pm radar.
this just came through the area. shame it didnt produce anything interesting.
But wet further south in Hawkes Bay - flooding near Dannevirke. Seems suprising considering the airflow is west/northwest up there today. (Ruahines should provide shelter)
Cloudy in Chch, though no rain yet. But probably not far off, looking at 7pm radar.
Indeed, the 8 pm radar looks even betterer!! (Note the distinct red bits!! )
Must be snowing on the higher parts of inland Otago/Caterbury tonight, certainly down to about 500m anyway.
Tomorrow Thursday could be an interesting day. Looking like BOP/Waikato/Auckland/Northland could get some thunder/hail. I'm less interested in the 'coldie cbs' in the Tasman Sea but more hopeful that daytime heating may trigger a freash crop of cb's over land. Main problem tomorrow is the cooler drier air knocking on our door and cloud cover.
Inny Binny wrote:I don't get it - it's been raining here steadily for the last couple of hours and yet nothing at all has registered on Jeff's station.
Hi Inny
It's only lightly raining outside, concrete is not really wet so less then 0.2mm here so far. Probably clock up 0.2mm in the next 30 mins or so if it keeps up.
...and they are coming in quick...will be interesting to see the next set of radar/sat loops... 
(Note the distinct red bits!! 
)