Tstorm Canterbury 14-09-07

[03Stormchaser]

I see metservie have thunderstorm warning out for Cnnaterbury today:

http://www.metservice.co.nz/default/ind ... ormoutlook

A complex but rather weak southerly change (may have two wind shifts) will move through Canterbury this afternoon and up the Kaikoura coast this evening. The associated low level wind convergence together with a pool of cold air aloft and afternoon heating gives rise to a moderate risk of a few thunderstorms. These are likely to develop in central parts early in the afternoon and then drift into north Canterbury later in the afternoon and then die away. Thunderstorms are not likely on the change as it moves up the Kaikoura Coast this evening.

Elsewhere, no thunderstorms or significant convection is expected.

Im confused as to why this is a mod risk? I will be surprised if we do get anything decent outta this, upper air just to warm.

[Razor]

Perhaps bet is on the second wind shift then?

[Lawrence]

Quite warm in the city this morning ,but gone cool now over the last 20-30 minutes.Can't see anything developing at this rate.M/S did state it was a weak southerly change but at this rate I can't see us getting that afternoon heating we need

[dogmelon]

Let us see what happens. Perhaps Paul Mallinson can give us some of his thoughts. I like reading what he has to say.

[Paul Mallinson]

We went for a moderate risk today since the forcing is not likely to be the strongest. This is the first classic setup in Canterbury of the new heating season. Temps aloft should be about -24C or -25C with an upper trough going over - is not really cold, but its all relative. If there is sufficient moisture at the surface (Christchurch is now T=18 and Td=8, I was looking for 17/7) and there is the low level trigger (sfc convergence) then hopefully things should fire. Today the surface convergence is weakish, so we will have to wait and see!

Cheers

Paul

[dogmelon]

Awesome Paul, you delivered! Thank you.
Is an upper trough some sort of void that passes over where the air pressure is low? and so buoyancy of the air underneath is enhanced so it can bubble up into the void?
Keep up the good work with the thunderstorm forecasting.

[NZstorm]

Temps aloft should be about -24C or -25C

I don't think those 500mb temps will be cold enough for thunderstorms at this time year in Canterbury.

[Storm Struck]

Horray forum is working again .
I think we will have to wait and see because it is really muggy out there at the moment warm on 19C and a light southerly which isnt affecting the temperature at all.
Some isolated showers inland at the moment with some weakish CU going up in places a start lets hope the finish is even better .
That mamamtus last night was incredible, the best ive seen in a long time a real back end of a thunderstorm look with the sun setting on it.
Cheers
Jason.

[Lawrence]

Warmed up again now here in CBD, 20.0C with a bit of a cool breeze,baro 1013mb.

[Paul Mallinson]

Some heavy showers now coming off the foothills northwest of Ashburton. Precip tops above 8 to 9km and small hail likely.

Paul

[Storm Struck]

I see that paul interesting wind has swung breezy Easterly here so should go well up against the next wind change hopefully .
Cheers
Jason.

[Andrew Massie]

Great comments, Paul, I have to admit, it's great having someone like you on the forum.. I'm always learning from you!
Keeping watch.. View down south isn't much at the mo..

[tich]

Looks like virga over Chch this afternoon, rather than thunderstorm clouds. Recent radar shows nothing near us - most action in the foothills.

[Paul Mallinson]

Strong cell north-nrthwest of Ashburton with several lightning strikes now. Small hail likely associated.

Paul

[spwill]

Very good surface conditions for Sep in Canterbury today. Chch 19C with a dewpoint of 8C I think Met Service were going for 16C.

[dogmelon]

Metservice got their thunderstorm prediction right. Good work. The weather forecasts are always correct anyway.

[Andrew Massie]

N-NW Ashburton? Are you sure?

[spwill]

Current cell is moving east but may propogate NE toward Chch

[Paul Mallinson]

The direction of the strikes on your image is good but the range is wrong. The thunderstorm is north north of Ashburton and west south west of CHCH.

Paul

[dogmelon]

Is there something special about the area around Ashburton that makes thunderstorms want to start there? Time and again I see storms develop down in that direction every spring/summer.
Any ideas?

[Storm Struck]

Good to see things are starting to fire, very light E here sun coming out now so some welcome heating .
Cheers
Jason.

[Andrew Massie]

TonyT told me there's a hill or range that heats really well, generating the convection to start the process. I think it's near Mt. Somers township.

[Lawrence]

Not getting any strikes near Ashburton as I can see on the NET,using Steven Grahams site for tracking.

[Gary McConnochie]

Looking very dark to the south now. Looks very promising.

[Razor]

Yup things looking like lining up nicely at the moment for sure...fingers crossed for my first storm since coming home!!