Timing and Thunderstorms

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Timing and Thunderstorms

Unread post by NZ Thunderstorm Soc »

Depending on timing, I think that this week could be the best bet for this month for thunderstorms here in Canterbury for this month :)
This morning we had a wonderful display of st castellatus ( I refuse to use the other latin word to describe as it sounds rude, just like the 7th planet in our solar system :mrgreen: )
...buttock course .. castellatus clouds means that usually in the summer time there is a good chance of thunderstorm development within 24 hours.
That is the rule.
Here in Canterbury we have an exception to the rule...
timing.
Tonight's front shoud come through around midnight.
I recorded a 24C maximum today today...and even though I rode home form work on my bike in a NW. I was pleasantly rewarded to find that closer to home a slight NE greeted my face. This was about 3pm.
If the front had of been sooner, there could of been a chance of a 'clap or two' \:D/

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Unread post by NZstorm »

Yes, but i think there is one factor far more important than timing(time of day). And that is time of year. Really need the insolation to get thermals rising and get decent sea breeze activity. Labour weekend onward as you will be aware. But late summer(Feb/Mar) tend to be dud months for thunder in the east of the South Island because the upper air tends to be a lot warmer by then. As I have suggested in an earlier post, cold upper air is the usual form of instability in the east of the South Island rather than humid conditions on the surface, which can be the cause of instability from Waikato northward.
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Unread post by NZ Thunderstorm Soc »

Tonight wont be very good anyway as we are having very strong NW winds over us at the moment :(

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Unread post by 03Stormchaser »

I wouldnt have even given any thought to any activety tonight, im almost surprized any of you are!! With such a Nor'wester even a light E wind would do much so far out of the southerly to hit.

Thurs with any luck would be a better bet :lol:
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Unread post by spwill »

Thurs looks a chance for Thunder over the SouthIsland and perhaps over the NorthIsland on Friday as a Trough moves across.
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Unread post by Thunder »

Yes John, I noticed the NE spring up to:

http://www.weatherforum.org.nz/forum/vi ... 01&start=0

3rd to last post on the page above. The dewpoint went up to 4C but then went down again as the NW established itslef again and which it currently is now.

I didn't notice the st castellatus this morning but was it to the east or over B'sP? On the earlier sat pics this morning some interesting cloud brushed passed the coast with some ok rain on the radar and maybe small hail out at sea.

Landcare 5:43am:

http://satellite.landcareresearch.co.nz ... d21094.txt

Landcare 10:27am:

http://satellite.landcareresearch.co.nz ... d21094.txt

But yes John, this week looks good at some point for maybe a thunderstorm, there'll be a thunderstorm somewhere that's for sure! At the moment my forecasting techniques narrow it down to somewhere in the South Island :D

We had a thunderstorm on Feb 14th!! earlier this year ;)

http://www.escootersnz.com/fastpage/fpe ... 0/menuid/3
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Unread post by NZstorm »

We had a thunderstorm on Feb 14th!! earlier this year
Considering February is Canterburys hottest month, you would think it was the most thundery but October to January are more thundery months. :)
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Unread post by Thunder »

Yes, I agree with you there. I guess there's always the chance thunderstorms can occur outside the typical season but yeah, Oct to Jan sounds good for the Canterbury thunderstorm season.
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Unread post by 03Stormchaser »

Aaron thursday is looking like the day this week,

http://metservice.com/default/index.php ... key=205505

Fingers crossed :)

Southerly came thru last night around midnight, gust up 65kmph and no rain. Went back NW for a while, now its calm as can be.
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Unread post by Thunder »

That Southerly (the rain part of it) looks as if it just brushed over B'sP, looks like some ok rain fell continuing out to sea from B'sP.

Do you mean Friday Stephen? If so yes, there's meant to be a pool of cold air of about -29 (500mb) brush just over Chch on Friday around or just after lunch, so depending on the surface temp and lower level moisture we could have something here! 8)
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Unread post by wxgirl »

Aaron, i can see some good clouds brewing out the end of the Peninsula now.
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Unread post by wxgirl »

oops - they're gone now
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Unread post by tich »

I noticed some virga to the southeast this morning, but due to the southwest nature of the flow, it doesn't like like heading in the direction of the city. (cloud to the southwest looks more stable)
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Unread post by tich »

Most cloud has cleared from Chch, with just abit to the southeast. But the gusty southerly (which sprung up late morning) is persisting and keeping the temperatures down. I believe the wind's been an even stronger southwesterly about coastal Southland and Otago, with warnings for gusts up to 130kph. :twisted:
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Unread post by 03Stormchaser »

Today could be a wee bit interesting with easterlies forecasted and a low sitting right on top, Probably not thunderous but interesting all the same.

temperture, dew point on the rise, so is wind speed E. Pressure on the drop 998 hPa
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Unread post by tich »

Today could be a wee bit interesting with easterlies forecasted and a low sitting right on top, Probably not thunderous but interesting all the same.
A warm front is supposed to be crossing the South island this morning. We've had drizzle/light rain earlier this morning in Chch, but it should clear and probably become warm if the flow is west or northwest behind this front. A cold front should follow, reaching the far south later today. So I don't think there'll be thunder here today, but possibly on the inland high country.

Looks like a warm advection snowfall overnight and early this morning in the inland valleys and basins in the South Island high country. Not much of a time gap between the departure of yesterday's cold southerly and the incoming front/trough.
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Unread post by 03Stormchaser »

I got my days mucked up low over us tomorrow, Tony whats ur thoughts on thunder tomorrow?
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Unread post by TonyT »

Pretty unlikely I'd say. But what do i know :)
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Unread post by dogmelon »

the most critical thing for thunderstorm development is to live somewhere where they actually happen.
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Unread post by TonyT »

I've just had a look at some of the 0Z progs and the instability does seem to be there for tomorow, more so than any time in the last 10 days. Its the trigger which might be missing - if the wind change comes through overnight as forecast and the skies stay fairly cloudy then TS development in Canty looks farily unlikely. But if there is enough of a dry zone to allow clear skies in the morning followed by increasing moisture and winds in the afternoon (which is one interpretation of the model data) then it could be a goer with the instability which is forecast.
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Unread post by Thunder »

What are these models you look at? Are they secret forecasters only models 8), or are they public ones? NOGAPS, GFS? is it one of those?.......ECMWF maybe?

Thanks ;)
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Unread post by TonyT »

Australian LAPS, plus the GFS.
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Unread post by NZ Thunderstorm Soc »

NZstorm wrote:Yes, but i think there is one factor far more important than timing(time of day). And that is time of year. Really need the insolation to get thermals rising and get decent sea breeze activity. Labour weekend onward as you will be aware. But late summer(Feb/Mar) tend to be dud months for thunder in the east of the South Island because the upper air tends to be a lot warmer by then. As I have suggested in an earlier post, cold upper air is the usual form of instability in the east of the South Island rather than humid conditions on the surface, which can be the cause of instability from Waikato northward.
Yes well Steven.
I was refering to the first sentence of my statement.
For this time of year, timing is a major factor.
As we become warmer and the colder southerlies develop there is an excellent chance of thunderstorm development especially here in Canterbury, as long as the skies are clear.
The timing factor may become lesser in the warmer summer months but then now with the cooler summers we are getting, there is a lesser chance of thunderstorm development because there is is not that stimulation, mainly because of increase cloud cover, and to the fact that cold fronts from the south have to go over in the afternoon to actually produce a thunderstorm. It dosen't happen in the air behind it because the wind has gone around the the south.
Thre Prognosis for a good thunderstorm in Canterbury is that is has to be of these factors.
1: A good NE onshore sea-breeze, ENE the better
2: Lots of sunshine prior to the front arriving
3: Low barometer = 1000hPa, or lower the better
4: ENE "Hanging in there" until taken over by the southerly
5: The actual front/convergence line moving across about 3pm ish? this depending on the how active the front is

Cheers :)
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Unread post by 03Stormchaser »

Nice temp and Dew point this morning, 8 C and dew point of 7 C With Easterlies :)
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Unread post by NZstorm »

Temperature 16c, dewpoint 14C here in Auckland this morning. Some sunshine would lift the temperature to 20C today but skies look solid 8/8 stratocumulus with westerly15kts.

Upper air looks a bit unstable over South island today but as Tony alerted to in a previous post, there is no trigger. Surface temps will stay to cool.
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