General December Weather
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For today's weather discussion head to: New Zealand Weather & Climate
These topics are a read-only archive and may be subject to out-of-date information.
For today's weather discussion head to: New Zealand Weather & Climate
- NZstorm
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General December Weather
Looks like the first day of summer will be coolish with that SW. But a gradual warm up coming with gfs indicating hot temps possible later in the first week of December.
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Re: December Weather
some places though are hot in a SW wind, if there is good clearing skies over the land
e.g BOP
e.g BOP
- David
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Re: December Weather
Perhaps some rain from a subtropical low in the first week. Would be good to get another burst of rain soon.
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- NZstorm
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Re: December Weather
Yes, looks like a potential heavy rainfall event for northern areas mid week. Subtropical low will bring moist air. If last nights gfs run is verified then falls exceeding 200mm likely in the Coromandel and Bay of Plenty.
Auckland gets rain from later Tuesday.
Auckland gets rain from later Tuesday.
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Re: December Weather
The very moist air will spread across much of NZ.
dewpoint chart for later in the week
dewpoint chart for later in the week
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- Storm Struck
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Re: December Weather
Even looking good for inland thunderstorms for Marlborough/Canterbury Thursday with the mix of the air from the low to the north and another incoming low from the south tasman.
An interesting mix between those southern and northern lows attacking the country could make for an interesting month.
An interesting mix between those southern and northern lows attacking the country could make for an interesting month.
Canterbury, home of good rugby and severe storms
- Storm Struck
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Re: December Weather
Weak unstable skies on a southerly wind change just now, some large drops of rain and the odd intermixed small hail stone around 5mm in diameter so pea size.
Might be a weak storm for Kaikoura in an hour or so
Might be a weak storm for Kaikoura in an hour or so
Canterbury, home of good rugby and severe storms
- NZstorm
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Re: December Weather
LIfted index chart for Thursday.
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- Nev
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Re: December Weather
A bit similar to the southerly change that came over Oamaru on the Saturday of Show WE, there Jase.Storm Struck wrote:Weak unstable skies on a southerly wind change just now, some large drops of rain and the odd intermixed small hail stone around 5mm in diameter so pea size.
Might be a weak storm for Kaikoura in an hour or so
Cold blustery wind and a few heavy drops falling from what scattered cloud there was.
JohnGaul
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- NZstorm
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Re: December Weather
Models still indicating good thunderstorm potential over the North Island on Thursday.
The surface NE will be a key wind and if that eventuates as modeled watch out western North Island!
Thunder also possible over eastern high ground of the South Island on Thursday.
The surface NE will be a key wind and if that eventuates as modeled watch out western North Island!
Thunder also possible over eastern high ground of the South Island on Thursday.
- Tornado Tim
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Re: December Weather
There is better mid level moisture forecast in the lower half of the north island. The upper air is forecast to be too dry in the upper north Island, even dry enough for the saturated adiabatic lapse rate to wobble slightly!NZstorm wrote:Models still indicating good thunderstorm potential over the North Island on Thursday.
The surface NE will be a key wind and if that eventuates as modeled watch out western North Island!
The cap is not expected to be there, so I am not entirely optimistic for this setup, but then again forecasts change.....
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- NZstorm
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Re: December Weather
For thunderstorms you need moisture in the lowest 100-150mb (surface moisture). Dry air in the mid levels is considered favourable for storms. You only need mid level moisture for elevated storms.Tornado Tim wrote:There is better mid level moisture forecast in the lower half of the north island. The upper air is forecast to be too dry in the upper north Island, even dry enough for the saturated adiabatic lapse rate to wobble slightly!NZstorm wrote:Models still indicating good thunderstorm potential over the North Island on Thursday.
The surface NE will be a key wind and if that eventuates as modeled watch out western North Island!
The cap is not expected to be there, so I am not entirely optimistic for this setup, but then again forecasts change.....
The looming problem for Thursday is the low clouds in a saturated NE flow. Its a case of seeing how bad the cloud situation is on the day. We need 24-25C to get the CAPE. If storms can develop they will move quickly SE but the upper flow/shear will help energize them.
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Re: December Weather
wow, that rain had really developed and pushed south fast over the far north
might get all the way to auckland by the late afternoon?
might get all the way to auckland by the late afternoon?
- Tornado Tim
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Re: December Weather
I dont see how very dry air air is favourable for storm development, especially when the layer extends all the way to the trop. Strong lift can compensate for this, but this by no means does it rule out that the air won't mix out. The 26th of November was a prime example where the SFC moisture remained moist but the upper air mixed out, resulting in more showers than thundershowers.NZstorm wrote: For thunderstorms you need moisture in the lowest 100-150mb (surface moisture). Dry air in the mid levels is considered favourable for storms. You only need mid level moisture for elevated storms.
Pockets of dry air are very common especially in caps and yes in those cases I would think that they enhance the convection, but because of temp inversion not the dry air.
For the interest of clarification: 100-150mb is the upper atmosphere not the SFC.
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- David
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Re: December Weather
Just to clarify the clarificationTornado Tim wrote: For the interest of clarification: 100-150mb is the upper atmosphere not the SFC.
Steven said the lowest 100-150mb, i.e the range from sea-level pressure up the height which corresponds to 100-150mb below the SLP.
- Tornado Tim
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Re: December Weather
Oh woops, I read too quickly........ hahaDavid wrote: Steven said the lowest 100-150mb
Mostly cloudy here with a mild 19.9 and a light northerly.
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- Richard
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Re: December Weather
It was a cooker of a day here today with 33deg,cooled now to 27deg with a southerly breeze.
- Richard
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Re: December Weather
Something for me to look forward to on Wednesday being in the middle of this moderate risk area,where i am is an area where two converging winds often meet,a NE /easterly over the northern Amuri plains meeting a southerly from the Waipara plains,certainly this sea breeze convergence has produced some memorable storms in the past.Valid to: Midnight Wednesday 4 Dec 2013
Issued at: 10:30am Tuesday 3 Dec 2013
A front is expected to move slowly south over the Tasman Sea just west of the North Island. There is a low risk of elevated thunderstorms over the North Island from about Auckland northwards.
Over northern Canterbury, sea-breeze convergence and daytime heating is likely to lead to showers with a moderate risk of thunderstorms developing in the afternoon and evening. Any thunderstorms that form will be slow-moving and may have rainfall rates of 10 to 25mm per hour.
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Re: December Weather
Waiting with interest with your reports on this as you are right in the area
Last edited by NZ Thunderstorm Soc on Tue 03/12/2013 22:18, edited 1 time in total.
JohnGaul
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Re: December Weather
Thursday looks good for you Richard aswell.
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- Richard
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- Richard
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Re: December Weather
yep,that arrow is point right to my placeNZ Thunderstorm Soc wrote:Waiting with interest with you reports on this as you are right in the area
- NZstorm
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Re: December Weather
Dry mid level air is said to enhance convective buoyancy. I remember reading an explanation for it but can't quite remember how it goes.Tornado Tim wrote:I dont see how very dry air air is favourable for storm development, especially when the layer extends all the way to the trop. Strong lift can compensate for this, but this by no means does it rule out that the air won't mix out. The 26th of November was a prime example where the SFC moisture remained moist but the upper air mixed out, resulting in more showers than thundershowers.NZstorm wrote: For thunderstorms you need moisture in the lowest 100-150mb (surface moisture). Dry air in the mid levels is considered favourable for storms. You only need mid level moisture for elevated storms.
Pockets of dry air are very common especially in caps and yes in those cases I would think that they enhance the convection, but because of temp inversion not the dry air.
The regions of the world that get severe thunderstorms essentially have dry upper air masses from the desert regions with tropical surface moisture under running. USA Midwest plains is the best example but eastern Australia is also a case of this.
- Tornado Tim
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Re: December Weather
Yea I do see that storms do develop in a dry upper atmosphere, but I think that lift in those case's is much stronger than what we get here in NZ.NZstorm wrote: The regions of the world that get severe thunderstorms essentially have dry upper air masses from the desert regions with tropical surface moisture under running. USA Midwest plains is the best example but eastern Australia is also a case of this.
The way I see it, dry air surrounding moist air containing water vapour (in liquid state) acts like a sponge and helps mix and transfer the water vapour from one body to another, depleting the saturated body of air. However from what I understand this doesn't happen as quickly(if at all) when water vapour is frozen.
Fluid dynamics and Meteorology I find is soo interesting, Id be very keen to read that paper. I love learning these things. If you dont find it Steven don't worry I'll do a bit googling.......
Perhaps I should have done Meteorology instead of I.T (Web Dev).....
Oh hang on..... Metservice (NZ).....Shift Work?!!!
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