General July Weather
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For today's weather discussion head to: New Zealand Weather & Climate
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General July Weather
2 cents worth. Significant cold signals are appearing for July.
- Sister lower stratospheric vortex's appearing on all models in early July.
- Coupling down effect then distorts and weakens the tropospheric polar vortex structure. Polar jet will be cut loose into the mid latitudes.
- SAM (AAO) index is now falling off the cliff on most GEFS ensemble members. Some near negative 4 in mid July.
Rug up
- Sister lower stratospheric vortex's appearing on all models in early July.
- Coupling down effect then distorts and weakens the tropospheric polar vortex structure. Polar jet will be cut loose into the mid latitudes.
- SAM (AAO) index is now falling off the cliff on most GEFS ensemble members. Some near negative 4 in mid July.
Rug up
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Re: General July Weather
Hadn't seen that but there were some signs the other day of the vortex starting to distort somewhat. Might look and post in the strat thread later. If the tropospheric modelling is looking at cold signals in July as a result that would be a reasonably short lag time?
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Re: General July Weather
The polar vortex is displaced around 2 - 5 July. You will see that GFS 18Z is now incorporating a significant propagating Rossby wave into the NZ region medium term. At the moment it's a signal, finer details still unknown.Chris W wrote: ↑Mon 29/06/2020 14:46 Hadn't seen that but there were some signs the other day of the vortex starting to distort somewhat. Might look and post in the strat thread later. If the tropospheric modelling is looking at cold signals in July as a result that would be a reasonably short lag time?
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Re: General July Weather
The weekend of July 11/12 is starting to shape up for a significant cold impact. Time will tell if its a snow to low levels job or too light on the moisture. The following week will probably see -10deg or colder frosts for the inland South Island under intense high pressure.
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Re: General July Weather
Quite a lot of rain around before that as well, doesn't look settled early-mid month at least.
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Re: General July Weather
Ruapehu district gets its first snow fall of the year tomorrow into Thursday.
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Re: General July Weather
Thanks Tony thought that isn't like you to talk about events so far out, is there something in the models that is leading you to think that it is a possibility? Negative AAO combined with a favourable phase of the MJO perhaps?TonyT wrote: ↑Mon 29/06/2020 21:11 The weekend of July 11/12 is starting to shape up for a significant cold impact. Time will tell if its a snow to low levels job or too light on the moisture. The following week will probably see -10deg or colder frosts for the inland South Island under intense high pressure.
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Re: General July Weather
Well I have been quite vague, deliberately!Bradley wrote: ↑Tue 30/06/2020 09:46Thanks Tony thought that isn't like you to talk about events so far out, is there something in the models that is leading you to think that it is a possibility? Negative AAO combined with a favourable phase of the MJO perhaps?TonyT wrote: ↑Mon 29/06/2020 21:11 The weekend of July 11/12 is starting to shape up for a significant cold impact. Time will tell if its a snow to low levels job or too light on the moisture. The following week will probably see -10deg or colder frosts for the inland South Island under intense high pressure.
MJO is spiking into 2 and expected to be declining in 3 by then. So that is supportive of the idea (well lets put it this way, you wouldn't put money on a mild N airflow with that MJO pattern). But really its just something which has been in the longer range modelling for some time (so consistency is a factor) and backed by the posts above - in a time when meridional flow is dominant over zonal and the polar vortex is wobbly (not unusual) then a leak of cold air onto the country is likely, but when?. Those dates just fit with what the longer term modelling is saying.
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Re: General July Weather
The signal for cold, stormy weather into July is pretty strong now, and the SAM/AAO is tanking fast! I am not sure that even the super ridge can halt this
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Re: General July Weather
I'm not convinced. The anticyclone which will settle into the cold air after 11th/12th could be hard to budge till the end of the month.
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Re: General July Weather
I hope you are right Tony, planning a school hols trip up the West coast that week
Christchurch Rocks
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Re: General July Weather
Guess I'm talking mostly til the middle of the month. I haven't studied the stratosphere as much lately (model fatigue and vortex looked pretty darn strong) so I wasn't sure what would happen later in the month. Guessing the vortex distortion could come into play late-month?
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Re: General June Weather
only 8.7c with a fresh wind blowing
(i.e so windchill makes it much colder)
thats a big change of 12c lows we were getting
(i.e so windchill makes it much colder)
thats a big change of 12c lows we were getting
Brian Hamilton
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Re: General July Weather
Coldest morning of the year in Howick so far, 3.3C. Was noticeably warmer than that arriving in the city about 7.30, felt more like 8C.
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Re: General June Weather
woa I see Ricky got down to 5.6c with still a bit of a breeze
will be a shock for aucklanders this morning
will be a shock for aucklanders this morning
Brian Hamilton
www.weather-display.com/windy/gb/grahamsbeach.htm
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Re: General June Weather
even worse you are currently at 3.4c David
thats colder than Invercargil is at the moment
thats colder than Invercargil is at the moment
Brian Hamilton
www.weather-display.com/windy/gb/grahamsbeach.htm
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Re: General July Weather
Met Service have a heavy snow warning out for the central North Island with snow to 500m. I can see the SH1 Desert Road closing by the end of the day.
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Re: General July Weather
1.4mm overnight, not looking like much more than that from this system. A light dusting around the hills which looks about what the MetS had forecast
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Re: General July Weather
Snow to approx 7-800m on the Seaward Kaikouras, quite a lot of it in the gullies at least.
Biting wind today in Kaikoura, feels like temperature of 1C is accurate.
Biting wind today in Kaikoura, feels like temperature of 1C is accurate.
Last edited by Chris W on Wed 01/07/2020 15:22, edited 1 time in total.
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Re: General July Weather
May have been my eyes deceiving me but I believe I just spotted some snow over towards banks peninsula way
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Re: General July Weather
There was a dusting on Mt Herbert yesterday, and it's even colder today so almost certainly some. (non-settling flurries reported on Port hills this morning)
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Re: General July Weather
Cold day here to start off the second half of 2020.
A partly cloudy day with only a trace in the rain-gauge, probably from a few spits overnight.
South-westerly winds more so towards the coast, where you see those cold rain showers, out to sea, moving north or NE towards ChCh/BP.
8.7C for today.
A partly cloudy day with only a trace in the rain-gauge, probably from a few spits overnight.
South-westerly winds more so towards the coast, where you see those cold rain showers, out to sea, moving north or NE towards ChCh/BP.
8.7C for today.
JohnGaul
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Re: General July Weather
Nothing on Port Hills tonight, nor over the Harbour below the cloud base on Herbert ie 800-900m. Maybe some up there overnight
Christchurch Rocks
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Re: General July Weather
cold heavy rain showers going through the auckland area!
5c here with rain
i.e cold air trapped at the surface with rain showers going over the top of that
we dont get it much colder than that!
5c here with rain
i.e cold air trapped at the surface with rain showers going over the top of that
we dont get it much colder than that!
Brian Hamilton
www.weather-display.com/windy/gb/grahamsbeach.htm
www.weather-display.com/windy/gb/grahamsbeach.htm