General May Weather

[NZ Thunderstorm Soc]

Meteotsunami (or meteorological tsunami) is a proper meteorological/oceanic term though…

....bugger

[melja]

Models are by design limited to what the programmers of them think they know. They are not artificially intelligent. Most of the time they work well because the atmosphere is working within well known (I was tempted to write "understood" but I will stick with "known") parameters and processes. When the atmosphere gets to the fringes of what the physics thinks ought to happen, weirdness is the result. There are a number of factors which are only going to make this worse in the next few years in my opinion (geomagnetic changes, changing upper atmospheric dynamics, deep solar minimum to name a few).

I see a certain FB page is using this information to inform there avid followers, not sure it will mean much to Jo average though.

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[Dean.]

A week or so of westerlies on the horizon.A mild day today

[talbotmj15]

Have now moved on. Lets stick to the weather. I see there is still alot of uncertainty in the models next week. I think CT might be correct with a surprise next week.

[melja]

Don't think I mentioned names or copy and paste and Dean's post has since been edited so no problems here.
But go for your life.

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[Dean.]

Yes there was no copy and paste...will move on

[Cyclone Tracy]

Moderate WSW and 18.7c here. Starting to feel a bit more like late Autumn.

SSW event at the moment seems to be going to script. Check list has lots of ticks, time will tell on the true impact zone but the polar vortex displacement is well and truly underway. GFS showing the vertically propagating 500 hPa Rossby wave ballooning around NZ currently, which will have an influence on any polar jet displacement or fracture, especially around mountain ranges and warmish sea surface temperatures.

I'm quite interested on whether the polar jet is split in 2 as it gets into the upper cold core cyclone sequence towards the end of the week. Some models are starting to hint this by next weekend.... the result could be the interaction of poleward-flowing divergent limbs of the subtropical and fractured polar jet, spawning a nasty surface cut off low east of the SI. IMO, this is one of the main reasons why the big models are so erratic and occasionally show a cut off low. For now, I’ll keep chewing the popcorn and watch each run with gaining interest

[TonyT]

Moderate WSW and 18.7c here. Starting to feel a bit more like late Autumn.

SSW event at the moment seems to be going to script. Check list has lots of ticks, time will tell on the true impact zone but the polar vortex displacement is well and truly underway. GFS showing the vertically propagating 500 hPa Rossby wave ballooning around NZ currently, which will have an influence on any polar jet displacement or fracture, especially around mountain ranges and warmish sea surface temperatures.

I'm quite interested on whether the polar jet is split in 2 as it gets into the upper cold core cyclone sequence towards the end of the week. Some models are starting to hint this by next weekend.... the result could be the interaction of poleward-flowing divergent limbs of the subtropical and fractured polar jet, spawning a nasty surface cut off low east of the SI. IMO, this is one of the main reasons why the big models are so erratic and occasionally show a cut off low. For now, I’ll keep chewing the popcorn and watch each run with gaining interest

Longer term data has hinted at a period of on-shore airflow for the east coast around QB weekend ahead of incoming high pressure. While I dont really go for the deep cut off low idea, some sort of low pressure between the mainland and the Chathams is probably coming.

[Avalanche]

Moderate WSW and 18.7c here. Starting to feel a bit more like late Autumn.

SSW event at the moment seems to be going to script. Check list has lots of ticks, time will tell on the true impact zone but the polar vortex displacement is well and truly underway. GFS showing the vertically propagating 500 hPa Rossby wave ballooning around NZ currently, which will have an influence on any polar jet displacement or fracture, especially around mountain ranges and warmish sea surface temperatures.

I'm quite interested on whether the polar jet is split in 2 as it gets into the upper cold core cyclone sequence towards the end of the week. Some models are starting to hint this by next weekend.... the result could be the interaction of poleward-flowing divergent limbs of the subtropical and fractured polar jet, spawning a nasty surface cut off low east of the SI. IMO, this is one of the main reasons why the big models are so erratic and occasionally show a cut off low. For now, I’ll keep chewing the popcorn and watch each run with gaining interest

Honestly CT and Tony T, really appreciate your weather knowledge to this coming southwesterly weather event. I still have many things to learn about how the weather works and what the numbers all mean. But your ongoing input recently has been really awesome. Thanks so much i look forward to your updates and get excited when i see you have posted further details, Its a highlight for me to read thats for sure. Thanks again

[Iloveweather]

Moderate WSW and 18.7c here. Starting to feel a bit more like late Autumn.

SSW event at the moment seems to be going to script. Check list has lots of ticks, time will tell on the true impact zone but the polar vortex displacement is well and truly underway. GFS showing the vertically propagating 500 hPa Rossby wave ballooning around NZ currently, which will have an influence on any polar jet displacement or fracture, especially around mountain ranges and warmish sea surface temperatures.

I'm quite interested on whether the polar jet is split in 2 as it gets into the upper cold core cyclone sequence towards the end of the week. Some models are starting to hint this by next weekend.... the result could be the interaction of poleward-flowing divergent limbs of the subtropical and fractured polar jet, spawning a nasty surface cut off low east of the SI. IMO, this is one of the main reasons why the big models are so erratic and occasionally show a cut off low. For now, I’ll keep chewing the popcorn and watch each run with gaining interest

Honestly CT and Tony T, really appreciate your weather knowledge to this coming southwesterly weather event. I still have many things to learn about how the weather works and what the numbers all mean. But your ongoing input recently has been really awesome. Thanks so much i look forward to your updates and get excited when i see you have posted further details, Its a highlight for me to read thats for sure. Thanks again

I second that! Glad I’m not the only one who is excited to see an update from these two!

[Chris W]

It certainly is a fascinating start to winter, looking at exactly what comes at us from the south. The Tasman is not getting a look in within the current modelling trends. Mid-to-late next week could be very cold going by the BOM Access output alone. I’ll add my thanks to Cyclone Tracy for explaining the southern SSW in such superb detail, keep it coming!

[Orion]

Misty night here now, after a clear sunny day.

[Richard]

A mostly gentle wind here, but the odd stronger puff as high as 6 (M/S). Looking like double pegging the undies on the line weather Sunday. Interesting days ahead.

[treetop]

Metvuw showing the end of the westerlies next Sat and a potentialy very cold outbreak for Sth Is.Maybe the more confused jet stream pattern of late establishing again ? [ more heavy rain for us northerners]]

[melja]

To be honest though people have been saying "it looks very cold in the south next week" for about 3 weeks now and it's been nothing.

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[NZstorm]

The Jet stream across the South Island Sunday should be good for lightning activity over the Alps and lee side ranges. And then a bit of snow on the hills in the deep south Monday to 300m.

[Richard]

The models as expected are showing variability 10 days out, problem here is those ten day models work best when weather patterns are stable, we're far from stable at peasant, five days out is as far ahead as i would be looking.

[Orion]

At 6am observed stars in a clear sky with swathes of fog-cloud on the horizon;

now quite thick fog here, visibility <50 metres, chilly.

[spwill]

The westerly pattern which has arrived with some pulses of colder air over the next week or 10 days has been well signalled. My thoughts are we will see the westerlies retreating by the start of June with Highs and lows more the feature across the NZ area.

[Cyclone Tracy]

Fairly standard Autumn day here, 17c, light to moderate westerly.

Tropospheric polar vortex weakened and flapping around like a loose ribbon in the breeze at the moment. High pressure locked in over Australia between the jet streams. Lots of energy in the polar jet south east of Africa. Some models have the southern hemisphere omega block breaking down late in the week, other maintain the block…. All are erratic every 12 hours from about next Wednesday. Fascinating to watch it all come together and the models struggling to maintain scenario's even within 100 hours

Current conditions @250 hPa
https://earth.nullschool.net/#2018/05/1 ... 52,-43.520

[treetop]

Great data CTracy. Certainly vollitile and hard to predict at present. The northern hemisphere polar/jet activity has been in major turmoil over the last 5 years.

[RODALCO]

Some nice cumulus cloud clusters. Seen from 520 Swanson Road, Ranui. May result in some thunder at some stage.

IMG_7169.JPG

[Cyclone Tracy]

Westerly flow becoming quite unstable around upper NI and Auckland near the trough and front

[NZ Thunderstorm Soc]

Some nice stacks of Altocumulus Lenticularis to the West/SW of here in the Pleasant Point direction.

[Cyclone Tracy]

These showers have some punch. Just very briefly hit a 164 mm/h rainfall rate and 11 mm in that quick downpour.