Intense Low Tuesday 7th November

[NZ Thunderstorm Soc]

An intense low is forecasted to move across southern districts on Tuesday.
Lets see how this pans out.

[Cyclone Tracy]

EC has liked this beast for a while now. Latest run has a Tasman freight train bombing at 967 hPa half between Invercargill and Dunedin early Wednesday morning. Basically a water bomb on the west coast of South Island, with a prefrontal sub tropical water slide into the north island. Wind spinning out of the cold core gyre on the western flank will be a touch nasty across a wide area. I'd say the MetService severe weather team will be clocking up some overtime with this one.

[NZstorm]

850mb temperature chart for 12Z Tuesday. A big thermal contrast over the SI with this low.

Snow looking possible in inland Otago/Southland to 500m?

Alpine thunder north of Cook. And gfs hints at convection over the upper North Island as there is an influx of moisture. Not sure about that though, 500mb temps will be warm.

[Orion]

EC has liked this beast for a while now. Latest run has a Tasman freight train bombing at 967 hPa half between Invercargill and Dunedin early Wednesday morning. Basically a water bomb on the west coast of South Island, with a prefrontal sub tropical water slide into the north island. Wind spinning out of the cold core gyre on the western flank will be a touch nasty across a wide area. I'd say the MetService severe weather team will be clocking up some overtime with this one.

A beast, a freight train, a water bomb and a water slide - sounds wonderfully exciting

[Cyclone Tracy]

The German model going a touch extreme on the 18z run for a SI northerly wrap around assault on Tuesday night. Other models thinking lesser and that the gyre will launch 120 to 140 km/h gusts in exposed areas of SI and NI.

[Thunder081]

EC has liked this beast for a while now. Latest run has a Tasman freight train bombing at 967 hPa half between Invercargill and Dunedin early Wednesday morning. Basically a water bomb on the west coast of South Island, with a prefrontal sub tropical water slide into the north island. Wind spinning out of the cold core gyre on the western flank will be a touch nasty across a wide area. I'd say the MetService severe weather team will be clocking up some overtime with this one.

A beast, a freight train, a water bomb and a water slide - sounds wonderfully exciting

[Thunder081]

Yeah MS will probably say 130 - 140 km/h gusts for exposed areas of Wellington.

[NZstorm]

Latest gfs suggests some snow flurries as low as 300m in Southland on Wednesday morning. 500m in inland Otago. Unseasonal snow fall for the higher roads.

[Bradley]

Places like Lake Tekapo could be right in the firing line with around 15-25cm of snow overnight Tuesday into Wednesday. Mid Canterbury looks more like 800m snowline at this stage...

[tich]

Undercutting might affect snow levels in the east should the cold change be preceded be strong, moist northwesterly flow.

[melja]

I can't understand why the chch forecast for Tuesday doesn't match there warning with only a mention of strong northerlies not 100kph NW. Most people probably only read the brief forecast.

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[NZ Thunderstorm Soc]

Yes, the same for here down Timaru way.
Maybe it won't be as strong along the coast but mainly an inland event?

[melja]

Warning says 130kph inland and 100kph further east.

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[Richard]

They have Culverden with nothing over 15kmph, mind you Culverden never gets strong wind forecasts

[Cyclone Tracy]

The gyre is starting to spin off NSW. Check out the 2,500 km line of sparks spawning from trough connected to the developing surface low.....

[NZ Thunderstorm Soc]

Yes, sadly dying out before reaching New Zealand, because of this rodent's quick movement to the SE.

[Orion]

I'm confused by the term "gyre" which it seems should refer to the rotation of water within an ocean?

As for "rodent"

[Tornado Tim]

The way I understand the term "rodent", is usually when a polar system starts separating itself from the main longwave trough as it progresses north/northwest and starts behaving like a rodent (ie: scarpering in whatever direction).

Some very very tight isobars in the latest prognostic ECMWF run, the upperhalf of the South Island is going to experience some very strong winds coming up. Parts of North Island getting to strong Gale Wednesday/late Thursday.

[Richard]

Some very very tight isobars in the latest prognostic ECMWF run, the upperhalf of the South Island is going to experience some very strong winds coming up.

And this is why i think the MS saying that average winds speeds for the likes of Culverden, Omarama and Twizel are ridiculously low, 19, 22,and 20kmph, but like i posted earlier none of these towns have ever had strong winds forcasted over at least the last 6+years that i remember.

[Cyclone Tracy]

Core is starting to organise on the 1pm snapshot.

@Orion, I use the term gyre as the surface layer circulates in sync with the atmosphere kicking off the cyclogenesis. The mother of all gyres is the Asian monsoon gyre, that spawns the Super Typhoons http://glossary.ametsoc.org/wiki/Monsoon_gyre

[Cyclone Tracy]

Atmospheric river now running at 35 to 45mm. Sub tropical waterslide targeting the upper North Island for tomorrow morning. http://tropic.ssec.wisc.edu/real-time/m ... anim=html5

[Orion]

Tornado Tim - thanks for the "rodent" explanation - my researches show that the term may have been used by Jim Hickey, but having no television it kind of passed me by

Cyclone Tracy - thanks re "gyre" which I had more associated with much larger systems.

A fresh NNW breeze has sprung up here in the past hour or so.

[NZ Thunderstorm Soc]

Cloudy with a light northerly here but looking as though it is raining along the Alps.
Yes, Jim Hickey used the word 'rodent' quite often in describing situations like this.
Also he conned the phrase "A gone-burger" when such a system had moved on.

[Cyclone Tracy]

A couple of private weather stations around Wellington have just clocked around 110 km/h

[Richard]

Winds been coming and going, light at the moment though