NZ Weather Forum

It's that time of year again, 26c sea surface temperatures have now lowered to around the Tropic of Capricorn. Past La Nina's have thrown up late December, early January cyclones in the South Pacific and Australian basins. Several factors including strong central equatorial pacific easterlies, a potential incoming MJO pulse and the standing wave now arriving in SE Asia, increases the chances for the end of 2020 into early 2021.

GFS in 5 days encloses a vortex @850 hPa above the subtropical ridge on the South Pacific convergence zone near Fiji and Vanuatu. A 60mm total precip water easterly feed with sea surface temperatures around 29 to 30c in that area. Wind shear will determine how this plays out in the next 10 days but other factors are favourable for tropical cyclogenesis. Other global models are also spotting a depression in this area.

EC aligning with GFS in 10 days on the 00z run, New Caledonians take note. No 2 storms are the same but the position of the sub tropical ridge and mid latitude trough on both models is a very similar set up to 1997's Cyclone Drena.

GFS currently has this cyclone developing around the 11th, crossing Vanuatu then New Caledonia and impacting the North Island on the 19th. La Nina really beginning to make its presence felt, potentially.

Chris W wrote: ↑Tue 08/12/2020 12:15 GFS currently has this cyclone developing around the 11th, crossing Vanuatu then New Caledonia and impacting the North Island on the 19th. La Nina really beginning to make its presence felt, potentially.

Yes that will be good for rain for the north island. i hope it eventuates and not goes off to the east like the last ones did.

Yesterday's CME could suggest a South Pacific TC spool up in around 7-10 days time if waters are favourable.

the idea is still there in models...every day that it is makes it a bit more likely it will happen
but calling it and telling the public this early on like one weather outlet has done just to say they exclusively called it....humm,

The eastward movement of the standing wave and MJO is kick starting the season. Signs of the monsoonal north westerly flow over the Oz top end by early next week. Invest 91P AND 90P vortexes will likely merge from an fujiwhara effect in the next 48 hours, then its show time. On a side note, a new subtropical low spinning near Qld /NSW by the weekend from a break away surface trough in the southern coral sea.

I'm no expert, but it looks to be a slow moving system according to the models. In no hurry to go anywhere....but then it hasn't even been born yet.

At this stage re the models its artist license re for say 1 to 2 weeks out

Invest 90P NE of Fiji is now under a formation cyclone alert with JTWC.

MS increasing the likelihood of development over the weekend through to high by Sunday, looks like we're on.

TROPICAL CYCLONE POTENTIAL BULLETIN ISSUED BY METEOROLOGICAL SERVICE OF NEW ZEALAND AT 2236 UTC 09-Dec-2020

CURRENT STATUS OF CYCLONE ACTIVITY

There are presently no tropical cyclones in the Coral Sea or South
Pacific areas.

FORECAST TO 1200 UTC FRI 11-DEC-2020

TD01F was analysed near 12.7S 176.1W, close to Wallis and another
tropical low (91P) was analysed near 11.5S 171.6E, between Rotuma and
northern Vanuatu at 7am 10 December(NZDT). The environment is
currently unfavourable, hence the chance for either of these systems
to develop into a tropical cyclone till midnight Friday is LOW.

OUTLOOK UNTIL 1200 UTC MON 14-DEC-2020

TD01F is expected to track west merge with tropical low 91P to the
northeast of Vanuatu on Saturday. The environment is expect to become
favourable hence the potential for a tropical cyclone to lie
somewhere between northern Vanuatu to Rotuma,Fiji is very Moderate on
Saturday and High from Sunday onwards.

The next bulletin will be issued by 0000 UTC Fri 11-Dec-2020

Funded by the Ministry of Foreign Affairs and Trade.

(C) Copyright Meteorological Service of New Zealand Ltd 2020

xmas day cyclone.
there i called it.

TC Santa, haha. "It's a bold strategy Cotton, let's see how it works out for him..."

Chris W wrote: ↑Fri 11/12/2020 10:11 TC Santa, haha. "It's a bold strategy Cotton, let's see how it works out for him..."

Careful now...history is not kind to such timelines...

https://en.wikipedia.org/wiki/Cyclone_Tracy

JTWC already calling our tropical low a TC (based on 1-minute mean winds)…

The number 1 hurricane model turns the new cyclone into a cat 4 beast on Tuesday between Vanuatu and Fiji with a slow south easterly steer along the ridge.

TD 01F (04P) has been displaying a fully exposed LLCC today, with convection well sheared to the NE. Fiji Met looks to have taken GFS and ECMWF's lead with TD 02F (91P) now becoming the dominant system as they merge (rather than the other way round) and reaching TC status (35 kt) by tomorrow afternoon. JTWC have also just issued a TC Formation Alert for TD 02F (91P).

http://www.data.jma.go.jp/mscweb/data/h ... p?area=nzl
then select pacific island 5 from drop down

for good sat animation

JTWC now also calling TD 02F (05P) a TC (based on 1-minute mean winds) after issuing their final advisory for TD 01F (04P)…

so name yet?

Awhituobs wrote: ↑Sun 13/12/2020 07:25 so name yet?

JTWC's thresholds are usually lower than those used by Fiji Met, BoM and JMA, particularly given their use of 1-minute mean winds. However, I expect it won't be too long before Fiji name TD 02F.

Haha all the hype over this as a Christmas cyclone. Look at it now.


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GFS and UK Met still loves it according to windy maps

Mod Note: TC Yasa was named by Fiji Met this morning, so thought it might be worthy of a separate thread...