Tropical & EX-Tropical cyclone season 2018-19 Sth Pacific / Oz

[Cyclone Tracy]

Season is now underway with the first tropical disturbance becoming likely near Vanuatu and the Solomon Islands by the weekend. There is potential for a depression to form but is not likely to become a cyclone with less favourable conditions next week. A subtropical disturbance will also form near the Cook islands by Friday and weaken with the strength of the subtropical ridge later in the weekend.

Longer term, there are signs the Hadley cell is moving poleward and deeper into the mid latitudes. The 26c sea surface temperatures line will move steadily south over the next 6 weeks.

[Cyclone Tracy]

The Canadians are the first to pull the trigger on the tropical disturbance near the Solomon Islands with an invest 95P on a 15 knot circulation. Both the main Canadian and the ensemble believe a depression will spin into a potential low end TC. The U.S Navy on the 12Z also now shows the beginnings of a stronger cyclone moving towards Fiji next week.

EC, UK, GEFS still only project a disturbance or weak depression at this stage.

[Cyclone Tracy]

A significant MJO signal is approaching this part of the world. EC ensemble and control is also becoming alert to tropical depression formations around OZ and Fiji from the monsoon gyre near the New year. Chances of cyclone season becoming quite active within the next 2 weeks has increased.

[Willoughby]

Yes, GEFS ensembles (NCEP) really going hard now with a strong MJO westerly wind burst between about New Guinea and the Samoan islands into the new year.

14% of the normal December rainfall here... Cairns 300-600% of December mean.

[Cyclone Tracy]

Exploding hot towers in multiple locations this morning along the monsoon trough. A very active area of convection around the SPCZ (South Pacific Convergence Zone). Fiji Met now have a track map out on disturbance TD03F (Invest 94P). Deep convection around the top of Queensland but plenty of unfavourable wind shear in the short term. Chances are rising of at least 2 cyclones forming in the next 24 to 72 hours between Fiji and the Northern Territory.

[Cyclone Tracy]

The monsoon gyre is feeding the SPCZ (South Pacific Convergence Zone) and setting off tropical cyclonic chaos for models, ensembles and Met agencies. This is my take on it and I'm using the EC ensemble spaghetti 01012018 12 run as the base but Fiji needs to watch the 2nd batch of depressions very closely as a fujiwhara effect looks likely between 2 circulations.

EX TC Penny which is about to be TC Penny again off Queensland is another rogue worth watching for Queenslanders as she potentially steers back along the ride towards Oz .

[Nev]

Mod Note: Have split TC Penny and TC Mona into separate threads for ease of reference.

[Cyclone Tracy]

A strengthening MJO signal is being picked up moving into the Maritime continent phase on the latest EC and GFS ensembles. This will likely mean a monsoonal flow will develop north of Australia in the next 3 to 6 days.
The EC ensemble is now projecting 2 tropical depressions spawning from an enhanced monsoonal flow by early next week. Northern OZ may have 2 cyclones in its territory around a week from now. There is also the chance of a subtropical storm developing from a trough NE of NZ, south of the Cook Islands in the same period.

Longer term, the bullet proof subtropical ridge NW of NZ looks like closing any exit route for tropical cyclones towards NZ until at least early Feb.

[Cyclone Tracy]

First TC watch issued by the BoM for the tropical low (invest 94S) off the north west coast of W.A. The next Australian region cyclone will be named 'Riley'. Another low at the top of Queensland (invest 95P) is in competition for this name but is a less organised convective disturbance at the moment.


IDW24100
Australian Government Bureau of Meteorology
Western Australia
Tropical Cyclone Warning Centre
Media: The Standard Emergency Warning Signal should NOT be used with this warning.
PRIORITY
TROPICAL CYCLONE ADVICE NUMBER 1
Issued at 2:52 pm WST on Tuesday 22 January 2019
Headline:
Cyclone Watch declared for the northwest Kimberley coast for a developing tropical low

[Cyclone Tracy]

Tropical cyclone Riley officially named by the BoM. Projected to become a severe tropical cyclone moving away from the W.A coast. Outer rain bands may brush the coast but it seems oil rigs and fish will be the only ones affected at this stage.

[Cyclone Tracy]

With the monsoon trough now quite active in the tropics, EC ensemble is becoming quite keen on this mornings 26/01/2019 12Z run for an eastward moving depression in a weeks time around the coral sea and it likely to become a cyclone soon after. Conditions look quite favourable.

Longer term, this possible cyclone may become interesting for NZ with a potential strong upper tropospheric cyclonic vortex from the south, weakening the subtropical ridge, leaving an exit point poleward in 10 to 14 days.

[Cyclone Tracy]

The monsoon gyre is in full swing, with it possibly spawning multiple low level circulations across the trough in the next 6 days. The EC ensemble 0402 12z run is becoming quite interested in a decent tropical cyclone around the Fijian region in 4 to 7 days. UKMet is also coming on board with this scenario.

As you can see from the EC members, the steering of any cyclonic vortex is still uncertain until the strength of the subtropical ridge is fully known.

[Cyclone Tracy]

South Pacific convergence zone exploding to life this morning. Multiple hot towers are punching through the top layer of the troposphere with widespread deep convection elsewhere. Chances of a low level circulation becoming tropical cyclone strength within 72 hours are increasing. Currently there are 3 separate invest systems that the Americans are following in this region. 90P, 91P and 96P.

[Nev]

Just for the record, ex-TC Neil, currently over Tonga, was named by RSMC Nadi around 7pm yesterday and declared an Ex-TC around 7am this morning.

JTWC on the other hand (after issuing a TC Formation Alert very early this morning) have declared Neil a weak warm-cored TC (based on 1-minute mean-winds) around 10am this morning, albeit with a fully exposed LLCC and persistent deep convection sheared about 150-170 km to the east.

[Thunder081]

A slow season

[Cyclone Tracy]

Invest 96P now moving into favourable conditions near Vanuatu. JTWC now have a Tropical cyclone formation alert in place. 2 other tropical disturbances in the Fiji region are modelled to be swallowed in a fujiwhara effect with 96P, spawning a large scale tropical cyclonic vortex, that moves towards New Caledonia.

[Cyclone Tracy]

EC's high res 72 hour version has given an upgrade from the 12Z to 18Z run on the 96P system. Projecting a deepening Cat 2 this Friday morning heading towards New Caledonia.

[Cyclone Tracy]

JTWC has now upgraded 96P to tropical storm 15P. Fiji met might name the cyclone today if it passes their threshold.


Edit TC Oma has been named and now has its own thread at https://www.weatherforum.nz/phpBB3/view ... 19#p180228

[Cyclone Tracy]

JTWC has just issued a tropical storm advice for the system north east of Fiji. Currently named 16P with winds at 35 knots. Will most likely be named overnight by the Fiji Met Service when it passes their threshold.

[Cyclone Tracy]

Fiji Met named TC Pola overnight. It will have a few good days between Fiji and Tonga days before encountering the ridge.

[Cyclone Tracy]

Pola now upgraded by Fiji Met to a Cat 3 severe tropical cyclone. Gale force winds will likely affect Tonga in the next 24 hours

[TonyT]

There's something very confusing about a Pola tropical cyclone...

[Cyclone Tracy]

Fiji Met service has lifted TC Pola 1 step closer to the big league and is now upgraded to a cat 4. Pola has a robust inner eyewall and has rapidly increased intensity under very favourable conditions over the last 12 hours. Tonga is dodging a bullet at the moment.

[NZ Thunderstorm Soc]

There's something very confusing about a Pola tropical cyclone...

Imagine the media going on about a "Pola Blast from the north" ?

[cbm]

The EC model has Pola almost dying out completely by next Friday, then getting a revival tonic and almost but not quite comming close enough to affect NZ weather, before it gets pushed away again. Wonder if it might even do two huge loops.