NZ Weather Forum

The south west pacific basin has just started warming up its engine, with a La Nina looking sea surface temperature set up along with the atmosphere already in a La Nina state. The walker cell is starting to line up this way at the moment. Coral sea waters are also bubbling for this early in the season. I have a feeling this season could see a few gargantuan warm core cyclonic gyre's riding the ridge and maybe some potent extra tropical cyclonic activity for NZ.

EC showing lots of convection for this early in the coming weeks ATM. OZ showing signs of pre monsoonal activity.

This will very likely be an active season in the South Pacific tropics and sub tropics.

Ocean and Atmosphere are currently brewing

26c lines are pushing southward. Equatorial heat potential looking strong near the Solomons. Thunderstorm activity is about to increase in the tropics.

With the Americans officially announcing an active La Nina event is now underway overnight, I thought I'd have a quick check of current SW pacific conditions.

Water is simmering, EC 51 member is starting is show signs of depressions and GFS has just modelled its first TC of the season, although this can't be taken too serious this far out.

Moonsoon trough becoming more active in a week or so. IMO early January looks likely for TC development based off the latest guidance.

It's almost show time. Monsoon trough pushing into the Southern Hemisphere Tropics. Plenty of CAPE, depressions will soon start to appear

This might be the largest mismatch I've ever seen between GFS and EC under 100 hours. GFS has a Category 5 monster off Broome W.A and EC doesn't even have a depression. Someone is going to have egg on their face

Cyclone Tracy wrote: ↑Sat 23/12/2017 13:31 This might be the largest mismatch I've ever seen between GFS and EC under 100 hours. GFS has a Category 5 monster off Broome W.A and EC doesn't even have a depression. Someone is going to have egg on their face

913 hPa within 92 hours is just absurd. I'd be inclined to go with the EC.

Willoughby wrote: ↑Sat 23/12/2017 13:39

Cyclone Tracy wrote: ↑Sat 23/12/2017 13:31 This might be the largest mismatch I've ever seen between GFS and EC under 100 hours. GFS has a Category 5 monster off Broome W.A and EC doesn't even have a depression. Someone is going to have egg on their face

913 hPa within 92 hours is just absurd. I'd be inclined to go with the EC.

I'm with you..... cue - the GFS downgrades

At least the GFS sticks to it's guns though!

GIF shows last 10 model runs of the GFS for 26/12Z

GFS certainly is... it's liking the 30c SST and favourable shear one would assume.

I suppose we have to wait and see if good circulation occurs in the next 48 hours.

EC 51 member doesn't rate it above a depression at this stage.

GFS and the GEFS ensemble have a lot of egg on the faces for the initial phases of the low. Enormous downgrades in the last 48 hours and now similar to most models. GFS really does struggle with tropical systems and estimated pressure of late. I suppose that's why the BoM use the EC ensemble probability outlook as it's base for tropical systems and 3 day outlook.

There is definitely monsoonal activity starting to fire though. Darwin looking wet today.

EC 25122017 12z becoming more keen this morning on a mid latitude cyclonic Tasman gyre at 978 hPa for early in the new year. Too early to lock it in but EC keeps liking it ATM.

1st landfall TC cyclone of the season for Oz. Hilda won't be around for too long before she's becomes a landphoon.

The Suicide Palms came down in Broome

They are due to die anyway since they just flowered.

Was: https://www.flickr.com/photos/barkochre/34723221680

Now:

Interesting, BoM just upgraded the cyclone to a Cat 2 as it passed Broome...post event. Might explain the suicide Palms and a few others struggling to stand up.

Almost locked in that a Tropical cyclone will form off the WA coast within a few days. When formed it will be named 'Joyce'.

Big upper polar injection into the upcoming Tasman low. This has potential is get the uppers in the SW Pacific tropics moving. It's true impact might be known in a few weeks around Fiji region.

First significant widespread monsoonal activity across and off Australia on the EC ensemble in the next 7 to 10 day range.

Most models indicating the monsoon gyre setting up near the south pacific convergence zone in the coming week. EC members becoming very keen on multi tropical depressions within 4 to 6 days, one of which could become a tropical storm near Vanuatu.

Conditions becoming very favourable in the Coral sea within the next few days. Currently models suggests a Category 1 TC to form North west of New Caledonia. The high pressure ridge in the Tasman on Sunday will be calling the shots as to where the system will go. Most models suggests that the ridge will weaken and move east, allowing the cyclone to enter the Tasman in the middle of next week. If the ridge maintains its strength, there is an outside chance the cyclone could push into SE Queensland and Northern NSW maintaining its warm core with SST’s currently over 26c to support its core.

Impact on NZ is still too early to tell but EC and GFS suggest a significant intensification transition from warm core to cold core with a major direct hit on the west coast of the south island. At this point though, there is a long way to go

Low level circulation centre with deep convective banding. Good circulation and should be a cyclone within 24 hours with current winds now around 33 knots.

Current development stunted by unfavourable wind shear but very close to being officially named.

Edit: officially named Fehi

Get ready for what looks like a very active South Pacific basin!

MJO forecasts from NCEP and ECMWF showing a continued very strong pulse of enhanced convection as it heads east into the Pacific.
An incredible monsoon burst here in Darwin.