The Tropical March Begins

Craig Brokensha picture
Craig Brokensha (Craig)
Swellnet Analysis

Over the coming fortnight, the formation of at least one - if not a couple - swell-producing systems looks almost certain in the Coral and Tasman Seas.

The catalyst for the storms will be increasing tropical activity to our east-northeast into the end of the month.

The increased convection and instability will be linked to the strengthening Madden Julian Oscillation (MJO). The MJO is, in effect, a wave of increased tropical activity and convection that propagates east along the equator.

Also, sea surface temperatures are primed in the Coral Sea for the formation of a tropical cyclone (well above the required 26.5C), as well as a lack of strong upper atmospheric winds (that create wind shear) forecast for the start of March.

Chance of tropical storm formation (%) for the period Sunday 26th February to Sunday 5th March (ECMWF)

This bodes well for northern NSW and south-east Queensland surfers in regards to swell potential, but of greater interest is what's taking place in the Tasman Sea.

The East Australian Current has been sending significant plumes of warm water down the East Coast towards southern NSW.

Sea surface temperatures in the middle of the EAC are now 26-27°C off of Seal Rocks, with water temperatures off Jervis Bay coming in around 25°C - which is 2-3°C above average.

Warm water brings with it stored potential energy which enhances and feeds into any instability that forms adjacent to the coast or offshore. Take for example the flooding downpours seen across the Shoalhaven region a fortnight ago, and the Northern Beaches earlier this week.

While it's too early to forecast the track or movement of any potential tropical cyclone/storm from the Coral Sea, the leading global forecast models are in general agreement regarding the movement of any tropical disturbance that may form, plotting a southward path towards the Tasman Sea.

A couple of pools of cold air are also forecast to be transported up from the Southern Ocean, across the south-east of the country during the start of March. These will sit above the warm water signal sitting off the southern NSW coast and could be the catalyst for the development of a more significant low.

There's no guarantee of great waves or large swell, or even the development of such a low in the Tasman Sea, but we'll be entering an unstable and dynamic period with plenty of potential thanks to the combination of warm, unstable air and cooler air aloft.

So be prepared to ride the long-range model forecast fluctuations and keep an eye on the regional Forecaster Notes over the coming weeks.

Comments

Chipper's picture
Chipper's picture
Chipper Thursday, 23 Feb 2023 at 2:22pm

I'm excited ...

sean killen's picture
sean killen's picture
sean killen Thursday, 23 Feb 2023 at 2:30pm

Since the last cyclone swell .. the banks are terrible..( waves have been shithouse as well ) fingers crossed for this potential swell forecasts

dawnperiscope's picture
dawnperiscope's picture
dawnperiscope Thursday, 23 Feb 2023 at 2:46pm

Scary

bbbird's picture
bbbird's picture
bbbird Thursday, 23 Feb 2023 at 9:25pm

Surfs up, means crowds may... thin out.

Those crocodiles & Irukandji drifting down the coast could spoil a good Qld surf though,
https://en.wikipedia.org/wiki/Irukandji_jellyfish
https://www.sydney.edu.au/news-opinion/news/2019/05/01/pain-researchers-...
(& ...covert a hardcore hedonist to some deity asap)
https://www.dictionary.com/browse/deity

Dust off the big board & take a spare legrope... those tradewind lines look long.....

P.S. Metvuw models shows a cyclone moving directly over New Caledonia next Friday..... I hope these models are off.

JodyP's picture
JodyP's picture
JodyP Thursday, 23 Feb 2023 at 9:05pm

Notice over the next few days, the eastern side of a 1042 High over China, augmenting the NE trades in the South China Sea, to create an extra burst of moist wind feeding into the tropical W-NW Monsoon tradewind belt above Australia. To the south of that, off the NW WA coast, winds rotating around a low pressure system there will be adding to and thus further increasing that W-NW wind flow.

That strengthening of the W-NW monsoon wind will then feed all of that moist tropical air across through the Arafura and Timor Seas and into the Coral Sea, where it will run into the NE trades feeding in from the north of the monsoon trough, and the SE trades feeding into it from the south. The rotation from the 3 coming together there in the Coral Sea, will set off that circulation of hot, tropical, rising air.

BOM also mentions a strengthening of the MJO over the Western Pacific coming up as we head into the end of February too, so combine all of that extra convection and instability and moist tropical rising air, and a tropical revolving storm doesn't really come as a surprise. Are you seeing similar Craig?

Actually ... reminds me of commercial fishing on the outer GBR off the Far North Qld Coast through the cyclone seasons decades ago. As the monsoon trough would become 'active', we would start seeing a mass of huge dark scud clouds and squalls build up around us. It was pretty eerie actually. That was the indicator to go north towards the Torres Straits, above the trough line and out of harms way, before something set in. Sitting in a 19' fibreglass dinghy one afternoon, around 40nm offshore and maybe a similar distance SE of Cape York from memory, but still within the outer 'barrier' reef edge, I remember seeing 4 full raging waterspouts simultaneously, all pouring out of one big single dark scud cloud.

Cyclones can build up quickly and without warning, and especially years ago before better forecasting technology. We saw plenty of E coast lows and tropical lows and isolated storms and squalls form up, that the Met Bureau only mentioned AFTER they formed. Have seen lots of gales and lows and severe winds form in multiples of different oceans that the local met offices neither predict, nor even bother to mention after they have formed up.

AlfredWallace's picture
AlfredWallace's picture
AlfredWallace Friday, 24 Feb 2023 at 8:20am

JodyP. Interesting stuff. Thanks.AW.

freeride76's picture
freeride76's picture
freeride76 Friday, 24 Feb 2023 at 8:39am

Thats interesting that you would go north to get above the trough line.

JodyP's picture
JodyP's picture
JodyP Friday, 24 Feb 2023 at 8:39pm

Several reasons:
1. I believe the islands of the Torres Straits generally do not get cyclones. Close either side and to the south yes, but seems like a little window there that is clear.
2. Cyclones in that area generally dont travel north above that trough line. If you were to the south of it and it forms and matures, you stand that chance of it coming over you.
3. If you were to the south of it, or even to the west or east, that could also put you in the 'dangerous quadrant' of the cyclone, in an area of often much stronger winds and much bigger seas.
4. If you get a large high pressure system underneath (to the south of) the cyclone you not only get the cyclone winds, but the winds off the high underneath as well ... the 'squeeze'. That can add strong to gale force winds and a far larger fetch and much bigger waves and swell, for hundreds of miles south, underneath the cyclone.
5. There can be almost a vaccuum behind a cyclone as it moves. So a cyclone forming up up there and then moving south'ish, you do not have to be far away to be out of the strong winds.
6. There are some excellent cyclone havens / cyclone anchorages further north, and you have to have thise close by and in mind if anticipating the possibility of any strong wind. Escape River, just south of Cape York was a favourite for any strong winds - including when huge winter high pressure systems augment the normal winter trades.

And that Far northern Qld and Torres Straits area has, I believe, some of the strongest and most prolongued winter trade winds in the world. We fished it one time for three and a half months starting in April. Six days of nice weather at the start, then the entire rest of the time nothing under a strong wind warning.

* On that note something of a rule of thumb I have found in tradewind areas around the world. Whatever the central pressure of the high pressure system in hectopascals, take the last 2 digits, minus 5-10, use that as an estimate of expected wind strength. Example, 1030 high gives you 20-25 knots. 1040 high gives you 30-35knots. If there is a slight trough 'squeezing' the top of the high, add maybe 20%.

NickT's picture
NickT's picture
NickT Friday, 24 Feb 2023 at 9:28am

Is that you Jody Perry?

JodyP's picture
JodyP's picture
JodyP Friday, 24 Feb 2023 at 8:04pm

Yep.

Craig's picture
Craig's picture
Craig Saturday, 25 Feb 2023 at 8:18pm

Thanks Jody, yeah moisture in-feeding from both the west-northwest and east-northeast, all converging in the Western Pacific.

Most of the activity looks to be forming a touch too far east than ideal for swell potential at this stage. But this will be a prolongoged period of tropical activity.

bbbird's picture
bbbird's picture
bbbird Thursday, 23 Feb 2023 at 9:43pm

spinafex's picture
spinafex's picture
spinafex Friday, 24 Feb 2023 at 9:05am

What are the chances of NZ getting hammered by another cyclone? Shocked at what happened in Hawkes Bay

Cruisin's picture
Cruisin's picture
Cruisin Friday, 24 Feb 2023 at 11:21am

Indeed global models are beginning to look juicer for the coral sea by late this month aswell.

freeride76's picture
freeride76's picture
freeride76 Friday, 24 Feb 2023 at 11:27am

I would not like to speculate Spinafex, but we are in the middle of cyclone season and models are showing a system tracking south through the South Pacific slot.

donweather's picture
donweather's picture
donweather Friday, 24 Feb 2023 at 4:53pm

Both EC and GFS not forecasting great swell production from this tropical development out near Fiji. The compact nature and fairly rapid movement to the SE once it pokes below New Cal and into our swell window all points to nothing of huge size or substance from this one at present. Cradling high and slower movement or even better a westward retrograde and that could make me smile.

Craig's picture
Craig's picture
Craig Saturday, 25 Feb 2023 at 8:18pm

No, the initial developments aren't ideal.

donweather's picture
donweather's picture
donweather Monday, 27 Feb 2023 at 11:55am

Each successive model run progs less and less swell potential.

burleigh's picture
burleigh's picture
burleigh Monday, 27 Feb 2023 at 12:11pm

yeah its got so much potential, but i feel we are going to miss out.

Craig's picture
Craig's picture
Craig Monday, 27 Feb 2023 at 12:17pm

Yep, there'll be swell, fun in size but overall nothing too significant now.

Looks like there'll be a decent frontal progression pushing up across the south-east of the country to follow, but a little after the major tropical developments.

Cruisin's picture
Cruisin's picture
Cruisin Monday, 27 Feb 2023 at 7:03pm


dawnperiscope's picture
dawnperiscope's picture
dawnperiscope Monday, 27 Feb 2023 at 12:24pm

I imagine all that moisture feeding in from South China Sea will take a while to get to the Coral Sea. I wonder if the setup might be ripe in a couple of weeks once the Gabrielle track warms back up again.

tiger's picture
tiger's picture
tiger Monday, 27 Feb 2023 at 4:20pm

As is often the case with tropical activity.... downgrade... downgrade...downgrade. Unfortunately no catchers mitt, and a conga line to the graveyard.

freeride76's picture
freeride76's picture
freeride76 Monday, 27 Feb 2023 at 6:53pm

yep.

need a better catchers mitt.

Craig's picture
Craig's picture
Craig Monday, 27 Feb 2023 at 7:17pm

Ha, good terminology!

donweather's picture
donweather's picture
donweather Tuesday, 28 Feb 2023 at 1:46pm

That tropical disturbance progged on the long range charts up in the NT is an interesting one to watch over the coming weeks!!!

dawnperiscope's picture
dawnperiscope's picture
dawnperiscope Tuesday, 28 Feb 2023 at 3:07pm

Catcher’s mitt creeping into place as well

Craig's picture
Craig's picture
Craig Tuesday, 28 Feb 2023 at 3:18pm

And Judge Judy enters the room. Tropical Cyclone Judy that is.

freeride76's picture
freeride76's picture
freeride76 Tuesday, 28 Feb 2023 at 3:28pm

Looks like a bad time for Port Vila.

dawnperiscope's picture
dawnperiscope's picture
dawnperiscope Thursday, 2 Mar 2023 at 2:47pm

PV in for another round with Kevin

Cruisin's picture
Cruisin's picture
Cruisin Thursday, 2 Mar 2023 at 5:48pm


looks more like a mid-winter cold anom for down south. Would be some weather in that shortwave as well if the model verifies.

Craig's picture
Craig's picture
Craig Friday, 3 Mar 2023 at 9:53am

Yep, big slow moving gyre.

donweather's picture
donweather's picture
donweather Friday, 3 Mar 2023 at 3:53pm

Autumn coming with a bang for our SE friends.

Cruisin's picture
Cruisin's picture
Cruisin Monday, 6 Mar 2023 at 8:00am


Also a little more wow factor with control en sniffing a decent cradled cutoff cruiser, a tad more march madness.

donweather's picture
donweather's picture
donweather Friday, 3 Mar 2023 at 3:53pm

I'm def liking the looks of the long range model setup from the Coral Sea stretching out into the Tropical South Pacific (TSP). LOTS of potential in that long elongated monsoon trough right from the top end out into the TSP. Watch this space I say.

donweather's picture
donweather's picture
donweather Tuesday, 7 Mar 2023 at 1:04pm

Looks like the Tasman Sea might steal our thunder now!!!

freeride76's picture
freeride76's picture
freeride76 Monday, 6 Mar 2023 at 11:48am

I get nervous when I see that N'ly orientation of the high pressure belt.

4 days in a row with winds with an N in front of them is not what I want to see in March.

Thats a Spring type pattern.

donweather's picture
donweather's picture
donweather Tuesday, 7 Mar 2023 at 1:05pm

Yes super unseasonal.

dawnperiscope's picture
dawnperiscope's picture
dawnperiscope Monday, 6 Mar 2023 at 11:53am

Might need to re-energise the season reversal article.

freeride76's picture
freeride76's picture
freeride76 Thursday, 9 Mar 2023 at 9:32am

SST's have dropped 6 degrees on the Byron Buoy after 4 days of N'lies!

From 27 to 21.

lostdoggy's picture
lostdoggy's picture
lostdoggy Thursday, 9 Mar 2023 at 9:41am

Surfed in straight boardies and lovely and refreshing for a change.

adsi's picture
adsi's picture
adsi Friday, 10 Mar 2023 at 3:29pm

Really felt that temp drop yesty arvo, paddled out in boardies and it was freeziing compared to few days ago. Lasted about 45mins, woulda gone longer if the waves were better

Craig's picture
Craig's picture
Craig Friday, 10 Mar 2023 at 3:36pm

Here's the latest data..

Cruisin's picture
Cruisin's picture
Cruisin Thursday, 9 Mar 2023 at 4:19pm

GFS 00Z was not doing the island chain any favors with another cyclone in the region. Still early i know. The wedged between ridges with no steering and just meandering is not a good scenario. Better to get a fast mover.

trevbucky's picture
trevbucky's picture
trevbucky Thursday, 9 Mar 2023 at 9:52pm

What about for the West coast Craig?

Cruisin's picture
Cruisin's picture
Cruisin Saturday, 18 Mar 2023 at 8:30pm

GFS sniffing a heavy a precipitation period. For some central tableland regions.

Just a heads up for anyone who may have to travel that way in the said timeframe.