Cyclone Ex-TC Tasman Low 13-15th FEB impacting NSW/SE QLD

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Fast Eddie

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ECL or wandering cyclone?
Screen Shot 2020-02-07 at 3.41.39 pm.png
 
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POW Hungry

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This tropical depression/Tasman Low is looking to span multiple regions.

Currently identified as 91P by JTWC the expected track is South through the Tasman Sea.
Not an ECL, by definition, the Tasman Low has been trending on deterministics since Tuesday.

Likely to affect maritime & perhaps coastal areas of NSW & QLD.
Looks to bring some moisture onshore, which would largely benefit chiefly coastal regions.
ecmwf_z500_mslp_swpac_9.png


Significant wave heights are looking serious:
ww3_wavehgt_swpac_52.png


Note: This is a predictions thread only for forecasts impacting SE QLD & NSW (extra-tropical).
TC Development can be discussed here, as usual:
19/20 TC Season Thread
 

Tsunami

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Ok
So yesterday saw an animated model that showed the TC next week getting close to NSW.
It further showed another TC hitting frazer island on 21st
Is this still been forcast
 

POW Hungry

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Ok
So yesterday saw an animated model that showed the TC next week getting close to NSW.
It further showed another TC hitting frazer island on 21st
Is this still been forcast
Wobbles of GFS, but yes, same system.
EC has the system tracking much, much further offshore.
 
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Nature's Fury

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This looks more promising for a coastal crossing, along with CMC's deterministic coast hugger in NSW. GFS keeping the hope alive. I actually wouldn't be surprised if the cyclone just washed out and ended up blowing around into the central Coral Sea. I think that also happened a couple of years ago with a system that threatened SEQ on the models for a while.

gefs 06z.png
 

Wavey

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When it comes to anything weather related, steer clear of fb.
You get better, more considered info on ski.com.

More so than we ever got on WZ in fact

GFS has the ECL passing pretty close to the coast on the weekend. Really not what we need after the rain we've just had. And now any of the south facing beaches that may have been protected by erosion from the ENE swell will cop the full brunt if that setup was to eventuate.

Screenshot_20200210-091641_Chrome.jpg
 

Gleno71

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FB is constantly tossing up things in my feed that are a few days old (not just weather stuff, people wishing others happy birthday etc). Off topic, but it’d be nice to be able to force the feed to be chronological
yeah it's all over the shop, im still getting posts from 3 days ago about the weather event that is irrelevant now
 

Bello Weather

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yeah it's all over the shop, im still getting posts from 3 days ago about the weather event that is irrelevant now
Yep, same, hate it...some computer in Silicon Valley deciding what I want to see...I tend to use Twitter feeds now for weather info, as you can organise them in chronological order with the latest first.
And to keep us on our toes....latest 00z from ICON has it crossing the Mid North Coast...now that would be a situation for Sydney :eek: Other models not showing this happening right now...but ICON can be on the mark sometimes so one to watch.

xx_model-en-304-4_moddeu_2020021000_180_1532_149.png
 
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Ken Kato

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Sorry about the somewhat dumbed down language in the post below but it was targeted mainly towards people on fb and I don't have time to edit it atm... but you get the general gist of my opinion on Uesi:

" The possibility of powerful long-period swells starting to spread down the far southern QLD & NSW coast from the end of the week & weekend still looks like a reasonable one (although if the TC or ex-TC doesn’t make it as far south as expected as a strong system, the swells will be much smaller).
Tropical cyclone Uesi was named by the Fiji Met Service and is currently a Cat 2 system north of New Caledonia at this time.

TECHNICAL TALK:
Its forecast track scenarios still haven’t changed much i.e. the majority of them still suggest it’ll continue to drift further south towards New Caledonia for a few days (Fiji Met service is currently forecasting gales to develop for western parts of the island group).…. then curve around to the SW into the southeastern and southern Coral Sea later this week, partially steered by the midlevel ridging to its south and southeast…. but there could be noticeable deviations in this track at times.

Although there’s still reasonable confidence in that general S then SW track, most of the uncertainty still currently centres around 1) how far south it’ll stay a TC before it undergoes extratropical transition into a non-tropical low, and how strong or weak that low will be, and 2) whether it’ll cross the coast or stay out to sea.

Regarding point no.1, although sea surface temps are currently warm enough to sustain a TC down to waters off northern NSW/southern QLD, TC’s are highly sensitive to shear (strong shear disrupts a TC’s vertical structure and weakens it, unlike individual severe thunderstorms)…. and some of the current forecasts suggest it could encounter stronger shear by the time it reaches the southern Coral Sea/northern Tasman Sea to the point that it transitions into a non-TC system. There might also be a bit of dry air intrusion starting into its northern flank by then but this is probably a lesser factor.
Its future intensity or lack thereof can also affect its track because once TC’s weaken especially if their tops get sheared off, their structure becomes much shallower which means they tend to start getting steered by winds and other weather systems in the lower atmosphere, rather than by winds and systems through a deeper slab of the atmosphere (for example, a midlevel ridge).

It’s worth remembering though that ex-TC’s can sometimes find a new reinvigorated life as a punchy subtropical or midlatitude low when they move poleward into a baroclinic environment (an environment that’s typical outside of the tropics where temperature contrasts at given heights fuel frontal low pressure systems, rather than relying purely on warm ocean waters and heat released by condensation that TC’s do in the tropics).

Regarding point no.2, many of the track scenarios still have it eventually coming close to waters off the NSW or southern QLD coast, while some make it hug the coast or actually cross the coast onto land.

For this system have a realistic shot of getting close to the east coast, a) if it’s still a TC, the big upper low and trough over inland eastern Australia at the moment must not move too far east and capture it before dragging it away (having said that though, occasionally the strong winds aloft from a nearby upper trough can help vent the air flowing out the top of TC’s away via outflow channels and sustain its strength).
or b) if it’s a non-TC, there needs to be at least some ridging in the lower atmosphere to its south and southeast to help steer it towards the coast.

ADDITIONAL POINTS FROM LAST POST:
1). If anyone’s hoping for heavy rain from this system, I wouldn’t pin your hopes on that – most systems that manage to make it down into the southwest Coral Sea or Tasman Sea actually tend to eventually decrease rainfall for SEQ after they go south of our latitudes because they deflect the winds to a drier, more southerly direction (the only exception is if they come close just to our north in which case, they can cause heavy rain… but at this stage, this is an outlier scenario).
2). In the very hypothetical scenario of an actual NSW coastal crossing, the overall orientation of much of the NSW coastline apart from the far northeast corner and the SSW track of the system (if it does manage to come close to NSW) means that its track would likely be almost parallel to the coast… which would make a coastal crossing a touch and go proposition, although not completely impossible.
3). Whenever it’s mentioned that there’s still uncertainty about a particular scenario, please never interpret it as something that’s impossible (e.g. this system crossing the coast as an ex-TC or TC). It’s quite a realistic possibility, just that it’s not the only one.

It’s also not completely impossible that it eventually weakens out before it goes too far south, gets swept away by an upper trough, ends up being a weak non-influential ex-TC once it heads much further south, or even drift back up into the NW Coral Sea off central or north QLD.... although these scenarios appear less likely.
Of course, TC’s can, and have impacted SE QLD/NE NSW in the past (although they’re still far more common in the tropics in comparison)… but it does always take a lot of things to line up for that to happen.

SUMMARY:
So in a nutshell, there’s reasonable confidence in the general S then SW track although with some deviations… just that the scenarios currently still differ as to whether it crosses the coast or stays well out to sea, and how strong or weak the ex-TC/TC will be.

This map via NOAA shows the 10-day forecast track scenarios from the ECMWF, UK, and GFS ensembles (ensembles are versions of models that are run many times to generate a range of scenarios).
These are colour coded by intensity – the “warmer” the colour, the stronger the TC/ex-TC it is. I’ve intentionally left out the colour scale because it uses the Saffir Simpson scale which isn’t exactly the same as ours. "
 

Nature's Fury

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EC determ has become very close to the coast on its recent two runs. CMC still holding a coast hugger. NAVGEM very close too.

GFS determ and ensembles have now become a lot more offshore dominant and don't have the cyclone as close. HWRF is miles offshore. Access-G going for a washed-out low sweeping into the Coral Sea and reforming into a powerful cyclone up off Cape York.
 

Bello Weather

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Latest runs from some of the models....close but still offshore...some decent consistency between them:


ezgif.com-gif-maker (26).gif


EC control has a decent system not far offshore...looks like more of a swell maker than flood maker right now, but geez there is not much in it:

xx_model-en-304-4_modez_2020021012_99_15943_149_m0.png


....but looking at the ensembles most of them keep the system well offshore with only the odd outlier sending into E Aus:

xx_cyclone-en-304-4_euro_2020021012_6412_480_uesi-240.png
 

POW Hungry

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Latest runs from some of the models....close but still offshore...some decent consistency between them:


ezgif.com-gif-maker (26).gif


EC control has a decent system not far offshore...looks like more of a swell maker than flood maker right now, but geez there is not much in it:

xx_model-en-304-4_modez_2020021012_99_15943_149_m0.png


....but looking at the ensembles most of them keep the system well offshore with only the odd outlier sending into E Aus:

xx_cyclone-en-304-4_euro_2020021012_6412_480_uesi-240.png
Ideal.
Fine with me.
Less wind and increased swell propagation.
 

Jellybeans

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With UKMO going along with the coastal hugging models:
xx_model-en-304-0_modgbr_2020021012_120_10_149.png


So basically GFS and friends vs UKMO, EC and CMC.
I can't see GFS beating all the other determinstic models, but it does also have a degree of ensemble support. Will be interesting to see which model pulls through
 

Bello Weather

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Latest Access R throws a (temporary?) spanner in the works by weakening the system and developing a new low close to the Se Qld coast....almost looks like the monsoon trough dipping a long way south. Needless to say would be a huge rainmaker if it came off:

IDY20114.mslp-precip.072.png

IDY20301.mslp-precip.072 (1).png
 

Nature's Fury

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Good pick-up Bello. GFS was forecasting a coastal trough/dip like this yesterday for consecutive runs, but dropped it. It had about 300-400 mm. A few other models have had variations of this, either with less activity or just offshore. I think it will be all about the positioning of the low as it approaches - it needs to angle in toward the coast to push this dip right over SEQ ahead of it.
 

Nature's Fury

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I think that might be the main way we get rain from this system. I don't fancy our chances of a coastal crossing or hugger much now. GFS deterministic and ensembles have well and truly decided on a curve well offshore - only one ensemble member has a crossing. EC ensemble is similar. I expect we'll see the others align soon and unfortunately if the cyclone is too far offshore any troughing or monsoonal dip will be off the coast too.
 
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Jacko4650

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yeah it's all over the shop, im still getting posts from 3 days ago about the weather event that is irrelevant now
Causing unwarranted concern here on the Fraser Coast. We are getting yet more cancellation due to flood alerts that are (a) days old and (b) wrong as the river gauges were wrong and nobody bothered to look out the window to see if they were accurate. One of the key indicators for the mary River was wrong, so they withdrew it to recalibrate (otherwise working OK). The other one working got vandalised a few hours later and stopped working. In the meantime, Emergency Services issue a Flood Watch (based on dodgy data) and we are still seeing the ramifications. Nobody seems to validate information any more; no sanity check, quick phone calls; not even the local (and only) newspaper that loves to print headlines based on Facebook speculation as it sells more papers. Sigh. Imagine ourselves, when the internet breaks (highly unlikely in the middle of disaster's right)?
 
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Rainbomb

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Laugh of the night. Access G the outlier weakens the system significantly while rapidly moving it west towards the SE QLD coast during Thursday/Friday SE QLD. before intensifying again and moving south as a ECL.
 
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Nature's Fury

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Laugh of the night. Access G the outlier weakens the system significantly while rapidly moving it west towards the SE QLD coast during Thursday/Friday SE QLD. before intensifying again and moving south as a ECL.

Yeah what a joke. Last run it was off to the SE. Nearly every model is in agreement that it won't even come that close to the coast. Access-G late to the party.
 
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