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#1455651 - 04/03/2018 17:19 Re: QLD Tropical Cyclone Season 2017/2018 [Re: @_Yasified_shak]
rainthisway Offline
Weather Freak

Registered: 09/11/2015
Posts: 808
Loc: Mutarnee.....70km north of Tow...
Should start guessing if we do get a TC, where will it hit if anywhere.

Water vapour loop still showing circulation NE of townsville, infrared satelite is showing it too...maybe something trying to organise?


Edited by rainthisway (04/03/2018 17:22)
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Nikko

Travelling - Current location= Toomulla

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#1455655 - 04/03/2018 17:31 Re: QLD Tropical Cyclone Season 2017/2018 [Re: rainthisway]
Nature's Fury Offline
Weatherzone Addict

Registered: 29/11/2009
Posts: 2109
Loc: Brisbane Western Suburbs
So there is actually some model agreement already about this low/TC forming at the same time period. Beyond that who knows.

NAVGEM and EC - Weak area of low pressure to the NW (EC) and NE Coral Sea (NAVGEM)

CMC - Weak low moving south through the Coral Sea adjacent to coast

Access - Strong cyclone moving south through Coral Sea adjacent to coast

GFS - My personal favourite. Mid-Cat strength cyclone swings into CQ and hugs the coast before exiting SEQ as a Cat 1.

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#1455657 - 04/03/2018 17:33 Re: QLD Tropical Cyclone Season 2017/2018 [Re: @_Yasified_shak]
Ken Kato Offline
Meteorological Motor Mouth

Registered: 05/03/2012
Posts: 5244
I'm assuming many people realise this but the Gulf system that intensifies in some of the models is the same low that's currently over inland northwest QLD (which then eventually drifts out over Gulf waters for those scenarios).

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#1455659 - 04/03/2018 17:35 Re: QLD Tropical Cyclone Season 2017/2018 [Re: @_Yasified_shak]
Mega Offline
Meteorological Motor Mouth

Registered: 03/02/2003
Posts: 7054
Loc: Maryborough, Wide Bay, QLD
The GFS ensemble members are all over the shop, as to be expected so far out - some move it faster, some slower, some into the gulf, some down the coast, and others I'd imagine that have nothing at all.


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#1455660 - 04/03/2018 17:38 Re: QLD Tropical Cyclone Season 2017/2018 [Re: Ken Kato]
Nature's Fury Offline
Weatherzone Addict

Registered: 29/11/2009
Posts: 2109
Loc: Brisbane Western Suburbs
Originally Posted By: Ken Kato
I'm assuming many people realise this but the Gulf system that intensifies in some of the models is the same low that's currently over inland northwest QLD (which then eventually drifts out over Gulf waters for those scenarios).


Wow that would be incredible.

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#1455661 - 04/03/2018 17:54 Re: QLD Tropical Cyclone Season 2017/2018 [Re: Ken Kato]
rainthisway Offline
Weather Freak

Registered: 09/11/2015
Posts: 808
Loc: Mutarnee.....70km north of Tow...
Originally Posted By: Ken Kato
I'm assuming many people realise this but the Gulf system that intensifies in some of the models is the same low that's currently over inland northwest QLD (which then eventually drifts out over Gulf waters for those scenarios).


I thought that was the case. Even though BOM are expecting it to weaken. Does anyone know how they come up with for3casts...do they use one model or a combination of all of them.
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Nikko

Travelling - Current location= Toomulla

MTD (July 2018]: 0.9mm
JUNE 2018: 0.9mm

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#1455664 - 04/03/2018 17:59 Re: QLD Tropical Cyclone Season 2017/2018 [Re: @_Yasified_shak]
Mega Offline
Meteorological Motor Mouth

Registered: 03/02/2003
Posts: 7054
Loc: Maryborough, Wide Bay, QLD
Well the difference is huge when you look at the 500mb heights between EC & GFS. GFS has complete ridging through the CS which sends this bugger straight into the coast whereas EC has yet another upper trough poking up into QLD and the CS, which unless it retrogrades would keep anything off the coast and probably weaker due to higher VWS from the trough.

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#1455671 - 04/03/2018 18:42 Re: QLD Tropical Cyclone Season 2017/2018 [Re: Mega]
MangroveJack70 Offline
Weather Freak

Registered: 01/02/2011
Posts: 218
Originally Posted By: Mega
The GFS ensemble members are all over the shop, as to be expected so far out - some move it faster, some slower, some into the gulf, some down the coast, and others I'd imagine that have nothing at all.



Hey Mega. That's a really neat Chart. Question: what do the numbers within the Redish section east of Cairns refer too ? Are they Wind Speed perhaps ? Interested in understanding the Blue number (12) slightly north of Cairns. I'm assuming the Normalised Spread refer to Standard Deviation perhaps.

Just trying to wrap my head about the Chart.

Thanks.

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#1455674 - 04/03/2018 18:46 Re: QLD Tropical Cyclone Season 2017/2018 [Re: rainthisway]
Ken Kato Offline
Meteorological Motor Mouth

Registered: 05/03/2012
Posts: 5244
Originally Posted By: rainthisway
Does anyone know how they come up with for3casts...do they use one model or a combination of all of them.

For forecasting TC formation over the water, all the leading models are looked at together with knowledge of all the principles of TC formation (e.g. shear, sea surface temps, triggers, synoptics, etc).

Once a low becomes a designated system, a sophisticated piece of software is used which allows you to include a combination of up to several models of your choosing - it then calculates a consensus track of all the models you chose. The grey cone of uncertainty surrounding that track is based on a certain proportion of past forecast track errors plus the uncertainty in the analysis position. Manual adjustments can be made by the forecaster as necessary.

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#1455683 - 04/03/2018 19:10 Re: QLD Tropical Cyclone Season 2017/2018 [Re: MangroveJack70]
Mega Offline
Meteorological Motor Mouth

Registered: 03/02/2003
Posts: 7054
Loc: Maryborough, Wide Bay, QLD
Originally Posted By: MangroveJack70
Originally Posted By: Mega
The GFS ensemble members are all over the shop, as to be expected so far out - some move it faster, some slower, some into the gulf, some down the coast, and others I'd imagine that have nothing at all.



Hey Mega. That's a really neat Chart. Question: what do the numbers within the Redish section east of Cairns refer too ? Are they Wind Speed perhaps ? Interested in understanding the Blue number (12) slightly north of Cairns. I'm assuming the Normalised Spread refer to Standard Deviation perhaps.

Just trying to wrap my head about the Chart.

Thanks.


The numbers you see inside each orange shading correlates to an individual ensemble member, where surface pressure is used (so extreme orange shading = extremely low pressure / cyclone, blue shading = high pressure). So say you see those numbers tightly clustered right over or near each other, that means there is good agreement over that particular area between the ensembles. In the above chart, there really isn't - you can see a couple at that timeframe want a low/TC off Gladstone, one or two have held it off the coast of Cairns, and some even drift it into the gulf, which you can also see really clearly if you loop the chart on https://www.tropicaltidbits.com/analysis...8030400&fh=300. The rogue '12' you see might just be an outlier that wants higher than normal pressures from one particular ensemble member? I'm not too sure to be honest, someone else may be able to answer that.

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#1455688 - 04/03/2018 19:28 Re: QLD Tropical Cyclone Season 2017/2018 [Re: Ken Kato]
rainthisway Offline
Weather Freak

Registered: 09/11/2015
Posts: 808
Loc: Mutarnee.....70km north of Tow...
Originally Posted By: Ken Kato
Originally Posted By: rainthisway
Does anyone know how they come up with for3casts...do they use one model or a combination of all of them.

For forecasting TC formation over the water, all the leading models are looked at together with knowledge of all the principles of TC formation (e.g. shear, sea surface temps, triggers, synoptics, etc).


Once a low becomes a designated system, a sophisticated piece of software is used which allows you to include a combination of up to several models of your choosing - it then calculates a consensus track of all the models you chose. The grey cone of uncertainty surrounding that track is based on a certain proportion of past forecast track errors plus the uncertainty in the analysis position. Manual adjustments can be made by the forecaster as necessary.


Thank you Ken. Your information is appreciated as usual.
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Nikko

Travelling - Current location= Toomulla

MTD (July 2018]: 0.9mm
JUNE 2018: 0.9mm

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#1455697 - 04/03/2018 20:13 Re: QLD Tropical Cyclone Season 2017/2018 [Re: Mega]
MangroveJack70 Offline
Weather Freak

Registered: 01/02/2011
Posts: 218
Originally Posted By: Mega
Originally Posted By: MangroveJack70
Originally Posted By: Mega
The GFS ensemble members are all over the shop, as to be expected so far out - some move it faster, some slower, some into the gulf, some down the coast, and others I'd imagine that have nothing at all.



Hey Mega. That's a really neat Chart. Question: what do the numbers within the Redish section east of Cairns refer too ? Are they Wind Speed perhaps ? Interested in understanding the Blue number (12) slightly north of Cairns. I'm assuming the Normalised Spread refer to Standard Deviation perhaps.

Just trying to wrap my head about the Chart.

Thanks.


The numbers you see inside each orange shading correlates to an individual ensemble member, where surface pressure is used (so extreme orange shading = extremely low pressure / cyclone, blue shading = high pressure). So say you see those numbers tightly clustered right over or near each other, that means there is good agreement over that particular area between the ensembles. In the above chart, there really isn't - you can see a couple at that timeframe want a low/TC off Gladstone, one or two have held it off the coast of Cairns, and some even drift it into the gulf, which you can also see really clearly if you loop the chart on https://www.tropicaltidbits.com/analysis...8030400&fh=300. The rogue '12' you see might just be an outlier that wants higher than normal pressures from one particular ensemble member? I'm not too sure to be honest, someone else may be able to answer that.




Ahhhh. Got it. Great explanation Mega.

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#1455699 - 04/03/2018 20:33 Re: QLD Tropical Cyclone Season 2017/2018 [Re: MangroveJack70]
MangroveJack70 Offline
Weather Freak

Registered: 01/02/2011
Posts: 218
Originally Posted By: MangroveJack70
Originally Posted By: Mega
Originally Posted By: MangroveJack70
Originally Posted By: Mega
The GFS ensemble members are all over the shop, as to be expected so far out - some move it faster, some slower, some into the gulf, some down the coast, and others I'd imagine that have nothing at all.



Hey Mega. That's a really neat Chart. Question: what do the numbers within the Redish section east of Cairns refer too ? Are they Wind Speed perhaps ? Interested in understanding the Blue number (12) slightly north of Cairns. I'm assuming the Normalised Spread refer to Standard Deviation perhaps.

Just trying to wrap my head about the Chart.

Thanks.


The numbers you see inside each orange shading correlates to an individual ensemble member, where surface pressure is used (so extreme orange shading = extremely low pressure / cyclone, blue shading = high pressure). So say you see those numbers tightly clustered right over or near each other, that means there is good agreement over that particular area between the ensembles. In the above chart, there really isn't - you can see a couple at that timeframe want a low/TC off Gladstone, one or two have held it off the coast of Cairns, and some even drift it into the gulf, which you can also see really clearly if you loop the chart on https://www.tropicaltidbits.com/analysis...8030400&fh=300. The rogue '12' you see might just be an outlier that wants higher than normal pressures from one particular ensemble member? I'm not too sure to be honest, someone else may be able to answer that.




Ahhhh. Got it. Great explanation Mega.


Hmmm. Quite interesting when you look for specific numbers as you suggest. So if I understand it correctly, if we have multiples of the same number in close proximity, it's suggestive of higher confidence in the Ensemble and the forecast position at that particular point in time.

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#1455704 - 04/03/2018 20:56 Re: QLD Tropical Cyclone Season 2017/2018 [Re: @_Yasified_shak]
MangroveJack70 Offline
Weather Freak

Registered: 01/02/2011
Posts: 218


Hey Mega. That's a really neat Chart. Question: what do the numbers within the Redish section east of Cairns refer too ? Are they Wind Speed perhaps ? Interested in understanding the Blue number (12) slightly north of Cairns. I'm assuming the Normalised Spread refer to Standard Deviation perhaps.

Just trying to wrap my head about the Chart.

Thanks. [/quote]

The numbers you see inside each orange shading correlates to an individual ensemble member, where surface pressure is used (so extreme orange shading = extremely low pressure / cyclone, blue shading = high pressure). So say you see those numbers tightly clustered right over or near each other, that means there is good agreement over that particular area between the ensembles. In the above chart, there really isn't - you can see a couple at that timeframe want a low/TC off Gladstone, one or two have held it off the coast of Cairns, and some even drift it into the gulf, which you can also see really clearly if you loop the chart on https://www.tropicaltidbits.com/analysis...8030400&fh=300. The rogue '12' you see might just be an outlier that wants higher than normal pressures from one particular ensemble member? I'm not too sure to be honest, someone else may be able to answer that.[/quote]



Ahhhh. Got it. Great explanation Mega. [/quote]

Hmmm. Quite interesting when you look for specific numbers as you suggest. So if I understand it correctly, if we have multiples of the same number in close proximity, it's suggestive of higher confidence in the Ensemble and the forecast position at that particular point in time. [/quote]

That's cool. Had a look at the system over on the Indian Ocean toward Africa (102 hours) and it makes sense. Thanks for sharing.

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#1455710 - 04/03/2018 21:15 Re: QLD Tropical Cyclone Season 2017/2018 [Re: @_Yasified_shak]
Mega Offline
Meteorological Motor Mouth

Registered: 03/02/2003
Posts: 7054
Loc: Maryborough, Wide Bay, QLD
I didn't really make it clear in my above post - but the numbers represent the pressure that particular ensemble is is showing at that time. So in that chart, two ensembles show a 974hpa TC off Gladstone, (74), two 971's off Cairns, (71), O3s and 04s (1003hpa, 1004hpa) across the top end etc. If there were a heap of, say 971's (71s) clustered together then that'd mean good agreement between ensembles that a strong TC is in that area in that point in time.

I really like to look at ensemble spread like this and not just single model runs because it gives a better idea of the potential factors that could come into play at that particular time, but that's just me.

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#1455711 - 04/03/2018 21:28 Re: QLD Tropical Cyclone Season 2017/2018 [Re: Mega]
bundybear Offline
Weatherzone Addict

Registered: 28/12/2010
Posts: 2232
Loc: Between Bundy and Gladstone
Originally Posted By: Mega
I didn't really make it clear in my above post - but the numbers represent the pressure that particular ensemble is is showing at that time. So in that chart, two ensembles show a 974hpa TC off Gladstone, (74), two 971's off Cairns, (71), O3s and 04s (1003hpa, 1004hpa) across the top end etc. If there were a heap of, say 971's (71s) clustered together then that'd mean good agreement between ensembles that a strong TC is in that area in that point in time.


I do not like any of them to be honest that show any wet weather system heading my way. I am absolutely sodden. Any wet weather system is going to mean that I won't be going anywhere for a month again. Wet and windy means chances are high my power will be gone for a good week. So sorry, no wet and windy things are allowed. grin

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#1455725 - 04/03/2018 23:48 Re: QLD Tropical Cyclone Season 2017/2018 [Re: MangroveJack70]
Ken Kato Offline
Meteorological Motor Mouth

Registered: 05/03/2012
Posts: 5244
Originally Posted By: MangroveJack70
Hmmm. Quite interesting when you look for specific numbers as you suggest. So if I understand it correctly, if we have multiples of the same number in close proximity, it's suggestive of higher confidence in the Ensemble and the forecast position at that particular point in time.

Another useful way of visualising confidence in an ensemble or lack thereof is to look at probability maps.

The probabilities simply represent the percentage of that ensemble's forecast members meeting a given threshold. In the examples below, it shows the percentage of the EC ensemble's members forecasting a TC (using a system created by the ECMWF to try and identify warm cored tropical systems meeting TC-like criteria) for the 48hrs up to next Saturday night, and for the 48hrs up to the forecast day that Mega's chart was for (albeit using a different ensemble).

The higher the percentages, the higher the confidence in that particular ensemble.
Note that it's normal for the probabilities to appear modest at long ranges but that's only because of the naturally higher uncertainty that's common at those longer ranges:





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#1455742 - 05/03/2018 09:40 Re: QLD Tropical Cyclone Season 2017/2018 [Re: @_Yasified_shak]
KevD Offline
Occasional Visitor

Registered: 23/09/2001
Posts: 5194
Loc: Bellingen NSW 2454
In terms of confidence of something coming together, GFS has been impressively consistent across the last four runs (clickable for the full image):









Obviously a long way out and small differences in initial position can have a magnifying impact on final location down the track, so picking landfall if anything does come together is way too far out (for example the latest 18z run shows an upper trough approaching from the west...the run does not go as far out yet as to show what that means, but my guess would be increased likelihood of missing the east coast altogether), but certainly a decent and consistent signal at this stage from GFS. Now going to wait and watch it disappear on the 00z run crazy

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#1455781 - 05/03/2018 14:52 Re: QLD Tropical Cyclone Season 2017/2018 [Re: @_Yasified_shak]
Mad Elf #1.5 Offline
Weatherzone Addict

Registered: 05/03/2012
Posts: 3385
Loc: Mt Hallen QLD
Da Media got wind of not 1 but 2 cyclones next week. Good grief, I can already see the armageddon headlines.

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#1455791 - 05/03/2018 15:50 Re: QLD Tropical Cyclone Season 2017/2018 [Re: @_Yasified_shak]
Raindammit Offline
Weatherzone Moderator

Registered: 14/02/2002
Posts: 12969
Loc: Townsville & Bilyana NQ
Latest GFS has it crossing near Port Douglas. Still early days yet.
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