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#950194 - 01/02/2011 22:19 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: Steamy]
jss Offline
Cloud Gazer

Registered: 16/11/2008
Posts: 31
Loc: Docklands, VIC
It's rather hard to tell without microwave imagery, which is lacking at the moment. But since it's just reached cat 4 and contiuning to intensify, it's quite likely to see EWR cycles starting, should get at least one more in before it hits! Taking of disrupting the voritcity ring, I'm really hoping to see some eyewall mesovortices like with larry, maybe another paper grin not long till it's on radar.

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#950236 - 01/02/2011 22:30 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: jss]
CraigA74 Offline
Weatherzone Addict

Registered: 27/03/2007
Posts: 1253
Loc: Diamond Valley Qld
With the EWRC that may be happening,correct me if I'm wrong but will this inhibit intensification and possibly increase the actual size of the system even further?

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#950272 - 01/02/2011 22:41 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: CraigA74]
Wet Wet Wet Offline
Weatherzone Addict

Registered: 08/01/2008
Posts: 2332
Loc: Mackay, Qld


We really do take technology for granted. When you really think about it, its awesome how we can watch Yasi unfold on our computer screens with images taken from space during the night.
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#950281 - 01/02/2011 22:43 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: CraigA74]
jss Offline
Cloud Gazer

Registered: 16/11/2008
Posts: 31
Loc: Docklands, VIC
It's a cycle. As/if the eyewall recorganises, the convection about the eyewall is disrupted by low reflectivty inflow, weakening the winds about the eye region. Quite a few things can happen after a ERC, but it is not directly related to TC intensifcation or diameter. Wiki has a nice simple explanation with a few theories.

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#950294 - 01/02/2011 22:49 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: CraigA74]
opplevelse Offline
Weather Freak

Registered: 27/08/2006
Posts: 735
Loc: Christiania, slightly east of ...
LOL How many acronyms do you want for the same thing (an Eyewall Replacement Cycle)! I always thought it was just an ERC LOL smile

Anyway, yes, ERC's are often associated with a brief weakening of the system as the outer eyewall replaces the inner eyewall, but the storm will typically re-intensify rapidly. It is not at all surprising to see a storm of this size undergoing ERCs at this stage, and in fact given the small tight nature of the eye in the few Microwave shots we have actually been able to get, it is almost expected.

As was mentioned earlier in the thread a second "trough" formed outside the main eye. This is the first step of an ERC as an outer eyewall forms and sucks moisture away from the inner eyewall, causing it to collapse.

Anyway, Yasi has probably undergone a few ERCs while the eye was covered by the CDO, and is possibly undergoing one now. You don't need to rely on the MW data to tell either. You can often tell with visible sat shots with the sun at an oblique angle (so you can pick up surface features on the CDO. Or at night on the microwave shots.

Of course the best way to tell is if you have radar of the eye, and we should do in a few hours as it approaches Willis island smile
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#950308 - 01/02/2011 22:53 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: opplevelse]
StormySpott Offline
Weather Freak

Registered: 05/11/2009
Posts: 178
Loc: Wellington Pt, SE Qld
Mods, if you don't mind, I'll post this video link of this American guy who I believe is a Met doing an analysis of various Weather events around the world and Australia and posting his thoughts via You Tube. Some technical data can be found in his comments.

Latest Analysis of STC Yasi

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#950339 - 01/02/2011 22:59 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: opplevelse]
jss Offline
Cloud Gazer

Registered: 16/11/2008
Posts: 31
Loc: Docklands, VIC
If there's any vortex rossby wave activity I might post of some wavelet anaylsis if anyones interested as the tc comes within range tomorrow, probably just the fourier analysis of the eyewall as it's the most interesting. If activity is strong enough, true storm surge heights could become very 'unresolved' indeed. *Avoids media*

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#950380 - 01/02/2011 23:09 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: StormySpott]
He who once was ITN Offline
Weather Freak

Registered: 18/05/2007
Posts: 578
Hmm gunna try my luck with this one



Slide 62 say pick the (thick) surrounding shade & I think it has to be light grey as black is too thin -> 5.0
Slide 64 is eye adjust and that is the thin surrounding shade which is black and the inside shade is off white -> + 0.5

Since the eye is round that makes a 5.5 - same as before -> 234 km/hr.

If that white wraps all the way round it would be 6.0 + 0.5 which would be a scary 290! Fortunately not there yet though.

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#950396 - 01/02/2011 23:12 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: opplevelse]
TC Poncho Offline
Weatherzone Addict

Registered: 07/01/2010
Posts: 2199
Loc: Point Cartwright, Sunny Coast,...
Originally Posted By: opplevelse
LOL How many acronyms do you want for the same thing (an Eyewall Replacement Cycle)! I always thought it was just an ERC LOL smile

Anyway, yes, ERC's are often associated with a brief weakening of the system as the outer eyewall replaces the inner eyewall, but the storm will typically re-intensify rapidly. It is not at all surprising to see a storm of this size undergoing ERCs at this stage, and in fact given the small tight nature of the eye in the few Microwave shots we have actually been able to get, it is almost expected.

As was mentioned earlier in the thread a second "trough" formed outside the main eye. This is the first step of an ERC as an outer eyewall forms and sucks moisture away from the inner eyewall, causing it to collapse.

Anyway, Yasi has probably undergone a few ERCs while the eye was covered by the CDO, and is possibly undergoing one now. You don't need to rely on the MW data to tell either. You can often tell with visible sat shots with the sun at an oblique angle (so you can pick up surface features on the CDO. Or at night on the microwave shots.

Of course the best way to tell is if you have radar of the eye, and we should do in a few hours as it approaches Willis island smile


does a wobble like we sometimes see on the IR sat indicate a EWR?
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#950404 - 01/02/2011 23:14 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: jss]
TC Poncho Offline
Weatherzone Addict

Registered: 07/01/2010
Posts: 2199
Loc: Point Cartwright, Sunny Coast,...
Originally Posted By: uq-wx
If there's any vortex rossby wave activity I might post of some wavelet anaylsis if anyones interested as the tc comes within range tomorrow, probably just the fourier analysis of the eyewall as it's the most interesting. If activity is strong enough, true storm surge heights could become very 'unresolved' indeed. *Avoids media*


yeah, that would be awesome grin
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#950426 - 01/02/2011 23:17 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: He who once was ITN]
TC Poncho Offline
Weatherzone Addict

Registered: 07/01/2010
Posts: 2199
Loc: Point Cartwright, Sunny Coast,...
So really its actually stronger, as its giving the same result as before but this one has a much better eye structure.

Originally Posted By: He who once was ITN
Hmm gunna try my luck with this one



Slide 62 say pick the (thick) surrounding shade & I think it has to be light grey as black is too thin -> 5.0
Slide 64 is eye adjust and that is the thin surrounding shade which is black and the inside shade is off white -> + 0.5

Since the eye is round that makes a 5.5 - same as before -> 234 km/hr.

If that white wraps all the way round it would be 6.0 + 0.5 which would be a scary 290! Fortunately not there yet though.

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#950450 - 01/02/2011 23:22 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: TC Poncho]
!SCHUMMY! Offline
Weatherzone Addict

Registered: 22/04/2008
Posts: 2915
Loc: Jimboomba, SEQ
ok..take 2! smile Here is the MPI (Maximum Potential Intensity) progged for the Coral Sea ahead of STC YASI



it really shows what she (YASI) is capable of if conditions are perfect for further rapid intensification....which is a possibility after the current EWRC (Eye Wall Replacement Cycle)

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#950452 - 01/02/2011 23:23 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: jss]
opplevelse Offline
Weather Freak

Registered: 27/08/2006
Posts: 735
Loc: Christiania, slightly east of ...
Originally Posted By: uq-wx
If there's any vortex rossby wave activity I might post of some wavelet anaylsis if anyones interested as the tc comes within range tomorrow, probably just the fourier analysis of the eyewall as it's the most interesting. If activity is strong enough, true storm surge heights could become very 'unresolved' indeed. *Avoids media*
I'd be interested! I've never really understood the motivation behind the study of VRW, I thought it was essentially an academic exercise. I can see how it may somehow be useful in helping understand wind distributions in the inner spiral bands but even then, what is the practical application- or isnt there any? Is it just to aid our understanding of the physical phenomena (a worthwhile goal in it-self). Or is the ultimate goal microscale or even storm scale forecasts of TC wind fields for application in the real world?
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#950511 - 01/02/2011 23:37 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: opplevelse]
crikey Offline
Weatherzone Addict

Registered: 01/02/2011
Posts: 3184
Loc: Tweed Heads
20 metre waves of Nth queensland coastline +6.00am wed morning 2/2/2011 just off coastline
What does this data mean?
http://www.weatheronline.co.uk/marine/weather?LEVEL=5&LANG=en&MENU=0&TIME=30&MN=gfs&CONT=aupa
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#950542 - 01/02/2011 23:45 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: opplevelse]
Subtropical Offline
Weather Freak

Registered: 26/11/2006
Posts: 560
Loc: The Subtropics
Could TC Yasi intensify to a Category 5?

How valid is BOM's Ann Farrell's statement on TC Yasi's potential severity reported in The Sydney Morning Herald? BOM senior forecaster Ann Farrell said Yasi was continuing to intensify and she could not rule out the chance of it reaching category five.It is possible it could reach category five intensity, and that would push winds up to around the 300km/h mark, Ms Farrell said. Yasi could become category five monster

The Australian Bureau of Meteorology tropical cyclone severity categories

Category 5 ≥280 km/h (Maximum wind gusts), ≥200 km/h (Maximum sustained winds)
Category 4 225-279 km/h (Maximum wind gusts), 160-199 km/h (Maximum sustained winds)
Category 3 170-224 km/h (Maximum wind gusts), 118-159 km/h (Maximum sustained winds)
Category 2 125-169 km/h (Maximum wind gusts), 89-117 km/h (Maximum sustained winds)
Category 1 90-124 km/h (Maximum wind gusts), 63-88 km/h (Maximum sustained winds)

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#950553 - 01/02/2011 23:49 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: Subtropical]
He who once was ITN Offline
Weather Freak

Registered: 18/05/2007
Posts: 578
If the white band were to wrap around in the infrared image then I think it would be 6.5 which is 290 - but I'm no expert and am just following the rules in the dvorak powerpoint


Edited by He who once was ITN (01/02/2011 23:55)
Edit Reason: clarification

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#950644 - 02/02/2011 00:06 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: He who once was ITN]
marakai Offline
Weatherzone Addict

Registered: 05/01/2006
Posts: 2270
Loc: Maryfarms NQ
Latest chart is out with not much difference so far http://www.bom.gov.au/products/IDQ65002.shtml seeming to become more consistent with each run.

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#950648 - 02/02/2011 00:07 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: He who once was ITN]
Dave-Wx Offline
Weatherzone Addict

Registered: 27/08/2001
Posts: 4950
Loc: Heritage Park, Brisbane, QLD
Certainly going by the last 2 IR frames (1030 and 1130UTC) I think Yasi has bumped up another notch...be interesting Mr ITN if you had a look at the 1130UTC frame (or of course wait for the next one in 10-20 mins smile ) Actually there we go...260km/h in the latest TC advice, certainly along my lines of thinking!

Am wondering if the missing piece in the puzzle for Yasi trying to be a Cat 5 will be the higher energy just off the Cairns coastline as in the image posted by ITN a little earlier (http://i53.tinypic.com/1q3jno.gif). Yasi is steadily going to move into that area over the next 6 hours. Given that Yasi is already a high Cat 4, that would make the odds of Cat 5 between now and landfall certainly better than 50% I reckon.

Edit: Also just noticed that the latest track map has landfall (10pm tomorrow night) as 1 hour after high tide...just about couldn't time it any worse could you Yasi!


Edited by Dave-Wx (02/02/2011 00:11)

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#950649 - 02/02/2011 00:07 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: marakai]
marakai Offline
Weatherzone Addict

Registered: 05/01/2006
Posts: 2270
Loc: Maryfarms NQ
IDQ20018
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - EASTERN REGION
Issued by BRISBANE TROPICAL CYCLONE WARNING CENTRE
at: 1303 UTC 01/02/2011
Name: Severe Tropical Cyclone Yasi
Identifier: 14U
Data At: 1200 UTC
Latitude: 15.0S
Longitude: 153.1E
Location Accuracy: within 20 nm [35 km]
Movement Towards: west southwest [252 deg]
Speed of Movement: 18 knots [34 km/h]
Maximum 10-Minute Wind: 100 knots [185 km/h]
Maximum 3-Second Wind Gust: 140 knots [260 km/h]
Central Pressure: 940 hPa
Radius of 34-knot winds NE quadrant: 160 nm [295 km]
Radius of 34-knot winds SE quadrant: 250 nm [465 km]
Radius of 34-knot winds SW quadrant: 250 nm [465 km]
Radius of 34-knot winds NW quadrant: 120 nm [220 km]
Radius of 48-knot winds NE quadrant: 90 nm [165 km]
Radius of 48-knot winds SE quadrant: 120 nm [220 km]
Radius of 48-knot winds SW quadrant: 120 nm [220 km]
Radius of 48-knot winds NW quadrant: 60 nm [110 km]
Radius of 64-knot winds:
Radius of Maximum Winds: 20 nm [35 km]
Dvorak Intensity Code: T6.0/6.0/D1.0/24HRS
Pressure of outermost isobar: 1002 hPa
Radius of outermost closed isobar: 210 nm [390 km]
Storm Depth: Deep
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
[UTC] : degrees : nm [km]: knots[km/h]: hPa
+12: 02/0000: 16.1S 149.6E: 050 [095]: 105 [195]: 937
+24: 02/1200: 17.1S 146.0E: 080 [150]: 105 [195]: 937
+36: 03/0000: 18.4S 142.8E: 110 [205]: 050 [095]: 986
+48: 03/1200: 19.6S 140.0E: 130 [240]: 030 [060]: 998
+60: 04/0000: 20.8S 137.5E: 160 [295]: 025 [045]: 1001
+72: 04/1200: 21.5S 135.4E: 190 [350]: 025 [045]: 1000
REMARKS:
Yasi has intensified in the last 6 hours. The environment of low shear and good
upper level outflow, assisted by an upper low to the south, is conducive to
maintaining current intensity. There is the possibility of some further
intensification before landfall.

Dvorak intensity based on eye pattern [EIR B surround, OW eye] giving DT=6.0,
consistent with adjusted MET. Mean winds estimated at 100 knots.

Forecast motion is steady to the west southwest with a persisting mid-level
ridge to the south. Models are quite consistent with the forecast motion.

The combined factors of being intense, large, and motion at 18 knots are
conducive for greater wave/swell generation to the south of of the forecast
track.

With the expectation of being a large and intense system, cyclone intensity may
be maintained further inland than normal.

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#950652 - 02/02/2011 00:08 Re: Severe Tropical Cyclone Yasi (SPAC, Coral Sea) - Technical Discussion Only [Re: He who once was ITN]
TC Poncho Offline
Weatherzone Addict

Registered: 07/01/2010
Posts: 2199
Loc: Point Cartwright, Sunny Coast,...
Originally Posted By: He who once was ITN
If the white band were to wrap around in the infrared image then I think it would be 6.5 which is 290 - but I'm no expert and am just following the rules in the dvorak powerpoint


did you see the one Scott A posted in the Yazi chat thread? Can you please do one on that, it was a beauty!!
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