ATL: KATIA - Post Tropical - Discussion

[GCANE]

Looks like the anti-cyclone is to the east of the LLC indicating it is tracking away into a lowering tropopause height.

This would limit spin up.

So, this could indicate IMHO that the models maybe a bit aggressive on spin up in the short term and this could track a bit more due-west.

[gatorcane]

You can see TD #12 entering the NHC Atlantic Wide view satellite loop on far bottom right-hand side of image:

http://www.ssd.noaa.gov/goes/east/tatl/loop-vis.html

[SFLcane]

Speaking of models, has anyone compared the early models to where Irene actually went? Would that help with reliability in any of these early models for where 12 might end up?

You can check the model plot archive on Colorado State's website here:

http://euler.atmos.colostate.edu/~vigh/ ... c/archive/

Storm ID is aal09_xxxx. Here's the first model plot, taking Irene west of FL:
http://euler.atmos.colostate.edu/~vigh/ ... ck_gfs.png

Models were too far south and west with Irene with almost every run.

You can also get irene archived plots here...

http://www.tropicalatlantic.com/models/data.cgi?basin=al&year=2011&storm=09&display=archive

[CrazyC83]

I think the models are all off on this. I think it is too far south for any recurve before the Caribbean. I expect this to be a Caribbean or Gulf storm.


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[Graham1973]

000
WTNT32 KNHC 291436
TCPAT2

BULLETIN
TROPICAL DEPRESSION TWELVE ADVISORY NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011
1100 AM AST MON AUG 29 2011

...DEPRESSION OVER THE WATERS OF THE FAR EASTERN ATLANTIC...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...9.8N 27.5W
ABOUT 405 MI...650 KM SSW OF THE SOUTHERNMOST CAPE VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 275 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...1008 MB...29.77 INCHES


WATCHES AND WARNINGS
--------------------
THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 1100 AM AST...1500 UTC...THE CENTER OF TROPICAL DEPRESSION TWELVE
WAS LOCATED NEAR LATITUDE 9.8 NORTH...LONGITUDE 27.5 WEST. THE
DEPRESSION IS MOVING TOWARD THE WEST NEAR 15 MPH...24 KM/H. A TURN
TO THE WEST-NORTHWEST WITH SOME INCREASE IN FORWARD SPEED IS
EXPECTED OVER THE NEXT 48 HOURS.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS FORECAST DURING THE NEXT COUPLE OF
DAYS...AND THE DEPRESSION COULD BECOME A TROPICAL STORM BY TONIGHT.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB...29.77 INCHES.


HAZARDS AFFECTING LAND
----------------------
NONE


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...500 PM AST.

$$
FORECASTER PASCH




000
WTNT42 KNHC 291438
TCDAT2

TROPICAL DEPRESSION TWELVE DISCUSSION NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011
1100 AM AST MON AUG 29 2011

SATELLITE IMAGES INDICATE THAT THE CLOUD PATTERN OF THE DEPRESSION
HAS CHANGED LITTLE IN ORGANIZATION FROM EARLIER THIS MORNING.
THERE ARE SOME BROKEN BANDS OVER THE WESTERN AND SOUTHERN PORTION
OF THE CIRCULATION...AND THE CENTER OF THE CYCLONE IS NEAR THE
NORTHEASTERN EDGE OF THE MAIN AREA OF DEEP CONVECTION. DVORAK
INTENSITY ESTIMATES REMAIN AT 25 AND 30 KT FROM SAB AND TAFB...
RESPECTIVELY...AND THE INTIAL INTENSITY IS KEPT AT 30 KT. CURRENTLY
THERE IS MODERATE TO STRONG EAST-NORTHEASTERLY SHEAR OVER THE
SYSTEM AS EVIDENCED BY ITS APPEARANCE AND GLOBAL MODEL OUTPUT. THE
SHIPS GUIDANCE INDICATES THAT THIS SHEAR WILL SOON LESSEN...WHICH
SHOULD ALLOW THE DEPRESSION TO STRENGTHEN. THE OFFICIAL INTENSITY
FORECAST IS A LITTLE BELOW THE LATEST LGEM GUIDANCE.

THE INITIAL MOTION IS WESTWARD OR 275/13. THERE IS A MID-LEVEL
RIDGE TO THE NORTH OF THE DEPRESSION AT THIS TIME...BUT A MID- TO
UPPER-LEVEL LOW IS FORECAST TO CREATE A WEAKNESS IN THE RIDGE NEAR
40-50W OVER THE NEXT COUPLE OF DAYS. THIS FEATURE SHOULD CAUSE THE
TROPICAL CYCLONE TO TURN TOWARD THE WEST-NORTHWEST WITHIN THE NEXT
DAY OR SO. LATER IN THE FORECAST PERIOD...GLOBAL MODELS SHOW THE
WEAKNESS IN THE RIDGE SHIFTING WESTWARD AND THIS SHOULD PREVENT THE
CYCLONE FROM MOVING SIGNIFICANTLY POLEWARD DURING THE FORECAST
PERIOD. THE OFFICIAL TRACK FORECAST IS SIMILAR TO THE PREVIOUS ONE
AND ON THE SOUTHERN SIDE OF THE GUIDANCE ENVELOPE.

FORECAST POSITIONS AND MAX WINDS

INIT 29/1500Z 9.8N 27.5W 30 KT 35 MPH
12H 30/0000Z 10.3N 29.2W 35 KT 40 MPH
24H 30/1200Z 11.2N 31.4W 45 KT 50 MPH
36H 31/0000Z 12.3N 34.1W 50 KT 60 MPH
48H 31/1200Z 13.4N 37.2W 55 KT 65 MPH
72H 01/1200Z 15.0N 43.0W 70 KT 80 MPH
96H 02/1200Z 16.5N 48.5W 80 KT 90 MPH
120H 03/1200Z 18.5N 53.0W 90 KT 105 MPH

$$
FORECASTER PASCH

[CrazyC83]

Models take 12 north of Irene's track.

[otowntiger]

Speaking of models, has anyone compared the early models to where Irene actually went? Would that help with reliability in any of these early models for where 12 might end up?

You can check the model plot archive on Colorado State's website here:

http://euler.atmos.colostate.edu/~vigh/ ... c/archive/

Storm ID is aal09_xxxx. Here's the first model plot, taking Irene west of FL:
http://euler.atmos.colostate.edu/~vigh/ ... ck_gfs.png

Models were too far south and west with Irene with almost every run.

So can we take that to mean that the models are too far south and west with this system? Is this a trend with the models and their inherent uncertainties this far out or is this something unique to the synoptics of this season? Or is it just coincidence?

[RL3AO]

So can we take that to mean that the models are too far south and west with this system? Is this a trend with the models and their inherent uncertainties this far out or is this something unique to the synoptics of this season? Or is it just coincidence?

1st - The models are off by large amounts in the long term. The fact it took them so long to get a final track on Irene is normal.

2nd - The pattern is quite different then the one Irene had. The SAL is gone and the ridge is weaker. This means 12L is moving slower east of the islands which is allowing it to develop. Irene dealt with dry air and fast LL steering winds until it neared the Caribbean .

[johngaltfla]

Not to mention its at total odds with the GFS/ECM, which at this range tend to be the two models that need to be most closely watched.

Have to agree with you there 100%. The ECM really rebuilds the ridge back towards the U.S. in the latter part of the forecast period.

http://weather.myfoxtampabay.com/maps/W ... ecmwf.html

[Graham1973]

Now that Jose is out of the way...

Lets see if 'Katia to be' can live up to the hype.

[hipshot]

Note sure if the OT or not but here goes. This may be a stupid question but it just struck me that if the main wind pattern in the northern hemisphere is west to east, why do these waves move east to west? They come out above or in the ITCZ so they are not in the southern hemisphere. Stupid question?

The northern hemisphere has three main belts. The tropics (about to 30N) moves east to west. The mid latitudes, which most of our weather comes from goes west to east, and the polar region which is kinda irregular in terms of winds.

Thank you very much, I never realized there were 3 zones in our hemisphere. I am just so accustomed to watching the weather in the lower 48 and have just recently started to follow the weather in the tropics. Thanks again.

[wxman57]

So can we take that to mean that the models are too far south and west with this system? Is this a trend with the models and their inherent uncertainties this far out or is this something unique to the synoptics of this season? Or is it just coincidence?

Nope, the question was about model performance for Irene. Just because the models tended to take Irene too far south and west doesn't mean they'll be off in the same direction for Twelve/Katia.

[Aric Dunn]

This is what I mentioned earlier. them models the past few runs have been a little too aggressive with this mid to upper low and the effect of it seems to be lessening with every run.

from the 11am discussion

"THIS FEATURE SHOULD CAUSE THE
TROPICAL CYCLONE TO TURN TOWARD THE WEST-NORTHWEST WITHIN THE NEXT
DAY OR SO. LATER IN THE FORECAST PERIOD...GLOBAL MODELS SHOW THE
WEAKNESS IN THE RIDGE SHIFTING WESTWARD AND THIS SHOULD PREVENT THE
CYCLONE FROM MOVING SIGNIFICANTLY POLEWARD DURING THE FORECAST
PERIOD. THE OFFICIAL TRACK FORECAST IS SIMILAR TO THE PREVIOUS ONE
AND ON THE SOUTHERN SIDE OF THE GUIDANCE ENVELOPE. "

[DESTRUCTION5]

So can we take that to mean that the models are too far south and west with this system? Is this a trend with the models and their inherent uncertainties this far out or is this something unique to the synoptics of this season? Or is it just coincidence?

Nope, the question was about model performance for Irene. Just because the models tended to take Irene too far south and west doesn't mean they'll be off in the same direction for Twelve/Katia.

Too be fair if you look at modeling for Irene and reduce to an average of GFS and EURO They both had her approach on FL nailed since 12z Sunday and she passed safely in that exact area by 12Z Thurs...4 full days out they had her path for FL concerns nailed..Cant ask for much more than that..

[LarryWx]

Not to mention its at total odds with the GFS/ECM, which at this range tend to be the two models that need to be most closely watched.

Have to agree with you there 100%. The ECM really rebuilds the ridge back towards the U.S. in the latter part of the forecast period.

http://weather.myfoxtampabay.com/maps/W ... ecmwf.html

I don't see why the latter part of this ECM run concerns you. It has the storm recurving well east of the U.S. and it has a persistent trough centered just inland from the SE coast with no sig. high pressure in the western Atlantic off the east coast or over the NE U.S.

[WeatherGuesser]

But I also remember so many people saying there was no way the models could be right and that Irene couldn't possibly make that sharp right; that it was going to hit FL.

I'm just trying to figure out if the models can be trusted on this one. We just broke a 3 year streak of no U.S. Mainland landfalls and I really don't want to see this one hit. People are having a hard enough time right now. They don't need this kind of thing.

Yeah, Texas and parts of Florida could use rain, and a lot of it. But not with all that goes with it in a hurricane.

[HurricaneWarning92]

This is what I mentioned earlier. them models the past few runs have been a little too aggressive with this mid to upper low and the effect of it seems to be lessening with every run.

from the 11am discussion

"THIS FEATURE SHOULD CAUSE THE
TROPICAL CYCLONE TO TURN TOWARD THE WEST-NORTHWEST WITHIN THE NEXT
DAY OR SO. LATER IN THE FORECAST PERIOD...GLOBAL MODELS SHOW THE
WEAKNESS IN THE RIDGE SHIFTING WESTWARD AND THIS SHOULD PREVENT THE
CYCLONE FROM MOVING SIGNIFICANTLY POLEWARD DURING THE FORECAST
PERIOD. THE OFFICIAL TRACK FORECAST IS SIMILAR TO THE PREVIOUS ONE
AND ON THE SOUTHERN SIDE OF THE GUIDANCE ENVELOPE. "

yep i see... so this could mean models may shift on a wnw track in the long term as opposed to NW like are showing now?

[Blown Away]

This is what I mentioned earlier. them models the past few runs have been a little too aggressive with this mid to upper low and the effect of it seems to be lessening with every run.

from the 11am discussion

"THIS FEATURE SHOULD CAUSE THE
TROPICAL CYCLONE TO TURN TOWARD THE WEST-NORTHWEST WITHIN THE NEXT
DAY OR SO. LATER IN THE FORECAST PERIOD...GLOBAL MODELS SHOW THE
WEAKNESS IN THE RIDGE SHIFTING WESTWARD AND THIS SHOULD PREVENT THE
CYCLONE FROM MOVING SIGNIFICANTLY POLEWARD DURING THE FORECAST
PERIOD. THE OFFICIAL TRACK FORECAST IS SIMILAR TO THE PREVIOUS ONE
AND ON THE SOUTHERN SIDE OF THE GUIDANCE ENVELOPE. "

That may be the case through 120 hours, but beyond that the globals want to turn TD12 well E of the CONUS.

[HurricaneWarning92]

Tropical Depression #12 entering the central Atlantic...

http://www.ssd.noaa.gov/goes/east/catl/loop-vis.html

[Aric Dunn]

This is what I mentioned earlier. them models the past few runs have been a little too aggressive with this mid to upper low and the effect of it seems to be lessening with every run.

from the 11am discussion

"THIS FEATURE SHOULD CAUSE THE
TROPICAL CYCLONE TO TURN TOWARD THE WEST-NORTHWEST WITHIN THE NEXT
DAY OR SO. LATER IN THE FORECAST PERIOD...GLOBAL MODELS SHOW THE
WEAKNESS IN THE RIDGE SHIFTING WESTWARD AND THIS SHOULD PREVENT THE
CYCLONE FROM MOVING SIGNIFICANTLY POLEWARD DURING THE FORECAST
PERIOD. THE OFFICIAL TRACK FORECAST IS SIMILAR TO THE PREVIOUS ONE
AND ON THE SOUTHERN SIDE OF THE GUIDANCE ENVELOPE. "

That may be the case through 120 hours, but beyond that the globals want to turn TD12 well E of the CONUS.

right, not talking about anything that far out. thats a whole different synoptic reasoning with the weakness from Irene still there past 60W which is very unlikely..