ATL: KATIA - Post Tropical - Discussion

[GCANE]

GFS seems to be building a cut-off low at the end of its forecast period over the OH valley.

Will be interesting to see how this evolves on future model runs.


http://www.atmos.albany.edu/student/cor ... ecast.html

[SuperLikeNintendo]

I just wanted to introduce the possibility of Lee sucking Katia in. It IS the Gulf and stranger things have happened.

I'm still of the opinion that we're a few days away to having a semi-clear picture of what to expect on the east coast. Troughs are forming and dissipating every 12 to 24 hours and nothing is certain at this point.

Just my OPINION.

Personal Forecast Disclaimer:
The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[stewart715]

I think it's possible that the NHC will downgrade Katia to a tropical storm, half of the center is exposed, however I think it still can be a major hurricane down the looong road it has ahead.

Where do you see this exposure?

[jhpigott]

I think it's possible that the NHC will downgrade Katia to a tropical storm, half of the center is exposed, however I think it still can be a major hurricane down the looong road it has ahead.

If Katia doesn't deepen like the NHC has forecasted and in fact weakens - can we expect a further westward track?

[stewart715]

I just wanted to introduce the possibility of Lee sucking Katia in. It IS the Gulf and stranger things have happened.

I'm still of the opinion that we're a few days away to having a semi-clear picture of what to expect on the east coast. Troughs are forming and dissipating every 12 to 24 hours and nothing is certain at this point.

Just my OPINION.

Personal Forecast Disclaimer:
The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

I've seen models that bring Katia and Lee to CONUS Northeast and Katia absorbs Lee. Either way, I don't think the next 10 days are going to be 'textbook' tropics. Tropics altogether are unpredictable but I think the next 10 days will be especially unpredictable, even with our fancy computer models

[clfenwi]

Microwave image from ~ 3 hrs ago

[Aric Dunn]

The center is nearly exposed on satellite... hmmmm...

[BigA]

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

My best guess: The shear from the ULL will weaken Katia, but not fatally. By tomorrow or Saturday the ULL will be weakening/moving out to the northeast and Katia will find more favorable conditions. That said, the bit of weakening may induce something of more westward track in the short run, but shouldn't affect long term track very much.

[dolebot_Broward_NW]

Center exposed:

http://www.ssd.noaa.gov/goes/flt/t2/flash-rgb.html

[BigA]

The NHC's thinking on the shear affecting Katia (from the 11AM discussion)

SOUTHWESTERLY SHEAR OF ABOUT 15 KT...AS ANALYZED BY UW-CIMSS...IS
CURRENTLY AFFECTING KATIA. THIS SHEAR IS ASSOCIATED WITH AN
UPPER-LEVEL LOW LOCATED TO THE NORTHWEST OF THE HURRICANE. THE
UPPER LOW IS EXPECTED TO CONTINUE TO IMPOSE MODERATE SHEAR OVER
KATIA FOR ANOTHER 24 TO 36 HOURS. IN ADDITION...SOME DRY AIR
APPEARS TO BE ENTRAINING INTO THE CIRCULATION OF KATIA AND
THIS...IN COMBINATION WITH THE AFOREMENTIONED SHEAR...COULD INHIBIT
SIGNIFICANT DEVELOPMENT IN THE SHORT-TERM. BEYOND 36 HOURS...THE
GLOBAL MODELS SHOW THE UPPER LOW LIFTING OUT...CREATING A MORE
FAVORABLE UPPER-LEVEL WIND PATTERN. THEREFORE...STEADY
STRENGTHENING IS FORECAST IN THE LONGER RANGE. THE OFFICIAL
FORECAST IS LOWERED SLIGHTLY FROM THE PREVIOUS ONE IN THE
SHORT-TERM...BUT STILL BRINGS KATIA TO A MAJOR HURRICANE IN A FEW
DAYS.

[Aric Dunn]

finally a little info on the divergent models in the discussion. more too come as that time frame is inside the 5 day forecast period of the NHC

[stewart715]

Hurricane Katia: 11 AM ET, 75 mph winds, Cat 1, 987 mb, moving W at 18 mph.

[stewart715]

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

My best guess: The shear from the ULL will weaken Katia, but not fatally. By tomorrow or Saturday the ULL will be weakening/moving out to the northeast and Katia will find more favorable conditions. That said, the bit of weakening may induce something of more westward track in the short run, but shouldn't affect long term track very much.

I think this weakening is bad news for CONUS. Just a hunch.

Disclaimer: I usually am wrong (kidding, but take everything I say with a grain of salt).

[gatorcane]

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

My best guess: The shear from the ULL will weaken Katia, but not fatally. By tomorrow or Saturday the ULL will be weakening/moving out to the northeast and Katia will find more favorable conditions. That said, the bit of weakening may induce something of more westward track in the short run, but shouldn't affect long term track very much.

I think this weakening is bad news for CONUS. Just a hunch.

Disclaimer: I usually am wrong (kidding, but take everything I say with a grain of salt).

Well if it gets more shallow than expected could easily see the cone keep nudging more westwards. We'll see but at least the GFS and ECMWF are on the eastern side of the model guidance envelope, and usually they are very reliable.

The NOGAPs is more west, but usually not as reliable.

[Aric Dunn]

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

My best guess: The shear from the ULL will weaken Katia, but not fatally. By tomorrow or Saturday the ULL will be weakening/moving out to the northeast and Katia will find more favorable conditions. That said, the bit of weakening may induce something of more westward track in the short run, but shouldn't affect long term track very much.

I think this weakening is bad news for CONUS. Just a hunch.

Disclaimer: I usually am wrong (kidding, but take everything I say with a grain of salt).

Well if it gets more shallow than expected could easily see the cone keep nudging more westwards. We'll see but at least the GFS and ECMWF are on the eastern side of the model guidance envelope, and usually they are very reliable.

The NOGAPs is more west, but usually not as reliable.

besides yesterdays 12z euro run.... cant forget the models just are not sure what to do with the trough thats supposed to come. all the models are basically on the cusp of turning out to see or turning back west. very tough forecast coming up the next few days.

and besides the nogaps.... we have the cmc and now the ukmet along with the 12z nam bending westerly ....

[Gustywind]

000
WTNT32 KNHC 011449
TCPAT2

BULLETIN
HURRICANE KATIA ADVISORY NUMBER 14
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011
1100 AM AST THU SEP 01 2011

...KATIA CONTINUES WESTWARD WITH LITTLE CHANGE IN STRENGTH...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...15.5N 47.5W
ABOUT 1050 MI...1685 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/H
PRESENT MOVEMENT...W OR 280 DEGREES AT 18 MPH...30 KM/H
MINIMUM CENTRAL PRESSURE...987 MB...29.15 INCHES

[gatorcane]

Looks like the UKMET 00Z is building a strong Bermuda High ridge overtop and bending it back west at 120 hours:

http://raleighwx.americanwx.com/models/ ... tLoop.html

[Blown Away]

FROM 11 AM DISCO: THE MODEL GUIDANCE BECOMES VERY DIVERGENT IN
4 TO 5 DAYS WITH THE UKMET...NOGAPS...AND GFDL MODELS ON THE SOUTH
SIDE OF THE ENVELOPE AND THE GFS...ECMWF...AND HWRF MODELS ON THE
NORTH SIDE. THIS SPREAD APPEARS TO BE ASSOCIATED WITH THE STRENGTH
OF A TROUGH MOVING OVER THE NORTHEASTERN UNITED STATES AND THE
POSITION OF THE SUBTROPICAL HIGH. THE OFFICIAL TRACK FORECAST IS
ONLY NUDGED A LITTLE TO THE LEFT...IN PART BECAUSE OF THE INITIAL
MOTION AND POSITION...AND IS VERY NEAR THE MULTI-MODEL CONSENSUS.

NHC finally acknowledging the models divergence.

[HurricaneWarning92]

And i think the UKMET has a better handle in the long range than the EURO. Of course the EURO i believe is better overall but not so sure if it is much in the long range.

[AdamFirst]

Weather Channel convinced Katia is going out to sea, with a possible impact on Bermuda. Their tropics hype machine is focused on the Gulf of Mexico invest.