ATL: KATIA - Post Tropical - Discussion

[supercane]

NOGAPS is well known for accurate long term forecasting.

NOGAPS is well known, but for the exact opposite reason: it is not one of the more reliable models. From the most recent (2010) NHC model verification report (pdf file, page 11):

The best-performing dynamical model in 2010 was EMXI, followed by GFSI. The GHMI, GF5I, HWFI, and EGRI made up the “second tier” of three-dimensional dynamical models, and NGPI and GFNI performed less well, with skill comparable to or even lower than the two-dimensional BAM collection.

where the ending I's mean the last-model run interpolated to the current position, EMX=ECMWF, GFSI=GFS, GHMI=GFDL, HWFI=HWRF, EGRI=EGRR, NGPI=NOGAPS, and GFNI=GFDN.[/quote]

This doesn't necessarily mean that NOGAPS can't be right in a given situation, but to favor it over the more reliable ECMWF and GFS requires an explanation of why the synoptic handling is better in the former than the latter two star performers.

[supercane]

BTW Katia looking somewhat ragged and sheared this morning. Latest ATCF best track signals this may be downgraded to TS with the next advisory:
AL, 12, 2011090306, , BEST, 0, 190N, 547W, 60, 991, TS, 34, NEQ, 150, 120, 75, 135, 1013, 275, 25, 0, 0, L, 0, , 0, 0, KATIA, D,

[MWatkins]

Glenn in Kill Devil Hills, NC here. First post, but I've been reading the mail here for a while, and learning a lot.

I saw where one of the models (NOGAPS, I think) is predicting a landfall at or near the OBX. I'm wondering if this type of thing, with 2 hurricanes making landfall in the same area within a 2 week period or so, has happened before? Anyone? Anyone? Bueller? Bueller?

I've lived on the OBX since January of 99, and Irene was the first time I ever left for a storm. (Had all my storm supplies ready to go, such as they are, and the other half said "I'm going to Wake Forest, and you're coming with me") Hoping we don't have a repeat of that situation coming up.

Glenn
KC4SJU
KDH NC

Yep as recently as 2004. Frances and Jeanne made landfall at the exact lat/long pair for Vero Beach, FL within 10 days of each other.

MW

[supercane]

000
WTNT42 KNHC 030900
TCDAT2

HURRICANE KATIA DISCUSSION NUMBER 21
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011
500 AM AST SAT SEP 03 2011

KATIA CONTINUES TO STRUGGLE THIS MORNING WITH BURSTS OF CONVECTION
FORMING AN UNSHAPELY CENTRAL DENSE OVERCAST. THE OVERALL PATTERN
IS NOT WELL ORGANIZED EITHER WITH THE HURRICANE HAVING TROUBLE
MAINTAINING BANDING FEATURES. SATELLITE CLASSIFICATIONS ARE A
LITTLE LOWER THAN EARLIER...BUT STILL SUPPORT 65 KT ON THIS
ADVISORY. IT WOULD NOT BE SURPRISING IF IT WERE A LITTLE WEAKER
GIVEN THE RAGGED SATELLITE APPEARANCE.

SOUTHWESTERLY SHEAR AND SOME DRY AIR CONTINUE TO PREVENT SIGNIFICANT
STRENGTHENING OF THE TROPICAL CYCLONE. THE UPPER-LEVEL TROUGH TO
THE NORTHWEST OF KATIA...HOWEVER...HAS BEEN WEAKENING...AND MOST OF
THE GLOBAL MODELS SUGGEST THE SHEAR WILL DECREASE STARTING ON
SUNDAY. THUS SLOW INTENSIFICATION IS INDICATED AT THAT TIME IN THE
NHC FORECAST. AFTERWARD...VERTICAL WIND SHEAR COULD BECOME RATHER
LOW BY DAY 4 AS AN UPPER-HIGH BUILDS CLOSER TO THE TROPICAL CYCLONE
WHILE KATIA MOVES OVER 29C WATER TEMPERATURES. THE NHC FORECAST IS
SIMILAR TO THE PREVIOUS ONE EARLY ON...NEAREST THE LGEM/SHIPS
MODELS...BUT THEN IS BLENDED A LITTLE HIGHER AT THE END OF THE
FORECAST PERIOD WITH THE DYNAMICAL MODEL CONSENSUS. BOTH THE HWRF
AND GFDL ARE SIGNIFICANTLY STRONGER THAN THE NHC FORECAST...BUT
THEY ARE PROBABLY NOT HANDLING THE MODERATE TO STRONG VERTICAL
SHEAR ENVIRONMENT CORRECTLY.

KATIA CONTINUES MOVING TOWARD THE NORTHWEST AT ABOUT 9 KT. ALMOST
ALL OF THE GUIDANCE KEEP THIS GENERAL TRACK GOING FOR THE NEXT
SEVERAL DAYS AS THE CYCLONE APPROACHES THE WESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE. THE UKMET MODEL HAS BEEN STUBBORNLY FORECASTING
A MUCH STRONGER RIDGE...WHICH FORCES THE CYCLONE ON A WESTWARD
COURSE CLOSER TO THE BAHAMAS. THIS WESTWARD TRACK SEEMS HIGHLY
UNLIKELY DUE TO A PRONOUNCED TROUGH OVER THE WESTERN ATLANTIC OCEAN
AND THE UKMET SOLUTION IS DISREGARDED FOR THIS FORECAST.
OTHERWISE...THE MOST RELIABLE GUIDANCE HAS SHIFTED NORTHWARD
TONIGHT...PROBABLY DUE TO THE AFOREMENTIONED TROUGH OVER THE
WESTERN ATLANTIC BEING A BIT STRONGER THAN EARLIER ANTICIPATED.
THE NHC FORECAST IS NEAR THE PREVIOUS ONE FOR THE FIRST COUPLE OF
DAYS...THEN IS SHIFTED TO THE NORTH...BUT NOT NEARLY AS FAR AS THE
MOST RECENT ECMWF/GFS/GFDL MODEL SOLUTIONS.


FORECAST POSITIONS AND MAX WINDS

INIT 03/0900Z 19.3N 55.1W 65 KT 75 MPH
12H 03/1800Z 20.1N 56.3W 65 KT 75 MPH
24H 04/0600Z 21.1N 57.9W 65 KT 75 MPH
36H 04/1800Z 22.2N 59.7W 70 KT 80 MPH
48H 05/0600Z 23.4N 61.5W 75 KT 85 MPH
72H 06/0600Z 26.0N 64.5W 90 KT 105 MPH
96H 07/0600Z 28.5N 67.5W 100 KT 115 MPH
120H 08/0600Z 31.0N 70.0W 95 KT 110 MPH

$$
FORECASTER BLAKE

[supercane]

Latest advisory kept it as a hurricane:
BULLETIN
HURRICANE KATIA ADVISORY NUMBER 21
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011
500 AM AST SAT SEP 03 2011

...KATIA STILL A HURRICANE...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...19.3N 55.1W
ABOUT 530 MI...850 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...988 MB...29.18 INCHES

[Gustywind]

Katia 5AM

[Gustywind]

Looks like Katia is steadily moving away of the Lesser Antilles

[cycloneye]

Looks like Katia is steadily moving away of the Lesser Antilles
http://sirocco.accuweather.com/sat_mosa ... aeatle.gif

Yes,she has cleared all the islands from a direct hit,but still we have to watch for the high swells on the beaches and for the mariners who venture out to fish and for pleasure on this weekend.

[Nimbus]

You can see the high Cirrus clouds being pulled northeast by the remnants of the current trough. There is another trough off the east coast that looks like it is going to close off and roll southwest allowing the ridging to build back in along the east coast. By the time Katia crosses 60W they should have the ridge better modeled, if that east coast trough does close off and roll southwest the east coast will need hurricane warnings.

[jpigott]

06 GFS gets awfully close to New England

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

[Gustywind]

Looks like Katia is steadily moving away of the Lesser Antilles
http://sirocco.accuweather.com/sat_mosa ... aeatle.gif

Yes,she has cleared all the islands from a direct hit,but still we have to watch for the high swells on the beaches and for the mariners who venture out to fish and for pleasure on this weekend.

You're definitely right Cycloneye ... and Meteo-France Guadeloupe have issued since yesterday 11AM an yellow alert due to strong and dangerous seas for Guadeloupe and the Northern Leewards Islands. They [Meteo-France] expect this morning waves reaching 3meters, 3meters 30 and less tonight and tommorow (2meters, 2meters 50).

[Gustywind]

Ragged appearence for Katia, thanksfully she continues to leave the Lesser Antilles...

[tolakram]

MIMIC-TPW shows the problem, lots of dry air.

[jpigott]

Sure looks to me like Katia has resumed more of a wnw heading the past 3 or 4 hours. Riding just below the 20N line. It also looks like the trough is pulling away in the last few frames. Who knows - maybe the Ukie is onto something??

http://rammb.cira.colostate.edu/ramsdis ... opical.asp

[shaggy]

Big difference I am seeing is they all kick Lee out to the NE much faster now. This destroys the ridge and allows Katia to make the turn. Lee is the key it seems and as long as they keep showing him moving to the NE instead of stalling then we should be OK here in NC.

[Airboy]

06 GFS gets awfully close to New England

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

is something new comming up in the gulf at the end of the run?

[brunota2003]

Could this be another Dennis/Floyd situation, except for the NE? Irene dumped tons of rain on the NE, now Lee is going to move through later in the week...then if Katia hits ontop of all of that, could you imagine what the flooding would be like?

[northjaxpro]

Big difference I am seeing is they all kick Lee out to the NE much faster now. This destroys the ridge and allows Katia to make the turn. Lee is the key it seems and as long as they keep showing him moving to the NE instead of stalling then we should be OK here in NC.

You are absolutely correct. As long as Lee doesn't stall out next week , the interaction with Lee and that trough will not allow the Atlantic ridge to build back in westward, which should in turn pick up Katia just in time away from the U.S. East Coast. But, this is still going to be a close call so the model watching will continue closely for sure.

But, yes, Lee, or his remnants, is the key for next week.

[HurricaneWarning92]

Sure looks to me like Katia has resumed more of a wnw heading the past 3 or 4 hours. Riding just below the 20N line. It also looks like the trough is pulling away in the last few frames. Who knows - maybe the Ukie is onto something??

http://rammb.cira.colostate.edu/ramsdis ... opical.asp

i agree with you. im seeing that too. Im not discounting the UKMET just yet. It sure is interesting and has my attention that is the only model doing that...

[meriland23]

gfs 6z model shows katia a sliver away from hitting maine....