000
WTNT42 KNHC 311435
TCDAT2

TROPICAL STORM KATIA DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST WED AUG 31 2011

KATIA REMAINS A WELL-ORGANIZED TROPICAL CYCLONE WITH DISTINCT
BANDING FEATURES AND A DEVELOPING CENTRAL DENSE OVERCAST.  DVORAK
CLASSIFICATIONS ARE T3.5 FROM BOTH AGENCIES AND THE CURRENT
INTENSITY IS HELD AT 55 KT.  THE SYSTEM HAS A WELL-DEFINED
UPPER-LEVEL OUTFLOW PATTERN.  AT THE MOMENT...IT DOES NOT APPEAR
THAT THE DRY AIR ADJACENT TO THE STORM IS BEING ENTRAINED INTO THE
CIRCULATION.  THE SHIPS MODEL INDICATES THAT VERTICAL SHEAR WILL BE
WEAK FOR THE NEXT DAY OR TWO WHICH SHOULD FAVOR STRENGTHENING AT
LEAST FOR THE EARLIER PART OF THE FORECAST PERIOD.  A LARGE
UPPER-LEVEL LOW TO THE NORTHWEST OF KATIA COULD PLAY A ROLE IN THE
INTENSITY OF THE TROPICAL CYCLONE IN THE LATTER PART OF THE
FORECAST PERIOD.  AS NOTED EARLIER...SOME OF THE GLOBAL MODELS
SUGGEST THAT THIS LOW COULD PRODUCE INCREASING SOUTHWESTERLY SHEAR
IN 4 TO 5 DAYS WHICH WOULD INHIBIT INTENSIFICATION.  THE OFFICIAL
INTENSITY FORECAST IS THE SAME AS THAT FROM THE PREVIOUS ADVISORY
AND IS SLIGHTLY ABOVE THE NUMERICAL CONSENSUS.

KATIA CONTINUES TO MOVE SWIFTLY TOWARD THE WEST-NORTHWEST OR 285/18
TO THE SOUTH OF A MID-TROPOSPHERIC SUBTROPICAL ANTICYCLONE.  THE
DYNAMICAL GUIDANCE IS IN RATHER GOOD AGREEMENT ON A CONTINUATION OF
THIS WEST-NORTHWESTWARD TRACK FOR THE NEXT COUPLE OF DAYS WITH SOME
DECELERATION AS THE TROPICAL CYCLONE NEARS A WEAKNESS IN THE RIDGE.
IN THE LATTER PART OF THE FORECAST PERIOD...MOST OF THE GUIDANCE
SHOWS A TURN TOWARD THE NORTHWEST AS KATIA APPROACHES THE SOUTHWEST
SIDE OF THE SUBTROPICAL ANTICYCLONE.  THE OFFICIAL TRACK FORECAST
FOR THIS ADVISORY PACKAGE IS AN UPDATE OF THE PREVIOUS ONE AND IS
CLOSE TO THE VARIOUS MODEL CONSENSUS TRACKS.

FORECAST POSITIONS AND MAX WINDS

INIT  31/1500Z 14.2N  40.8W   55 KT  65 MPH
 12H  01/0000Z 14.7N  43.3W   65 KT  75 MPH
 24H  01/1200Z 15.4N  46.3W   75 KT  85 MPH
 36H  02/0000Z 16.2N  48.7W   85 KT 100 MPH
 48H  02/1200Z 17.3N  51.0W   90 KT 105 MPH
 72H  03/1200Z 19.5N  54.5W   95 KT 110 MPH
 96H  04/1200Z 21.5N  57.5W  100 KT 115 MPH
120H  05/1200Z 23.5N  60.5W  105 KT 120 MPH

$$
FORECASTER PASCH

000
WTNT42 KNHC 010248
TCDAT2

HURRICANE KATIA DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST WED AUG 31 2011

THE CLOUD PATTERN ASSOCIATED WITH KATIA CONTINUES TO GRADUALLY
IMPROVE.  THE CENTER IS LOCATED NEAR THE MIDDLE OF AN EXPANDING
CENTRAL DENSE OVERCAST AND THERE IS A LARGE CURVED BAND OF DEEP
CONVECTION OVER THE SOUTHERN SEMICIRCLE OF THE CYCLONE.  RECENT
SSMIS MICROWAVE DATA SHOWED THE BEGINNINGS OF A BANDING EYE
FEATURE...HOWEVER THE CONVECTION OVER THE SOUTHERN PORTION OF THE
EYE IS STILL A BIT THIN.  SUBJECTIVE AND OBJECTIVE DVORAK SATELLITE
INTENSITY ESTIMATES HAVE INCREASED TO 65 KT...AND THE INITIAL
INTENSITY HAS BEEN RAISED ACCORDINGLY.  KATIA IS THE SECOND
HURRICANE OF THE 2011 ATLANTIC HURRICANE SEASON.

THE HURRICANE IS EXPECTED TO REMAIN IN A LOW SHEAR ENVIRONMENT
AND OVER WARM WATER DURING THE NEXT DAY OR SO...WHICH SHOULD FAVOR
ADDITIONAL STRENGTHENING.  AFTER THAT TIME...A MID- TO UPPER-LEVEL
TROUGH SEEN IN WATER VAPOR IMAGERY BETWEEN 50W AND 60W IS FORECAST
BY THE GLOBAL MODELS TO WEAKEN.  THIS SHOULD KEEP THE HURRICANE IN
A FAVORABLE UPPER-LEVEL WIND PATTERN AND KATIA IS FORECAST TO
BECOME A MAJOR HURRICANE WITHIN 72 HOURS.  THE NEW NHC INTENSITY
FORECAST SHOWS A SLIGHTLY FASTER RATE OF INTENSIFICATION DURING THE
FIRST 2-3 DAYS THAN INDICATED IN THE PREVIOUS ADVISORY...AND IS A
BLEND OF THE STATISTICAL AND DYNAMICAL GUIDANCE.

THE INITIAL MOTION ESTIMATE IS 285/17 KT.   THE HURRICANE IS
EXPECTED TO CONTINUE MOVING WEST-NORTHWESTWARD TO THE SOUTH OF A
SUBTROPICAL RIDGE DURING THE NEXT 2-3 DAYS.  AFTER 72 HOURS...
KATIA WILL BE NEARING THE SOUTHWESTERN PORTION OF THE RIDGE.  THIS
SHOULD RESULT IN A REDUCTION IN FORWARD SPEED AND A GRADUAL TURN
TOWARD THE NORTHWEST.  THE NEW TRACK FORECAST IS ESSENTIALLY AN
UPDATE OF THE PREVIOUS NHC FORECAST AND LIES BETWEEN THE
MULTI-MODEL CONSENSUS AND THE RELIABLE GFS AND ECMWF MODELS.

THE WIND RADII HAVE BEEN ADJUSTED SLIGHTLY ON THE BASIS OF RECENT
ASCAT DATA.

FORECAST POSITIONS AND MAX WINDS

INIT  01/0300Z 15.0N  44.4W   65 KT  75 MPH
 12H  01/1200Z 15.6N  46.7W   75 KT  85 MPH
 24H  02/0000Z 16.3N  49.1W   85 KT 100 MPH
 36H  02/1200Z 17.3N  51.3W   90 KT 105 MPH
 48H  03/0000Z 18.4N  53.1W   95 KT 110 MPH
 72H  04/0000Z 20.5N  56.0W  100 KT 115 MPH
 96H  05/0000Z 22.5N  59.0W  105 KT 120 MPH
120H  06/0000Z 24.0N  61.5W  105 KT 120 MPH

$$
FORECASTER BROWN