Hurricane KATIA

...KATIA ALMOST A HURRICANE...

5:00 PM AST Wed Aug 31
Location: 14.6°N 42.6°W
Max sustained: 70 mph
Moving: WNW at 20 mph
Min pressure: 990 mb

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

...KATIA CHANGES LITTLE IN STRENGTH DURING THE PAST SEVERAL HOURS...

5:00 AM AST Thu Sep 1
Location: 15.2°N 45.9°W
Max sustained: 75 mph
Moving: W at 20 mph
Min pressure: 987 mb

200motels wrote: »

Is this hurricane just going to blow itself out and wander around the Atlantic or will it hit land as a hurricane.

It will almost certainly miss the Lesser Antilles to the northwest but beyond that is too early to know for sure because the models become too unreliable at that range. Most storms in the past that were in Katia's position ended up recurving back out to sea, so based on that the chances are it will do the same, but it's just too early to say for sure.

11:00 AM AST Thu Sep 1
Location: 15.5°N 47.5°W
Max sustained: 75 mph
Moving: W at 18 mph
Min pressure: 987 mb

000
WTNT42 KNHC 011450
TCDAT2

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

KATIA HAS CHANGED LITTLE IN STRUCTURE DURING THE LAST SEVERAL HOURS.
BASED ON MICROWAVE DATA...THE LOW-LEVEL CENTER IS LOCATED NEAR THE
WESTERN PERIPHERY OF THE CORE CONVECTION. A CURVED BAND STILL
EXISTS OVER THE SOUTHERN SEMICIRCLE OF THE STORM...BUT CLOUD TOPS
HAVE BEEN WARMING IN THIS BAND DURING THE PAST FEW HOURS. THE
INITIAL WIND SPEED REMAINS AT 65 KT FOR THIS ADVISORY...IN
AGREEMENT WITH THE LATEST SATELLITE CLASSIFICATIONS.

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.

KATIA IS MOVING WESTWARD AT 16 KT TO THE SOUTH OF A SUBTROPICAL
HIGH. THE HURRICANE IS EXPECTED TO SLOW DOWN AND TURN TO THE
WEST-NORTHWEST DURING THE NEXT 12-24 HOURS AS IT APPROACHES A
WEAKNESS IN THE RIDGE. 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.

FORECAST POSITIONS AND MAX WINDS

INIT 01/1500Z 15.5N 47.5W 65 KT 75 MPH
12H 02/0000Z 16.1N 49.5W 70 KT 80 MPH
24H 02/1200Z 17.0N 51.7W 75 KT 85 MPH
36H 03/0000Z 18.0N 53.4W 85 KT 100 MPH
48H 03/1200Z 19.0N 55.0W 95 KT 110 MPH
72H 04/1200Z 20.8N 58.0W 100 KT 115 MPH
96H 05/1200Z 22.3N 61.0W 105 KT 120 MPH
120H 06/1200Z 23.8N 64.0W 105 KT 120 MPH

$$
FORECASTER CANGIALOSI/ZELINSKY

Katia has been downgraded to a Tropical Storm due to shear. It is forecast to soon regain hurricane strength again and the NHC is still forecasting Katia to become a major hurricane.

The latest discussion highlights the split with the models regarding the late period track:



TROPICAL STORM KATIA DISCUSSION NUMBER 15

NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011

500 PM AST THU SEP 01 2011

KATIA HAS TAKEN THE APPEARANCE OF A SHEARED TROPICAL CYCLONE.
VISIBLE AND MICROWAVE SATELLITE IMAGERY CONTINUE TO INDICATE THAT
THE LOW-LEVEL CENTER IS DISPLACED TO THE WEST OF THE CONVECTION.
THE CURVED BAND THAT WAS LOCATED SOUTH OF THE CENTER HAS
DISSIPATED...AND CONVECTION IS NOW LIMITED TO THE NORTHEAST
QUADRANT OF THE SYSTEM. BASED ON A BLEND OF DVORAK CI AND T NUMBERS
FROM SAB AND TAFB...THE INTENSITY HAS BEEN LOWERED TO 60 KT FOR
THIS ADVISORY.

UW-CIMMS SHEAR ANALYSIS CONTINUES TO INDICATE THAT SOUTHWESTERLY
SHEAR OF ABOUT 15 KT IS CURRENTLY IMPACTING KATIA. AN UPPER-LEVEL
LOW LOCATED TO THE NORTHWEST OF THE CYCLONE APPEARS TO BE THE
PRIMARY SOURCE OF THIS SHEAR. KATIA IS EXPECTED TO CONTINUE TO
INTERACT WITH THIS LOW FOR THE NEXT 24 TO 36 HOURS. AFTER
THAT...THE UPPER-LEVEL LOW IS EXPECTED TO LIFT TO THE
NORTH...RESULTING IN A MORE CONDUCIVE ENVIRONMENT FOR
INTENSIFICATION. THE OFFICIAL FORECAST HAS BEEN LOWERED SLIGHTLY
DUE TO THE MARGINAL ENVIRONMENTAL CONDITIONS IN THE SHORT
TERM...HOWEVER IT STILL BRINGS KATIA TO A MAJOR HURRICANE IN A FEW
DAYS.

KATIA CONTINUES TO MOVE TO THE WEST AT 16 KT. IT IS EXPECTED TO SLOW
DOWN AND BEGIN A GRADUAL TURN TO THE NORTHWEST AS IT APPROACHES A
WEAKNESS IN THE SUBTROPICAL RIDGE. THE GFS...ECMWF...AND HFIP
CONSENSUS MODELS ARE IN GOOD AGREEMENT FOR THE FIRST 3 DAYS. AFTER
THAT THERE IS MORE UNCERTAINTY IN THE FORECAST AS THE MODEL SPREAD
INCREASES. SOME MODELS SUGGEST A TURN TOWARD THE WEST AS THE
SUBTROPICAL RIDGE REBUILDS TO THE NORTH OF KATIA...WHILE OTHERS
SUGGEST THAT THE WEAKNESS WILL PERSIST...BRINGING THE CYCLONE
FARTHER NORTH. THE OFFICIAL FORECAST LIES BETWEEN THESE SCENARIOS
AND IS VERY CLOSE TO THE HFIP CONSENSUS.

FORECAST POSITIONS AND MAX WINDS

INIT 01/2100Z 16.1N 49.2W 60 KT 70 MPH
12H 02/0600Z 16.8N 51.0W 65 KT 75 MPH
24H 02/1800Z 17.7N 52.9W 70 KT 80 MPH
36H 03/0600Z 18.7N 54.6W 75 KT 85 MPH
48H 03/1800Z 19.7N 56.1W 85 KT 100 MPH
72H 04/1800Z 21.6N 59.0W 95 KT 110 MPH
96H 05/1800Z 23.5N 62.0W 100 KT 115 MPH
120H 06/1800Z 25.5N 65.0W 105 KT 120 MPH

$$
FORECASTER ZELINSKY/CANGIALOSI

UKMET is way south. Other models are in fairly good agreement on the general motion of Katia for the next several days.

Katia is back to hurricane status. Intensity forecast dropped a bit. No track change. UKMET dropped. We'll have to wait and see what the 12Z models do.

000
WTNT42 KNHC 021454
TCDAT2

HURRICANE KATIA DISCUSSION NUMBER 18
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011
1100 AM AST FRI SEP 02 2011

THE CONVECTIVE DEPICTION OF KATIA HAS IMPROVED THIS MORNING AS BOTH
MICROWAVE IMAGERY FROM SSMIS AND CONVENTIONAL VISIBLE SATELLITE
IMAGERY INDICATE THAT AN EYE MAY BE FORMING. BECAUSE OF THE
IMPROVED STRUCTURE...BOTH TAFB AND SAB DVORAK CLASSIFICATIONS CAME
IN AT A 4.0...OR 65 KT...AS DID A 1053Z CIMSS AMSU INTENSITY
ESTIMATE. THUS KATIA HAS REGAINED HURRICANE STATUS.

THE HURRICANE IS MOVING TOWARD THE WEST-NORTHWEST AT ABOUT 12
KT...AS IT IS BEING ADVECTED AROUND THE SOUTHWEST PERIPHERY OF A
DEEP-LAYER RIDGE. KATIA SHOULD MOVE TOWARD THE WEST-NORTHWEST OR
NORTHWEST FOR THE NEXT FEW DAYS AT A SLIGHTLY SLOWER RATE OF SPEED.
ALL OF THE RELIABLE GUIDANCE...WITH THE EXCEPTION OF THE UKMET WHICH
HAS A MUCH MORE EQUATORWARD SOLUTION DUE TO A SHORT-WAVE TROUGH OFF
OF THE U.S. EAST COAST LIFTING OUT TO THE NORTHEAST MORE QUICKLY...
IS IN EXCELLENT AGREEMENT. THE TRACK FORECAST IS VERY SIMILAR TO
THE PREVIOUS ADVISORY AND THE CONSENSUS OF THE GLOBAL AND HURRICANE
MODELS LESS THE UKMET MODEL.

DESPITE BECOMING A HURRICANE AGAIN...KATIA FACES A RELATIVELY
HOSTILE ENVIRONMENT WITH SOUTHWEST VERTICAL SHEAR OF 15-20 KT
SUGGESTED FOR THE NEXT DAY OR TWO. BEYOND 48 HOURS...THE SHEAR
FROM THE GLOBAL MODELS IS ANTICIPATED TO DECREASE...BUT THE
THERMODYNAMICS MAY NOT BE IDEAL WITH LOW HUMIDITIES AND A MORE
STABLE ENVIRONMENT ANTICIPATED. SOME OF THE UPPER-LEVEL
TEMPERATURE INCREASES ANALYZED IN THE SHIPS/LGEM STATISTICAL
MODELS...HOWEVER...MAY BE SPURIOUS...AS THE STRONGER VORTEX FROM
THE GFS MAY BE THE CAUSE OF THESE VALUES RATHER THAN THE
ENVIRONMENT. THUS THE SHIPS/LGEM GUIDANCE MAY BE TOO LOW AT DAYS
THREE TO FIVE. THE INTENSITY PREDICTION IS SLIGHTLY LOWER THAN A
SHIPS/LGEM/HWRF BLEND BUT HIGHER THAN THE PREVIOUS ADVISORY DURING
THE NEXT TWO DAYS.

FORECAST POSITIONS AND MAX WINDS

INIT 02/1500Z 17.5N 52.4W 65 KT 75 MPH
12H 03/0000Z 18.6N 53.8W 65 KT 75 MPH
24H 03/1200Z 19.6N 55.2W 70 KT 80 MPH
36H 04/0000Z 20.6N 56.4W 75 KT 85 MPH
48H 04/1200Z 21.7N 57.9W 80 KT 90 MPH
72H 05/1200Z 24.0N 61.0W 90 KT 105 MPH
96H 06/1200Z 26.0N 64.0W 95 KT 110 MPH
120H 07/1200Z 27.0N 67.0W 100 KT 115 MPH

...KATIA BARELY A HURRICANE...

11:00 AM AST Sat Sep 3
Location: 19.6°N 55.8°W
Max sustained: 75 mph
Moving: NW at 10 mph
Min pressure: 989 mb

ZCZC MIATCDAT2 ALL
TTAA00 KNHC DDHHMM

HURRICANE KATIA DISCUSSION NUMBER 22
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011
1100 AM AST SAT SEP 03 2011

SEVERAL MICROWAVE OVERPASSES FROM EARLIER THIS MORNING INDICATED
THAT KATIA IS TILTED...WITH A MID-LEVEL MICROWAVE EYE DISPLACED
ABOUT 20 N MI NORTH OF THE LOW-LEVEL CENTER. FINAL T-NUMBERS ARE
DOWN TO T3.5 FROM BOTH SAB AND TAFB...ALTHOUGH CI NUMBERS ARE STILL
HOLDING AT 4.0. UW-CIMSS ADT ESTIMATES HAVE BEEN DECREASING AND ARE
NOW T4.1. KATIA WILL BE KEPT AS A HURRICANE FOR NOW...BUT IF TRENDS
CONTINUE IT COULD ONCE AGAIN WEAKEN TO A TROPICAL STORM LATER
TODAY.

KATIA IS BEGINNING TO MOVE AROUND THE SOUTHWESTERN PERIPHERY OF A
MID-LEVEL HIGH LOCATED OVER THE CENTRAL ATLANTIC...AND TOWARDS A
DEEP-LAYER TROUGH OVER THE WESTERN ATLANTIC. WITH THE EXCEPTION OF
THE UKMET...WHICH IS DISREGARDED IN THIS FORECAST...THE MODELS ARE
IN GOOD AGREEMENT ON MAINTAINING A MOTION OF ABOUT 305 DEGREES AT 9
TO 10 KT FOR THE NEXT 48 HOURS. BEYOND 72 HOURS...THE TRACK
FORECAST BECOMES A LITTLE MORE COMPLEX AND PARTLY DEPENDS ON HOW
TROPICAL STORM LEE AND U.S. EAST COAST TROUGHING EVOLVE OVER THAT
TIME. AS AN EXAMPLE...THE ECMWF DEVELOPS A DEEP-LAYER CLOSED LOW
OVER THE OHIO VALLEY BY DAY 5 WHILE THE GFS HAS A SHARP TROUGH
ALMOST READY TO CLOSE OFF OVER NEW YORK AND PENNSYLVANIA. DESPITE
THESE DIFFERENCES...BOTH MODELS HAVE SHIFTED TO THE EAST...WITH THE
GFS BEING THE FASTEST DUE TO THE MORE PROGRESSIVE FLOW. THE NHC
TRACK FORECAST IS ALSO SHIFTED TO THE EAST YET STILL LIES TO THE
WEST OF THOSE USUALLY RELIABLE MODELS.

STRONG SOUTHERLY SHEAR IS AFFECTING KATIA AND IS LIKELY ALLOWING DRY
AIR TO ERODE THE DEEP CONVECTION ON THE SOUTHERN SIDE. THIS SHEAR
IS EXPECTED TO PERSIST FOR THE NEXT 24 HOURS OR SO...DURING WHICH
TIME NO STRENGTHENING IS INDICATED IN THE FORECAST. THEREAFTER...
THE SHIPS MODEL SHOWS THAT UPPER-LEVEL WINDS COULD BECOME MORE
CONDUCIVE FOR STRENGTHENING...BUT THIS WILL ALL DEPEND ON THE
LOCATION OF KATIA RELATIVE TO THE DEEP-LAYER TROUGH OR CLOSED LOW
OVER THE EASTERN UNITED STATES. THE NHC INTENSITY FORECAST WILL
CONTINUE TO INDICATE INTENSIFICATION BETWEEN DAYS 2 AND 4...AND IS
STILL ABOVE THE INTENSITY CONSENSUS AND STATISTICAL MODELS.

IT IS ADVISABLE NOT TO FOCUS ON SLIGHT FORECAST INTENSITY CHANGES
NEAR THE MAJOR HURRICANE THRESHOLD OF 100 KT SINCE THERE IS VERY
LITTLE DIFFERENCE BETWEEN A 95- AND 100-KT HURRICANE. BASED ON THE
CURRENT FORECAST AND RECENT NHC INTENSITY ERRORS...AT THIS TIME
THERE IS ROUGHLY A 50/50 CHANCE OF KATIA STILL BECOMING A MAJOR
HURRICANE DURING THE NEXT 5 DAYS.

FORECAST POSITIONS AND MAX WINDS

INIT 03/1500Z 19.6N 55.8W 65 KT 75 MPH
12H 04/0000Z 20.3N 57.0W 65 KT 75 MPH
24H 04/1200Z 21.3N 58.7W 65 KT 75 MPH
36H 05/0000Z 22.5N 60.4W 70 KT 80 MPH
48H 05/1200Z 23.7N 62.1W 75 KT 85 MPH
72H 06/1200Z 26.5N 65.0W 85 KT 100 MPH
96H 07/1200Z 29.5N 67.5W 95 KT 110 MPH
120H 08/1200Z 32.0N 69.5W 90 KT 105 MPH

$$
FORECASTER BERG

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