[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 180245
TCDAT2
TROPICAL STORM KARL DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT FRI SEP 17 2004

KARL HAS BECOME A LITTLE BETTER ORGANIZED THIS EVENING AS OUTER
BANDING FEATURES HAVE IMPROVED. A 17/2148Z SSMI OVERPASS SUGGESTS
THAT KARL MAY POSSESS A VERY SMALL EYE...AND THIS WAS LATER
SUPPORTED BY A 17/2317Z TRMM OVERPASS. WHILE DVORAK INTENSITY
ESTIMATES ARE 77 KT FROM TAFB...65 KT FROM SAB...AND 55 KT FROM
AFWA...I AM A LITTLE RELUCTANT TO DESIGNATE KARL AS A HURRICANE AT
THIS TIME DUE TO THE LACK OF PERSISTENT ORGANIZATION AND DEPTH OF
THE INNER-CORE CONVECTION...WHICH MAY BE DUE TO DRY AIR WRAPPING
INTO THE CENTER. THEREFORE...THE INITIAL INTENSITY IS ONLY BEING
INCREASED TO 60 KT FOR THIS ADVISORY. HOWEVER...IF CONVECTIVE TOPS
BEGIN COOLING AGAIN...THEN THE INTENSITY WILL LIKELY HAVE TO BE
SIGNIFICANTLY INCREASED ON THE NEXT ADVISORY.

THE INITIAL MOTION IS NOW 315/12. THERE IS NO SIGNIFICANT CHANGE TO
THE PREVIOUS FORECAST TRACK REASONING. KARL APPEARS TO BE MAKING A
LITTLE MORE OF A WESTWARD BEND...BUT IS BASICALLY ON TRACK. THE NHC
18Z GLOBAL MODEL GUIDANCE IS TIGHTLY PACKED AND HAS MADE A SLIGHT
SWING TO THE LEFT. HOWEVER...THE MODEL CONSENSUS...WHILE TIGHTLY
PACKED...HAS ALSO BEEN CONSISTENTLY WELL TO THE LEFT OF TRACK AND
DID NOT PICK UP THE JOG TO THE RIGHT EARLIER TODAY. WATER VAPOR
IMAGERY INDICATES LITTLE CHANGE TO THE OVERALL FLOW PATTERN
SURROUNDING KARL...SO THE FORECAST TRACK WAS NOT BROUGHT AS FAR TO
THE WEST AS THE MODEL CONSENSUS. BY 72 HOURS...A STRONG HIGH
AMPLITUDE RIDGE IS FORECAST TO DEVELOP OVER THE NORTHEASTERN U.S.
AND EASTERN CANADA AND A DEEP-LAYER TROUGH IS EXPECTED TO DEVELOP
DOWNSTREAM OVER THE CENTRAL ATLANTIC IN RESPONSE TO THE STRONG
RIDGING.  THE RESULT IS THAT THE SUBTROPICAL RIDGE TO THE NORTH OF
KARL SHOULD GRADUALLY WEAKEN AND ALLOW FOR MORE NORTHWARD MOTION.

KARL ALREADY HAS VERY IMPRESSIVE OUTFLOW AND...WHEN COMBINED WITH
THE TIGHT INNER-CORE WIND FIELD AND SSTS OF AT LEAST 28C...STEADY
INTENSIFICATION THROUGH 96 HOURS IS EXPECTED... AND KARL COULD EVEN
BECOME THE FIFTH MAJOR HURRICANE OF THE SEASON BY 72 HOURS. AFTER
96 HOURS...INCREASING SOUTHWESTERLY SHEAR AHEAD OF THE DEEP-LAYER
TROUGH SHOULD BEGIN TO INITIATE WEAKENING.

FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS

INITIAL      18/0300Z 14.2N  37.4W    60 KT
 12HR VT     18/1200Z 15.0N  38.6W    65 KT
 24HR VT     19/0000Z 15.9N  40.2W    75 KT
 36HR VT     19/1200Z 16.9N  42.0W    85 KT
 48HR VT     20/0000Z 18.0N  43.5W    95 KT
 72HR VT     21/0000Z 20.5N  45.5W   100 KT
 96HR VT     22/0000Z 25.5N  47.0W   105 KT
120HR VT     23/0000Z 31.0N  46.5W    95 KT


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