649
WTNT45 KNHC 070848
TCDAT5
TROPICAL STORM HENRI DISCUSSION NUMBER 3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL102009
500 AM AST WED OCT 07 2009
INFRARED SATELLITE IMAGERY AFTER THE ECLIPSE SHOWS A LARGE MASS OF
VIGOROUS DEEP CONVECTION ASSOCIATED WITH HENRI...WITH CLOUD TOP
TEMPERATURES COLDER THAN -80C. IN FACT...THE AREAL COVERAGE OF DEEP
CONVECTION HAS EXPANDED CONSIDERABLY SINCE YESTERDAY EVENING...
THOUGH THERE ARE NO BANDING FEATURES. HOWEVER...A 0531 UTC AMSR-E
PASS INDICATED THAT THE CENTER WAS STILL PARTIALLY EXPOSED...
LOCATED ON THE WESTERN EDGE OF THE MAIN CONVECTIVE CLUSTER. BASED
UPON THE IMPROVEMENT IN ORGANIZATION DURING THE PAST SEVERAL
HOURS...THE INITIAL INTENSITY IS RAISED TO 45 KT IN ACCORDANCE WITH
0600 UTC DVORAK CLASSIFICATIONS OF 3.0 FROM TAFB AND RECENT
OBJECTIVE ESTIMATES NEAR 3.0 FROM UW CIMSS.
PERSISTENT SOUTHWESTERLY SHEAR OF 20-25 KT CONTINUES TO PREVENT
HENRI FROM STRENGTHENING MUCH. SHIPS MODEL GUIDANCE INDICATES THAT
HIGH WESTERLY SHEAR SHOULD PREVAIL OVER HENRI FOR AT LEAST THE NEXT
24 HOURS...WITH A POSSIBLE RELAXATION THEREAFTER. THIS DOES NOT
SEEM ENTIRELY REALISTIC...AS A MAJORITY OF GLOBAL MODELS INDICATE
THAT HENRI SHOULD CROSS A SHARP SHEAR AXIS NORTH OF THE NORTHEAST
CARIBBEAN ISLANDS IN 36-48 HOURS AND ENCOUNTER STRONG UPPER-LEVEL
NORTHERLY OR NORTHEASTERLY FLOW. SHIPS MODEL OUTPUT ALSO FORECASTS
HENRI TO ENCOUNTER A CONVERGENT UPPER-LEVEL FLOW AND A RATHER
ANTICYCLONIC LOWER TROPOSPHERIC ENVIRONMENT...BOTH OF WHICH WOULD
HAVE A NEGATIVE INFLUENCE ON THE CYCLONE. GIVEN THESE FACTORS...THE
OFFICIAL FORECAST IS IN LINE WITH THE PREVIOUS ADVISORY AND A
MAJORITY OF LARGE-SCALE DYNAMICAL MODELS...CALLING FOR THE
DISSIPATION OF HENRI WITHIN 48 HOURS.
LATEST CENTER FIXES SUGGEST A RATHER UNCERTAIN INITIAL MOTION.
FORTUNATELY...A 0531 UTC AMSR-E PASS HAS ALLOWED FOR A MORE
CONFIDENT INITIAL MOTION ESTIMATE OF 280/11...FARTHER LEFT THAN IN
THE PREVIOUS ADVISORY. THE DOMINANT STEERING IS BEING PROVIDED BY
MID-LEVEL SUBTROPICAL RIDGING NORTH OF HENRI...WITH A MINOR
WEAKNESS AT UPPER LEVELS NORTHWEST OF THE CYCLONE. THIS FLOW
PATTERN SHOULD FAVOR A GENERALLY WESTWARD TO WEST-NORTHWESTWARD
TRACK UNTIL DISSIPATION. THE OFFICIAL FORECAST IS NUDGED SOUTH OF
THE PREVIOUS ADVISORY TO ACCOUNT FOR ITS MORE SOUTHERN INITIAL
POSITION AND MORE WESTERLY MOTION.
FORECAST POSITIONS AND MAX WINDS
INITIAL 07/0900Z 18.1N 56.1W 45 KT
12HR VT 07/1800Z 18.9N 58.0W 45 KT
24HR VT 08/0600Z 20.0N 60.3W 40 KT
36HR VT 08/1800Z 21.2N 62.5W 30 KT
48HR VT 09/0600Z 21.2N 63.2W 25 KT...REMNANT LOW
72HR VT 10/0600Z...DISSIPATED
FORECASTER KIMBERLAIN
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