Tropical Storm HALONG Advisory Tue Aug 05

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (HALONG) WARNING NR 33//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 11W (HALONG), LOCATED APPROXIMATELY 351 NM SOUTH-SOUTHEAST
OF KADENA AB, OKINAWA, HAS TRACKED NORTH-NORTHEASTWARD AT 10 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY AND
ENHANCED INFRARED SATELLITE IMAGERY SHOW A DEGRADATION OF THE DEEP
CONVECTION OVER THE NORTHERN HALF OF THE LOW LEVEL CIRCULATION CENTER
(LLCC) AS TY 11W TRACKS TOWARDS A TROPICAL UPPER TROPOSPHERIC TROUGH
(TUTT) TO THE NORTHEAST OF THE SYSTEM. SUBSIDENCE ASSOCIATED WITH THE
TUTT IS HAMPERING THE CONVECTIVE BAND WRAPPING ALONG THE NORTHERN
PERIPHERY. UPPER LEVEL ANALYSIS ALSO INDICATES THE SUBTROPICAL RIDGE
(STR) TO THE NORTHWEST OF TY 11W IS INTERACTING WITH THE TUTT TO
MAINTAIN VERTICAL WIND SHEAR (VWS) AT MODERATE LEVELS (15 TO 20
KNOTS) OVER THE LLCC. EQUATORWARD OUTFLOW REMAINS FAVORABLE IN THE
STRONG VWS, BUT IS BEING OFFSET BY THE SUBSIDENCE ALONG THE NORTHERN
HALF OF THE SYSTEM. THE CURRENT INTENSITY OF 85 KNOTS ACCOUNTS FOR
THE WEAKENING OBSERVED IN THE SATELLITE IMAGERY AND IS SUPPORTED BY
THE DVORAK ESTIMATES FROM PGTW AND RJTD. THE TRACK FOR TY 11W HAS
SHIFTED SLIGHTLY TO THE NORTH-NORTHEAST AS INDICATED BY THE PREVIOUS
FORECAST, BUT TRACK SPEEDS HAVE INCREASED SLIGHTLY AND HAS BEEN TAKEN
INTO ACCOUNT FOR THIS CURRENT FORECAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE PREVIOUS PROGNOSTIC
REASONING.
   B. THE SYSTEM WILL CONTINUE TO TRACK NORTH-NORTHEASTWARD THROUGH
TAU 36 AS THE DEEP LAYERED STR TO THE EAST OF TY 11W IS FORECAST TO
SHIFT UNDER THE INFLUENCE OF THE TUTT CELL TO THE NORTHEAST. AS THE
TUTT CELL RETROGRADES TO THE NORTH, AROUND TAU 36, TY 11W WILL SHIFT
TO A MORE NORTHERLY TRACK IN RESPONSE TO THE STR BUILDING BACK ALONG
THE EASTERN PERIPHERY OF TY HALONG, PERSISTING THROUGH TAU 72. THE
INTENSITY WILL STRUGGLE OVER THE NEXT 24 HOURS, BUT IS EXPECTED TO
INCREASE BRIEFLY FROM TAU 24 THROUGH TAU 36 AS THE SOUTHWESTERN
EXTENT OF THE TUTT FILLS, REDUCING SUBSIDENCE ALONG THE NORTHERN
PERIPHERY, IMPROVING POLEWARD OUTFLOW AHEAD OF MID-LATITUDE
WESTERLIES. FROM TAU 36 TO TAU 72 INCREASING INTERACTION WITH THE
MID-LATITUDE FLOW WILL WEAKEN THE POLEWARD OUTFLOW CHANNEL AND CAUSE
A SLIGHT INCREASE IN VWS. THIS WILL LEAD TO A STEADY DECREASE OF
INTENSITY THROUGH TAU 72.
   C. BEYOND TAU 72, MODEL GUIDANCE HAS INCREASED SIGNIFICANTLY IN
VARIABILITY, LEADING TO A SHIFT TO THE CONSENSUS OF AVAILABLE MODEL
GUIDANCE. NVGM AND JENS HAVE SHIFTED WELL TO THE WEST FROM THE
PREVIOUS MODEL RUNS, AND BASED ON THE MODEL FIELDS, NVGM HAS TWO
STRS BUILDING ON THE EAST AND WESTERN PERIPHERIES LEADING TO A
PERIOD OF QUASI-STATIONARY MOTION BEYOND TAU 72. THIS FORECAST IS IN
BETTER ALIGNMENT WITH AVNO, BUT DOES NOT INCREASE TRACK SPEEDS AS
QUICKLY IN THE LATER TAUS AS AVNO SUGGESTS. LANDFALL WITH JAPAN IS
CURRENTLY ESTIMATED TO OCCUR BY TAU 96. GIVEN THE EXPECTED WEAKENING
INFLUENCES AS THE NORTHERN INFLOW PATTERN IS ALTERED BY THE APPROACH
OF TY 11W TO THE JAPANESE COAST, PRIOR TO TAU 96, AND THE INCREASING
BAROCLINIC INTERACTION WITH THE MID-LATITUDE WESTERLIES AFTER TAU 72,
A RAPID WEAKENING TREND IS FORECAST BEYOND TAU 96. MODEL GUIDANCE
INDICATES TY HALONG WILL BEGIN EXTRA-TROPICAL TRANSITION AROUND TAU
96 AND CONTINUE THROUGH TAU 120. DUE TO THE LARGE SPREAD IN MODEL
SOLUTIONS, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC FORECAST AFTER
TAU 48.//
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