Tropical Storm HALONG Advisory mar, 05-08

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (HALONG) WARNING NR 31//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 11W (HALONG), LOCATED APPROXIMATELY 453 NM SOUTH-
SOUTHEAST OF KADENA AB, HAS TRACKED NORTHWARD AT 10 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL (MSI) SATELLITE IMAGERY
CONTINUES TO DEPICT A COLD DENSE OVERCAST FEATURE WITH HINT OF AN
EYE FEATURE FORMING. BASED ON THE MSI, THERE IS GOOD CONFIDENCE IN
THE CURRENT POSITION. MODERATE (20-30 KNOT) NORTHERLY VERTICAL WIND
SHEAR (VWS), ASSOCIATED WITH UPPER-LEVEL RIDGING IS AFFECTING THE
SYSTEM, CONTRIBUTING TO HALONG'S WEAKENING TREND. AS THE SYSTEM
CONTINUES NORTHWARD, THERE WILL BE GOOD EQUATORWARD OUTFLOW AS WELL
AS A POLEWARD CHANNEL OVER THE NORTHEAST PERIPHERY OF THE TYPHOON
PROVIDING GOOD VENTILATION FOR THE SYSTEM. THE INITIAL INTENSITY IS
ASSESSED AT 90 KNOTS BASED ON DVORAK CURRENT INTENSITY ESTIMATES
FROM PGTW AND RJTD. TY 11W IS CURRENTLY TRACKING ALONG THE WESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE PREVIOUS PROGNOSTIC
REASONING.
   B. THE SYSTEM WILL CONTINUE ITS NORTHWARD TRACK ALONG THE WESTERN
SIDE OF THE STR, WITH THE TUTT CELL TO THE NORTHEAST INDUCING A
SLIGHT EASTERLY COMPONENT IN THE TRACK IN THROUGH TAU 48. BETWEEN
TAUS 48 AND 72, HALONG'S MAIN STEERING INFLUENCE WILL BE THE STR,
WITH THE SYSTEM ROUNDING ITS WESTERN PERIPHERY. TY 11W WILL CONTINUE
TO WEAKEN OVER THE NEXT 24 HOURS DUE TO PERSISTENT NORTHERLY VWS IN
THE REGION, AND THEN RE-STRENGTHEN SLIGHTLY AS THE SYSTEM HAS AN
INCREASE IN POLEWARD OUTFLOW DUE TO AN UPPER LEVEL TROUGH.
   C. BEYOND TAU 72, MODEL GUIDANCE VARIES SIGNIFICANTLY IN BOTH
SPEED AND TRACK OF THE STORM. MOST MODELS HAVE THE SYSTEM MAKING
LANDFALL IN SOUTHERN JAPAN AROUND TAU 120, WITH GFDN BEING THE
OUTLIER, RECURVING SOUTH OF JAPAN INTO PACIFIC. DUE TO THE LARGE
SPREAD IN MODEL SOLUTIONS WITH REGARD TO THE DIFFERENT
INTERPRETATION OF THE TROUGH AND THE STRENGTH AND ORIENTATION OF THE
STR, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC FORECAST AFTER TAU
72. TY 11W IS EXPECTED TO SIGNIFICANTLY WEAKEN AS IT ENCOUNTERS
SOUTHERN JAPAN AND BEGINS EXTRA-TROPICAL TRANSITION.//
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