Tropical Storm HALONG Advisory Thu Aug 07

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (HALONG) WARNING NR 39//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 11W (HALONG), LOCATED APPROXIMATELY 224 NM EAST-SOUTHEAST
OF KADENA AB, OKINAWA, JAPAN HAS TRACKED NORTH-NORTHEASTWARD AT 08
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) DEPICTS A CLOUD-FILLED EYE WITH THINNING CONVECTION
OVER THE NORTHWESTERN QUADRANT. A 0623338Z SSMIS MICROWAVE IMAGE
REVEALS TIGHTLY-CURVED DEEP CONVECTIVE BANDING WRAPPING TOWARDS A
WELL-DEFINED MICROWAVE EYE. THE CURRENT POSITION IS BASED ON THE MSI
AND AFOREMENTIONED MICROWAVE IMAGE WITH HIGH CONFIDENCE. THE INITIAL
INTENSITY HAS REMAINED AT 90 KNOTS BASED ON CONSISTENT DVORAK
INTENSITY ESTIMATES FROM ALL REPORTING AGENCIES. ANIMATED WATER
VAPOR IMAGERY CONTINUES TO SHOW A TROPICAL UPPER TROPOSPHERIC TROUGH
(TUTT) CELL TO THE NORTHEAST ENHANCING THE POLEWARD OUTFLOW, WHILE A
SMALLER TUTT CELL OVER THE NORTHWEST QUADRANT CAUSES UPPER-LEVEL
CONVERGENCE, WEAKENING THE DEEP CONVECTION. HOWEVER, UPPER LEVEL
ANALYSIS INDICATES TY 11W REMAINS IN A FAVORABLE ENVIRONMENT WITH
LOW TO MODERATE VERTICAL WIND SHEAR (VWS) AND EXCELLENT EQUATORWARD
OUTFLOW. TY HALONG IS CURRENTLY TRACKING NORTH-NORTHEASTWARD UNDER
THE STEERING INFLUENCE OF A DEEP LAYERED SUBTROPICAL RIDGE (STR)
LOCATED TO THE EAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE PREVIOUS PROGNOSTIC
REASONING.
   B. TY 11 IS EXPECTED TO TRACK NORTHWARD AS THE STR TO THE EAST
REORIENTS THROUGH TAU 48. AFTERWARDS, TYPHOON HALONG WILL BE LOCATED
ON THE NORTH-WESTERN QUADRANT OF THE STR, SHIFTING TO A
NORTHEASTWARD TRACK THROUGH THE REMAINDER OF THE FORECAST PERIOD.
FAVORABLE CONDITIONS ARE EXPECTED TO PERSIST, ALLOWING TY 11W TO
MAINTAIN ITS INTENSITY OVER THE NEXT 24 HOURS. BY TAU 48, THE
WESTERLIES WILL BEGIN TO IMPINGE ON THE NORTHWESTERN QUADRANT OF THE
SYSTEM, LEADING TO A SLOW WEAKENING TREND AND THE START OF THE EXTRA-
TROPICAL TRANSITION (ETT) PROCESS.
   C. IN THE EXTENDED TAUS, TY HALONG WILL MAKE LANDFALL INTO
SHIKOKU, JAPAN AROUND TAU 60 AS THE SYSTEM STARTS TO BECOME FURTHER
ENTRENCHED WITHIN THE MID-LATITUDE WESTERLIES. THE COMBINED EFFECTS
OF INCREASING VWS AND FRICTIONAL EFFECTS WILL FURTHER WEAKEN THE
SYSTEM. TY 11 IS EXPECTED TO COMPLETE ETT BY TAU 120 AS THE SYSTEM
MOVES INTO THE NORTHEASTERN REGION OF THE SEA OF JAPAN AND IS FULLY
ABSORBED WITHIN THE MID-LATITUDE WESTERLIES. AVAILABLE MODEL
GUIDANCE IS IN GOOD AGREEMENT IN THE NEAR TERM AND DIVERGES AFTER
TAU 72. DUE TO VARIATIONS IN THE STEERING PATTERN AND COMPLEX UPPER-
LEVEL ENVIRONMENT IN THE EXTENDED TAUS, THERE IS OVERALL LOW
CONFIDENCE IN THE JTWC FORECAST.//
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