Tropical Storm BAVI Advisory Mon Aug 24

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (BAVI) WARNING NR
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 09W (BAVI), LOCATED APPROXIMATELY 548 NM SOUTH-
SOUTHWEST OF CHINHAE, SOUTH KOREA, HAS TRACKED NORTHEASTWARD AT
07 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY (MSI) DEPICTS A COMPACT SYSTEM WITH FLARING
CONVECTION WRAPPING INTO A TRANSIENT EYE. THE CONVECTION IN THE
MSI LOOP HAS CONTINUED TO BUILD AND CONSOLIDATE OVER THE PAST
6 HOURS BUT REMAINS LIMITED OVER THE NORTHWESTERN SEMICIRCLE.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
THE MICROWAVE EYE FEATURE PRESENT IN A 230506Z AMSR2 89GHZ
IMAGE AND THE CIRCULATION PRESENT IN THE COMPOSITE RADAR LOOP.
THE INITIAL INTENSITY OF 65 KTS IS PLACED WITH FAIR CONFIDENCE
AND IS BASED ON A PGTW DVORAK CURRENT INTENSITY ESTIMATE OF
T4.0 (65 KTS) AND FROM THE DATA PRESENT IN THE AMSR2 WIND
FIELD PRODUCT. TY BAVI IS TRACKING NORTHEASTWARD ALONG AN
EXTENSION OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE
SOUTHEAST AND THROUGH AN ENVIRONMENT FAVORABLE FOR FURTHER
INTENSIFICATION WITH VERY WARM (30-31 CELSIUS) SEA SURFACE
TEMPERATURES, LOW (05-10 KNOTS) VERTICAL WIND SHEAR AND
WELL-ESTABLISHED EQUATORWARD OUTFLOW IN THE UPPER LEVELS.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 09W WILL CONTINUE TO TRACK GENERALLY NORTHEASTWARD
THROUGH TAU 24 AS IT ROUNDS THE STR POSITIONED TO THE SOUTHEAST
AND CONTINUED FAVORABLE VWS AND SSTS WILL ALLOW IT TO INTENSIFY
TO 75 KTS BY THIS TIME. A SHORTWAVE TROUGH IN THE UPPER LEVELS
WILL INDUCE A REORIENTATION OF THE STEERING RIDGE AFTER TAU 24
LEADING TO A GENERALLY NORTH TO NORTH-NORTHWESTWARD TRACK AND
SLOWER TRACK SPEEDS BETWEEN TAU 24 AND TAU 48. SUFFICIENT OCEAN
HEAT CONTENT, LOW VWS AND WARM SSTS WILL ALLOW THE SYSTEM TO
REACH A PEAK INTENSITY OF 100 KTS BY TAU 48. BETWEEN TAU 48 AND
TAU 72 TY BAVI WILL TRACK ALONG THE WESTERN PERIPHERY OF A
BUILDING STR TO THE EAST AND BEGIN TO TRACK GENERALLY NORTHWARD.
THE SYSTEM WILL WEAKEN SLIGHTLY TO AN INTENSITY OF 95 KTS BY TAU
72 DURING THIS TIME DUE TO SLIGHTLY INCREASED VWS AND DECREASING
SSTS. THE CROSS TRACK SPREAD IN NUMERICAL MODELS SOLUTIONS
PRESENTS A FAIR DEGREE OF CERTAINTY IN THE TRACK WITH A MAXIMUM
143NM SPREAD AT TAU 72, LENDING FAIR CONFIDENCE IN THE INITIAL
PORTION OF THE JTWC FORECAST TRACK.
   C. AFTER TAU 72, STRONG (20-25 KTS) VWS AND COOLER (26-29
CELSIUS) SSTS WILL BEGIN TO WEAKEN TY BAVI AS IT CONTINUES TO
TRACK NORTHWARD TOWARDS THE KOREAN PENINSULA. BETWEEN TAU 72 AND
96 THE SYSTEM WILL MAKE LANDFALL AND BEGIN TO DISSIPATE DUE TO
LAND INTERACTION. AS IT TRACKS FURTHER INTO MAINLAND CHINA THE
SYSTEM WILL DISSIPATE FURTHER DUE TO THE FRICTIONAL EFFECTS OF
LAND AND FULLY DISSIPATE BY TAU 120. THERE IS A LARGE DEGREE OF
UNCERTAINTY IN NUMERICAL MODEL SOLUTIONS DURING THIS PERIOD DUE
TO THE TIMING OF THE SHORTWAVE TROUGH MOVEMENT, WITH A 352 NM
SPREAD IN CROSS TRACK SPREAD BY TAU 96 WHICH INCREASES TO 592
NM BY TAU 120. THE HIGH DEGREE IN ACROSS TRACK MODEL SPREAD
LENDS ONLY FAIR CONFIDENCE IN THE OVERALL JTWC FORECAST TRACK.
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