Tropical Storm TALIM Advisory lun, 18-06

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (TALIM)
WARNING NR 02//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION (TD) 06W (TALIM), LOCATED APPROXIMATELY 240 NM
SOUTH-SOUTHWEST OF HONG KONG, HAS TRACKED EAST-NORTHEASTWARD AT 07
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) SHOWS BANDING CONVECTION ALONG THE NORTHERN PERIPHERY
OF THE LOW LEVEL CIRCULATION CENTER (LLCC) HAS STARTED TO DEVELOP
WITHIN THE PAST SIX HOURS. DEEP CONVECTION APPEARS TO BE BUILDING
OVER THE LLCC, HOWEVER, BASED ON THE POORLY ORGANIZED LOW LEVEL
STRUCTURE, THERE IS LOW CONFIDENCE IN THE LLCC POSITION. UPPER LEVEL
ANALYSIS INDICATES A WEAK MESOSCALE ANTICYCLONE HAS STARTED BUILDING
OVER THE LLCC, WITH MARGINAL VERTICAL WIND SHEAR (VWS) (15-20 KNOTS)
HELPING TO PROVIDE AMPLE EQUATORWARD OUTFLOW. AN UPPER LEVEL
SUBTROPICAL RIDGE (STR) IS BUILDING EASTWARD OVER SOUTHERN CHINA AND
IS BEGINNING TO MOVE INTO THE SOUTH CHINA SEA (SCS). THIS RIDGE WILL
HAMPER THE ANTICYCLONE FROM VENTING THE SYSTEM POLEWARD. THE SYSTEM
HAS BEEN STEADILY TRACKING WITHIN THE LOW- TO MID-LEVEL GRADIENT
FLOW. AS TY 05W (GUCHOL) CONTINUES TRACKING POLEWARD, A STR IS
EXPECTED TO BECOME THE DOMINANT STEERING INFLUENCE. SEA SURFACE
TEMPERATURES (SSTS) THROUGHOUT THE SCS ARE FAVORABLE FOR FURTHER
DEVELOPMENT. THE INITIAL POSITION IS BASED ON THE MSI IMAGERY AND A
FIX FROM PGTW. THE CURRENT INTENSITY OF 30 KNOTS IS BASED A 2.5/2.5
DVORAK ESTIMATE FROM PGTW. 3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TD 06W IS EXPECTED TO SLOWLY TRACK EASTWARD OVER THE NEXT 24
HOURS WITHIN THE LOW- TO MID-LEVEL GRADIENT FLOW AS THE STR BEGINS
TO DOMINANT THE STEERING INFLUENCE. THROUGH TAU 48 TD 06W WILL
INTENSITY AS FAVORABLE SSTS PERSIST THROUGHOUT THE SCS AND GOOD
UPPER LEVEL SUPPORT ALLOWS THE SYSTEM TO VENT EQUATORWARD. THE
FORECAST TRACK WILL TAKE TD 06W INTO TAIWAN AROUND TAU 48 AND WILL
CAUSE THE SYSTEM TO WEAKEN DUE TO LAND INFLUENCE. ADDITIONALLY, THE
SSTS DROP OFF WITHIN THE TAIWAN STRAIT, NORTH OF 25N. AS THE SYSTEM
IS EXPECTED TO REACH STRONG TROPICAL STORM LEVELS, THE TRACK OVER
TAIWAN WILL LIKELY CAUSE SIGNIFICANT ORGANIZATIONAL ISSUES WITHIN
THE LLCC, REQUIRING TIME TO RE-DEVELOP ON THE LEEWARD SIDE OF
TAIWAN. BY THIS TIME DECREASING SSTS AND INCREASING VWS WILL KEEP TD
06W FROM INTENSIFYING BY TAU 72. CONFIDENCE REMAINS LOW WITH THE
FORECAST AS IT RELIES HEAVILY ON THE DEVELOPMENT OF THE STR, AND IF
THE TIMING IS NOT CORRECT, TD 06W WILL HAVE MORE TIME WITHIN THE SCS
TO INTENSIFY.
   C. IN THE EXTENDED FORECAST, TD 06W WILL CONTINUE TO TRACK ALONG
THE NORTHWESTERN PERIPHERY OF THE RE-ESTABLISHED STR TOWARDS
SOUTHWESTERN KYUSHU. DECREASING SSTS (22 TO 26 CELSIUS) AND
INCREASING VWS WILL NOT ALLOW FOR FURTHER DEVELOPMENT. HOWEVER,
THERE ARE INDICATIONS A WARM POOL OF WATER IS LOCATED TO THE NORTH
OF KADENA AB, OKINAWA WITH SSTS NEAR 29 CELSIUS. THE IMPACT THIS
WILL PROVIDE IN LIEU OF THE UNFAVORABLE UPPER LEVEL SUPPORT IS
QUESTIONABLE. THE POSSIBILITY EXISTS IT WILL ALLOW TD 06W TO REMAIN
A STRONG EXTRA-TROPICAL CIRCULATION AS EXTRA-TROPICAL TRANSITION
BEGINS AROUND TAU 72 AND COMPLETES BY TAU 120. CONFIDENCE REMAINS
LOW FOR THE EXTENDED TAUS BASED ON THE TIMING FOR THE STEERING STR
DEVELOPMENT AND IMPACTS TO LLCC DEVELOPMENT BY THE WARM POOL OF
SSTS. MODEL GUIDANCE IS IN GOOD AGREEMENT WITH THE FORECAST,
HOWEVER, THE MAJORITY OF THE GUIDANCE INDICATES THE STR SHOULD
ALREADY BE HELPING THE STEERING OF THE SYSTEM. THIS FORECAST IS
BASED PREDOMINANTLY ON THE CONSENSUS OF AVAILABLE MODEL GUIDANCE,
HOWEVER THE TAU 96 AND 120 POSITIONS ARE SLIGHTLY FASTER THAN
CONSENSUS TO KEEP WITH CLIMATOLOGICAL SPEEDS.//
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