Tropical Storm NANGKA Advisory Mon Jul 13

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (NANGKA) WARNING NR 39//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 11W (NANGKA), LOCATED APPROXIMATELY 902 NM SOUTH-
SOUTHEAST OF SASEBO, JAPAN, HAS TRACKED NORTHWARD AT 05 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL IMAGERY SHOWS THE
SYSTEM HAS BECOME MORE SYMMETRICAL AND APPEARS TO HAVE UNDERGONE
EYEWALL REPLACEMENT. THE INITIAL POSITION IS BASED ON A MICROWAVE
EYE FEATURE IN THE 122250Z 37GHZ SSMIS IMAGE WITH HIGH CONFIDENCE.
THE INITIAL INTENSITY OF 105 KNOTS IS HELD SLIGHTLY HIGHER THAN
AGENCY DVORAK ESTIMATES TO REFLECT THE IMPROVED CONVECTIVE SIGNATURE
OF THE SYSTEM. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM HAS MOVED
INTO AN AREA OF LOW TO MODERATE (10-15 KNOT) VWS. ADDITIONALLY,
EXCELLENT RADIAL OUTFLOW, ENHANCED BY A POINT SOURCE ALOFT,
CONTINUES TO PROVIDE VENTILATION TO THE SYSTEM. THE CYCLONE IS NOW
TRACKING ALONG THE WESTERN EDGE OF THE STEERING STR TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 11W IS FORECAST TO TRACK POLEWARD TOWARDS A BREAK IN THE
STEERING STR. AFTER TAU 36, THE STR IS EXPECTED TO STRENGTHEN AND
BUILD BACK IN, DEFLECTING THE SYSTEM NORTHWESTWARD TOWARDS THE
JAPANESE ISLAND OF KYUSHU. FAVORABLE UPPER LEVEL CONDITIONS, IN
ADDITION TO WARM SSTS, WILL PERSIST, RESULTING IN STEADY
INTENSIFICATION OVER THE NEXT 48 HOURS PEAKING AT 120 KNOTS.
   C. AFTER TAU 72, TY NANGKA WILL CONTINUE TO TRACK TO THE NORTHWEST
UNDER THE INFLUENCE OF THE AFOREMENTIONED STR, MAKING LANDFALL OVER
KYUSHU SHORTLY BEFORE TAU 96. INCREASING VWS, IN ADDITION TO LAND
INTERACTION, WILL BEGIN TO WEAKEN THE SYSTEM AT THE EXTENDED PORTION
OF THE FORECAST. DYNAMIC MODEL GUIDANCE HAS SIGNIFICANTLY SPREAD OUT
AT THE EXTENDED TAUS. ADDITIONALLY, THERE IS A DISTINCT DISCREPANCY
IN THE INITIAL TRACK SPEEDS, LENDING TO LOW CONFIDENCE IN THE JTWC
FORECAST TRACK.//
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