Tropical Storm NANGKA Advisory Sun Jul 12

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (NANGKA) WARNING NR 32//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 11W (NANGKA), LOCATED APPROXIMATELY 366 NM WEST OF
AGRIHAN, HAS TRACKED WEST-SOUTHWESTWARD AT 06 KNOTS OVER THE PAST
SIX HOURS. ANIMATED MSI SHOWS A SLIGHT WEAKENING OF THE SYSTEM WITH
AN EYE NO LONGER VISIBLE AND SIGNIFICANT SUBSTANCE ON THE NORTHERN
SIDE, FLATTENING OUT THE SYSTEM. A 110711Z AMSU-B IMAGE SHOWS THE
DEEP CONVECTION AMASSED ON THE SOUTHERN SIDE OF THE LLCC. THE
INTENSITY HAS BEEN LOWERED SLIGHTLY DUE TO THE DECAY IN OVERALL
STRUCTURE OF THE SYSTEM. UPPER LEVEL ANALYSIS INDICATES HIGH (20-40
KNOTS) NORTHERLY VWS OFFSET BY VIGOROUS EQUATORWARD OUTFLOW. THE
SYSTEM IS TRACKING ON THE SOUTHERN SIDE OF A STR ANCHORED SOUTH OF
SHIKOKU.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 11W WILL CONTINUE TO SLOWLY TRACK WESTWARD OVER THE NEXT 12
HOURS AS THE STR REMAINS TO THE NORTH. SOME FURTHER DECAY CAN BE
EXPECTED AS THE SUBSIDENCE REMAINS ON THE NORTHERN SIDE OF THE
SYSTEM. BY TAU 24, EXPECT THE STR TO BEGIN TO TRACK TO THE EAST,
ALLOWING TY NANGKA TO ROUND THE RIDGE AND MOVE POLEWARD. EXPECT SOME
INTENSIFICATION AS THE SYSTEM TRACKS TO THE NORTH AS THE VWS WILL
SUBSIDE AND A POLEWARD OUTFLOW SHOULD DEVELOP IN THE WAKE OF THE
STR. BY TAU 72, EXPECT TY 11W TO TRACK MORE TO THE NORTHWEST AS A
STR BUILDS IN OVER SOUTHERN JAPAN.
   C. IN THE EXTENDED FORECAST, TY NANGKA WILL CONTINUE TO TRACK TO
THE NORTHWEST UNDER THE INFLUENCE OF A DEVELOPING RIDGE IN SOUTHERN
JAPAN. EXPECT FURTHER INTENSIFICATION OF THE SYSTEM AS 11W INTERACTS
WITH THE KUROSHIO AND HAS GOOD UPPER-LEVEL SUPPORT. DYNAMIC MODEL
GUIDANCE IS IN POOR AGREEMENT WITH VARYING DEGREES OF TRACKING TO
THE WEST IN THE EARLY TAUS AND VARYING TRACKS WITH REGARD TO EXTEND
OF THE SYSTEM IN THE EXTENDED FORECAST. AS SUCH, THERE IS LOW
CONFIDENCE IN THE JTWC FORECAST TRACK WHICH IS LAID CLOSE TO THE
MULTI-MODEL CONSENSUS.//
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