Tropical Storm NEOGURI Advisory Sa, 08.07.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 08W (NEOGURI) WARNING NR 20//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 08W (NEOGURI), LOCATED APPROXIMATELY 189 NM SOUTH-
SOUTHWEST OF KADENA AB, OKINAWA, HAS TRACKED NORTH-NORTHWESTWARD AT
13 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY IN COMBINATION WITH RADAR IMAGERY FROM ISHIGAKIJIMA
DEPICT A SLOW WEAKENING TREND FOR THE ENTIRE EYEWALL BUT WITH GREATER
IMPACT ALONG THE NORTHWESTERN QUADRANT. THE CURRENT INTENSITY OF 110
KNOTS IS SLIGHTLY HIGHER THAN THE DVORAK ESTIMATES FROM PGTW, KNES,
AND RJTD, WHICH RANGE FROM 90 TO 102 KNOTS. THE EYE DIAMETER HAS
DECREASED FROM 40 TO 30 NM OVER THE PAST SIX HOURS, BUT ANIMATED
WATER VAPOR IMAGERY SUGGESTS THE EYEWALL HAS STABILIZED IN THE PAST
FEW HOURS. A DIGGING MID-LATITUDE TROUGH, TO THE NORTHWEST OF TY 08W,
HAS BEEN AMPLIFYING THE UPPER LEVEL POLEWARD OUTFLOW OVER THE PAST 12
HOURS, HELPING TO MAINTAIN THE INTENSITY OF THE SYSTEM. RECENTLY, AS
THE TROUGH CONTINUES TO DIG TO THE SOUTHWEST OVER EASTERN CHINA,
INCREASED SUBSIDENCE ALONG THE NORTHWESTERN QUADRANT OF TY 08W HAS
HINDERED DEVELOPMENT AND IS LEADING TO THE WEAKENING OBSERVED IN THE
PAST SIX HOURS. THE TRACK HAS SHIFTED SLIGHTLY MORE TO THE WEST THAN
THE PREVIOUS FORECAST SUGGESTED AS TY 08W TRACKS ALONG THE SOUTH-
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) ANCHORED NEAR
IWO TO. TRACK SPEEDS HAVE BEEN CONSISTENT OVER THE PAST 12 HOURS.
3. FORECAST REASONING.
   A. THIS FORECAST HAS SEVERAL PHILOSOPHY CHANGES AS MODEL GUIDANCE,
RECENT OBSERVATIONS, AND SATELLITE IMAGERY SUPPORT A CHANGE. THE
PRIMARY CHANGE IS ASSOCIATED WITH THE INTENSITY FORECAST. THE
PREVIOUS FORECAST INDICATED AN EYEWALL REPLACEMENT CYCLE WAS UNDER
WAY, AND THIS FORECAST SHIFTS TO A STEADY WEAKENING TREND WITH NO
EXPECTATION OF AN INCREASE IN THE INTENSITY OVER THE NEXT 12 TO 24
HOURS. ADDITIONALLY, THE WEAKENING TREND WAS ACCELERATED AFTER TY 08W
MAKES LANDFALL. THE SECOND CHANGE IS TO THE TRACK SPEED BEYOND TAU
36. BASED ON THE MODEL GUIDANCE, TRACK SPEEDS HAVE BEEN DECREASED AT
THE TAU 48, 72 AND 96 TIMES.
   B. TY 08W IS FORECAST TO SHIFT TO A MORE NORTHWARD TRACK OVER THE
NEXT 12 HOURS AND REMAIN ON A STEADY NORTHWARD TRACK THROUGH TAU 24.
THE DIGGING MID-LATITUDE TROUGH TO THE NORTHWEST OF TY 08W WILL TRACK
EASTWARD AND CAUSE THE STR TO SHIFT AFTER TAU 24, CAUSING TY 08W TO
TRACK MORE NORTHEASTWARD AFTER TAU 36. THE TROUGH HAS BEEN AMPLIFYING
THE UPPER LEVEL POLEWARD OUTFLOW OVER THE PAST 12 HOURS, HELPING TO
MAINTAIN THE INTENSITY OF THE SYSTEM BUT AS IT SHIFTS EASTWARD, THE
TROUGH WILL STIFLE THE STRONG POLEWARD OUTFLOW, LEADING TO A STRONGER
WEAKENING TREND BY TAU 48. THE TIMING OF LANDFALL IN SOUTHERN JAPAN
HAS BEEN SHIFTED FROM THE PREVIOUS FORECAST AND IS EXPECTED AROUND
00Z ON THE 10TH. THE SEA SURFACE TEMPERATURES REMAIN VERY FAVORABLE
THROUGH TAU 24, BUT WILL QUICKLY DECREASE ONCE THE SYSTEM APPROACHES
30N. INCREASING VERTICAL WIND SHEAR FROM THE MID-LATITUDE WESTERLIES
WILL ALSO BEGIN TO IMPACT THE STRUCTURE OF TY 08W AFTER TAU 36.
BEYOND TAU 48 A COMBINATION OF THESE ELEMENTS, IN ASSOCIATION WITH
THE TRACK OVER THE SOUTHERN JAPANESE TERRAIN, WILL LEAD TO A THE
BEGINNING OF EXTRA-TROPICAL TRANSITION (ETT) BY TAU 72.
   C. BEYOND TAU 72, TY NEOGURI WILL CONTINUE THE ETT PROCESS,
ACCELERATING TO THE NORTHEAST UNDER THE COMBINED INFLUENCE OF A DEEP
MID-LATITUDE LOW OVER NORTHERN JAPAN AND THE STR. TY NEOGURI IS
EXPECTED TO BY FULLY EXTRA-TROPICAL BY TAU 96. THE AVAILABLE DYNAMIC
MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT, LENDING TO HIGH CONFIDENCE
IN THE JTWC TRACK FORECAST TO THE MULTI-MODEL CONSENSUS.//
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