Tropical Storm NEOGURI Advisory Tue Jul 08

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 08W (NEOGURI) WARNING NR 21//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 08W (NEOGURI), LOCATED APPROXIMATELY 133 NM SOUTHWEST OF
KADENA AB, OKINAWA, HAS TRACKED NORTHWARD AT 13 KNOTS OVER THE PAST
SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY IN COMBINATION
WITH RADAR IMAGERY FROM ISHIGAKIJIMA INDICATE THE EYEWALL HAS
MAINTAINED ITS OVERALL STRUCTURE FOR THE PAST SIX HOURS. ANIMATED
WATER VAPOR IMAGERY SHOWS SOME DIURNAL FLARING WITHIN THE EYEWALL. A
RECENT 072313Z TRMM MICROWAVE PASS REVEALS THE EYEWALL CONTINUES TO
BE WEAKEST ALONG THE NORTHWESTERN QUADRANT. THE CURRENT INTENSITY
HAS BEEN KEPT AT 110 KNOTS, SLIGHTLY HIGHER THAN THE DVORAK ESTIMATES
FROM PGTW, KNES, AND RJTD, WHICH HAVE INCREASED ASSOCIATED WITH THE
RECENT FLARE OF CONVECTION OBSERVED IN WATER VAPOR IMAGERY. THE EYE
DIAMETER HAS PERSISTED AT 30 NM OVER THE PAST SIX HOURS. A DIGGING
MID-LATITUDE TROUGH, TO THE NORTHWEST OF TY 08W, HAS BEEN AMPLIFYING
THE UPPER LEVEL POLEWARD OUTFLOW OVER THE PAST 18 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. THE TRACK APPEARS TO BE ON A MORE NORTHWARD TRACK OVER
THE PAST SIX HOURS BASED ON RECENT ANIMATED RADAR IMAGERY. TY 08W
TRACKS ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR)
ANCHORED NEAR IWO TO. TRACK SPEEDS HAVE BEEN CONSISTENT OVER THE
PAST 18 HOURS.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 08W IS FORECAST TO TRACK NORTHWARD OVER THE NEXT SIX HOURS.
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 EAST-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. LANDFALL IN SOUTHERN JAPAN 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 48.
   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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