Tropical Storm PHANFONE Advisory Sat Oct 04

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 18W (PHANFONE) WARNING NR 19//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 18W (PHANFONE), LOCATED APPROXIMATELY 374 NM WEST-
SOUTHWEST OF IWO TO, HAS TRACKED NORTHWESTWARD AT 12 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
INDICATES A SLIGHT IMPROVEMENT WITH A 16-NM RAGGED EYE; HOWEVER,
DEEP CONVECTIVE BANDING WEAKENED OVER THE NORTHERN SEMI-CIRCLE. A
030455Z NOAA-19 89GHZ IMAGE DEPICTS A SMALL 210-NM DEEP CONVECTIVE
CORE WITH CONVECTIVE BANDING WRAPPING INTO AN OBLONG MICROWAVE EYE
FEATURE. OVERALL, THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION
AND RECENT MOTION. THE INITIAL INTENSITY REMAINS ASSESSED AT 110
KNOTS, HEDGED SLIGHTLY LOWER THAN DVORAK CURRENT INTENSITY ESTIMATES
OF 115 KNOTS. TY 18W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF
THE DEEP SUBTROPICAL RIDGE (STR) TOWARD A LARGE BREAK IN THE STR,
POSITIONED SOUTH OF WESTERN JAPAN, CAUSED BY A BROAD MIDLATITUDE
TROUGH CENTERED OVER THE KOREAN PENINSULA.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY
FROM THE PREVIOUS PROGNOSTIC REASONING BULLETIN.
   B. TY 18W IS FORECAST TO TRACK NORTHWARD THROUGH TAU 36 AS IT
TRACKS ALONG THE WESTERN PERIPHERY OF THE STR THEN SHOULD TURN
SHARPLY NORTHEASTWARD AS IT ROUNDS THE AXIS OF THE STR NEAR TAU 48
AND BEGINS EXTRA-TROPICAL TRANSITION (ETT) AND INTERACTS WITH THE
MIDLATITUDE WESTERLIES. DYNAMIC MODEL GUIDANCE CONTINUES TO INDICATE
UNCERTAINTY IN THE EXACT RE-CURVE POINT AND TIMING WITH SOME MODELS
SHOWING A SLOWER RE-CURVE, FURTHER WEST (NOTABLY JGSM, JENS, ECMWF)
WHILE THE REMAINING MODELS INDICATE FASTER TRACK SPEEDS. THERE IS
CURRENTLY A 150NM SPREAD IN SOLUTIONS AT THE RE-CURVE POINT NEAR TAU
36. AS TY 18W ACCELERATES EAST-NORTHEASTWARD TOWARD THE KANTO PLAIN,
UNDERGOING ETT THEY DIVERGE FURTHER WITH SEVERAL DYNAMIC MODELS
TRACKING THE SYSTEM INTO STRONG MIDLATITUDE WESTERLY FLOW, WHICH IS
FORECAST TO DEVELOP OVER CENTRAL JAPAN. THE JTWC FORECAST FAVORS A
TRACK FURTHER SOUTH RATHER THAN INTO THE STRONG WESTERLIES, WHICH IS
UNLIKELY, HOWEVER, TY 18W IS EXPECTED TO RAPIDLY COMPLETE ETT AND
GAIN FRONTAL CHARACTERISTICS NEAR THE KANTO PLAIN LENDING INCREASED
UNCERTAINTY TO POSITIONING DUE TO A BROADENING LOW PRESSURE AREA.
REGARDLESS OF WHETHER THE SYSTEM IS WARM-CORE OR COLD-CORE, STORM
FORCE WINDS ARE FORECAST DUE TO THE STRONG PRESSURE GRADIENT
ENHANCED BY A STRONG BAROCLINIC ZONE OVER JAPAN. OVERALL, THERE IS
LOW CONFIDENCE IN THE JTWC TRACK DUE TO SIGNIFICANT MODEL TRACK
SPEED DIFFERENCES AND TRACK UNCERTAINTY ASSOCIATED WITH THE RAPID
ETT PROCESS.//
NNNN
NNNN