Tropical Storm KROSA Advisory Sáb, 10-08

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (KROSA) WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 11W (KROSA), LOCATED APPROXIMATELY 126 NM SOUTH
OF IWO TO, JAPAN, HAS TRACKED NORTHWARD AT 03 KNOTS OVER THE PAST
SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS
SLIGHTLY IMPROVED CONVECTIVE BANDING WRAPPING INTO A DEFINED LOW-
LEVEL CIRCULATION CENTER (LLCC). HOWEVER, DEEP CONVECTION OVER THE
CORE AND NORTHWEST QUADRANT REMAIN WEAK DUE TO THE PRESENCE OF
CYCLONIC FLOW AND CONVERGENCE ALOFT WHILE STRONG DIFFLUENCE OVER THE
EASTERN AND SOUTHERN FLANK CONTINUE TO FUEL DEEP CONVECTIVE BANDING.
A 092130Z SSMIS 91GHZ IMAGE INDICATES TIGHTLY-CURVED BANDING
WRAPPING INTO A DEFINED, BROAD LLCC, WHICH SUPPORTS THE INITIAL
POSITION WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT
70 KNOTS, HEDGED SLIGHTLY BELOW DVORAK CURRENT INTENSITY ESTIMATES
OF 4.5 (77 KNOTS), BASED ON A 092054Z SMAP ESTIMATE OF 71 KNOTS (1-
MINUTE AVERAGE). WITH THE EXCEPTION OF THE COMPLEX, MARGINALLY-
FAVORABLE OUTFLOW, VERTICAL WIND SHEAR AND SST VALUES REMAIN
FAVORABLE. TY 11W IS LOCATED WITHIN A WEAK STEERING ENVIRONMENT WITH
A NORTH-SOUTH SUBTROPICAL RIDGE POSITIONED TO THE EAST, A WEAK STR
OVER WESTERN JAPAN AND A BREAK TO THE NORTH. THEREFORE, TY 11W IS
TRACKING SLOWLY POLEWARD (AND ERRATICALLY).
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. IN THE NEXT 72 HOURS, THE PRIMARY STEERING FOR TY 11W WILL
GRADUALLY TRANSITION TO THE BUILDING STR TO THE NORTH OF TY 11W AND
THE TRACK WILL SLOWLY SHIFT NORTHWESTWARD TOWARD JAPAN, PASSING
SOUTHWEST OF IWO TO AROUND TAU 24. SLIGHTLY DIMINISHED OUTFLOW, WEAK
SUBSIDENCE AND POSSIBLE UPWELLING COOLER WATER WILL MAKE THE
ENVIRONMENT SOMEWHAT UNFAVORABLE THROUGH TAU 48 WITH GRADUAL
WEAKENING TO ABOUT 60 KNOTS. AFTER TAU 48, AS THE SYSTEM BEGINS TO
ACCELERATE WEST-NORTHWESTWARD TO NORTHWESTWARD OVER WARM SST, SLIGHT
INTENSIFICATION IS EXPECTED.
   C. AFTER TAU 72, TY 11W WILL RECURVE POLEWARD ALONG THE SOUTHWEST
PERIPHERY OF THE STR, WHICH IS EXPECTED TO WEAKEN AND REORIENT WITH
THE APPROACH OF A DEEP MIDLATITUDE SHORTWAVE TROUGH. TY 11W SHOULD
RE-INTENSIFY TO A PEAK INTENSITY OF 70 KNOTS AS POLEWARD OUTFLOW
IMPROVES. SST VALUES WILL REMAIN CONDUCIVE (28-29C) DURING THIS
EXTENDED PERIOD. NUMERICAL MODEL GUIDANCE DIVERGES SLIGHTLY BUT
REMAINS IN GOOD AGREEMENT WITH A 95NM SPREAD IN SOLUTIONS AT TAU
120. BASED ON THE ERRATIC SHORT-TERM MOTION AND UNCERTAINTY IN THE
LATER TAUS, THERE IS OVERALL MODERATE CONFIDENCE IN THE JTWC
FORECAST TRACK.//
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