Tropical Storm FRANCISCO Advisory Mon Aug 05

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (FRANCISCO) WARNING
NR 11//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 09W (FRANCISCO), LOCATED APPROXIMATELY 602 NM
EAST-SOUTHEAST OF IWAKUNI, JAPAN, HAS TRACKED NORTHWESTWARD AT 16
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY REVEALS THE LOW LEVEL CIRCULATION CENTER (LLCC) BECOMING LESS
OBSCURED BY THE CENTRAL DENSE OVERCAST AS SOME RELATIVELY DRY AIR
WRAPS IN FROM THE SOUTH. THERE IS GOOD CONFIDENCE IN THE INITIAL
POSITION WHICH WAS EXTRAPOLATED FROM A 030441Z GMI 89 GHZ MICROWAVE
IMAGE THAT SHOWED A DEEP CONVECTIVE BAND WRAPPING IN ALONG THE
SOUTHERN EDGE OF THE LLCC AND MOSTLY SHALLOW BANDS TO THE NORTHEAST.
THE INITIAL INTENSITY OF 45 KNOTS FALLS BETWEEN MULTI-AGENCY DVORAK
FIXES FROM T2.5-T3.0 (35-45 KNOTS) AND A SATCON ESTIMATE OF 52 KNOTS.
A 032359Z METOP-B ASCAT PASS CONFIRMS THIS INTENSITY ESTIMATE AND
DISPLAYS AN ASYMMETRIC WIND FIELD WITH THE STRONGEST WINDS CONTAINED
IN THE NORTHERN SEMICIRCLE. THE ENVIRONMENT IS MARGINALLY FAVORABLE
WITH LOW (10-15 KNOTS) VERTICAL WIND SHEAR (VWS) AND WARM (28-29
CELSIUS) SEA SURFACE TEMPERATURE (SST) BEING OFFSET BY FAIR POLEWARD
OUTFLOW AND DRY AIR ENTRAINMENT FROM AN AREA OF UPPER-LEVEL
CONVERGENCE TO THE SOUTH. TS 09W IS TRACKING ALONG THE SOUTHWEST
PERIPHERY OF A SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE OVERALL FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. THROUGH TAU 48, TS 09W IS FORECAST TO TRACK GENERALLY
NORTHWESTWARD TOWARD SASEBO UNDER THE STEERING INFLUENCE OF THE
AFOREMENTIONED STR. MODEL GUIDANCE IS IN GOOD AGREEMENT FOR THIS
PORTION OF THE FORECAST WITH THE SPREAD AT 48 HOURS AT APPROXIMATELY
55 NM. AFTER PASSING SASEBO AROUND TAU 48, TS 09W IS EXPECTED TO
BEGIN A GRADUAL POLEWARD TURN AS IT ROUNDS THE STR AXIS. UNTIL
LANDFALL IN JAPAN AROUND TAU 36, TS 09W IS EXPECTED TO SLOWLY
INTENSIFY TO AROUND 55 KNOTS AS THE ENVIRONMENT REMAINS MARGINAL DUE
TO POOR UPPER LEVEL DIVERGENCE AND THE EFFECTS OF DRY AIR
ENTRAINMENT. AFTER MAKING LANDFALL, TS 09W SHOULD WEAKEN OVER KYUSHU
DUE TO THE RUGGED TERRAIN. A SECOND LANDFALL SHOULD OCCUR NEAR BUSAN,
KOREA AROUND TAU 54. BASED ON TIGHT GROUPING OF THE MODEL DATA AND
THE STEADY INFLUENCE OF THE STR, THERE IS HIGH CONFIDENCE IN THIS
PORTION OF THE JTWC TRACK FORECAST.
   C. AFTER TAU 72, TS 09W WILL CONTINUE RECURVING AS IT ROUNDS THE
STR AXIS, ACROSS THE EASTERN SIDE OF SOUTH KOREA, AND PASS INTO THE
SEA OF JAPAN. THROUGHOUT THIS PERIOD, LAND INTERACTION, INCREASING
VWS, AND COOLER SST SHOULD WEAKEN THE SYSTEM. BY TAU 96, TS 09W WILL
BEGIN INTERACTING WITH THE MID-LATITUDE BAROCLINIC ZONE AND START
UNDERGOING EXTRATROPICAL TRANSITION (ETT). ETT SHOULD COMPLETE PRIOR
TO TAU 120. AS THE SYSTEM ROUNDS THE STR AXIS, SPREAD IN MODEL
GUIDANCE INCREASES SIGNIFICANTLY, PRIMARILY DUE TO DIFFERENCES IN
ALONG-TRACK SPEED. FOR THIS REASON, THERE IS LOW CONFIDENCE IN THE
EXTENDED PORTION OF THE JTWC TRACK FORECAST.//
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