Tropical Storm FRANCISCO Advisory So, 04.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (FRANCISCO) WARNING
NR 10//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 09W (FRANCISCO), LOCATED APPROXIMATELY 44 NM
EAST-NORTHEAST OF CHICHI JIMA, HAS TRACKED NORTHWESTWARD AT 15 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 TO THE CENTER. THERE IS FAIR CONFIDENCE IN THE INITIAL
POSITION WHICH WAS EXTRAPOLATED FROM A 032107Z SSMIS 89 GHZ
MICROWAVE IMAGE THAT SHOWED A DEEP CONVECTIVE BAND WRAPPING IN FROM
THE SOUTH AND MOSTLY SHALLOW BANDS TO THE NORTH. THE INITIAL
INTENSITY OF 40 KTS FALLS BETWEEN MULTI-AGENCY DVORAK FIXES FROM
T2.5-T3.0 (35-45 KTS). THE ENVIRONMENT IS MARGINALLY FAVORABLE WITH
GOOD POLEWARD OUTFLOW, LOW (10-15 KT) VERTICAL WIND SHEAR (VWS), AND
WARM (28-29 CELSIUS) SEA SURFACE TEMPERATURE (SST) BEING OFFSET BY
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 BEING ABOUT 87
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
AROUND TAU 40, TS 09W IS EXPECTED TO SLOWLY INTENSIFY TO AROUND 50-
55 KTS AS THE ENVIRONMENT REMAINS MARGINAL. AFTER MAKING LANDFALL,
TS 09W SHOULD WEAKEN OVER KYUSHU DUE TO THE RUGGED TERRAIN. A SECOND
LANDFALL SHOULD OCCUR NEAR BUSAN, KOREA AROUND TAU 60. 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, TRACK 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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