Tropical Storm FRANCISCO Advisory 8月4日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (FRANCISCO) WARNING
NR 09//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 09W (FRANCISCO), LOCATED APPROXIMATELY 115 NM
EAST-SOUTHEAST OF CHICHI JIMA, HAS TRACKED WEST-NORTHWESTWARD AT 16
KNOTS OVER THE PAST SIX HOURS. AN APPROXIMATE 140 NM CENTRAL DENSE
OVERCAST IS OBSCURING THE LOW LEVEL CIRCULATION CENTER (LLCC) IN
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY. THERE IS FAIR
CONFIDENCE IN THE INITIAL POSITION WHICH WAS FOUND BY EXTRAPOLATING
FROM A 031548Z AMSR2 89 GHZ MICROWAVE IMAGE THAT SHOWED A DEEP
CONVECTIVE BAND TO THE SOUTH, AND SHALLOWER BANDS TO THE NORTH,
WRAPPING INTO THE LLCC. THE INITIAL INTENSITY OF 40 KTS FALLS
BETWEEN PGTW (T2.5, 35 KTS) AND RJTD (T3.0, 45 KTS) DVORAK FIX
INTENSITIES. 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 WEAK
UPPER-LEVEL CONVERGENCE TO THE SOUTH FROM A FILLING TUTT CELL. 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 72, TS 09W IS FORECAST TO TRACK GENERALLY
NORTHWESTWARD TOWARD SASEBO UNDER THE STEERING INFLUENCE OF THE
AFOREMENTIONED STR. THE BULK OF THE MODEL GUIDANCE IS IN GOOD
AGREEMENT FOR THIS PORTION OF THE FORECAST WITH THE SPREAD, WHEN
EXCLUDING THE SOUTHERNMOST (GALWEM) AND EASTERNMOST (NAVGEM)
MEMBERS, BEING UNDER 80 NM AT TAU 72. UNTIL MAKING LANDFALL AROUND TAU
48, TS 09W SHOULD INTENSIFY SLOWLY DUE TO THE CONTINUED INFLUENCE OF
THE TUTT CELL TO THE SOUTH. TS 09W SHOULD WEAKEN AFTER MAKING
LANDFALL OVER KYUSHU DUE TO THE RUGGED TERRAIN. A SECOND LANDFALL IS
EXPECTED NEAR BUSAN, KOREA AROUND TAU 72. 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 BEGIN 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 BY TAU 120. AS THE SYSTEM ROUNDS THE STR AXIS, SPREAD IN THE
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.//
NNNN
NNNN