Tropical Storm GUCHOL Advisory Cu, 15.06.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 05W (GUCHOL) WARNING NR 16//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 05W (GUCHOL), LOCATED APPROXIMATELY 695 NM EAST-
SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED JUST SOUTH OF WESTWARD
AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE
IMAGERY SHOWS THE SYSTEM HAS FURTHER DEEPENED AND CONSOLIDATED WITH
CONCURRENT IMPROVEMENT IN THE OUTFLOW FROM THE SOUTHWEST QUADRANT.
THE MAIN CONVECTION REMAINS COMPACT AND DENSE WITH A SLIGHT WESTWARD
TILT FROM THE LOW LEVEL CIRCULATION CENTER. UPPER LEVEL ANALYSIS
REVEALS THAT TY 05W IS JUST TO THE SOUTH OF A TROPICAL UPPER
TROPOSPHERIC TROUGH (TUTT) IN AN AREA OF LIGHT TO MODERATE (10-15
KNOT) EASTERLY VERTICAL WIND SHEAR (VWS), WHICH IS CAUSING THE
STRUCTURE TILT. THE TUTT TO THE NORTH IS INHIBITING POLEWARD OUTFLOW
AND CAUSING SUBSIDENCE ALONG THE NORTHERN RIM OF THE SYSTEM. THE
INITIAL POSITION WAS EXTRAPOLATED FROM A 141642Z AMSU-B MICROWAVE
IMAGE AND FROM MULTIPLE AGENCY FIXES WITH FAIR CONFIDENCE. THE
INITIAL INTENSITY WAS BASED ON THE AGGREGATE DVORAK ESTIMATES FROM
PGTW, KNES, AND RJTD AND REFLECTS THE DEEPENING AND CONSOLIDATING
TREND. THE CYCLONE IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A
DEEP-LAYERED LEAF OF THE SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 05W IS EXPECTED TO TRACK MORE NORTHWESTWARD AFTER TAU 12 AS
IT REACHES THE SOUTHWEST EDGE OF THE STEERING STR. THIS IS IN
RESPONSE TO A MID-LATITUDE TROUGH APPROACHING FROM THE NORTHWEST INTO
TAIWAN THAT IS DIGGING INTO THE STR. OVER THE NEXT 12-72 HOURS, THE
SYSTEM WILL TRACK POLEWARD INTO THIS BREAK IN THE RIDGE AND IS
EXPECTED TO STEADILY INTENSIFY WITH POSSIBLE RAPID INTENSIFICATION
TOWARD THE APEX OF THE TURN. THIS IS DUE TO CONTINUED FAVORABLE
ENVIRONMENT - LOW VWS, VERY WARM SEA SURFACE TEMPERATURES (SST), AND
RE-ESTABLISHMENT OF THE POLEWARD OUTFLOW CHANNEL, INDUCED BY THE
FRONT SLOPE OF THE APPROACHING TROUGH. THERE IS GOOD CONFIDENCE IN
THIS PORTION OF THE TRACK FORECAST AS THE AVAILABLE NUMERICAL MODEL
GUIDANCE, WITH THE EXCEPTION OF WBAR AS THE SOLE LEFT OUTLIER, HAS
COME INTO BETTER AGREEMENT.
   C. AFTER TAU 72, TYPHOON GUCHOL WILL BEGIN TO RECURVE
NORTHEASTWARD WEST OF OKINAWA, TOWARD KYUSHU AND INTO THE BAROCLINIC
ZONE. BY THE END OF THE FORECAST PERIOD, THE SYSTEM WILL COMMENCE
EXTRA-TROPICAL TRANSITION. ALTHOUGH THE MODEL GUIDANCE HAS COME INTO
A BETTER AGREEMENT OVER THE PAST 24 HOURS, THERE IS, HOWEVER, STILL
LOW CONFIDENCE IN THE EXTENDED TRACK DUE TO UNCERTAINTIES IN THE
WESTWARD EXTENT OF THE STR AND DEPTH AND ORIENTATION OF THE
MID-LATITUDE SHORTWAVE TROUGH EXPECTED TO DEEPEN OVER THE EAST CHINA
SEA AFTER TAU 72. DURING THIS PORTION OF THE FORECAST, TY 05W IS
EXPECTED TO GRADUALLY WEAKEN AS SST'S DECREASE AND VWS INCREASE,
HOWEVER, THE SYSTEM WILL REMAIN A STRONG STORM-FORCE LOW AS IT ENTERS
MAINLAND JAPAN.    //
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