Tropical Storm GUCHOL Advisory Fri Jun 15

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 05W (GUCHOL) WARNING NR 17//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 05W (GUCHOL), LOCATED APPROXIMATELY 665 NM EAST-
SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED JUST WESTWARD AT 06
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY SHOWS THE SYSTEM HAS FURTHER DEEPENED AND CONSOLIDATED AS A
TRACE OF AN OUTFLOW CHANNEL HAS BECOME APPARENT ON THE NORTHWEST
QUADRANT. THE MAIN CONVECTION REMAINS COMPACT AND DENSE WITH A SLIGHT
WESTWARD TILT FROM BUT COMPLETELY OVERSHADOWS 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 INITIAL POSITION WAS
EXTRAPOLATED FROM A 142257Z SSMIS MICROWAVE WITH HIGH CONFIDENCE. THE
INITIAL INTENSITY WAS BASED ON THE 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. 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 TO JUST 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 SSTS DECREASE AND
VWS INCREASE, HOWEVER, THE SYSTEM WILL REMAIN A STRONG STORM-FORCE
LOW AS IT ENTERS MAINLAND JAPAN.//
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