WDPN31 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 02W (HIGOS) WARNING NR 08//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 02W (HIGOS), LOCATED APPROXIMATELY 677 NM EAST OF 
ANDERSEN AFB, GUAM, HAS TRACKED WEST-NORTHWESTWARD AT 03 KNOTS OVER 
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS 
CONTINUED CONSOLIDATION OF THE CENTRAL CONVECTION WITH FEEDER BANDS
WRAPPING TIGHTER INTO THE WELL-DEFINED LOW LEVEL CIRCULATION CENTER
(LLCC). THIS IS ALSO CORROBORATED BY A 082055Z SSMIS 91 GHZ MICROWAVE
IMAGE SHOWING DEEP CONVECTIVE BANDING LOCATED ALONG THE NORTHERN AND
WESTERN PERIPHERIES OF THE SYSTEM. THE CURRENT POSITION IS BASED ON
THE PGTW FIX AND AFOREMENTIONED MICROWAVE IMAGE WITH FAIR CONFIDENCE.
THE CURRENT INTENSITY IS BASED ON AN OVERALL ASSESSMENT OF AGENCY
DVORAK ESTIMATES AND REFLECTS THE IMPROVED CENTRAL CONVECTION. THE
UPPER LEVEL ENVIRONMENT REMAINS UNCHANGED WITH LOW TO MODERATE (10 TO
20 KNOT) VERTICAL WIND SHEAR (VWS) BEING OFFSET BY VIGOROUS POLEWARD
OUTFLOW. TY 02W REMAINS IN A COMPETING STEERING ENVIRONMENT BETWEEN
TWO MID- TO HIGH-LEVEL SUB-TROPICAL RIDGES (STR), ONE TO THE EAST AND
THE OTHER TO THE WEST OF THE CYCLONE, LEADING TO THE QUASI-STATIONARY
MOVEMENT.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TY HIGOS WILL CONTINUE ON A SLOW WEST-NORTHWESTWARD TRACK OVER 
THE NEXT 6 TO 12 HOURS UNTIL THE STR EAST OF THE SYSTEM TAKES OVER 
AS THE DOMINANT STEERING MECHANISM. WITH THE DECREASE IN FORWARD 
MOTION, FAVORABLE UPPER-LEVEL CONDITIONS WILL PERSIST OVER THE 
SYSTEM FOR THE NEXT 24 HOURS ALLOWING TY 02W TO CONTINUE ITS 
INTENSIFICATION, REACHING A PEAK OF 85 KNOTS BY TAU 24. BEYOND TAU
24, TY HIGOS WILL BEGIN TO WEAKEN AS IT ENCOUNTERS INCREASED (20 TO
30 KNOT) SOUTHWESTERLY VWS. AFTER TAU 48, THE SYSTEM WILL TURN
POLEWARD AS IT ROUNDS THE SOUTHWESTERN PERIPHERY OF THE STR AND
ENTERS AN UNFAVORABLE ENVIRONMENT WITH 40 TO 50 KNOT VWS, DECREASING
SEA SURFACE TEMPERATURE, AND REDUCED OCEAN HEAT CONTENT.
   C. AFTER TAU 72, THE SYSTEM WILL RAPIDLY WEAKEN AS VWS INCREASES 
ABOVE 50 KNOTS LEADING TO DISSIPATION BY THE END OF THE FORECAST 
PERIOD. DYNAMIC MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT 
THROUGH TAU 72 WITH A 250NM SPREAD AFTERWARDS. BEYOND TAU 72, GFS 
AND JENS EMBED THE SYSTEM IN THE MID-LATITUDE WESTERLIES, WHILE THE 
REMAINING GUIDANCE DEPICTS DISSIPATION AT TAU 120. BASED ON THE 
ZONAL FLOW AND LACK OF TEMPERATURE ADVECTION IN THE WESTERLY FLOW, 
JTWC EXPECTS THE SYSTEM TO DISSIPATE. DUE TO CONTINUED UNCERTAINTY 
IN THE QUASI-STATIONARY MOTION AND THE EXTENDED MODEL GUIDANCE, THE 
JTWC FORECAST REMAINS LOW.//
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