WDPN31 PGTW 040300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (CHAN-HOM) WARNING 
NR 15//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 09W (CHAN-HOM), LOCATED APPROXIMATELY 219 NM 
EAST-SOUTHEAST OF ANDERSEN AFB, GUAM HAS TRACKED NORTH-NORTHWESTWARD 
AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL 
SATELLITE IMAGERY (MSI) DEPICTS ENHANCED CONVECTION DEEPENING ABOVE 
THE PREVIOUSLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC). A 
032022Z WINDSAT MICROWAVE IMAGE SHOWS AN ELONGATED LLCC WITH 
MULTIPLE SHALLOW CURVED BANDS WRAPPING INTO THE CENTER. THE INITIAL 
POSITION IS BASED ON THE MSI LOOP AND THE AFOREMENTIONED MICROWAVE 
IMAGE WITH HIGH CONFIDENCE. THE CURRENT INTENSITY OF 45 KNOTS IS 
BASED ON A 032332Z SCATTEROMETER PARTIAL PASS WITH 40 TO 45 KNOTS 
ALONG THE WESTERN PERIPHERY. UPPER LEVEL CONDITIONS HAVE IMPROVED 
WITH VERTICAL WIND SHEAR NOW 10 TO 15 KNOTS AND BEING OFFSET BY GOOD 
DIVERGENT OUTFLOW ALOFT, ALLOWING THE CONVECTION TO REMAIN 
VERTICALLY STACKED OVER THE LLCC. TS 09W HAS STARTED TO TRACK TO THE 
NORTH-NORTHWEST AS THE TUTT CELL IS RETREATING TO THE NORTH AND THE 
SUB-TROPICAL RIDGE (STR) IS BUILDING BACK IN NORTH OF THE SYSTEM.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TS 09W WILL CONTINUE TO PICK UP FORWARD TRANSLATIONAL SPEED ON 
A NORTHWESTWARD TRAJECTORY AS THE STEERING STR CONTINUES TO BUILD. 
FAVORABLE ENVIRONMENTAL CONDITIONS ARE EXPECTED TO PERSIST, ALLOWING 
TS CHAN-HOM TO REINTENSIFY TO TYPHOON INTENSITY IN 24 HOURS AND TO 
110 KNOTS BY TAU 72.
   C. BEYOND TAU 72, TS 09W WILL CONTINUE TO TRACK NORTHWESTWARD 
UNDER THE INFLUENCE OF THE DOMINANT STEERING STR. VWS AND UPPER 
LEVEL DIVERGENCE WILL REMAIN FAVORABLE THROUGH THE END OF THE 
FORECAST PERIOD; HOWEVER, SEA SURFACE TEMPERATURES AND OCEAN HEAT 
CONTENT WILL DECREASE CAUSING A SLOW DOWN IN INTENSIFICATION AND 
THEN A WEAKENING PHASE BEYOND TAU 96. DYNAMIC MODEL GUIDANCE IS IN 
TIGHT AGREEMENT THROUGHOUT THE FORECAST PERIOD WITH SOME DIVERGENCE 
BEYOND TAU 96. ALTHOUGH THERE IS HIGHER CONFIDENCE IN THE CURRENT 
TRACK BASED ON THE SYSTEM'S CURRENT MOVEMENT; OVERALL LOW CONFIDENCE 
REMAINS DUE TO RECENT ISSUES WITH THE MODEL GUIDANCE HANDLING THE 
NORTHEASTWARD MOVEMENT.//
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