WDPN31 PGTW 191500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W (RAI) WARNING NR 027//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.9N 110.8E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 116 NM EAST-SOUTHEAST OF DA NANG
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
THE WEAKENING PROCESS OF TYPHOON 28W CONTINUED AND ACCELERATED
DURING THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED IMAGERY SHOWS
CLOUD TOPS WARMING AND STRETCHING AND THE LOW LEVEL CIRCULATION 
CENTER 
IS NOW COMPLETELY CLOUD FILLED. DEEP CONVECTIVE BANDING IS ABSENT 
OVER 
MOST OF THE EASTERN SEMI-CIRCLE. TYPHOON 28W HAS ALSO ROLLED 
COMPLETELY OVER AND IS TRACKING EAST OF NORTH. THE LAST THREE 
BEARINGS 
OF MOVEMENT HAVE BEEN 305 325 AND NOW 005 DEGREES. ANIMATED WATER 
VAPOR IMAGERY SHOWS A VIGOROUS POLEWARD OUTFLOW CHANNEL AND AN 
EXPANSION OF THE UPPER LEVEL MOISTURE FIELDS AS THE OUTFLOW GETS 
SUCKED INTO A BELT OF STRONG WESTERLIES THAT EXTEND ALONG THE 20TH 
LATITUDE.  AT THE GRADIENT LEVEL A 1027MB HIGH PRESSURE CENTER THAT 
JUST MOVED OFF-SHORE OF SHANGHAI IS DRIVING COOL AND DRY GALE FORCE
NORTHEASTERLIES THAT ARE WEAKENING THE LOWER LEVELS OF THE SYSTEM.
BOTH SUBJECTIVE AND OBJECTIVE DVORAKS ARE FALLING RAPIDLY. THE
CURRENT ADT ASSESSMENT OF T5.7 AND 107KTS IS IN THE MIDDLE GROUND
OF SATCON AND AGENCY ASSESSMENTS FROM RJTD KNES AND PGTW AND SEEMS
TO BE THE BEST REPRESENTATIVE OF THE CURRENT INTENSITY. THAT IS ALSO 
IN KEEPING WITH THE EXPECTED DECLINE FROM THE 190600Z FIX.

INITIAL WIND RADII BASIS: THE CIRA MULTI-PLATFORM SATELLITE SURFACE
WIND ANALYSIS FROM 190900Z.

CURRENT STEERING MECHANISM: A WEAKNESS ALONG THE WESTERN FLANK OF
THE SUBTROPICAL RIDGE THAT IS ANCHORED IN AN ANTICYCLONE NORTHEAST
OF LUZON. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T6.0 - 115 KTS
   KNES: T6.0 - 115 KTS
   CIMSS SATCON: 116 KTS AT 190810Z
   CIMSS ADT: 107 KTS AT 191140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 10-15 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TYPHOON 28W IS ON A STEEP DECLINE. DRY AIR
ENTRAINMENT AT THE GRADIENT LEVEL ON TOP OF COOLING SEA WATERS AND
VERY LOW OCEAN HEAT CONTENT WILL COMBINE WITH INCREASING VERTICAL
WINDSHEAR TO WEAKEN AND DESTROY THE SYSTEM BEFORE IT CAN REACH
TAIWAN. DUE TO THE EXTREME INTENSITY OF THE SYSTEM AND THE
VORTICITY INDUCED BY THE SURGING NORTHEASTERLIES IT WILL TAKE SOME
TIME FOR THE SYSTEM TO SPIN DOWN. NOTE THAT THE SYSTEM HAD CRANKED
UP TO 140KTS A MERE 18 HOURS AGO. YET EVEN AS THE LOW LEVEL VORTEX
SURVIVES WHAT REMAINS OF TY 28W WILL BE GENERATING VERY LITTLE DEEP
CONVECTION BY THE TIME IT REACHES THE 18TH LATITUDE. 

MODEL DISCUSSION: TRACK GUIDANCE HAS BEEN EXCELLENT THROUGHOUT THE
LIFE CYCLE OF THE STORM AND THE JTWC TRACK FORECAST STAYS WITH THE
MULTI-MODEL CONSENSUS. THE GUIDANCE SPREADS AFTER TAU 48 AS THE
RAPIDLY WEAKENING VORTEX GETS CAUGHT UP IN THE NORTHEASTERLIES.
INTENSITY GUIDANCE TIGHTENED UP DURING THE LAST RUN AND HAS BROUGHT
MORE CERTAINTY TO THE RATE OF DECAY. THE JTWC FORECAST REMAINS ON
THE HIGH SIDE OF THE GUIDANCE ENVELOPE BUT FOLLOWS THE SAME SLOPE. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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