WDPN31 PGTW 101500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 14W (BEBINCA) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.6N 145.4E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 67 NM SOUTHEAST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SLOWLY 
CONSOLIDATING SYSTEM WITH A CENTRAL DENSE OVERCAST FEATURE OBSCURING 
THE LOW-LEVEL CIRCULATION CENTER. FORTUNATELY, GUAM RADAR IMAGERY DOES 
REVEAL WHAT APPEARS TO BE A CONSOLIDATING LLC WITH CONVECTIVE BANDING 
WRAPPING INTO A DEFINED CENTER AND STRONG CONVERGENT SOUTHERLY FLOW 
AND ASSOCIATED RAINBANDS OVER THE EASTERN SEMICIRCLE, WHICH ARE 
ASSOCIATED WITH A SWATH OF 25-30 KNOT SOUTHERLY WINDS OBSERVED IN THE 
101143Z ASCAT-B IMAGE. IN GENERAL, THE ASCAT IMAGERY CONTINUES TO 
SUGGEST A BROAD CIRCULATION AT THE SURFACE AND SOME UNCERTAINTY IN 
ASCERTAINING THE EXACT CENTER WHICH COULD LEAD TO SIGNIFICANT JUMPS IN 
BOTH THE INITIAL POSITION AND CPA CALCULATIONS OVER THE GUAM REGION. 
UPPER-LEVEL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT WITH A POINT 
SOURCE OVERHEAD PROVIDING NEAR RADIAL OUTFLOW AND LOW VERTICAL WIND 
SHEAR. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH HIGH 
CONFIDENCE BASED ON CONCURRENT SUBJECTIVE DVORAK ESTIMATE OF T2.0 FROM 
ALL AGENCIES AS WELL AS RADAR VELOCITY DATA. CIMSS OBJECTIVE INTENSITY 
ESTIMATES RANGE FROM 31 TO 34 KNOTS. SURFACE OBSERVATIONS FROM PGUM 
AND PGUA INDICATE SUSTAINED WINDS AS HIGH AS 22 KNOTS GUSTING TO 31 
KNOTS. UPPER-AIR DATA FROM THE 101200Z GUAM SOUNDING INDICATES 
INCREASING WINDS (27-28 KNOTS) BELOW THE GRADIENT LEVEL. 

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: LOW- TO MID-LEVEL SUBTROPICAL RIDGE
(STR) ENTRENCHED TO THE EAST AND NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 33 KTS AT 101200Z
   CIMSS AIDT: 34 KTS AT 101200Z
   CIMSS DPRINT: 31 KTS AT 101200Z
  
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL DEPRESSION (TD) 14W IS SLOWLY 
CONSOLIDATING BUT IS EXPECTED TO GRADUALLY INTENSIFY TO MINIMAL 
TROPICAL STORM STRENGTH AS IT TRACKS NEAR GUAM OVER THE NEXT SIX 
HOURS. AFTER TAU 12, THE SYSTEM WILL TRACK NORTHWESTWARD ALONG THE 
WESTERN PERIPHERY OF THE LOW- TO MID-LEVEL STR THROUGH TAU 48 WHILE 
INTENSIFYING AT A SLIGHTLY FASTER RATE TO ABOUT 55 KNOTS BY TAU 48. 
ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE THROUGH TAU 48. AFTER TAU 
48, THE SYSTEM WILL GRADUALLY TURN WEST-NORTHWESTWARD AS IT TRACKS 
UNDER THE STEERING INFLUENCE OF THE STR TO THE NORTH, WHICH SHOULD 
REMAIN STRONG THROUGH TAU 120 DUE TO THE ZONAL MIDLATITUDE FLOW AND 
LACK OF A SIGNIFICANT MAJOR SHORTWAVE TROUGH THAT WOULD TYPICALLY 
WEAKEN THE STR. SIGNIFICANT DRY AIR ENTRAINMENT IS FORECAST BY GFS AND 
ECMWF TO IMPACT AND HINDER DEVELOPMENT FROM TAU 48 TO TAU 72. DRY AIR 
ENTRAINMENT IS ALSO INDICATED IN THE MESOSCALE MODELS BUT WITH A 
LESSER, SHORT-TERM EFFECT. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE REMAINS IN FAIR
AGREEMENT THROUGH TAU 72, WITH A 90-95NM CROSS-TRACK SPREAD IN
GUIDANCE FROM TAU 48 TO TAU 72. HOWEVER, UNCERTAINTY IN THE
INITIAL POSITION SUPPORTS MEDIUM TRACK CONFIDENCE. AFTER TAU 72, MODEL 
GUIDANCE DIVERGES SHARPLY WITH INCREASING UNCERTAINTY IN THE TRACK AND 
LOW OVERALL CONFIDENCE. THE 100600Z GFS ENSEMBLE (GEFS) GUIDANCE 
INDICATES A LARGE SPREAD OF SOLUTIONS WITH STRAIGHT-RUNNER TRACKS OVER 
TAIWAN TO RECURVE TRACKS OVER THE KOREAN PENINSULA AND
WESTERN JAPAN. THE 100600Z ECMWF ENSEMBLE (EPS) IS IN BETTER ALIGNMENT 
WITH THE JTWC FORECAST TRACK SHOWING A TIGHTER GROUPING OF SOLUTIONS 
FROM TAIWAN (LOW PROBABILITY) TO SHANGHAI. RELIABLE INTENSITY GUIDANCE 
AND RAPID INTENSIFICATION GUIDANCE SUPPORTS THE JTWC INTENSITY 
FORECAST THROUGH TAU 48 AND ALSO SHOWS A FLATTER TREND FROM TAU 48 TO 
TAU 72 ASSOCIATED WITH A SHORT PERIOD OF DRY AIR ENTRAINMENT. AFTER 
TAU 72, THE INTENSITY GUIDANCE INDICATES INCREASING POTENTIAL FOR 
RAPID INTENSIFICATION (RI) AS THE SYSTEM RE-MOISTENS AND CONSOLIDATES 
QUICKLY. THE RI PHASE IS SUPPORTED BY THE 100000Z COAMPS-TC ENSEMBLE 
INTENSITY CHANGE PROBABILITY PRODUCT, WHICH INDICATES 50-60 PERCENT 
PROBABILITIES FROM TAU 72 TO TAU 120. DETERMINISTIC GUIDANCE, 
PARTICULARLY THE GFS MODEL, HAS COME INTO BETTER AGREEMENT WITH THE 
MESOSCALE MODELS WITH PEAK INTENSITY RANGING FROM 85 TO 110 KNOTS. 
ALTHOUGH, IT SHOULD BE NOTED THAT COAMPS-TC (GFS) SHOWS A PEAK 
INTENSITY OF 145 KNOTS AT TAU 120 BUT IS THE SOLE OUTLIER.      

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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