WDPN31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 12W (YAGI)    
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.5N 124.7E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 225 NM EAST-SOUTHEAST OF MANILA,
                         PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
RAPIDLY CONSOLIDATING LOW-LEVEL CIRCULATION WITH A COMPACT CENTRAL
DENSE OVERCAST FEATURE AND DEEP CONVECTIVE BANDING OVER THE WESTERN
SEMICIRCLE. A 010957Z SSMIS 91 GHZ MICROWAVE IMAGE REVEALS MULTIPLE
CONVECTIVE BANDS WRAPPING TIGHTLY FROM THE NORTHERN QUADRANT INTO
THE SOUTHERN QUADRANT, WITH THE CENTER POSITIONED JUST NORTH OF A
CURVED INNER CONVECTIVE BAND. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON THE SSMIS IMAGE. UPPER-LEVEL ANALYSIS
INDICATES NEAR-RADIAL OUTFLOW, WITH VIGOROUS EQUATORWARD OUTFLOW
ASSOCIATED WITH THE TEJ, AND LOW VERTICAL WIND SHEAR. SEA SURFACE
TEMPERATURES ARE VERY CONDUCIVE AT 30-31 C. THE INITIAL INTENSITY
OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE AND IS HEDGED ABOVE
THE AGENCY DVORAK ESTIMATES BASED ON THE RAPID CONSOLIDATION
EVIDENT IN SATELLITE IMAGERY. ALTHOUGH LATE IN THE FORECAST CYCLE,
A 011400Z CIMSS DPRINT OBJECTIVE INTENSITY ESTIMATE INDICATES 34
KNOTS.

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

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.5 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TROPICAL DEPRESSION 12W IS EXPECTED TO
INTENSIFY QUICKLY AS IT TRACKS NORTHWARD THROUGH TAU 36 DUE TO THE
HIGHLY FAVORABLE UPPER-LEVEL CONDITIONS, VERY WARM SSTS AND
EXCEPTIONALLY HIGH OCEAN HEAT CONTENT EAST OF LUZON. AFTER TAU 36,
THE SYSTEM WILL SLOW AND GRADUALLY TURN WESTWARD DUE TO A WEAK
STEERING ENVIRONMENT OR LARGE BREAK BETWEEN THE STR TO THE EAST AND
A STRONG STR ENTRENCHED OVER EASTERN CHINA. AS THE SYSTEM
TRANSITIONS TO THE STEERING INFLUENCE OF THE STR OVER EASTERN
CHINA, IT'S FORECAST TO RAPIDLY INTENSIFY TO 95 KNOTS BY TAU 72 DUE
TO THE CONTINUED STRONG EQUATORWARD OUTFLOW INTO THE TEJ AND
IMPROVING POLEWARD OUTFLOW INTO THE TUTT TO THE NORTHEAST.
ADDITIONALLY, SST VALUES WILL REMAIN IN THE 30-31 C RANGE WITH A
POOL OF HIGH OCEAN HEAT CONTENT NORTH OF LUZON. AFTER TAU 72, TD
12W IS FORECAST TO ACCELERATE WESTWARD UNDER THE DOMINANT STEERING
INFLUENCE OF THE STR TO THE NORTH.      

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE SHOWS TWO DISTINCT
CLUSTERS OF TRACKERS. THE JGSM, AEMN AND NAVGEM INDICATE A MORE
POLEWARD TRACK WELL EAST AND NORTH OF THE MAIN ENVELOPE WHILE THE
BULK OF THE GUIDANCE, INCLUDING THE MORE ACCURATE GUIDANCE (ECMWF,
GFS, EEMN, UEMN AND UKMET), SHOWS A SHARP, MORE REALISTIC WESTWARD
TRACK AFTER TAU 48. THE RELIABLE INTENSITY GUIDANCE INDICATES A
STEADY INTENSIFICATION TREND THROUGH THE FORECAST PERIOD, WITH
HAFS-A PEAKING THE INTENSITY AT 155 KNOTS AT TAU 120 AND COAMPS-TC
(GFS VERSION) PEAKING AT 125 KNOTS AT TAU 120. RAPID INTENSIFICATION 
GUIDANCE HAS TRIGGERED REFLECTING THE CONDUCIVE ENVIRONMENT. THE 
010000Z COAMPS-TC ENSEMBLE INTENSITY PROBABILITY PRODUCT SUPPORT THE 
RAPID INTENSIFICATION TREND WITH PEAK PROBABILITIES OF 40 TO 50 
PERCENT IN THE TAU 60 TO TAU 96 PERIOD. THE 010600Z ECMWF ENSEMBLE 
(EPS) SUPPORTS THE JTWC FORECAST TRACK WITH THE BULK (80 PERCENT) OF 
THE SOLUTIONS SHOWING A SHARP WESTWARD TRACK TOWARD HAINAN ISLAND. 
HOWEVER, THE EPS GUIDANCE ALSO SHOWS UNCERTAINTY IN THE TRACK, WITH A 
POSSIBLE TRACK OVER NORTHERN LUZON, WHICH WOULD OBVIOUSLY DAMPEN THE 
INTENSIFICATION TREND.   

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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