WDPN31 PGTW 242100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W (ONE)     
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.2N 125.5E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 333 NM SOUTHEAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 8 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY AND A 241639Z
ATMS 88.2 GHZ MICROWAVE IMAGE DEPICT A CONSOLIDATING LOW-LEVEL
CIRCULATION (LLC) WITH A NEARLY SYMMETRIC CLUSTER OF DEEP CONVECTION 
OVER THE CENTER AND WEAK BANDING OVER THE NORTHEAST QUADRANT. A 
241331Z ASCAT-C IMAGE REVEALED A CLOSED CIRCULATION WITH 25-30 KNOT 
WINDS OVER THE NORTHERN SEMICIRCLE. SURFACE OBSERVATIONS FROM GUIUAN 
(98558, 11.0N 125.7E, ELEVATION 197 FEET) INDICATED EASTERLY SUSTAINED 
(10-MINUTE AVERAGE) WINDS OF 23-29 KNOTS WITH A MINIMUM SLP VALUE OF 
1004 MB FROM 241500-1600Z AND A 24-HOUR SLP DECREASE OF 4 MB. BASED ON 
THIS OBSERVATIONAL DATA, THE SYSTEM IS CLASSIFIED AS A TROPICAL 
DEPRESSION WITH AN INTENSITY OF 25 KNOTS. DUE TO INTERACTION WITH LAND 
AND FRICTIONAL EFFECTS, THE OVERALL ENVIRONMENT IS ASSESSED AS 
MARGINALLY FAVORABLE, HOWEVER, THE UPPER-LEVEL OUTFLOW IS NEAR-RADIAL 
WITH LOW VERTICAL WIND SHEAR (VWS).

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

CURRENT STEERING MECHANISM: LOW-LEVEL SUBTROPICAL RIDGE (STR)
POSITIONED TO THE NORTH AND NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.0 - 25 KTS
   RJTD: T1.5 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY 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: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TROPICAL DEPRESSION (TD) 01W IS FORECAST TO
TRACK NORTHWESTWARD THROUGH TAU 24 THEN TURN SHARPLY POLEWARD AND
SLOW AS THE WESTERN EXTENT OF THE STR WEAKENS DUE TO SUBTROPICAL
WESTERLIES SHIFTING INTO THE SOUTH CHINA SEA. AFTER THE SYSTEM
RE-EMERGES OVER WATER EAST OF LUZON AND TRACKS AWAY FROM LAND, IT
IS FORECAST TO INTENSIFY STEADILY. AFTER TAU 36, THE SYSTEM WILL
TRACK ALONG THE WESTERN PERIPHERY OF A DEEP-LAYERED STR ENTRENCHED
OVER THE EAST PHILIPPINE SEA. THE SYSTEM WILL LIKELY EXPERIENCE
ENHANCED POLEWARD OUTFLOW, LEADING TO A FASTER INTENSIFICATION RATE
THROUGH TAU 96. NEAR TAU 96, THE SYSTEM WILL INTERACT WITH THE
SUBTROPICAL WESTERLIES AND INCREASING VWS, WHICH WILL LEAD TO A
WEAKENING TREND. BY TAU 120, THE SYSTEM WILL INTERACT WITH THE
BAROCLINIC ZONE AND COMMENCE EXTRA-TROPICAL TRANSITION (ETT).       

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT
THROUGH TAU 72 WITH A 70 NM CROSS-TRACK SPREAD AT TAU 72. AFTER TAU
72, THE DETERMINISTIC MODEL TRACKERS DIVERGE WITH INCREASING
UNCERTAINTY. THE COAMPS-TC INTENSITY PROBABILITY PRODUCT INDICATES
A HIGH PROBABILITY (60-80 PERCENT) OF RAPID INTENSIFICATION FROM
TAU 48 TO TAU 72. THE GEFS AND EPS ENSEMBLES INDICATE INCREASING
UNCERTAINTY NEAR TAU 24 WHEN THE SYSTEM IS EXPECTED TO TURN SHARPLY
POLEWARD, WITH THE BULK OF THE SOLUTIONS EAST OF LUZON.      

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