WDPN31 PGTW 010300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 09W (NINE) WARNING 
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 8.7N 163.3E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 151 NM EAST-SOUTHEAST OF UJELANG
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A 
CONSOLIDATING TROPICAL DEPRESSION (TD) 09W POSITIONED SOUTHWEST OF 
THE BIKINI ATOLL. ANALYSIS REVEALS AN ENVIRONMENT FAVORABLE FOR 
TROPICAL DEVELOPMENT, WITH WARM (29-30 C) SEA SURFACE TEMPERATURES 
(SST), LOW (0-5 KTS) VERTICAL WIND SHEAR (VWS), MODERATE POLEWARD 
OUTFLOW AND ABUNDANT MOISTURE AVAILABLE THROUGHOUT THE ATMOSPHERIC 
COLUMN. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON 
A 302314Z METOP-C ASCAT PASS SHOWING THE WESTERN PORTION OF THE LOW-
LEVEL CIRCULATION CENTER (LLCC), IN CONJUNCTION WITH THE VISIBLE 
SATELLITE IMAGERY LOOP. THE INITIAL INTENSITY OF 25 KTS IS ASSESSED 
WITH HIGH CONFIDENCE BASED ON THE SAME SCATTEROMETER PASS SHOWING 
MAXIMUM WIND SPEEDS OF 20-25 KTS AND THE DVORAK FIXES AND OBJECTIVE 
ESTIMATES LISTED BELOW.

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

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.0 - 25 KTS
   KNES: T1.5 - 25 KTS
   PHFO: T1.5 - 25 KTS
   CIMSS D-PRINT: 21 KTS AT 010000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TD 09W IS FORECAST TO TRACK NORTHWESTWARD
UNDER THE INFLUENCE OF A STR CENTERED TO THE NORTHEAST. SIMULTANEOUS 
SIGNIFICANT CONSOLIDATION IS EXPECTED OVER THE NEXT 48 HOURS, WITH 
THE CORE OF THE VORTEX TIGHTENING AND THE SYSTEM GAINING INTENSITY 
DUE TO HIGHLY FAVORABLE ENVIRONMENTAL PARAMETERS. AFTER TAU 48, 
ANOTHER STR, POSITIONED TO THE NORTHWEST, WILL EXTEND EASTWARD AND 
ASSUME PRIMARY STEERING. DURING THIS TRANSITION, THE SYSTEM IS 
EXPECTED TO SLOW DOWN. VWS IS EXPECTED TO INCREASE SLIGHTLY, 
RESULTING IN A SLOWER  INTENSIFICATION RATE. HOWEVER, THIS STEERING 
PATTERN TRANSITION WILL BE BRIEF, AND TD 09W IS EXPECTED TO BEGIN 
GAINING STRENGTH AT A HIGHER RATE RIGHT AFTER TAU 60. THE FORECAST 
TRACK IS CURRENTLY POSITIONED BETWEEN THE ISLANDS OF TINIAN AND ROTA, 
HOWEVER, THE LARGE WIND FIELD WILL RESULT IN SIGNIFICANT IMPACTS TO 
THE MAJORITY OF THE MARIANA ISLANDS. CURRENT PEAK WIND SPEEDS ARE 
PREDICTED TO BE 115 KTS AT TAU 120, WITH THE SYSTEM STILL 
INTENSIFYING AFTERWARDS. THE ONLY INHIBITING FACTOR TOWARDS THE END 
OF THE FORECAST PERIOD IS THE PRESENCE OF A PREDOMINANTLY DRY AIR 
MASS TO THE NORTHWEST. AT THE SAME TIME, NUMERICAL MODEL PREDICTION 
SYSTEMS INDICATE THAT THE LARGE SIGNATURE OF THE VORTEX AND 
ASSOCIATED WIND FIELD WILL ENABLE TD 09W TO COCOON ITSELF AGAINST DRY 
AIR ENTRAINMENT, AT LEAST THROUGHOUT THE CURRENT FORECAST PERIOD.

MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN STRONG AGREEMENT IN
REGARD TO THE PRIMARY STEERING MECHANISM THROUGHOUT THE CURRENT
FORECAST PERIOD, AS INDICATED BY A 90 NM CROSS-TRACK SPREAD BY TAU
36, EXPANDING TO 190 NM TOWARDS THE END OF THE FORECAST PERIOD. AS
SUCH, THE MAIN CONCERN REMAINS THE POSITION OF THE VORTEX IN
RELATION TO THE MARIANAS. THE JTWC OFFICIAL TRACK FORECAST IS 
ASSESSED WITH HIGH SHORT-TERM AND MEDIUM LONG-TERM CONFIDENCE AND IS 
ON THE SOUTHERN SIDE OF THE MULTI-MODEL CONSENSUS, AS THE GUIDANCE 
HAS BEEN SHIFTING SOUTH OVER THE LAST FEW MODEL RUN CYCLES. 
CURRENTLY, THE NORTHERNMOST TRACKERS ARE NAVGEM AND DETERMINISTIC 
GFS, WHILE ECMWF AND UKMET ARE SLOWER AND CLOSER TO GUAM. 
EXPERIMENTAL AI GUIDANCE ALSO SUGGESTS A TRACK CLOSER TO ROTA AND 
AWAY FROM TINIAN. IN TERMS OF INTENSITY, ALL AVAILABLE CONSENSUS 
MEMBERS INDICATE PERSISTENT CONSOLIDATION, WITH A STRONG PROBABILITY 
OF RAPID INTENSIFICATION, PARTICULARLY AFTER TAU 48. HAFS IS 
CURRENTLY THE MOST CONSERVATIVE, REACHING A PEAK OF 115 KTS, WITH 
COAMPS-TC SUGGESTING 135-155 KTS AT OR BEYOND TAU 120. THE OFFICIAL 
JTWC INTENSITY FORECAST IS ASSESSED WITH HIGH CONFIDENCE FOR THE 
SHORT-TERM, WITH THE GUIDANCE SPREAD INCREASING TO OVER 60 KTS LATER 
IN THE FORECAST, RESULTING IN MEDIUM LONG-TERM INTENSITY PREDICTION 
CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: HIGH
   INTENSITY 72-120 HR: MEDIUM//
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