WDPN31 PGTW 092100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (HAGUPIT) 
WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.8N 134.0E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 174 NM NORTH OF ANGAUR
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION (TD) 05W (HAGUPIT) MAINTAINING ITS ROBUST CONVECTION ON
THE EASTERN SEMICIRCLE WHILE THE WESTERN HALF REMAINS EXPOSED WITH
A WEAKER WIND FIELD. THE INITIAL POSITION IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON A 091530Z OSCAT IMAGE AND ANIMATED EIR LOOP.
THE LOW-LEVEL CIRCULATION CENTER (LLCC) HAS BEEN ELONGATING, WITH
TIGHTER CONVECTIVE WRAPPING PRESENT EXCLUSIVELY THROUGHOUT THE
EASTERN SEMICIRCLE. THE INITIAL INTENSITY IS ALSO ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND OBJECTIVE
AIDS LISTED BELOW, AS WELL AS A SHIP OBSERVATION FROM PALAU,
SHOWING 18 KTS. MINIMUM SEA LEVEL PRESSURE AND RADIUS OF MAXIMUM
WINDS BOTH DECREASED SLIGHTLY, INDICATING A STEADY 30 KT INTENSITY.
HOWEVER, ANALYSIS INDICATES THAT TD 05W IS IN A MARGINALLY
UNFAVORABLE ENVIRONMENT, AS IT IS EXPERIENCING LOW TO MODERATE
(15-20 KTS) VERTICAL WIND SHEAR (VWS), DRY AIR ENTRAINMENT FROM THE
WEST, MODERATE (20 KTS) MID-LEVEL VWS, OFFSET BY WARM (29-30 C) SEA
SURFACE TEMPERATURES (SSTS).

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

CURRENT STEERING MECHANISM: A COMBINATION OF THE SUBTROPICAL RIDGE
(STR) CENTERED FAR TO THE NORTHEAST AND LOW-LEVEL SOUTHERLY FLOW


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 39 KTS AT 091633Z
   CIMSS ADT: 39 KTS AT 091730Z
   CIMSS AIDT: 39 KTS AT 091730Z
   CIMSS D-MINT: 33 KTS AT 091634Z
   CIMSS D-PRINT: 28 KTS AT 091730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT AND HIGH WESTERLY VERTICAL
WIND SHEAR IN THE MID-LEVELS

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   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: TD 05W IS FORECAST TO CONTINUE TO TRACK
WEST-NORTHWESTWARD FOR THE REMAINDER OF THE FORECAST PERIOD AS THE
COMBINATION OF A SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST
AND SOUTHERLY LOW-LEVEL FLOW STEER TD HAGUPIT. THE COMPETING
INFLUENCE OF THESE TWO FACTORS COULD CAUSE TD 05W TO HAVE A SLOWER
AND SLIGHTLY MEANDERING PATH. IN REGARDS TO INTENSITY, TD HAGUPIT
IS FORECAST TO BEGIN WEAKENING BY TAU 24, DISSIPATING NO LATER THAN
TAU 36, AS IT ENCOUNTERS INCREASING MID-LEVEL SHEAR, AS WELL AS
ONGOING DRY AIR ENTRAINMENT THAT IS FORECAST TO CONTINUE FOR THE
DURATION OF THE FORECAST. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT
FOR THE REMAINDER OF THE FORECAST PERIOD, WITH CROSS TRACK SPREAD
AT TAU 36 STRETCHING 55 NM. HOWEVER, REMOVING AN OUTLIER OF THE
DETERMINISTIC UKMET, THIS DECREASES TO 30 NM. THE JTWC OFFICIAL
TRACK FORECAST LIES CLOSE TO THE MULTI MODEL CONSENSUS AND IS LAID
WITH HIGH CONFIDENCE. INTENSITY AIDS HAVE BECOME CLOSER IN
AGREEMENT, WITH COUPLED MODELS NOW ALSO DISPLAYING THE WEAKENING
TREND, IN LINE WITH THE MULTI-MODEL CONSENSUS. THE OFFICIAL JTWC
INTENSITY FORECAST IS THEREFORE ALSO LAID WITH HIGH CONFIDENCE,
ALIGNED WITH MAJORITY OF THE GUIDANCE IN DISSIPATION OCCURRING NO
LATER THAN TAU 36.

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