WDPN31 PGTW 090900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W (HAGUPIT) WARNING NR 
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.4N 135.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 136 NM WEST OF YAP
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 05W HAS TRACKED NORTHWESTWARD OVER THE PAST 6 HOURS, AS
THE SHALLOW AND WEAK VORTEX REMAINS HIGHLY SUSCEPTIBLE TO STEERING
FROM THE LOW-LEVEL SOUTHERLY FLOW. PERSISTENT CONVECTION REMAINS
CONFINED TO THE EASTERN SEMICIRCLE, WHILE THE RELATIVELY DRIER
AIRMASS TO THE WEST SUPPRESSES CONVECTION AND ENTRAINS INTO THE
CORE. ENVIRONMENTAL ANALYSIS REVEALS A MARGINAL ENVIRONMENT,
CHARACTERIZED BY LOW TO MODERATE (15-20 KTS) MID-LEVEL VERTICAL
WINDSHEAR INDUCING SIGNIFICANT DRY AIR ENTRAINMENT AND WEAK
DIVERGENCE ALOFT, OFFSET BY WARM (29-30) SEA SURFACE TEMPERATURES.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER PRESENT IN ANIMATED
MSI. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE SUBJECTIVE AGENCY DVORAK FIXES AND CIMSS
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

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: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 36 KTS AT 090640Z
   CIMSS ADT: 37 KTS AT 090640Z
   CIMSS AIDT: 36 KTS AT 090640Z
   CIMSS D-MINT: 31 KTS AT 090447Z
   CIMSS D-PRINT: 30 KTS AT 090640Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST TRACK SHIFTED NORTH IN
RESPONSE TO THE NORTHWESTWARD STORM MOTION OVER THE PAST 6 HOURS.

FORECAST DISCUSSION: TS 05W (HAGUPIT) IS FORECAST TO TRACK
NORTHWESTWARD FOR THE DURATION OF THE FORECAST PERIOD WHILE IT
REMAINS UNDER THE STEERING INFLUENCE OF THE STR CENTERED FAR TO ITS
NORTHEAST. HOWEVER, LOW-LEVEL SOUTHERLY FLOW IS EXPECTED TO PERSIST
THROUGH TAU 72, WHICH COULD INTRODUCE A MORE SEVERE NORTHWARD
MOTION VECTOR, RESULTING IN A NORTH-NORTHWESTWARD TRACK SIMILAR TO
THE MOTION 05W HAS SUSTAINED OVER THE LAST 6 HOURS. REGARDING
INTENSITY, HAGUPIT IS FORECAST TO REMAIN AT 35 KTS FOR THE NEXT 36
HOURS AS THE MARGINAL ENVIRONMENT PERSISTS AND PROHIBITS
DEVELOPMENT. BY TAU 48, THE ENVIRONMENT IS EXPECTED TO FURTHER
DETERIORATE -- A COMBINATION OF ANTICIPATED 25-30 KTS OF MID-LEVEL
SHEAR AND THE SIGNIFICANT DRY AIR SMOTHERING CONVECTION.
ULTIMATELY, DISSIPATION IS EXPECTED NO LATER THAN TAU 72.

MODEL DISCUSSION: DETERMINISTIC TRACK MODEL GUIDANCE IS IN GOOD
AGREEMENT THAT 05W WILL TRACK NORTHWESTWARD TO NORTH-NORTHWESTWARD
FOR THE DURATION OF THE FORECAST PERIOD. THE JTWC TRACK FORECAST
LIES CLOSE TO THE MULTI-MODEL CONSENSUS WITH OVERALL MEDIUM
CONFIDENCE. RELIABLE INTENSITY AIDS ARE IN GOOD AGREEMENT THAT
HAGUPIT WILL STALL INTENSIFICATION, WITH GFS, COAMPS-TC (NAVGEM
BOUNDARY CONDITIONS), AND HAFS-A INDICATING A STEADY 35KT INTENSITY
FOR THE DURATION OF THE FORECAST; AND COAMPS-TC (GFS BOUNDARY
CONDITIONS) INDICATING A BRIEF INTENSIFICATION TO 40 KTS BETWEEN
TAU 12-36 BEFORE TERMINAL WEAKENING. HWRF IS THE SOLE OUTLIER AND
DISPLAYS A PEAK INTENSITY OF 65 KTS AT TAU 60, WHICH WAS
DISREGARDED DUE TO THE ANTICIPATED HOSTILE ENVIRONMENT AT TAU 60.
AS A RESULT, THE JTWC INTENSITY FORECAST LIES VERY CLOSE TO HAFS-A
AND THE MULTI-MODEL CONSENSUS WITH OVERALL MEDIUM CONFIDENCE.

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