WDPN31 PGTW 071500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W (HAGUPIT) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 7.7N 142.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 266 NM EAST-SOUTHEAST OF YAP
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A MOSTLY
OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH POORLY ORGANIZED
DEEP CONVECTION LIMITED TO THE NORTHEASTERN QUADRANT. CONVECTIVE
BANDING WRAPPING INTO THE CIRCULATION HAS BECOME LIMITED TO THE
SOUTHEASTERN QUADRANT OVER THE PAST SEVERAL HOURS. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE ANIMATED EIR
AND AGENCY DVORAK FIXES AS THERE HAS BEEN A DROUGHT OF USEFUL
MICROWAVE IMAGERY AND SCATTEROMETRY OVER THE PAST 6 HOURS. THE
INITIAL INTENSITY OF 35 KTS IS SIMILARLY ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND CIMSS INTENSITY
ESTIMATES LISTED BELOW. THE ENVIRONMENT IS CHARACTERIZED AS 
MARGINALLY FAVORABLE WITH MODERATE OUTFLOW ALOFT, WARM (29-30 C)
SEA SURFACE TEMPERATURES, AND LOW-MODERATE DEEP-LAYER VERTICAL WIND
SHEAR (VWS). DRY AIR ENTRAINMENT FROM THE WEST AND MODERATE (15-20
KTS) WEST-NORTHWESTERLY MID-TROPOSPHERIC SHEAR ARE ACTING TO OFFSET
THE OTHER MORE FAVORABLE ENVIRONMENTAL FACTORS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE POSITIONED TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 36 KTS AT 071200Z
   CIMSS ADT: 39 KTS AT 071200Z
   CIMSS AIDT: 35 KTS AT 071200Z
   CIMSS D-PRINT: 26 KTS AT 071200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: DRY MID-LEVEL AIR ALONG THE WESTERN FLANK AND
ELEVATED MID-LEVEL WEST-NORTHWESTERLY SHEAR.

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL STORM (TS) 05W (HAGUPIT) IS FORECAST
TO CONTINUE ON A GENERALLY WEST-NORTHWESTWARD TRACK THROUGHOUT THE
ENTIRE FORECAST PERIOD, PASSING JUST SOUTH OF YAP AROUND 081800Z.
THE TRACK SPEED IS EXPECTED TO SLOW AFTER TAU 72 AS THE PRIMARY
STEERING RIDGE MIGRATES SLOWLY EASTWARD, SETTING UP A WEAK STEERING
ENVIRONMENT. TS HAGUPIT IS FORECAST TO INCREASE IN INTENSITY TO 40
KTS AT TAU 12, THEN MAINTAIN 40 KTS THROUGH TAU 48 AS ENVIRONMENTAL
CONDITIONS LIMIT ANY FURTHER INTENSIFICATION. THE SYSTEM IS
EXPECTED TO BEGIN WEAKENING OVER THE PHILIPPINE SEA AFTER TAU 48 IN
AN AREA OF ABUNDANT DRY MID-LEVEL AIR AND INCREASING VWS, BECOMING
FULLY DISSIPATED BY TAU 120.

MODEL DISCUSSION: MODEL TRACK GUIDANCE AGREES ON A
WEST-NORTHWESTWARD TRACK, HOWEVER, THE  CROSS-TRACK SPREAD AT TAU
72 HAS INCREASED TO 175 NM IN THE LATEST MODEL RUN. NOTABLY, THE
GFS DETERMINISTIC GUIDANCE MAKES UP THE NORTHERNMOST TRACK,
SUGGESTING A TRAJECTORY THAT PASSES ABOUT 35 NM NORTHEAST OF YAP
AROUND TAU 36. THE EARLIER DIVERGENCE OF TRACK GUIDANCE TRANSLATES
TO A CROSS-TRACK SPREAD OF 325 NM BY TAU 120. THE DISPARITY IN
TRACK GUIDANCE IS LARGELY ATTRIBUTABLE TO UNCERTAINTY IN THE
STEERING ENVIRONMENT AS A SUBTROPICAL RIDGE BUILDS EASTWARD FROM
THE SOUTH CHINA SEA AND 05W APPROACHES THE COL BETWEEN IT AND THE
CURRENT STEERING RIDGE TO THE NORTHEAST. THE JTWC TRACK FORECAST IS
PLACED NEAR THE MULTI-MODEL CONSENSUS, WHICH IS REPRESENTATIVE OF
THE BULK OF MODEL SOLUTIONS, WITH HIGH CONFIDENCE THROUGH TAU 72
AND MEDIUM CONFIDENCE THEREAFTER. MODEL INTENSITY GUIDANCE
BIFURCATES FROM TAU 0 WITH A GROUPING THAT INCLUDES SHIPS SOLUTIONS
AND TWO RAPID INTENSIFICATION AIDS (FRIA AND RI45) THAT SUGGEST
SIGNIFICANT DEVELOPMENT TO TYPHOON STRENGTH (AS HIGH AS 100 KTS FOR
FRIA) BY TAU 72. THE REMAINDER OF GUIDANCE REMAINS AT OR BELOW 40
KTS FOR THE ENTIRE FORECAST PERIOD. AS ENVIRONMENTAL CONDITIONS ARE
EXPECTED TO PRECLUDE ANY RAPID INTENSIFICATION SCENARIO, THE JTWC
INTENSITY FORECAST IS PLACED WITH MEDIUM CONFIDENCE AMONG THE
LATTER GROUPING.

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