WDPN31 PGTW 081500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W (HAGUPIT) WARNING NR
012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 8.7N 138.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 48 NM SOUTH OF YAP
   MOVEMENT PAST 6 HOURS: WESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN EXPOSED
LOW-LEVEL CIRCULATION CENTER DISPLACED WELL TO THE WEST OF THE
PREVIOUSLY ASSOCIATED DEEP CONVECTION AND MID-LEVEL CIRCULATION THAT
IS STILL EVIDENT. A 081143Z METOP-B MHS 89 GHZ MICROWAVE IMAGE
CONFIRMS THE SIGNIFICANT VORTEX TILT, DEPICTING THE DEEP CONVECTION
100 NM TO THE EAST OF THE ASSESSED LLCC POSITION. A 081147Z METOP-B
ASCAT IMAGE THAT PASSED OVER THE EASTERN SIDE OF THE MID-LEVEL
CIRCULATION AND ASSOCIATED CONVECTION FURTHER CONFIRMED THAT THE
LLCC IS NOT CO-LOCATED. THE ASCAT ALSO SHOWED A FIELD OF 25-30 KNOT
WINDS TO THE NORTH OF THE DEEP CONVECTION. THE INITIAL INTENSITY OF
35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE ASCAT WIND
SPEEDS BLENDED WITH THE AGENCY DVORAK FIXES AND CIMSS INTENSITY
ESTIMATES LISTED BELOW. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE EXPOSED LLCC IN EIR AND THE AFOREMENTIONED
METOP-B MICROWAVE IMAGE. THE ENVIRONMENT IS ASSESSED TO BE MARGINAL
WITH HIGH (29-30 C) SEA SURFACE TEMPERATURES AND MODERATE POLEWARD
OUTFLOW BEING MITIGATED BY THE APPARENT MID-LEVEL SHEAR CAUSING THE
VORTEX TILT AND PERSISTENT DRY AIR ENTRAINMENT FROM THE WEST.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA

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

AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 47 KTS AT 081200Z
   CIMSS AIDT: 38 KTS AT 081200Z
   CIMSS D-MINT: 27 KTS AT 080843Z
   CIMSS D-PRINT: 28 KTS AT 081200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY MID-LEVEL AIR ALONG THE WESTERN FLANK AND
   MODERATE MID-LEVEL WESTERLY SHEAR.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 STEADY WEST-NORTHWESTWARD TRACK UNDER THE STEERING
INFLUENCE OF THE STR TO THE NORTHEAST THROUGH TAU 72. AFTER TAU 72,
THE TRACK SPEED SLOWS AND DRIFTS POLEWARD AS THE PRIMARY STEERING
RIDGE CONTINUES AN EASTWARD MIGRATION AND THE WEAKENING VORTEX
SHALLOWS. IN REGARD TO INTENSITY, TS 05W HAS ALREADY BEGUN TO
EXHIBIT SIGNS OF A GRADUAL WEAKENING TREND IN CONJUNCTION WITH THE
EXAGGERATED VORTEX TILT, BUT IS EXPECTED TO MAINTAIN TROPICAL STORM
INTENSITY THROUGH TAU 36 IN THE MARGINAL ENVIRONMENTAL CONDITIONS.
STEADY WEAKENING IS FORECAST AFTER TAU 36 UNDER INCREASING
NORTHWESTERLY SHEAR AND CONTINUED DRY AIR ENTRAINMENT, UNTIL
DISSIPATION BY TAU 96.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS LARGELY IN AGREEMENT ABOUT
THE WEST-NORTHWESTWARD TRACK WITH A CROSS-TRACK SPREAD OF 170 NM AT
TAU 96, EXCLUDING AIFS AS A FAR EASTERN OUTLIER. THE JTWC TRACK
FORECAST IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH HIGH
CONFIDENCE THROUGH TAU 72 AND MEDIUM CONFIDENCE THEREAFTER AS A RESULT
OF UNCERTAINTY IN THE WEAK STEERING ENVIRONMENT. INTENSITY GUIDANCE IS
SPLIT IN TWO GROUPINGS, THE FIRST BEING GFS AND HWRF, WHICH DEPICT
GRADUAL WEAKENING THROUGHOUT THE FORECAST PERIOD. THE SECOND GROUPING
INCLUDES HAFS-A, COAMPS-TC (GFS BASED), AND SHIPS, WHICH SUGGESTS 05W
WILL MAINTAIN AN INTENSITY OF 30-45 KTS THROUGH TAU 96. GIVEN THE
RECENT DEGRADATION OBSERVED, THE JTWC INTENSITY FORECAST IS ALIGNED
WITH THE FORMER GROUP WITH OVERALL MEDIUM CONFIDENCE.

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