WDPN31 PGTW 160900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (NOKAEN) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.0N 128.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 437 NM EAST-SOUTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 01W (NOKAEN) WITH IMPROVING DEEP CONVECTION ALONG THE
NORTHWESTERN PERIPHERY OF THE LOW-LEVEL CIRCULATION CENTER (LLCC).
THE SOUTHERN AND EASTERN PORTIONS OF THE LLLCC REMAIN EXPOSED,
PRIMARILY ATTRIBUTED TO THE PERSISTENT EASTERLY SHEAR ACTING ON THE
SYSTEM. A 160438Z AMSR2 89 GHZ MICROWAVE IMAGE REVEALED DEFINED
LOW-LEVEL CLOUD LINES WRAPPING INTO THE ASSESSED CENTER. THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
AMSR2 IMAGE AND THE PARTIALLY EXPOSED LLCC IN ANIMATED MSI. THE
INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE AGENCY DVORAK FIXES AND OBJECTIVE INTENSITY ESTIMATES
LISTED BELOW. ENVIRONMENTAL ANALYSIS INDICATES THAT 01W IS IN A
MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD
OUTFLOW ALOFT, MODERATE (15-20 KTS) EASTERLY VERTICAL WIND SHEAR,
AND WARM (28-29 C) SEA SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA

CURRENT STEERING MECHANISM: AN ELONGATED SUBTROPICAL RIDGE (STR)
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: 42 KTS AT 160410Z
   CIMSS ADT: 37 KTS AT 160600Z
   CIMSS AIDT: 32 KTS AT 160600Z
   CIMSS D-MINT: 29 KTS AT 160729Z
   CIMSS D-PRINT: 29 KTS AT 160600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: SLIGHT DRY AIR ENTRAINMENT FROM THE SOUTH

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: 01W IS FORECAST TO TRACK NORTHWESTWARD, ALONG
THE WESTERN PERIPHERY OF THE STR, THROUGH TAU 36. NEAR TAU 48, 01W
IS FORECAST TO MAKE AN EAST-NORTHEASTWARD TURN AS IT BEGINS TO
ROUND THE NORTHERN PERIPHERY OF THE STR. TRACK SPEEDS ARE EXPECTED
TO SLOW AROUND THIS TIME DUE TO A COMPETING STEERING INFLUENCE FROM
A SEPARATE STR THAT BUILDS IN OVER THE SOUTH CHINA SEA. AN
EAST-NORTHEASTWARD TRAJECTORY IS FORECAST TO PERSIST THROUGH TAU 96
AS THE SYSTEM TRACKS ALONG THE NORTHERN PERIPHERY OF THE STR.
AROUND TAU 96, THE STR IS EXPECTED TO BREAK AND PROPAGATE EASTWARD,
CAUSING 01W TO MAKE A SOUTHEASTWARD TURN AS THE VORTEX TRACKS ALONG
THE EASTERN PORTION OF THE REMNANT STR CENTERED EAST OF LUZON.
REGARDING INTENSITY, 01W IS FORECAST TO INTENSIFY OVER THE NEXT 36
HOURS AS EASTERLY SHEAR SLIGHTLY WEAKENS AND THE CIRCULATION
CONSOLIDATES. NEAR TAU 48, SOUTHERLY SHEAR AND DRY AIR ENTRAINMENT
ARE BOTH EXPECTED TO INCREASE, CAUSING THE SYSTEM TO STEADILY
WEAKEN THROUGH THE REMAINDER OF THE FORECAST PERIOD.  

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN MODERATE
AGREEMENT THROUGH TAU 72 WITH THE NOTABLE EXCEPTION OF GFS, WHICH
SHARPLY TURNS THE SYSTEM SOUTHWARD NEAR TAU 36. THE REMAINDER OF
GUIDANCE GENERALLY AGREES ON THE MORE ROUNDED TURN TO THE EAST.
DISCOUNTING GFS, THERE IS A 190 NM CROSS-TRACK SPREAD AT TAU 72
WITH GALWEM BEING THE FASTEST MODEL AROUND THE TURN AND JGSM BEING
THE SLOWEST. AFTER TAU 72, MODELS SHOW A SIMILAR EQUATORWARD TURN.
THE JTWC TRACK FORECAST IS PLACED NEAR THE MULTI-MODEL CONSENSUS
THROUGH TAU 48, AND THEN CLOSER TO THE GOOGLE DEEPMIND AND ECMWF
TRACKERS THROUGH TAU 120 WITH OVERALL MEDIUM CONFIDENCE. INTENSITY
GUIDANCE GENERALLY AGREES ON INTENSIFICATION THROUGH TAU 36-48 AND
STEADY WEAKENING THEREAFTER WITH NO NOTABLE OUTLIERS. THE JTWC
INTENSITY FORECAST IS PLACED NEAR THE CONSENSUS THROUGHOUT THE
FORECAST PERIOD WITH MEDIUM CONFIDENCE.

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