WDPN31 PGTW 161500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (NOKAEN) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.2N 127.0E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 379 NM EAST-SOUTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM 01W (NOKAEN) WITH WIDESPREAD DEEP CONVECTION OBSCURING THE
LOW-LEVEL CIRCULATION CENTER (LLCC). CONVECTIVE ACTIVITY NEAR THE
LLCC HAS GREATLY INCREASED OVER THE PAST 6 HOURS, AND THE VORTEX
APPEARS TO BE ATTEMPTING TO BECOME MORE VERTICALLY ALIGNED. A
161200Z METOP-B ASCAT IMAGE REVEALED A SWATH OF 35-40 KTS CONFINED
TO THE NORTHWESTERN QUADRANT. THE INITIAL POSITION, INTENSITY, AND
WIND RADII ARE ALL PLACED WITH HIGH CONFIDENCE BASED ON THE TIMELY
ASCAT PASS. ENVIRONMENTAL ANALYSIS INDICATES THAT 01W IS IN A
MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG OUTFLOW
ALOFT AND WARM (28-29 C) SEA SURFACE TEMPERATURES OFFSET BY
MODERATE (15-20 KTS) EASTERLY SHEAR.

INITIAL WIND RADII BASIS: 161200Z METOP-B ASCAT SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: AN ELONGATED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 37 KTS AT 161100Z
   CIMSS AIDT: 35 KTS AT 161100Z
   CIMSS D-PRINT: 30 KTS AT 161100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: FORECASTED 34 KNOT WIND RADII HAVE
SIGNIFICANTLY CHANGED COMPARED TO THE PREVIOUS FORECAST. 34 KNOT
WIND RADII ARE NOW FORECAST TO REMAIN WITHIN THE WESTERN QUADRANTS.

FORECAST DISCUSSION: 01W IS FORECAST TO TRACK NORTHWESTWARD, ALONG
THE WESTERN PERIPHERY OF THE STR, THROUGH TAU 36. NEAR TAU 36, 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 MARGINALLY INTENSIFY OVER
THE NEXT 24-36 HOURS AS EASTERLY SHEAR SLIGHTLY WEAKENS AND THE
CIRCULATION CONSOLIDATES. IF THE SYSTEM IS ABLE MAINTAIN THE
CURRENT CONVECTIVE STRUCTURE AND BECOME VERTICALLY STACKED, IT
COULD INTENSIFY FURTHER THAN IS CURRENTLY FORECAST. 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 GOOD
AGREEMENT THROUGH TAU 72 WITH THE NOTABLE EXCEPTIONS OF GFS AND
JGSM, WHICH BOTH SHARPLY TURN THE SYSTEM SOUTHWARD NEAR TAU 48. THE
REMAINDER OF GUIDANCE GENERALLY AGREES ON THE MORE ROUNDED TURN TO
THE EAST. DISCOUNTING GFS AND JGSM, THERE IS A 90 NM CROSS-TRACK
SPREAD AT TAU 72. AFTER TAU 72, MODELS SHOW A SIMILAR EQUATORWARD
TURN, BUT WITH A SIGNIFICANT AMOUNT OF SPREAD. THE JTWC TRACK
FORECAST IS PLACED NEAR THE MULTI-MODEL CONSENSUS THROUGH TAU 72,
AND THEN CLOSER TO THE ECMWF ENSEMBLE MEAN THEREAFTER. MESOSCALE
MODELS GENERALLY AGREE ON INTENSIFICATION THROUGH TAU 24, A STEADY
INTENSITY THROUGH TAU 48, AND WEAKENING THEREAFTER. THE JTWC
INTENSITY FORECAST IS PLACED NEAR HAFS-A THROUGHOUT THE FORECAST
PERIOD WITH MEDIUM CONFIDENCE.

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