WDPN31 PGTW 181500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W (NOKAEN) 
WARNING NR 016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.3N 125.7E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 276 NM EAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION (TD) 01W (NOKAEN) WITH A RECENTLY OBSCURED LOW-LEVEL
CIRCULATION CENTER AS CONVECTION HAS STARTED TO BUILD IN CLOSE
PROXIMITY TO THE CENTER. FOR THE MAJORITY OF THE EVENING, TD 01W
HAS REMAINED LARGELY CONVECTION FREE, EXHIBITING A SHALLOW VORTEX
AS ASSOCIATED CONVECTION REMAINED FAR NORTH OF THE ASSESSED
POSITION. ENVIRONMENTAL ANALYSIS HAS REVEALED MARGINAL CONDITIONS,
CHARACTERIZED BY LOW VERTICAL WIND SHEAR (VWS) OF 10-15 KTS, 
INCREASING DRY AIR ENTRAINMENT, AND LOW TO MODERATE POLEWARD OUTFLOW 
ALOFT. THE INITIAL POSITION HAS BEEN PLACED WITH HIGH CONFIDENCE 
BASED ON THE PREVIOUSLY EXPOSED LLCC ON ANIMATED EIR IMAGERY. THE 
INITIAL INTENSITY HAS BEEN ASSESSED WITH MEDIUM CONFIDENCE, BASED ON 
SUBJECTIVE AGENCY DVORAK ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED
DIRECTLY TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.0 - 25 KTS
   RJTD: T1.5 - 25 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T1.5 - 25 KTS
   CIMSS ADT: 29 KTS AT 180840Z
   CIMSS AIDT: 31 KTS AT 180840Z
   CIMSS D-PRINT: 26 KTS AT 181000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: WEAK POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TD 01W IS FORECASTED TO CONTINUE TRACKING
NORTHEASTWARD AROUND THE NORTHWESTERN EXTENT OF THE STR CENTERED TO
THE EAST OVER THE NEXT 24 HOURS. FOLLOWING TAU 24, THE STR LOCATED
TO THE EAST WILL WEAKEN EASTWARD AS AN ADDITIONAL STR CENTERED OVER
VIETNAM BUILDS EASTWARD OVER THE PHILIPPINES. DURING THIS PERIOD,
THE SHALLOW VORTEX ASSOCIATED WITH TD 01W WILL BEGIN PROGRESSING
SOUTHWARD TOWARD DISSIPATION DUE TO EXCESSIVE DRY AIR ENTRAINMENT
AND MODERATE TO UNFAVORABLE VWS NEARING 25 KTS. REGARDING
INTENSITY, TD NOKAEN IS EXPECTED TO GRADUALLY INTENSIFY TO 40 KTS
BY TAU 36, AS VWS REMAINS LOW, AT 15 KTS OR LESS, AND SST REMAIN
WARM THROUGHOUT THE PHILIPPINE SEA. BETWEEN TAU 36 AND TAU 48, VWS
IS FORECASTED TO INCREASE ABOVE 20 KTS WHILE DRY AIR ENTRAINMENT
SUFFOCATES THE CENTRAL VORTEX THROUGHOUT THE MID-LEVELS. DUE TO THE
FORECASTED HOSTILE ENVIRONMENT AFTER TAU 48, TD 01W WILL BEGIN TO
UNDERGO A FORECASTED TERMINAL WEAKENING PHASE TOWARD 25 KTS BY TAU
96. BY TAU 96, FULL DISSIPATION IS FORECASTED FOR TD 01W, AS THE
SURFACE CIRCULATION IS ERODED BY A PERSISTENT NORTHEASTERLY SURGE
EVENT IMMEDIATELY TO THE NORTHWEST.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGHOUT THE NEXT 36 HOURS, AS TD 01W TRACKS
NORTHEASTWARD ALONG THE NORTHWESTERN EXTENT OF THE STR TO THE EAST.
THE CROSS-TRACK SPREAD AT TAU 36 REMAINS LOW, NEAR 55 NM. FOLLOWING
TAU 36, THE CROSS-TRACK SPREAD DIVERGES SIGNIFICANTLY DUE TO
COMPETING STEERING MECHANISMS, INCREASING TO OVER 900 NM BETWEEN
TAU 36 AND TAU 96. DUE TO UNCERTAINTY WITH THE AFOREMENTIONED STR
STEERING MECHANISMS BETWEEN TAU 36 AND TAU 96, THE JTWC TRACK
FORECAST HAS BEEN LAID WITH MEDIUM CONFIDENCE BETWEEN TAU 0 AND TAU
72 AND PLACED WITH LOW CONFIDENCE THEREAFTER. REGARDING INTENSITY,
THE JTWC INTENSITY CONSENSUS PACKAGE REMAINS IN GOOD AGREEMENT THAT
TD 01W WILL MAINTAIN INTENSITIES BETWEEN 30 KTS AND 35 KTS
THROUGHOUT THE NEXT 72 HOURS. FOLLOWING TAU 72, ALL JTWC INTENSITY
GUIDANCE CHARACTERIZES A GRADUAL WEAKENING TOWARD 25 KTS BY THE END
OF THE FORECAST PERIOD. THEREFORE, THE JTWC INTENSITY FORECAST HAS
BEEN ASSESSED WITH MODERATE CONFIDENCE DURING THE INITIAL 72 HOURS OF 
THE FORECAST PERIOD AND ASSESSED WITH LOW CONFIDENCE THEREAFTER DUE 
TO COMPETING NON-CONDUCIVE ENVIRONMENTAL FACTORS.

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