WDPN31 PGTW 170900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (NOKAEN) WARNING NR 
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.1N 124.4E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 200 NM EAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 01W (NOKAEN) WITH AN OBSCURED LOW-LEVEL CIRCULATION
CENTER (LLCC) AS DEEP CONVECTION HAS CONTINUED TO BURST IN CLOSE
PROXIMITY TO THE SURFACE CIRCULATION. THE MAJORITY OF CONVECTION
HAS REMAINED RELEGATED TO THE NORTHWEST QUADRANT OVER THE LAST FEW
HOURS, WHILE LOW-LEVEL CLOUD LINES HAVE BEEN OBSERVED WRAPPING
BENEATH THE AFOREMENTIONED CONVECTION NEAR THE CENTER IN THE
SOUTHERN QUADRANT. ON ANIMATED WATER VAPOR IMAGERY, TWO DISTINCT
AND SUPPORTIVE UPPER-LEVEL OUTFLOW CHANNELS HAVE ALSO EMERGED
THROUGHOUT THE PREVIOUS 12 HOURS. THERE IS A POLEWARD CHANNEL
ALOFT, INDICATED BY VISIBLE CIRRIFORM STRIATIONS EJECTING
NORTHWARD, WHILE AN EQUATORWARD CHANNEL HAS DEFINED THE SOUTHWEST
EXTENT OF THE CIRCULATION ALOFT. THE ENVIRONMENT REMAINS MARGINALLY
FAVORABLE, WITH WARM SEA SURFACE TEMPERATURES (SST) BETWEEN 27-28
C, ROBUST OUTFLOW ALOFT, AND LOW TO MODERATE VERTICAL WIND SHEAR
(VWS) BETWEEN 10-15 KTS. THE INITIAL POSITION HAS BEEN PLACED WITH
LOW CONFIDENCE BASED ON ANIMATED MSI AND LOCAL SURFACE OBSERVATIONS
THROUGHOUT SOUTHEASTERN LUZON. THE INITIAL INTENSITY HAS BEEN
ASSESSED WITH MEDIUM CONFIDENCE BASED ON A COMBINATION OF
SUBJECTIVE AGENCY DVORAK FIXES, CIMSS AUTOMATED OBJECTIVE INTENSITY
ESTIMATES, AND PERSISTENCE FROM AN EARLIER 170032Z METOP-B PASS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) POSITIONED TO
THE EAST-NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 50 KTS AT 170640Z
   CIMSS ADT: 59 KTS AT 170540Z
   CIMSS AIDT: 51 KTS AT 170540Z
   CIMSS D-MINT: 55 KTS AT 170448Z
   CIMSS D-PRINT: 59 KTS AT 170600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 01W IS FORECASTED TO TRACK NORTHWESTWARD
THROUGHOUT THE NEXT 12 HOURS ALONG THE SOUTHWESTERN EXTENT OF THE
STR POSITIONED TO THE EAST-NORTHEAST. FOLLOWING TAU 12, TS 01W IS
EXPECTED TO BEGIN SLOWLY ROUNDING THE STR AXIS BETWEEN TAU 12 AND
TAU 24. AFTER TAU 24, THE SYSTEM WILL BEGIN A NORTHEASTWARD TRACK
ALONG THE NORTHWESTERN EXTENT OF THE SAME STR NOW POSITIONED TO THE
EAST. DURING THIS SAME TIME, THE STR TO THE EAST WILL BEGIN
WEAKENING AND RETRACTING EASTWARD. AN ADDITIONAL STR CENTERED OVER
VIETNAM AND CAMBODIA WILL BEGIN BUILDING EASTWARD IN CONCERT WITH
THE STR TO EAST, INTRODUCING A COMPETING STEERING ENVIRONMENT TO TS
NOKAEN. BETWEEN TAU 36 AND TAU 120, TS 01W WILL BEGIN RECURVING TO
THE SOUTHEAST AND EVENTUALLY SOUTHWARD BETWEEN TAU 96 AND TAU 120
AS THE COMPLEX STEERING ENVIRONMENT FORCES THE TROPICAL STORM IN AN
ARC AND TOWARD THE EQUATOR WITHIN THE PHILIPPINE SEA. REGARDING
INTENSITY, TS 01W IS EXPECTED TO MAINTAIN A MAXIMUM OF 50 KTS
THROUGHOUT THE NEXT 12 HOURS AS THE ENVIRONMENT REMAINS MARGINALLY
FAVORABLE. FOLLOWING TAU 24, VWS IS FORECASTED TO INCREASE ABOVE 20
KTS THROUGH THE REMAINDER OF THE FORECAST PERIOD, LIMITING FURTHER
INTENSIFICATION AND INITIATING A VERY SLOW WEAKENING PHASE TO 35 KTS
BY TAU 120. DURING THE PERIOD BETWEEN TAU 24 AND TAU 120, AN
AMPLIFICATION OF DRY AIR THROUGHOUT THE MID-LEVELS WILL BEGIN
WRAPPING INTO THE SOUTHERN SEMICIRCLE, FURTHER ERODING ANY CHANCE
FOR SUBSTANTIAL INTENSIFICATION UNTIL THE END OF THE FORECAST PERIOD.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT
THROUGHOUT THE INITIAL 72 HOURS OF THE FORECAST PERIOD DURING THE
SYSTEMS ROUNDING OF THE STR AXIS AND TRACK SEGMENT NORTHEASTWARD.
FOLLOWING TAU 72, TRACK CONFIDENCE DEGRADES SUBSTANTIALLY, AS THE
MAJORITY OF JTWC CONSENSUS MEMBERS ILLUSTRATE VARYING DEGREES OF
SPEED THROUGH THE RECURVE SCENARIO SOUTHWARD TOWARD THE SYSTEMS
TERMINAL WEAKENING PHASE. A FEW OF THE ARTIFICIAL INTELLIGENCE (AI)
SOLUTIONS CHARACTERIZE AN EAST-SOUTHEASTWARD TRACK AFTER TAU 72,
WHILE THE BULK OF DETERMINISTIC AND PROBABILISTIC MEMBERS CARRY THE
SYSTEM DUE-SOUTH BETWEEN TAU 72 AND TAU 120. DUE TO THE DISCREPANCY
BETWEEN THE JTWC TRACK CONSENSUS AFTER TAU 72, THE TRACK HAS BEEN
PLACED WITH MEDIUM CONFIDENCE INTO TAU 72, AND LOW CONFIDENCE
THEREAFTER. REGARDING INTENSITY, ALL JTWC INTENSITY CONSENSUS
MEMBERS SHOW EITHER SUSTAINED INTENSITIES NEAR 50 KTS OVER THE NEXT
12 HOURS OR GRADUAL WEAKENING TOWARD 40 KTS. FOLLOWING TAU 12, ALL
JTWC INTENSITY CONSENSUS MEMBERS ILLUSTRATE A GRADUAL WEAKENING
TREND, LENDING MEDIUM CONFIDENCE THROUGHOUT THE ENTIRE FORECAST
PERIOD.

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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