WDPN31 PGTW 151500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W (NOKAEN) WARNING 
NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.0N 128.9E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 539 NM EAST-SOUTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION 01W (NOKAEN) WITH A FULLY-EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) THAT HAS STAYED NEARLY STATIONARY OVER THE PAST 6
HOURS. DEEP CONVECTION IS NOW DISPLACED FAR TO THE NORTHWEST AND IS
CONTINUING TO STRUGGLE TO FORM OVER THE CENTER DUE TO PERSISTENT
EASTERLY SHEAR ACTING ON THE SYSTEM. THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC IN ANIMATED EIR
IMAGERY. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND CIMSS OBJECTIVE
INTENSITY ESTIMATES LISTED BELOW. ENVIRONMENTAL ANALYSIS INDICATES
THAT 01W IS IN A MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY
STRONG POLEWARD OUTFLOW ALOFT AND WARM (28-29 C) SEA SURFACE 
TEMPERATURES OFFSET BY MODERATE TO HIGH (20-25 KTS) EASTERLY VERTICAL 
WIND SHEAR AND DRY AIR ENTRAINMENT.

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

CURRENT STEERING MECHANISM: A DEEP-LAYER 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: T2.0 - 30 KTS
   CIMSS ADT: 32 KTS AT 151200Z
   CIMSS AIDT: 32 KTS AT 151200Z
   CIMSS D-MINT: 32 KTS AT 150934Z
   CIMSS D-PRINT: 30 KTS AT 151200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE SOUTH

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: 01W IS FORECAST TO TRACK NORTHWESTWARD ALONG
THE WESTERN PERIPHERY OF THE STR TO THE EAST THROUGH TAU 48. NEAR TAU 
48, ANOTHER STR CENTERED OVER THE SOUTH CHINA SEA WILL COMPETE FOR THE 
STEERING INFLUENCE OF 01W. THIS WILL CAUSE TRACK SPEEDS TO SLOW AS THE 
SYSTEM APPROACHES THE 15TH LATITUDE. NEAR TAU 72, 01W IS FORECAST TO 
BEGIN SLOWLY TRACKING EASTWARD, ALONG THE NORTHERN PERIPHERY OF THE 
STR TO THE EAST THROUGH TAU 120. THERE IS A POSSIBILITY THAT THE 
SYSTEM STALLS OR HAS AN ERRATIC TRACK MOTION AROUND TAU 72 DUE TO THE 
COMPETING STEERING ENVIRONMENT. REGARDING INTENSITY, 01W IS FORECAST 
TO MARGINALLY INTENSIFY OVER THE NEXT 48 HOURS DUE PRIMARILY TO THE 
WARM SEA SURFACE TEMPERATURES AND ROBUST POLEWARD OUTFLOW. AFTER TAU 
48, THE SYSTEM IS FORECAST TO GRADUALLY WEAKEN AS SOUTHERLY SHEAR AND 
DRY AIR ENTRAINMENT FROM THE SOUTH BOTH INCREASE.  

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 48 WITH AN 85 NM CROSS-TRACK SPREAD AND
MINIMAL ALONG-TRACK SPREAD AT THAT TIME. AFTER TAU 48, UNCERTAINTY
GREATLY INCREASES DUE TO DIFFERENCES IN HOW THE MODELS HANDLE THE
VORTEX WITHIN THE COMPETING STEERING ENVIRONMENT. NOTABLY, GFS AND
ECMWF BOTH STALL THE SYSTEM AROUND TAU 72, NORTH-NORTHEAST OF
SAMAR. ON THE OTHER HAND, THE AI MODELS TRACK THE VORTEX EASTWARD
THROUGH TAU 120. THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE
MULTI-MODEL CONSENSUS THROUGH TAU 72, AND THEN CLOSER TO THE GOOGLE
DEEPMIND ENSEMBLE MEAN THROUGH TAU 120. INTENSITY GUIDANCE
GENERALLY AGREES ON A NEARLY STAGNANT INTENSITY THROUGH TAU 84 AND
WEAKENING THEREAFTER. THE JTWC INTENSITY FORECAST IS PLACED NEAR
THE CONSENSUS THROUGHOUT THE FORECAST PERIOD WITH OVERALL 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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