WDPN31 PGTW 180300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (NOKAEN) WARNING NR 
014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.4N 125.2E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 244 NM EAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) REVEALS TROPICAL
STORM (TS) 01W (NOKAEN) WITH A SHALLOW LOW-LEVEL CIRCULATION CENTER
(LLCC) AND MINIMAL DEEP CONVECTION CONFINED EXCLUSIVELY TO THE
WESTERN PERIPHERY. ENVIRONMENTAL ANALYSIS REVEALS MARGINAL CONDITIONS 
WITH LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), STRONG UPPER-LEVEL 
POLEWARD OUTFLOW, WARM (27-28 C) SEA SURFACE TEMPERATURES (SST), 
OFFSET BY SIGNIFICANT INTRUSION OF DRY AIR. THE ENTRAINMENT OF DRY 
MID-LEVEL AIR INTO THE VORTEX CORE HAS SUPPRESSED CENTRAL DEEP 
CONVECTION RESULTING IN SHALLOWING OF THE SYSTEM. THE INITIAL POSITION 
IS ASSIGNED WITH HIGH CONFIDENCE, BASED ON ANIMATED VISIBLE IMAGERY. 
THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, SUPPORTED BY 
SUBJECTIVE AGENCY DVORAK ESTIMATES AND OBJECTIVE ESTIMATES LISTED 
BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR)
CENTERED TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 39 KTS AT 180010Z
   CIMSS AIDT: 35 KTS AT 180010Z
   CIMSS D-MINT: 32 KTS AT 172128Z
   CIMSS D-PRINT: 28 KTS AT 180010Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TS 01W IS PROJECTED TO CIRCUMNAVIGATE THE
NORTHWESTERN QUADRANT OF THE STR CENTERED TO ITS EAST THROUGH THE
NEXT 48 HOURS. SUBSEQUENT TO TAU 24, THIS EASTERN STEERING RIDGE IS
FORECAST TO ATTENUATE AND PROPAGATE EASTWARD, COINCIDENT WITH THE
ZONAL EASTWARD EXPANSION OF A SEPARATE STR ORIGINATING TO THE WEST.
FOLLOWING THIS RECONFIGURATION OF THE SYNOPTIC STEERING PATTERN, TS
01W IS ANTICIPATED TO BE DEFLECTED ONTO AN EQUATORWARD TRAJECTORY
AFTER TAU 48 TRACKING ALONG THE EASTERN FLANK OF THE NOW-DOMINANT
WESTERN STR. WITH REGARD TO INTENSITY, SIGNIFICANT AMOUNT OF
DEEP-LAYER DRY AIR SURROUNDING THE SYSTEM WILL OFFSET THE OTHERWISE
FAVORABLE CONDITIONS, RESULTING IN STEADY INTENSITY OSCILLATING
AROUND 35 AND 40 KTS EXPECTED OVER THE NEXT 48 HOURS. AFTER THAT, 
INCREASINGLY HOSTILE ENVIRONMENT WILL RESULT IN BEGINNING OF THE 
DISSIPATION OF THE LOW-LEVEL CIRCULATION, WHICH IS EXPECTED TO 
CONCLUDE AROUND TAU 96. WIND SPEEDS AROUND THAT TIME ARE EXPECTED TO 
REMAIN BETWEEN 25 AND 30 KTS AS A RESULT OF A NORTHERLY SURGE FLOW, 
WHILE INCREASINGLY DRY AIR AND VWS WILL NOT PERMIT THE LLCC TO 
MAINTAIN ITS INTEGRITY. SHOULD THE SYSTEM FAIL TO ACHIEVE DEEP 
VERTICAL COUPLING AND REMAIN SHALLOW, A MORE ACCELERATED RATE OF 
ATTENUATION IS PLAUSIBLE, A SCENARIO POTENTIALLY EXACERBATED BY 
INTERACTION WITH A ROBUST LOW-LEVEL NORTHERLY FLOW REGIME OVER THE 
SOUTHERN PHILIPPINE SEA.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE EXHIBITS A
MODERATE DEGREE OF AGREEMENT THROUGH THE INITIAL 36 HOURS AS THE
SYSTEM NAVIGATES THE STEERING INFLUENCE OF THE EASTERN STR. AS TS
01W BECOMES INCREASINGLY SUBJECT TO THE STEERING FLOW OF THE STR
CENTERED OVER VIETNAM, A SIGNIFICANT DIVERGENCE IN MODEL SOLUTIONS
BECOMES APPARENT. THROUGH THE SHORT-TERM PERIOD, THE JTWC TRACK
FORECAST MAINTAINS CLOSE AGREEMENT TO THE MULTI-MODEL CONSENSUS,
SUPPORTING OVERALL MEDIUM CONFIDENCE IN THE SHORT-TERM FORECAST. 
BEYOND TAU 36, HOWEVER, FORECAST CONFIDENCE IS DOWNGRADED TO LOW, AS 
THEPRIMARY STEERING MECHANISM BECOMES INDETERMINATE AND COULD BE
SIGNIFICANTLY PERTURBED BY A REGIONAL, LOW-LEVEL NORTHERLY SURGE.
CONCERNING INTENSITY, THE JTWC INTENSITY CONSENSUS MEMBERS ARE IN
GENERAL AGREEMENT, DEPICTING A PERIOD OF SUSTAINED INTENSITY DUE TO
THE TEMPORARY ABATEMENT IN VWS. THIS IS CONTRASTED BY THE STATISTICAL-
DYNAMICAL GUIDANCE, WHICH ADVOCATES FOR A MORE RAPID DEMISE BEGINNING 
AT TAU 24 AND DISSIPATING THE SYSTEM PRIOR TO TAU 72. OTHER 
DETERMINISTIC MODELS MAINTAIN GALE-FORCE WINDS THROUGH THE EXTENT OF 
THE FORECAST PERIOD, HOWEVER CONFIDENCE REMAINS LOW FOR THE LONGER-
TERM PREDICTION, DUE TO UNCERTAINTY ASSOCIATED WITH THE STEERING 
PATTERN MECHANISM AND THE ABILITY OF THE LLCC TO MAINTAIN ITS 
STRUCTURE IN REALITY OF FIGHTING AGAINST INCREASING DRY AIR 
ENTRAINMENT AND VWS.

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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