WDXS31 PGTW 170300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 14S (DUDZAI) WARNING NR 
014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.4S 68.9E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 653 NM SOUTH-SOUTHWEST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) INDICATES
TROPICAL CYCLONE (TC) 14S (DUDZAI) CONTINUING ITS WEAKENING PHASE,
EVIDENCED BY AN ASYMMETRIC CENTRAL DENSE OVERCAST (CDO) AND
MID-LEVEL DRY AIR CONTINUING TO ENTRAIN FROM THE NORTH, FURTHER
AMPLIFIED BY A MODERATE TO HIGH (20-25 KTS) NORTHWESTERLY VERTICAL
WIND SHEAR (VWS). THE INITIAL POSITION IS DETERMINED WITH MEDIUM
CONFIDENCE UTILIZING EXTRAPOLATION FROM A 162017Z GCOMW1 AMSR2
COLOR 37 GHZ MICROWAVE PASS. THE INITIAL INTENSITY IS ASSESSED WITH
MEDIUM CONFIDENCE AS WELL, AND IS DERIVED PRIMARILY FROM AGENCY
DVORAK ESTIMATES AND OBJECTIVE ESTIMATES LISTED BELOW. ENVIRONMENTAL 
ANALYSIS REVEALS TC 14S IS SITUATED WITHIN A DETERIORATING 
ENVIRONMENT, WHEREIN FAVORABLE CONDITIONS OF ROBUST POLEWARD OUTFLOW 
AND WARM (27 28 C) SEA SURFACE TEMPERATURES (SST) ARE BEING NEGATED BY 
MODERATE TO HIGH (20-25 KTS) NORTHWESTERLY VWS AND CONTINUOUS DRY AIR 
ENTRAINMENT.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   FIMP: T4.5 - 77 KTS
   CIMSS ADT: 72 KTS AT 170100Z
   CIMSS AIDT: 71 KTS AT 170100Z
   CIMSS D-PRINT: 62 KTS AT 170100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TC 14S IS PROJECTED TO CONTINUE TRACKING
SOUTHWESTWARD UNDER THE INFLUENCE OF THE NORTHWESTERN PERIPHERY OF
THE GOVERNING SUBTROPICAL RIDGE (STR). THIS TRAJECTORY IS FORECAST
TO PERSIST THROUGH TAU 72 AS THE CYCLONE CONTINUES TO CIRCUMNAVIGATE 
THE PERIPHERY OF THE RIDGE. AT APPROXIMATELY TAU 96, THE SYSTEM WILL 
ATTAIN THE RIDGE CREST AND INITIATE A SOUTHEASTWARD RECURVATURE, 
NAVIGATING THE SOUTHWESTERN FLANK OF THE RIDGE. FORWARD MOTION IS 
PROJECTED TO ACCELERATE NEAR TAU 96 AS THE DEEP-LAYER STEERING FLOW 
INTENSIFIES AND THE SYSTEM BEGINS TO INTERACT WITH THE BAROCLINIC ZONE 
OF THE MIDLATITUDE WESTERLIES. AS THE SYSTEMS INTERACTS WITH THE DEEP 
UPPER-LEVEL TROUGH, THE VWS WILL INCREASE AND COOLER, DRIER AIR WILL 
ENTER THE CIRCULATION AT AN IMPRESSIVE RATE. THE SYSTEM WILL BEGIN TO 
LOSE ITS SYMMETRIC STRUCTURE, WHICH WILL MARK THE BEGINNING OF THE 
SUBTROPICAL TRANSITION PHASE EXPECTED TO CONCLUDE AT OR PRIOR TO TAU
120. CONCERNING INTENSITY, TC 14S IS FORECAST TO UNDERGO RAPID 
INTENSITY DECAY THROUGH TAU 24, DRIVEN BY THE STRONG NORTHWESTERLY
VWS AND A DECREASING OCEAN HEAT CONTENT AS IT MOVES OVER COOLER SEA
SURFACE TEMPERATURES. AROUND TAU 36, THIS ATTENUATION IS EXPECTED
TO TEMPORARILY ABATE DUE TO A RELAXATION OF THE VWS AND AN ENHANCEMENT 
OF THE POLEWARD OUTFLOW JET. THE WEAKENING TRAJECTORY IS FORECAST TO 
RESUME NEAR TAU 96 AS WESTERLY VWS AND THE INTRUSION OF A DRIER AIR 
MASS INCREASE. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE EXHIBITS A HIGH
DEGREE OF CONSENSUS THROUGHOUT THE FORECAST PERIOD, WITH NO
SIGNIFICANT DIVERGENCE AMONGST THE GUIDANCE SUITE. THE CROSS-TRACK
SPREAD AT TAU 72 IS ONLY 100 NM, DIVERGING TO 250 NM BY TAU 120.
THE ALONG-TRACK DISPERSION AT TAU 120 INCREASES SUBSTANTIALLY,
CORRESPONDING WITH THE PROJECTED SOUTHEASTWARD ACCELERATION OF THE
SYSTEM. THIS ALONG-TRACK SPREAD OF APPROXIMATELY 650 NM AT TAU 120
IS THE PRINCIPAL FACTOR DIMINISHING FORECAST CONFIDENCE IN THE JTWC
TRACK BEYOND TAU 72. THE JTWC TRACK FORECAST IS POSITIONED IN CLOSE
PROXIMITY TO THE MULTI-MODEL CONSENSUS MEAN THROUGHOUT THE FORECAST
PERIOD. INTENSITY GUIDANCE SHOWS A MODERATE CONSENSUS, WITH MOST
MODELS DEPICTING RAPID WEAKENING THROUGH TAU 24 FOLLOWED BY A
PERIOD OF RELATIVELY CONSTANT INTENSITY THROUGH TAU 96 AND WEAKENING 
AFTERWARDS. THE JTWC INTENSITY FORECAST IS SIMILARLY ALIGNED WITH THE 
CONSENSUS, HOLDING MEDIUM CONFIDENCE THROUGHOUT THE FORECAST PERIOD.

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