WDPN31 PGTW 080900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 29W (NAKRI) WARNING 
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.0N 138.5E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 381 NM SOUTH-SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED WITH
TROPICAL DEPRESSION (TD) 29W (NAKRI). THE SYSTEM HAS RECENTLY
CONSOLIDATED FROM A TROUGH CUP FEATURE, INTO A COMPLETE CIRCULATION
WITHIN THE LAST FEW HOURS, WHILE SIMULTANEOUSLY DEVELOPING
PERSISTENT CONVECTION NEAR THE CENTER. ENVIRONMENTAL ANALYSIS
REVEALS MARGINALLY FAVORABLE CONDITIONS. UPPER-LEVEL FLOW INDICATES
MODERATE WESTWARD AND EQUATORWARD OUTFLOW DRIVEN BY AN UPPER-LEVEL
ANTICYCLONIC FLOW CENTERED JUST TO THE NORTH OF THE SYSTEM, WITH
DIFFLUENT REGION TO THE SOUTH OF IT. SEA SURFACE TEMPERATURES (SST)
ARE WARM (29-30 C), WHILE VERTICAL WIND SHEAR (VWS) IS BORDERLINE
UNFAVORABLE WITH UPPER RANGE OF 15-20 KTS. ADDITIONALLY, DRY AIR CAN
BE OBSERVED THROUGHOUT THE NORTHERN AND EASTERN SECTION OF THE
CIRCULATION FURTHER INHIBITING ANY SERIOUS INTENSIFICATION. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
PARTIALLY EXPOSED LLCC PRESENT IN THE VISIBLE SATELLITE LOOP. THE
INITIAL INTENSITY OF 25 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED
ON THE AGENCY DVORAK FIXES, OBJECTIVE ESTIMATES LISTED BELOW, AS
WELL AS 20-30 KTS WIND SPEEDS SEEN IN A 080327Z OCEANSAT-3 OSCAT
PASS.

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

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.0 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS D-PRINT: 28 KTS AT 080600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: DRY AIR OVER THE NORTHEASTERN SECTOR OF THE
CIRCULATION

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TD NAKRI IS FORECAST TO TRACK NORTHWESTWARD
FOR THE NEXT 72 HOURS, UNDER PRIMARY INFLUENCE FROM A STR CENTERED
TO THE NORTHEAST. HOWEVER, ANOTHER STR BUILDING TO THE NORTH OF
TAIWAN WILL EVENTUALLY INTRODUCE A COMPLETING MECHANISM, WHICH WILL
RESULT IN SLOWER SPEED OVER WATER AND POTENTIALLY EVEN A SLIGHT
WESTWARD TURN JUST PRIOR TO TAU 72. CURRENTLY AVAILABLE NUMERICAL
MODEL GUIDANCE INDICATES THAT THE RIDGE TO THE EAST-NORTHEAST WILL
BEGIN TO BUILD AGAIN SOON AFTER, RESULTING IN ASSUMING THE PRIMARY
STEERING YET AGAIN, AND RESULTING IN A RECURVATURE OF THE TRACK FOR
TD NAKRI. IN TERMS OF INTENSITY, THE SYSTEM IS FORECAST TO REMAIN
IN A MARGINALLY FAVORABLE ENVIRONMENT FOR INTENSIFICATION, DRIVEN
BY OFFSETTING PARAMETERS MENTIONED EARLIER. AS A RESULT, MULTI-MODEL
INTENSITY CONSENSUS INDICATES MODERATE INTENSIFICATION OF THE
SYSTEM THROUGHOUT THE FORECAST PERIOD. OF NOTE, AFTER THE
NORTHEASTWARD TURN, MOST MODELS INDICATE SIGNIFICANT INTRUSION OF
DRY AIR, AS WELL AS GRADUALLY INCREASING VWS RESULTING IN A CAP ON
PEAK INTENSITY, WHICH IS CURRENTLY ASSESSED AT 55-60 KTS, AND
FORECAST TO OCCUR AROUND TAU 96.

MODEL DISCUSSION: SHORT-TERM TRACK GUIDANCE IS ASSESSED WITH MEDIUM
CONFIDENCE, AS WITNESSED BY A CROSS-TRACK SPREAD OF 75 NM AT TAU 36
EXPANDING TO 190 NM AT TAU 72, NEAR THE RECURVATURE POINT. TRACK
GUIDANCE AFTERWARDS IS IN RELATIVELY FAIR AGREEMENT, WITH JUST 120
NM CROSS-TRACK SPREAD NEAR THE END OF THE FORECAST PERIOD. HOWEVER,
LONG-TERM TRACK FORECAST IS PREDICTED WITH LOW CONFIDENCE, DUE TO
HIGH UNCERTAINTY RELATED TO THE TIMELINE OF THE STEERING PATTERN
SHIFT AND EVENTUAL RECURVATURE SCENARIO. MAJOR OUTLIER OF THE
GUIDANCE TRACK ENVELOPE IS NAVGEM, WHICH PREDICTS A SHARPER AND
QUICKER RECURVATURE. JTWC TRACK FORECAST IS LAID NEAR THE
MULTI-MODEL CONSENSUS, GIVEN THE UNCERTAINTY ASSOCIATED WITH THE
FIRST WARNING. SIMILARLY, AND FOR THE SAME REASONS, INTENSITY
PREDICTION IS ALSO ASSESSED WITH MEDIUM CONFIDENCE FOR THE SHORT
TERM, FOLLOWED BY LOW IN THE LONG-TERM. OF NOTE, THE MAIN OUTLIERS
ARE THE DETERMINISTIC GFS REMAINING AROUND 25 KTS THROUGHOUT THE
FORECAST PERIOD, AND COAMPS-TC ON THE OTHER END OF THE SPECTRUM,
PREDICTING PEAK INTENSITY RANGING FROM 70 TO 95 KTS, BETWEEN TAUS
72 AND 120.

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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