WDPN32 PGTW 190300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (USAGI) WARNING NR 10//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 17W (USAGI), LOCATED APPROXIMATELY 610 NM SOUTHEAST
OF TAIPEI, TAIWAN, HAS TRACKED WEST-SOUTHWESTWARD AT 05 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
(MSI) DEPICTS A WELL CONSOLIDATED SYSTEM WITH DEEP CONVECTION 
WRAPPING COMPLETELY AROUND A PERSISTENT FILLED-EYE FEATURE. 
A 190122Z MICROWAVE IMAGE REVEALS THAT MULTIPLE DEEP CONVECTIVE 
BANDING FEATURES ARE NOW LOCATED ACROSS THE NORTHERN SEMI-CIRCLE 
WRAPPING AROUND THE WESTERN PERIPHERY AND INTO THE LOW-LEVEL 
CIRCULATION CENTER (LLCC). THERE IS HIGH CONFIDENCE IN THE 
CURRENT POSITION BASED UPON THE ESTABLISHED FILLED-EYE FEATURE 
SEEN IN THE MSI AND MICROWAVE IMAGE. THE CURRENT INTENSITY HAS 
BEEN MAINTAINED AT 90 KNOTS BASED ON CONGRUENT DVORAK INTENSITY 
ESTIMATES RANGING FROM 77 TO 102 KNOTS. UPPER-LEVEL ANALYSIS 
CONINUES TO INDICATE A POINT-SOURCE ANTICYCLONE LOCATED OVER 
THE LLCC, WHICH IS PROVIDING EXCELLENT RADIAL OUTFLOW AND LOW 
(05-10 KNOTS) VERTICAL WIND SHEAR (VWS). HOWEVER, AN AREA OF 
SUBSIDENCE HAS FORMED NORTH OF THE SYSTEM (~27N) AND APPEARS TO 
BE SUPPRESSING SOME OF THE POLEWARD OUTFLOW, WHICH MAY BE A 
FACTOR IN LIMITING INTENSIFICATION. TY 17W IS SLOWLY TRACKING 
WESTWARD ALONG THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE 
(STR) THAT EXTENDS FROM CENTRAL CHINA THROUGH THE NORTHWESTERN 
PACIFIC.
3. FORECAST REASONING.
   A. NO CHANGES TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TY 17W IS FORECAST TO TRACK NORTHWESTWARD UNDER THE INFLUENCE 
OF THE BUILDING STR TO THE NORTH OVER THE NEXT 48 HOURS. AFTER TAU 
48, THE STR IS EXPECTED TO HAVE ESTABLISHED ITSELF IN A MORE EAST-
WEST ORIENTATION, TURNING THE SYSTEM MORE WESTWARD AS TY 
17W TRACKS THROUGH LUZON STRAIT. FAVORABLE SSTS ALONG THE FORECAST 
TRACK (29 TO 30 CELSIUS) AS WELL AS A FAVORABLE UPPER-LEVEL 
ENVIRONMENT WILL CONTINUE SUPPORT THE INTENSIFICATION OF THE SYSTEM 
THROUGH TAU 36 TO A PEAK INTENSITY OF 115 KNOTS. HOWEVER, LAND 
INTERACTION WITH TAIWAN AND NORTHERN LUZON WILL INTERRUPT THE LOW-
LEVEL FLOW, LEADING TO A WEAKENING TREND AFTER TAU 48 AND INTO TAU 
72.
   C. IN THE EXTENDED TAUS, TY 17W IS EXPECTED TO PROCEED WESTWARD 
AS THE STR WILL HAVE ESTABLISHED ITSELF IN AN EAST-WEST ORIENTATION. 
LAND EFFECTS FROM TAIWAN AND COASTAL CHINA WILL KEEP TY 17W ON A 
WEAKENING TREND THEREAFTER. THE SPREAD IN MODEL GUIDANCE AFTER TAU 
36 REMAINS SIGNIFICANT, LEADING TO LOW CONFIDENCE IN THIS PORTION OF 
THE FORECAST TRACK. JGSM, NAVGEM, AND EGRR INDICATE A MORE CONTINUOUS 
NORTHWEST TRACK ACROSS OR NEAR THE SOUTHERN TIP OF TAIWAN AND INTO 
MAINLAND CHINA IN THE EXTENDED TAUS. ECMWF AND GFDN INDICATE A MORE 
EQUATORWARD TRACK THAN THE MUTLI-MODEL CONSENSUS (CONW), WHILE GFS 
AND THE GFS ENSEMBLE REMAIN CLOSE TO CONW. DUE TO THIS UNCERTAINTY IN 
THE MODEL GUIDANCE, THE FORECAST TRACK IS POSITIONED CLOSE TO CONW, 
BUT SLIGHTLY FASTER, IN ORDER TO DISCOUNT THE POLEWARD OUTLIERS AND 
FAVORS GFS AND ECMWF WHICH HAVE BEEN MORE CONSISTENT WITH A PASSAGE 
THROUGH THE LUZON STRAIT. OVERALL, THERE IS LOW CONFIDENCE IN THE 
FORECAST TRACK AS THE STR CONTINUES TO BUILD IN AND RE-ORIENT ITSELF.//
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