WDPN31 PGTW 041500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (HALONG) WARNING NR 29//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 11W (HALONG), LOCATED APPROXIMATELY 555 NM SOUTH-
SOUTHEAST OF KADENA AB, HAS TRACKED NORTH-NORTHWESTWARD AT 06 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE 
IMAGERY DEPICTS A CLOUD-FILLED EYE WITH THE BULK OF DEEP CONVECTIVE 
BANDING DISPLACED OVER THE SOUTHERN SEMI-CIRCLE. BASED ON THE EIR, 
THERE IS GOOD CONFIDENCE IN THE CURRENT POSITION. A 041116Z GMI 89 
GHZ IMAGE AND A 040834Z TRMM 85 GHZ IMAGE DEPICT AN ERODING INNER 
EYEWALL SURROUNDED BY A BROKEN SECONDARY EYEWALL. RECENT MICROWAVE 
IMAGERY SUGGESTS AN ON-GOING EYEWALL REPLACEMENT CYCLE (ERC) WHICH 
CORRELATES TO THE RECENT WEAKENING TREND. THIS WEAKENING TREND IS 
FURTHER EXACERBATED BY PERSISTENT NORTH-NORTHEASTERLY VERTICAL WIND 
SHEAR (VWS) ASSOCIATED WITH UPPER-LEVEL RIDGING SOUTH OF JAPAN. 
ANIMATED WATER VAPOR IMAGERY, HOWEVER, REVEALS EXCELLENT EQUATORWARD 
OUTFLOW AND ALSO INDICATES A TUTT CELL NEAR 28N 142E, WHICH IS 
BEGINNING TO PROVIDE A POLEWARD CHANNEL OVER THE NORTHEAST PERIPHERY 
OF THE SYSTEM. THE INITIAL INTENSITY IS ASSESSED AT 100 KNOTS BASED 
ON DVORAK CURRENT INTENSITY ESTIMATES OF 102 KNOTS FROM ALL 
AGENCIES. RECENT 500 MB ANALYSES INDICATE A WEAKENING, NORTH-SOUTH 
ORIENTED SUBTROPICAL RIDGE (STR) POSITIONED SOUTH OF CENTRAL JAPAN 
WITH PERSISTENT SOUTHWESTERLY FLOW FROM TAIWAN TO THE RYUKYU 
ISLANDS. TY 11W IS CURRENTLY TRACKING ALONG THE SOUTHWESTERN 
PERIPHERY OF THIS STR.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY.
   B. THIS SYNOPTIC STEERING ENVIRONMENT IS FORECAST TO MAINTAIN FOR 
THE NEXT THREE DAYS, WHICH SHOULD ALLOW TY 11W TO TRACK NORTHWARD 
THROUGH TAU 72. THE BULK OF THE DYNAMIC MODEL GUIDANCE IS IN GOOD 
AGREEMENT THROUGH TAU 72 WITH A 115-NM SPREAD IN SOLUTIONS AT TAU 
72, THEREFORE, THE JTWC FORECAST IS POSITIONED CLOSE TO THE MULTI-
MODEL CONSENSUS. OVERALL, TY 11W IS FORECAST TO CONTINUE WEAKENING 
DUE TO THE ERC AND PERSISTENT NORTHERLY VWS, HOWEVER, THE SYSTEM 
SHOULD RE-STRENGTHEN NEAR TAU 72 AS POLEWARD OUFLOW IMPROVES.
   C. IN THE EXTENDED TAUS, THERE IS INCREASING UNCERTAINTY IN THE 
TRACK WITH GREATER SPREAD IN THE SOLUTIONS. IN GENERAL, THE DYNAMIC 
MODELS HAVE COME INTO BETTER AGREEMENT WITH RESPECT TO THE TRACK 
DIRECTION TOWARD WESTERN JAPAN, HOWEVER, TRACK SPEEDS VARY 
CONSIDERABLY. AN APPROACHING MIDLATITUDE SHORTWAVE TROUGH IS 
FORECAST TO DIG OVER THE KOREAN PENINSULA AND WESTERN JAPAN, 
CREATING A BREAK IN THE STR, HOWEVER, THE DYNAMIC MODELS BUILD THE 
STR AHEAD OF THE TROUGH TO VARYING DEGREES. GFS CONTINUES TO DEPICT 
A VERY LARGE SYSTEM, THEREFORE, GFS BREAKS DOWN THE STR QUICKLY AND 
DEPICTS FASTER TRACK SPEEDS. THE JTWC FORECAST CONTINUES TO FAVOR 
THE ECMWF SOLUTION WITH TRACK SPEEDS 08 TO 10 KNOTS AND IS 
POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS AFTER TAU 72. DUE TO 
THE LARGE SPREAD IN MODEL SOLUTIONS AFTER TAU 72 AND THE DIFFERENT 
DEPICTION OF THE TROUGH AND STR IN THE EXTENDED TAUS, THERE IS 
OVERALL LOW CONFIDENCE IN THE JTWC FORECAST. TY 11W SHOULD INTENSIFY 
AS POLEWARD OUTFLOW INTO THE MIDLATITUDE WESTERLIES INCREASES. NEAR 
TAU 120, TY 11W SHOULD BEGIN EXTRA-TROPICAL TRANSITION AS THE SYSTEM 
BEGINS TO INTERACT WITH THE BAROCLINIC ZONE POSITIONED OVER THE EAST 
SEA.//
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