Tropical Storm WUTIP Advisory Paz, 29.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (WUTIP) WARNING NR 09//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 20W (WUTIP), LOCATED APPROXIMATELY 480 NM EAST-
SOUTHEAST OF HANOI, VIETNAM, HAS TRACKED WESTWARD AT 06 KNOTS OVER
THE PAST SIX HOURS. ANIMATED INFRARED (IR) SATELLITE IMAGERY DEPICTS
A CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC) WITH A 150-NM
CENTRAL DENSE OVERCAST FEATURE AND A DEVELOPING EYE. RADAR IMAGERY
FROM PADDLE ISLAND ALSO INDICATES THE DEVELOPMENT OF A SYMMETRIC
EYEWALL OVER THE PAST SIX HOURS. THERE IS GOOD CONFIDENCE IN THE
INITIAL POSITION AND RECENT MOTION BASED ON THE IR IMAGERY. THE
INITIAL INTENSITY IS ASSESSED AT 70 KNOTS BASED ON AN AVERAGE OF
DVORAK INTENSITY ESTIMATES RANGING FROM 65 TO 77 KNOTS. THE 28/12Z
500 MB ANALYSIS SHOWS THAT THE DEEP MIDLATITUDE SHORTWAVE TROUGH,
WHICH HAD WEAKENED THE SUBTROPICAL RIDGE (STR), IS FILLING AND
TRACKING NORTHEASTWARD INTO EASTERN CHINA AS EXPECTED. CONSEQUENTLY,
THE STR IS RE-BUILDING OVER SOUTHERN CHINA AND TY 20W IS NOW
ACCELERATING WESTWARD AFTER A SHORT PERIOD OF QUASI-STATIONARY
MOVEMENT.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 20W IS FORECAST TO CONTINUE TRACKING GENERALLY WESTWARD
THROUGH THE FORECAST PERIOD ALTHOUGH RADAR IMAGERY INDICATES THAT
THE SYSTEM HAS TRACKED WEST-SOUTHWESTWARD OVER THE PAST TWO HOURS.
DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT (115 NM SPREAD IN
SOLUTIONS AT TAU 36) AND DOES SUPPORT THE WEST-SOUTHWESTWARD DIP
THROUGH TAU 12 THEN A RETURN TO A MORE WESTWARD TRACK THROUGH TAU
36. TY 20W IS FORECAST TO MAINTAIN GOOD POLEWARD VENTING THROUGH TAU
24 AND IS FORECAST TO PEAK AT 85 KNOTS BY TAU 24. AFTER TAU 24,
POLEWARD VENTING WILL WEAKEN AS THE AFOREMENTIONED SHORTWAVE TROUGH
MOVES FURTHER NORTHEAST AND THE UPPER-LEVEL STR BUILDS INTO EASTERN
CHINA. TY 20W WILL WEAKEN SLIGHTLY THROUGH TAU 12 THEN, AFTER MAKING
LANDFALL NEAR TAU 36, WEAKEN RAPIDLY DUE TO LAND INTERACTION. TY 20W
IS EXPECTED TO TRACK WEST-NORTHWESTWARD THROUGH TAU 72 AND SHOULD
DISSIPATE BY TAU 72. BASED ON THE IMPROVED, TIGHT AGREEMENT BETWEEN
THE DYNAMIC MODELS, THERE IS HIGH CONFIDENCE IN THE JTWC TRACK
FORECAST, WHICH IS POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS.//
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