Tropical Storm TEMBIN Advisory Mon Aug 27

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (TEMBIN) WARNING NR 35//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 15W (TEMBIN), LOCATED APPROXIMATELY 240 NM SOUTH-
SOUTHWEST OF TAIPEI, TAIWAN, HAS TRACKED EAST-NORTHEASTWARD AT 14
KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY
DEPICTS A SMALL CENTRAL DENSE OVERCAST FEATURE OVER THE CENTER OF A
WELL-DEFINED, TIGHTLY-WRAPPED LOW-LEVEL CIRCULATION CENTER. A
271215Z SSMIS 37 GHZ IMAGE SHOWS A MICROWAVE EYE FEATURE WITH
TIGHTLY-WRAPPED BANDING. THERE IS HIGH CONFIDENCE IN THE INITIAL
POSITION BASED ON THIS IMAGERY AS WELL AS RADAR FIXES. THE CURRENT
INTENSITY IS ASSESSED AT 65 KNOTS BASED ON DVORAK CURRENT INTENSITY
ESTIMATES OF 65 KNOTS FROM PGTW CONSISTENT WITH THE WELL-ORGANIZED
STRUCTURE EVIDENT IN SATELLITE IMAGERY. TY 15W IS TRACKING ALONG THE
NORTHERN PERIPHERY OF THE NEAR-EQUATORIAL RIDGE (NER) WITHIN A WEAK
STEERING ENVIRONMENT.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 15W IS FORECAST TO TRACK NORTHEASTWARD UNDER THE STEERING
INFLUENCE OF THE NER THROUGH TAU 36 BUT WILL THEN TRACK INCREASINGLY
NORTHWARD AS IT BEGINS TO STEER ALONG THE WESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE (STR). DYNAMIC MODEL GUIDANCE IS IN POOR AGREEMENT
WITH MAJOR DIFFERENCES IN TRACK SPEED. NOGAPS, GFS AND UKMO INDICATE
A RAPID TRACK NORTH-NORTHEASTWARD WHILE ECMWF, GFDN AND JGSM
INDICATE SLOWER TRACK SPEEDS NORTHWARD. THE JTWC FORECAST FAVORS THE
ECMWF AND JGSM MODEL SOLUTIONS, WHICH HAVE BEEN VERY CONSISTENT.
   C. AFTER TAU 72, TY 15W IS FORECAST TO TRACK NORTHWARD ALONG THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE TOWARD THE SHANGHAI
REGION. DYNAMIC MODEL GUIDANCE IS IN POOR AGREEMENT WITH A LARGE
SPREAD AT TAU 96 AND 120 AND, WITH THE EXCEPTION OF ECMWF AND JGSM,
HAS BEEN VERY ERRATIC OVER THE PAST 36 HOURS. THERE ARE CURRENTLY
TWO DISTINCT CLUSTERS OF MODELS: GFDN, ECMWF AND JGSM TRACKING
TOWARD SHANGHAI AND NORTHWARD ALONG THE CHINA COAST; AND NOGAPS,
UKMO AND GFS TRACKING THE SYSTEM INTO THE EASTERN YELLOW SEA. THE
MAJOR DIFFERENCE BETWEEN THE MODELS IS THAT THE EASTERN CLUSTER OF
MODELS DO NOT BUILD THE STR WESTWARD OVER THE SOUTHERN YELLOW SEA
AFTER TY 16W TRACKS INTO MANCHURIA. INSTEAD THEY INDICATE A
MIDLATITUDE TROUGH DIGGING INTO THE YELLOW SEA, WHICH WILL DRIVE THE
SYSTEM QUICKLY NORTHEASTWARD. THE WESTERN CLUSTER OF MODELS HAVE
BEEN VERY CONSISTENT IN BUILDING THE STR WESTWARD AND INDICATE A
SLOWER MORE GRADUAL RE-CURVE IN THE NORTHERN YELLOW SEA. THE JTWC
FORECAST CONTINUES TO FAVOR THE ECMWF AND JGSM SOLUTIONS. TY 15W IS
EXPECTED TO WEAKEN AFTER TAU 72 DUE TO COOLER SST AND SHOULD BEGIN
EXTRA-TROPICAL TRANSITION BY TAU 120 AS IT BEGINS TO INTERACT WITH
THE SHORTWAVE TROUGH. BASED ON THE COMPLEX STEERING PATTERN AND THE
ERRATIC NATURE OF HALF THE DYNAMIC MODELS, THERE IS LOW CONFIDENCE
IN THE EXTENDED FORECAST TRACK.//
NNNN
NNNN