Tropical Storm HAISHEN Advisory Sun Sep 06

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (HAISHEN) WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 11W (HAISHEN), LOCATED APPROXIMATELY 230 NM EAST-
SOUTHEAST OF KADENA AB, HAS TRACKED NORTHWESTWARD AT 08 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
SHOWS THE SYSTEM HAS MAINTAINED A WELL-DEFINED 20-NM ROUND EYE. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EYE
FEATURE SEEN IN MSI AND ENHANCED INFRARED IMAGERY. THE INITIAL
INTENSITY OF 115 KTS IS HEDGED BELOW THE MULTI-AGENCY CURRENT
INTENSITY DVORAK ESTIMATES OF T6.5 (127 KTS), CLOSER TO A 050600Z
AUTOMATED ADVANCED DVORAK TECHNIQUE ESTIMATE OF 110 KNOTS. IT
APPEARS TY 11W IS CURRENTLY UNDERGOING AN EYEWALL REPLACEMENT CYCLE
GIVEN THE CONCENTRIC RINGS SEEN IN A 050751Z SSMIS MICROWAVE IMAGE.
THERE IS OVERALL POOR CONFIDENCE IN THE CURRENT INTENSITY GIVEN THE
CURRENT SPREAD IN GUIDANCE. TY 11W IS STILL IN AN OVERALL FAVORABLE
ENVIRONMENT WITH LOW (05-10KT) NORTHEASTERLY VERTICAL WIND SHEAR
(VWS), EXCELLENT POLEWARD OUTFLOW AND STRONG EQUATORWARD OUTFLOW IN
ADDITION TO HIGH (30-31C) SEA SURFACE TEMPERATURES (SST). HOWEVER,
SUBSIDENCE IS BEGINNING TO ERODE TY 11W ALONG THE NORTHWEST QUADRANT
OF THE SYSTEM. THE CYCLONE IS TRACKING UNDER THE STEERING INFLUENCE
OF THE DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTHEAST, NOW
EAST-SOUTHEAST OF HOKKAIDO, JAPAN.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE LAST PROGNOSTIC REASONING MESSAGE.
   B. THERE IS A SLIGHT POSSIBILITY OF LIMITED STRENGTHENING GIVEN
THE CURRENT ERC STATE BEFORE THE SYSTEM GRADUALLY BEGINS TO WEAKEN
THROUGH TAU 36 AS SST VALUES DECREASE AND OUTFLOW BECOMES LESS
FAVORABLE. INCREASING VWS (30-50 KNOTS) AROUND TAU 48, COOLING SSTS,
AND LAND INTERACTION WILL RAPIDLY ERODE THE SYSTEM, AND BY TAU 72,
TY 11W WILL BE REDUCED TO 40 KNOTS AFTER IT CROSSES INTO CHINA.
CONCURRENTLY, THE CYCLONE WILL BEGIN EXTRA-TROPICAL TRANSITION
AROUND TAU 48 AS IT ENTERS THE BAROCLINIC ZONE AND TRANSFORM INTO A
COLD CORE LOW BY TAU 72. THE APPROACHING SHORTWAVE TROUGH IS
EXPECTED TO WEAKEN THE STEERING STR AND ALLOW TY 11W TO TRACK MORE
NORTH-NORTHWESTWARD, PASS JUST TO THE WEST OF KYUSHU, JAPAN, ACROSS
THE KOREA STRAIT, MAKE LANDFALL JUST SLIGHTLY WEST OF BUSAN, SOUTH
KOREA SHORTLY BEFORE TAU 48, THEN PASS THROUGH THE MOUNTAIN RANGES
OF THE KOREAN PENINSULA. NUMERICAL MODELS REMAIN IN TIGHT AGREEMENT,
WITH THE EXCEPTION OF AFUM, AS THE ONLY MAJOR OUTLIER AS IT DEVIATES
140NM FROM THE REST OF CONSENSUS MEMBERS. THERE IS OVERALL HIGH
CONFIDENCE IN THE JTWC TRACK FORECAST THAT IS LAID JUST LEFT OF THE
MULTI-MODEL CONSENSUS BEYOND TAU 36 TO OFFSET THE OUTLIER.//
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