Tropical Storm HAISHEN Advisory Fri Sep 04

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (HAISHEN) WARNING NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 11W (HAISHEN), LOCATED APPROXIMATELY 646 NM EAST-
SOUTHEAST OF KADENA AB, OKINAWA, HAS TRACKED NORTHWESTWARD AT 08 KNOTS
(KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS A CLOUD-FILLED RAGGED EYE SURROUNDED BY DEEP
CONVECTION. A 030634Z SSMI 85 GHZ MICROWAVE IMAGE REVEALS CONVECTIVE
BANDING WRAPPING TIGHTLY INTO THE LOW LEVEL CIRCULATION CENTER, WHICH
SUPPORTS THE INITIAL POSITION WITH GOOD CONFIDENCE. THE INITIAL
INTENSITY IS SET AT 95 KTS BASED ON DVORAK CURRENT INTENSITY ESTIMATES
OF T5.0-5.5 (90-102 KTS, RJTD/PGTW) ALONG WITH A 030410Z SATCON
ESTIMATE OF 98 KTS. UPPER-LEVEL ANALYSIS REVEALS A FAVORABLE
ENVIRONMENT CHARACTERIZED BY NEAR-RADIAL OUTFLOW AND LOW VERTICAL WIND
SHEAR (VWS). WARM (30-31 CELSIUS) SEA SURFACE TEMPERATURES (SST) AND
OCEAN HEAT CONTENT VALUES REMAIN CONDUCIVE FOR CONTINUED DEVELOPMENT.
THE 03/0000Z 500 MB ANALYSIS SHOWS A DEEP MIDLATITUDE SHORTWAVE TROUGH
LOCATED OVER THE EAST CHINA SEA AND WESTERN JAPAN WITH A BROAD
SUBTROPICAL RIDGE (STR) ENTRENCHED NORTH OF THE SYSTEM. A COL REGION
IS POSITIONED NORTHWEST OF THE SYSTEM AND NORTHEAST OF OKINAWA WITH
MID-LEVEL WESTERLY FLOW OVER OKINAWA REFLECTING THE POSITION OF THE
AFOREMENTIONED TROUGH. TY 11W IS TRACKING NORTHWESTWARD UNDER THE
STEERING INFLUENCE OF THE DEEP-LAYERED STR AND IS TRACKING TOWARDS THE
COL REGION.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE LAST PROGNOSTIC REASONING MESSAGE.
   B. IN THE NEAR TERM, TY 11W IS FORECAST TO TRACK WEST-NORTHWESTWARD
AS THE STR BUILDS OVER JAPAN. THEN AS THE SHORTWAVE TROUGH GRADUALLY
FILLS OVER THE KOREAN PENINSULA, THE SYSTEM WILL ENTER THE COL REGION
AND TURN TO A POLEWARD TRACK ALONG THE EASTERN EDGE OF THE SHORTWAVE
TROUGH THROUGH TAU 72. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
WITH A SPREAD OF 51 NM AT TAU 36 INCREASING TO 122 NM BY TAU 72 AS
NAVGEM, THE SOLE OUTLIER, TRACKS THE SYSTEM FURTHER WESTWARD PRIOR TO
TURNING POLEWARD. DESPITE THIS, ALL MODEL SOLUTIONS CURRENTLY FORECAST
THE SYSTEM TO PASS EAST AND NORTHEAST OF OKINAWA. TY 11W IS FORECAST
TO RAPIDLY INTENSIFY TO A PEAK INTENSITY OF 130 KTS BY TAU 36 DUE TO
CONTINUED FAVORABLE CONDITIONS. HOWEVER, THE PEAK MAY OCCUR EARLIER IN
THE FORECAST PERIOD.
   C. IN THE EXTENDED PERIOD, NUMERICAL MODEL GUIDANCE DIVERGES,
INCREASING THE UNCERTAINTY IN THE EXACT TRACK WHICH COULD SHIFT
EASTWARD CLOSER TO KYUSHU. THE BULK OF THE 02/12Z ECMWF SOLUTIONS ARE
GROUPED FROM 129-131E NEAR KYUSHU. BY TAU 96, TY 11W IS EXPECTED TO
BEGIN EXTRATROPICAL TRANSITION (ETT) AS IT INTERACTS WITH THE
SHORTWAVE TROUGH. THIS WILL ACCELERATE THE SYSTEM POLEWARD WHERE IT
WILL COMPLETE ETT BY TAU 120 AND GAIN FRONTAL CHARACTERISTICS.
OVERALL, THERE IS MODERATE CONFIDENCE IN THE JTWC FORECAST TRACK,
WHICH LIES NEAR THE MULTI-MODEL CONSENSUS.//
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