Tropical Storm MAYSAK Advisory Mon Aug 31

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (MAYSAK) WARNING NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 10W (MAYSAK), LOCATED APPROXIMATELY 491 NM SOUTH OF
KADENA AB, OKINAWA, HAS TRACKED NORTH-NORTHEASTWARD AT 11 KNOTS
(KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY SHOWS TIGHTLY-CURVED BANDING WRAPPING INTO A CONSOLIDATING
LOW LEVEL CIRCULATION CENTER (LLCC) OBSCURED BY DEEP CONVECTION. A
300510Z AMSR2 36 GHZ MICROWAVE IMAGE DEPICTS A WELL-DEFINED
MICROWAVE EYE FEATURE, LENDING GOOD CONFIDENCE TO THE INITIAL
POSITION. ADDITIONALLY, THE AFOREMENTIONED MICROWAVE IMAGE SHOWS A
CYAN RING AROUND THE LLCC, INDICATIVE OF AN IMMINENT RAPID
INTENSIFICATION PHASE. THE INITIAL INTENSITY IS SET AT 75 KTS HEDGED
BETWEEN A 300435Z SATCON ESTIMATE OF 68 KTS AND MULTIAGENCY DVORAK
CURRENT INTENSITY ESTIMATES OF T4.5-5.0 (77-90 KTS) BY PGTW, RCTP,
AND RJTD WITH GOOD CONFIDENCE. UPPER LEVEL ANALYSIS INDICATES A VERY
FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH LOW (5-10 KTS) VERTICAL
WIND SHEAR (VWS) PAIRED WITH EXCELLENT POLEWARD AND EQUATORWARD
OUTFLOW. ADDITIONALLY, WARM (30-31 CELSIUS) SEA SURFACE TEMPERATURES
(SST) AND HIGH OCEAN HEAT CONTENT VALUES ARE CONDUCIVE FOR
INTENSIFICATION. CURRENTLY, COMPETITION BETWEEN AN STR TO THE EAST
AND AN UPPER LOW TO THE NORTHEAST OF THE LLCC IN THE 500MB AND 200MB
STREAMLINES IS CAUSING THE WEAK STEERING ENVIRONMENT. HOWEVER, OVER
THE PAST SIX HOURS, TY 10W HAS SPED UP AND IS TRACKING NORTH-
NORTHEASTWARD ALONG A WEAK STEERING RIDGE.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. THE UPPER LOW IS FORECAST TO TRACK WESTWARD ALONG THE NORTHERN
PERIPHERY OF TY 10W WHERE IT WILL WEAKEN OVER THE NEXT SEVERAL
HOURS. AS THIS OCCURS, THE WEAK STEERING SUBTROPICAL RIDGE (STR) TO
THE EAST WILL BUILD, SUPPORTING A NORTHWARD TO NORTH-NORTHWESTWARD
TRACK THROUGH TAU 48. FURTHERMORE, AN EXTENSION OF THE STR TO THE
NORTH OF THE LLCC (OVER WESTERN JAPAN AND THE KOREAN PENINSULA)
SHOULD ENHANCE THE NORTH-NORTHWESTWARD TRACK AROUND TAU 48. AFTER
TAU 48, AN APPROACHING DEEP MIDLATITUDE SHORTWAVE TROUGH IS EXPECTED
TO ERODE THE STR EXTENSION, ALLOWING TY 10W TO SHIFT TO A POLEWARD
TRACK BRIEFLY BEFORE IT TURNS NORTH-NORTHEASTWARD. NUMERICAL MODEL
GUIDANCE IS IN FAIR AGREEMENT THROUGH TAU 36 WITH A SPREAD OF 70NM
AT TAU 36. AFTER TAU 36, MODEL SOLUTIONS COME INTO BETTER AGREEMENT
WITH CROSS-TRACK SPREAD DECREASING TO 29 NM BY TAU 72. OF NOTE, THE
ECMWF AND ECMWF ENSEMBLE MODEL SOLUTIONS ARE OUTLIERS TO THE WEST OF
THE MULTI-MODEL CONSENSUS. ENJOYING VERY FAVORABLE CONDITIONS, TY
10W IS FORECAST TO RAPIDLY INTENSIFY TO A PEAK INTENSITY OF 120 KTS
BY TAU 36 THEN SLIGHT WEAKENING IS ANTICIPATED BY TAU 72 AS SST
VALUES COOL TO 28-29 CELSIUS.
   C. IN THE EXTENDED PERIOD, TY 10W IS FORECAST TO ACCELERATE NORTH-
NORTHEASTWARD AS IT BEGINS EXTRATROPICAL TRANSITION (ETT) AND
INTERACTS WITH THE AFOREMENTIONED MIDLATITUDE SHORTWAVE TROUGH.
DURING THIS TRANSITION, TY 10W WILL BEGIN TO SIGNIFICANTLY WEAKEN AS
IT TRACKS OVER SIGNIFICANTLY COOLER SST, INTERACTS WITH THE
MOUNTAINOUS KOREAN PENINSULA, AND EXPERIENCES INCREASING VWS FROM
THE MIDLATITUDE JET. ETT COMPLETION IS ANTICIPATED BY TAU 120 AS THE
SYSTEM GAINS FRONTAL CHARACTERISTICS AND MOVES UNDER THE JET FLOW.
AFTER TAU 72, NUMERICAL MODEL SOLUTIONS DIVERGE WITH CROSS-TRACK
SPREAD INCREASING TO 215 NM BY TAU 120. IN THE EXTENDED RANGE, THE
JTWC FORECAST TRACK IS POSITIONED NEAR THE MULTI-MODEL CONSENSUS,
CLOSER TO THE ECMWF SOLUTION. OVERALL, THERE IS ONLY FAIR CONFIDENCE
IN THE JTWC FORECAST TRACK DUE TO THE WEAK STEERING ENVIRONMENT IN
THE NEAR TERM ALONG WITH THE UNCERTAINTY IN THE EXTENDED PERIOD.//
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