Tropical Storm MAYSAK Advisory Tue Sep 01

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (MAYSAK) WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 10W (MAYSAK), LOCATED APPROXIMATELY 144 NM SOUTH OF
KADENA AB, OKINAWA, HAS TRACKED NORTH-NORTHWESTWARD AT 18 KNOTS (KTS)
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
DEPICTS AN IRREGULAR CLOUD-FILLED EYE WITH SPIRAL BANDING WRAPPING
FROM THE SOUTH, PLACING HIGH CONFIDENCE IN THE INITIAL POSITON AND
RECENT TRACK MOTION. THE INITIAL INTENSITY OF 100 KTS IS HEDGED
BETWEEN DVORAK CURRENT INTENSITY ESTIMATES OF T5.0 (90 KTS) BY RJTD
AND T5.5 (102 KTS) BY PGTW/KNES/RCTP WITH GOOD CONFIDENCE. THE
INTENSITY IS FURTHER SUPPORTED BY A 310507Z SATELLITE CONSENSUS
ESTIMATE OF 104 KTS. UPPER LEVEL ANALYSIS INDICATES A FAVORABLE
ENVIRONMENT WITH A STRONG POLEWARD OUTFLOW CHANNEL, GOOD EQUATORWARD
OUTFLOW, AND LOW TO MODERATE VERTICAL WIND SHEAR (VWS). ADDITIONALLY,
WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURE VALUES AND FAVORABLE
OCEAN HEAT CONTENT VALUES ARE CONDUCIVE FOR FURTHER DEVELOPMENT. THE
30/12Z-31/00Z 500MB ANALYSES INDICATE THAT THE SUBTROPICAL RIDGE (STR)
HAS BUILT EAST OF THE SYSTEM WITH A STR EXTENSION TO THE NORTH. A
MIDLATITUDE SHORTWAVE TROUGH HAS DEEPENED AND SHIFTED SOUTHEASTWARD
OVER CENTRAL CHINA NEAR 108E. THEREFORE, TY 10W IS TRACKING NORTH-
NORTHWESTWARD UNDER THE COMBINED STEERING INFLUENCE OF THE STR TO THE
EAST AND THE EXTENSION TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. THROUGH TAU 24, TY 10W IS FORECAST TO CONTINUE TRACKING NORTH-
NORTHWESTWARD UNDER THE COMBINED STEERING INFLUENCE OF THE STR TO THE
EAST AND THE STR EXTENSION TO THE NORTH. THE SYSTEM IS EXPECTED TO
STEADILY INTENSIFY TO A PEAK INTENSITY OF 120 KNOTS BY TAU 24 UNDER
FAVORABLE CONDITIONS. WITH THE EXCEPTION OF GALWEM, WHICH REMAINS THE
SOLE OUTLIER, NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT (49 NM
SPREAD IN SOLUTIONS AT TAU 24). THE ECMWF ENSEMBLE IS ALSO IN GOOD
AGREEMENT WITH ALL SOLUTIONS WEST OF OKINAWA; HOWEVER, THERE IS STILL
SOME UNCERTAINTY IN THE EXACT CPA FROM OKINAWA. AFTER TAU 24, THE STR
EXTENSION SHOULD BEGIN TO ERODE AS THE AFOREMENTIONED DEEP MIDLATITUDE
SHORTWAVE TROUGH APPROACHES FROM THE WEST. THIS EROSION IS EXPECTED TO
SHIFT TY 10W TO A POLEWARD TRACK BEFORE TURNING THE SYSTEM NORTH-
NORTHEASTWARD THROUGH TAU 60. DURING THIS TIME, COOLING SST,
INCREASING VWS, AND LAND INTERACTION WILL STEADILY WEAKEN THE SYSTEM
AFTER TAU 36. TY 10W SHOULD COMMENCE EXTRATROPICAL TRANSITION (ETT)
AROUND TAU 48 AS IT INTERACTS WITH THE MIDLATITUDE TROUGH CAUSING THE
SYSTEM TO RAPIDLY WEAKEN AND ACCELERATE POLEWARD AS IT BECOMES
EMBEDDED WITHIN THE STRONG SOUTHERLY FLOW. ETT COMPLETION IS EXPECTED
BY TAU 72 AS TY 10W TAKES ON FRONTAL CHARACTERISTICS. DUE TO THE LOW
MODEL SPREAD (UNCERTAINTY), THERE IS OVERALL HIGH CONFIDENCE IN THE
JTWC FORECAST TRACK WHICH IS POSITIONED NEAR THE MULTI-MODEL
CONSENSUS.//
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