Tropical Storm MAYSAK Advisory Sat Aug 29

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (MAYSAK) WARNING NR
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 10W (MAYSAK), LOCATED APPROXIMATELY 579 NM
SOUTH OF KADENA AB, OKINAWA, HAS TRACKED WEST-NORTHWESTWARD AT 03
KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY SHOWS BANDING WRAPPING INTO A LOW LEVEL CIRCULATION
CENTER (LLCC) OBSCURED BY FLARING DEEP CONVECTION. A 291001Z MHS 89
GHZ MICROWAVE IMAGE SHOWS DEEP BANDING WRAPPING INTO THE SYSTEM FROM
THE WEST. A 291302Z BULLSEYE METOP-B ASCAT IMAGE PLACES GOOD
CONFIDENCE IN THE INITIAL POSITION AND SHOWS STRONGER WINDS IN THE
NORTHEASTERN QUADRANT OF THE SYSTEM. BASED ON A 291130Z ADVANCED
DVORAK TECHNIQUE ESTIMATE OF T3.4 (53 KTS) AND MULTI-AGENCY DVORAK
CURRENT INTENSITY ESTIMATES OF T3.5-4.0 (55-65 KTS) BY PGTW, RJTD,
RCTP, AND KNES, THE INITIAL INTENSITY IS SET AT 55 KTS WITH GOOD
CONFIDENCE. ENVIRONMENTAL ANALYSIS REVEALS LOW (5-10 KTS) VERTICAL
WIND SHEAR (VWS), WARM (30-31 CELSIUS) SEA SURFACE TEMPERATURES (SST),
AND HIGH OCEAN HEAT CONTENT (OHC) VALUES. ANIMATED WATER VAPOR IMAGERY
REVEALS THAT THE TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL TO THE
NORTH-NORTHEAST HAS BEGUN TO ENHANCE THE POLEWARD OUTFLOW. PAIRED WITH
THE PREVIOUSLY ROBUST EQUATORWARD OUTFLOW, THE ENVIRONMENT IS
FAVORABLE FOR CONTINUED DEVELOPMENT. TS 10W IS TRACKING SLOWLY
NORTHWESTWARD WITHIN AN UNCERTAIN STEERING ENVIRONMENT.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE. WIND RADII HAVE BEEN UPDATED BASED ON
THE AFOREMENTIONED ASCAT DATA.
   B. IN THE NEAR TERM, TS 10W IS EXPECTED TO TRACK GENERALLY
NORTHWARD AS A STEERING RIDGE TO THE EAST REORIENTS. AFTER TAU 12, THE
SYSTEM WILL BEGIN TO FOLLOW A NORTH-NORTHWESTWARD TRACK ALONG THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR). THROUGH TAU 72, THE
ENVIRONMENT IS FORECAST TO REMAIN FAVORABLE FOR INTENSIFICATION. DUAL
CHANNEL OUTFLOW, LOW VWS, AND WARM SSTS WILL ALLOW TS 10W TO INTENSIFY
TO A PEAK INTENSITY OF 115 KTS BY TAU 48. INTENSITY GUIDANCE INDICATES
THAT RAPID INTENSIFICATION MAY OCCUR IN THE NEAR TERM. NUMERICAL MODEL
GUIDANCE IS IN FAIR AGREEMENT THROUGH TAU 48 WITH A CROSS-TRACK SPREAD
OF 91 NM. HOWEVER, MODEL SPREAD INCREASES TO 140 NM BY TAU 72. ECMWF,
NAVGEM, UKMET, AND JGSM SOLUTIONS TRACK TO THE WEST OF THE MULTI-MODEL
CONSENSUS WHILE GFS (DETERMINISTIC AND ENSEMBLE) AND GALWEM LIE TO THE
EAST. DESPITE THE IMPROVING MODEL SPREAD FROM PREVIOUS MODEL RUNS,
THERE IS ONLY FAIR CONFIDENCE IN THE JTWC FORECAST TRACK WHICH IS
PLACED NEAR THE MULTI-MODEL CONSENSUS.
   C. IN THE EXTENDED PERIOD, A CONTINUED REORIENTATION OF THE STR
WILL ALLOW TS 10W TO ROUND THE STR AXIS AND RECURVE TO A NORTH-
NORTHEASTWARD TRACK AROUND TAU 72. DURING THIS TIME, COOLING SSTS WILL
SLIGHTLY WEAKEN THE SYSTEM BUT INCREASED TRACK SPEED, LOW VWS, AND
FAVORABLE UPPER LEVEL DIVERGENCE WILL ALLOW THE SYSTEM TO MAINTAIN THE
MAJORITY OF ITS STRENGTH. AROUND TAU 96, INTERACTION WITH A PASSING
SHORTWAVE TROUGH WILL CAUSE UPPER-LEVEL DIVERGENCE TO DECREASE.
COMBINED WITH SIGNIFICANTLY COOLER WATERS (23-27 CELSIUS), THIS
INTERACTION WILL WEAKEN THE SYSTEM AS IT BEGINS EXTRATROPICAL
TRANSITION AND BEGINS TO ACCELERATE TO THE NORTH-NORTHEAST. IN THE
EXTENDED RANGE, THE CROSS-TRACK MODEL SPREAD IS 130 NM AT TAU 96.
AFTERWARDS, AS THE SYSTEM INTERACTS WITH THE PASSING TROUGH AND BEGINS
EXTRATROPICAL TRANSITION, ALONG-TRACK MODEL SPREAD ALSO INCREASES.
THUS, THERE IS OVERALL FAIR CONFIDENCE IN THE JTWC FORECAST TRACK DUE
TO THE CONTINUED SPREAD IN MODEL SOLUTIONS.//
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