Tropical Storm MAYSAK Advisory 8月28日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (TEN) WARNING NR
01//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 10W (TEN), LOCATED APPROXIMATELY 603 NM
SOUTH-SOUTHEAST OF KADENA AB, OKINAWA, HAS TRACKED WEST-NORTHWESTWARD
AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) DEPICTS A SOMEWHAT DISORGANIZED CIRCULATION, WITH DEEP
FLARING CONVECTION DISPLACED SOUTHWEST OF THE LOW LEVEL CIRCULATION
CENTER (LLCC). A 270030Z AMSU-B 89GHZ COMPOSITE MICROWAVE IMAGE
REVEALS FORMATIVE BANDING WRAPPING INTO AN INCREASINGLY CONSOLIDATED
LLCC, WITH THE AFOREMENTIONED DEEP CONVECTION DISPLACED WELL
SOUTHWEST OF THE LLCC. THE INITIAL POSITION IS PLACED WITH MODERATE
CONFIDENCE BASED ON AN ANALYSIS OF THE LOW LEVEL CONVECTIVE BANDS,
SUPPORTED BY A 270030Z ASCAT-B PASS WHICH CONFIRMS THAT THE CENTER IS
STILL FAIRLY BROAD BUT QUICKLY CONSOLIDATING INTO A TIGHTER
CIRCULATION. THE INITIAL INTENSITY OF 25 KNOTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON DVORAK CURRENT INTENSITY ESTIMATES OF T1.5 (25
KNOTS) FROM BOTH PGTW AND RJTD, AS WELL AS THE PREVIOUSLY MENTIONED
ASCAT PASS, WHICH CONFIRMS A LARGE SWATH OF 25 KNOTS WINDS TO THE
SOUTH AND A SMALLER AREA OF 25 KNOT WINDS TO THE NORTH OF THE
ASSESSED CENTER. THE ASCAT DATA ALSO SHOWS AN AREA OF 30-35 KNOT,
WITH EVEN HIGHER WINDS ON THE EDGE OF THE SWATH, TO THE SOUTHWEST;
HOWEVER, THE 30-35 KNOT WINDS ARE ISOLATED AND ARE UNDER A BURST OF
DEEP CONVECTION DISPLACED FROM THE CENTER OF CIRCULATION AND ARE
ASSESSED AS NOT REPRESENTATIVE OF THE OVERALL INTENSITY.
ENVIRONMENTAL CONDITIONS ARE CONDUCIVE FOR FURTHER DEVELOPMENT WITH
LOW TO MODERATE (10-20 KNOTS) VERTICAL WIND SHEAR (VWS), STRONG
DIVERGENT EQUATORWARD OUTFLOW AS WELL AS VERY WARM SST VALUES (31C)
AND HIGH OCEAN HEAT CONTENT VALUES
REFLECTING A DEEP, WARM POOL OF WATER. TD 10W IS CURRENTLY TRACKING
SLOWLY WESTWARD IN A WEAK STEERING ENVIRONMENT BETWEEN A NEAR
EQUATORIAL RIDGE (NER) THAT EXTENDS FROM THE PHILIPPINES EASTWARD
ALONG 10 DEGREES NORTH LATITUDE, A STRONG SUBTROPICAL RIDGE (STR) TO
THE NORTH AND A DEEP-LAYER SUBTROPICAL LOW CENTERED NEAR THE NORTHERN
MARIANAS.
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING MESSAGE FOR THIS
SYSTEM AND SETS THE FORECAST PHILOSOPHY.
   B. THE WEAK STEERING PATTERN IS FORECAST TO REMAIN RELATIVELY
STAGNANT THROUGH THE NEXT DAY, WHICH WILL RESULT IN A SLOW WESTWARD
TRACK MOTION THROUGH TAU 24. ENVIRONMENTAL CONDITIONS REMAIN
FAVORABLE THROUGH TAU 24 AS WELL, WITH DIVERGENT EQUATORWARD OUTFLOW,
VERY WARM SSTS, HIGH OHC AND STEADILY DECREASING VWS, ALLOWING FOR
STEADY INTENSIFICATION. BETWEEN TAU 24 AND TAU 36, THE UPPER LEVEL
PATTERN BEGINS TO CHANGE, WITH THE NER MOVING NORTHWARD AND
REORIENTING INTO A NORTH-SOUTH ORIENTATED RIDGE AXIS ALONG ROUGHLY
THE 140 EAST LONGITUDE LINE, ALLOWING TD 10W TO SLOWLY TURN
NORTHWARD. AT THE SAME TIME, A TROPICAL UPPER TROPOSPHERIC TROUGH
(TUTT) CELL CURRENTLY NORTH OF GUAM WILL MOVE WEST INTO A POSITION
NORTH-NORTHEAST OF THE SYSTEM. WHILE EQUATORWARD OUTFLOW WILL REMAIN
ROBUST DURING THIS TIMEFRAME, THE TUTT WILL PROVIDE SOME CONVERGENT
FLOW ON THE NORTH SIDE OF THE SYSTEM, LEADING TO A PERIOD OF SLOWER
DEVELOPMENT. FROM TAU 36 TO TAU 72, THE NER-STR RIDGE COMPLEX TO THE
EAST BECOMES ORIENTED NORTHWEST-SOUTHEAST, PUSHING TD 10W ONTO A
FASTER TRACK TOWARDS THE NORTH-NORTHWEST. AT THIS TIME, THE TUTT WILL
CONTINUE MOVING WEST AND AN UPPER LEVEL ANTICYCLONE IS FORECAST TO
DEVELOP JUST EAST OF TD 10W ALLOWING FOR DEVELOPMENT OF A STRONG
POLEWARD OUTFLOW CHANNEL, IN ADDITION TO THE ALREADY ESTABLISHED
EQUATORWARD CHANNEL, LEADING TO A PERIOD OF RAPID INTENSIFICATION
BETWEEN TAU 36 AND TAU 72. DYNAMIC MODEL GUIDANCE IS IN STRONG
AGREEMENT IN THE OVERALL SCENARIO BUT DO HAVE SOME DISAGREEMENT IN
THE EXACT TIMING OF THE TURN NORTH AND IN THE EXTENT OF THE WESTWARD
MOTION IN THE NEAR-TERM, LEADING TO A 140NM SPREAD AT TAU 72.
   C. IN THE EXTENDED PERIOD, THE AFOREMENTIONED RIDGE COMPLEX TO THE
EAST WILL REORIENT ONCE AGAIN TO A MORE NORTH-SOUTH AXIS, ALLOWING
FOR A SLOW TURN ONTO A MORE NORTHWARD TRACK AFTER TAU 96. TD 10W IS
FORECAST TO REACH PEAK INTENSITY OF 110 KNOTS AT TAU 96 UNDER VERY
FAVORABLE CONDITIONS OF LOW VWS, ROBUST, DIVERGENT POLEWARD OUTFLOW
AND VERY WARM SSTS. AS THE SYSTEM ENTERS THE EAST CHINA SEA, IT IS
FORECAST TO WEAKEN SLIGHTLY, AS COOLER SSTS IN THE WAKE OF THE
PASSAGE OF TY 09W THROUGH THE AREA AND INCREASING VWS, WILL OFFSET
STRONG POLEWARD OUTFLOW INTO THE BASE OF AN APPROACHING MID-LATITUDE
TROUGH. DYNAMIC MODEL GUIDANCE IS IN FAIR AGREEMENT THROUGH TAU 120.
CROSS-TRACK SPREAD INCREASES TO A MODEST 178NM AT TAU 120 BUT ALONG-
TRACK SPREAD INCREASES SIGNIFICANTLY FROM TAU 96 TO TAU 120 AS THE
MODELS DIFFER IN THE AMOUNT OF INTERACTION WITH THE APPROACHING MID-
LATITUDE TROUGH. THE JTWC FORECAST TRACK LIES WEST OF THE MULTI-MODEL
CONSENSUS THROUGH TAU 72, FAVORING THE ECMWF SOLUTION, THEN LIES VERY
CLOSE TO THE CONSENSUS, BUT FASTER, THROUGH TAU 120, WITH OVERALL
MODERATE CONFIDENCE IN THE OFFICIAL TRACK.//
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