Western North Pacific: TS 10W(MA-ON) and TS 11W(TOKAGE), 22/09utc

JTWC IS ISSUING 6HOURLY WARNINGS ON 10W AND 11W. 3HOURLY SATELLITE BULLETINS ARE ISSUED ON BOTH SYSTEMS.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) DISPLACED TO THE NORTH OF DEEP FLARING CONVECTION, JUST EAST OF NORTHERN LUZON. THE SHARP NORTHEASTERN EDGE OF CONVECTION IS INDICATIVE OF THE RELATIVELY HIGH NORTHEASTERLY VWS CURRENTLY AFFECTING THE SYSTEM. A WELL-TIMED 220147Z ASCAT-B BULLSEYE PASS SHOWED 35 KNOTS IN ALL QUADRANTS EXCEPT NORTHWEST, AND A BAND OF 40 KNOT WINDS EXTENDING FROM SOUTH TO EAST OF THE LLCC. HENCE, EVEN IN THE FACE OF THE PERSISTENT SHEAR, THE SYSTEM IS MANAGING TO INTENSIFY. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC, WHILE THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE, HEDGED ABOVE THE AVAILABLE AGENCY AND OBJECTIVE FIXES, BASED ON THE SCATTEROMETER DATA. THE SYSTEM HAS PROGRESSED FURTHER SOUTH THAN ANTICIPATED BUT IS SHOWING SIGNS OF FLATTENING OUT AND MOVING MORE WEST OVER THE PAST SIX HOURS, ALONG THE SOUTHERN SIDE OF A STR TO THE NORTH. THE ENVIRONMENT IS MARGINALLY FAVORABLE WITH STRONG EQUATORWARD OUTFLOW AND VERY WARM SSTS BEING OFFSET BY THE STRONG SHEAR.

SIGNIFICANT FORECAST CHANGES. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. FORECAST DISCUSSION: TS MA-ON IS FORECAST TO START TO TURN MORE NORTHWESTWARD IMMINENTLY AS THE STEERING RIDGE IS EXPECTED TO BEGIN TO REORIENT TO A MORE NORTHWEST-SOUTHEAST AXIS. THE SYSTEM IS EXPECTED TO MAKE LANDFALL ALONG THE EAST COAST OF LUZON BY AROUND TAU 12, THEN MOVE ACROSS THE NORTHERN PORTION OF THE ISLAND BEFORE EMERGING BACK INTO THE SOUTH CHINA SEA BETWEEN TAU 24 AND TAU 36. ONCE BACK OVER THE WATER, THE SYSTEM IS FORECAST TO CONTINUE TRACKING NORTHWESTWARD TOWARDS A SECOND LANDFALL JUST SOUTH OF HONG KONG AROUND TAU 72. AS THE SYSTEM HAS ALREADY DEMONSTRATED, IT CAN INTENSIFY EVEN IN THE FACE OF STRONG VWS AND THIS TREND IS EXPECTED TO CONTINUE THROUGH TAU 12, REACHING 50 KNOTS PRIOR TO LANDFALL. TERRAIN INTERACTION WILL CAUSE THE SYSTEM TO WEAKEN SLIGHTLY AS IT MOVES OVER LUZON. ONCE OVER WATER AGAIN BY TAU 36 THE SYSTEM IS FORECAST TO INTENSIFY ONCE AGAIN, BUT AT A SLOW PACE DUE TO A MARGINAL UPPER-LEVEL ENVIRONMENT EXPECTED TO BE IN PLACE AT THAT TIME. WHILE THE FORECAST PEAK IS 55 KNOTS, IT IS POSSIBLE THE SYSTEM COULD REACH A SLIGHTLY HIGHER PEAK BETWEEN TAU 48 AND TAU 72, PRIOR TO LANDFALL. AFTER LANDFALL IN SOUTHERN CHINA, THE SYSTEM WILL RAPIDLY TRACK WESTWARD AND RAPIDLY WEAKEN AND DISSIPATE BY TAU 96.

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN GENERALLY GOOD AGREEMENT, WITH A MODERATE AMOUNT OF SPREAD BETWEEN THE NAVGEM ON THE SOUTHERN SIDE OF THE ENVELOPE AND THE ECMWF ON THE NORTHERN SIDE. THE NAVGEM TAKES THE SYSTEM TO JUST NORTH OF HAINAN BY TAU 96, WHILE ECMWF MOVES DIRECTLY OVER HONG KONG. SIMILARLY, THE ENSEMBLE SPREAD IS MODERATE, WITH BOTH THE ECENS AND GEFS ENVELOPE CONSTRAINED BETWEEN NORTHERN HAINAN AND THE VERY SOUTHERN TIP OF TAIWAN. THE JTWC FORECAST TRACK LIES NEAR THE CONSENSUS MEAN, WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS MIXED AND LIMITED DUE TO TECHNICAL ISSUES, BUT WHAT IS AVAILABLE SHOWS A FAIRLY LARGE SPREAD BETWEEN THE COAMPS-TC (GFS) PEAKING AT 75 KNOTS AT TAU 48, AND THE COAMPS-TC (NAVGEM) PEAKING AT ONLY 45 KNOTS. THE JTWC FORECAST LIES BELOW THE CONSENSUS MEAN BY ABOUT 10 KNOTS DUE TO THE EXPECTED MARGINAL UPPER-LEVEL ENVIRONMENT IN THE SOUTH CHINA SEA, WHICH SHOULD INHIBIT MUCH IN THE WAY OF INTENSIFICATION. CONFIDENCE IS LOW DUE TO THE IMPACT OF LAND INTERACTION CROSSING LUZON, AND THE LIMITED GUIDANCE AVAILABLE.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TS TOKAGE HAS RAPIDLY CONSOLIDATED AND INTENSIFIED OVER THE PAST 12 HOURS IN THE OPEN WATERS EAST OF JAPAN. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS BANDS OF DEEP CONVECTION WRAPPING INTO A WELL-DEFINED LOW LEVEL CIRCULATION CENTER. A 220541Z SSMIS 91GHZ MICROWAVE IMAGE SHOWED THE MUCH IMPROVED STRUCTURE, WITH INTENSE BANDS OF CONVECTIVE ACTIVITY WRAPPING IN A COMMA-SHAPED ARC FROM WEST TO SOUTHEAST OF THE LLCC. A 212311Z ASCAT-B BULLSEYE MEANWHILE REVEALED A TIGHT LLCC WITH LIGHT WINDS TO THE WEST AND AN RELATIVELY LARGE AREA OF 25 KNOT OR HIGHER WINDS EXTENDING THROUGH THE REMAINDER OF THE CIRCULATION, WITH A PATCH OF 35 KNOT WINDS TO THE SOUTHEAST OF THE CENTER. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE SSMIS DATA AND THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE SCATTEROMETER DATA, PROVIDING GOOD CONFIDENCE TO HEDGE ABOVE THE BULK OF THE AGENCY FIX INTENSITIES. THE SYSTEM IS MOVING NORTHWARD ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. THE ENVIRONMENT IS FAVORABLE FOR ADDITIONAL INTENSIFICATION, AS THE SYSTEM LIES UNDER DIFFLUENT UPPER-LEVEL FLOW TO THE EAST OF A TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) PROVIDING VERY GOOD POLEWARD OUTFLOW AND LOW VWS, SUPPORTED BY WARM (29-30C) SSTS.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES. THIS IS THE FIRST WARNING AND ESTABLISHES THE FORECAST REASONING. FORECAST DISCUSSION: TS 11W IS CURRENTLY MOVING RELATIVELY SLOWLY ALONG THE SOUTHWESTERN SIDE OF A DEEP STR TO THE NORTHEAST. OVER THE NEXT 12 HOURS THE RIDGE IS ANTICIPATED TO BUILD TOWARDS THE WEST-SOUTHWEST AND TS 11W IS FORECAST TO TURN THE RUDDER OVER TO THE NORTHWEST. THE GENERALLY NORTHWEST TRACK IS EXPECTED TO CONTINUE THROUGH ABOUT TAU 36, BEFORE THE SYSTEM WILL ROUND THE RIDGE AXIS AND ACCELERATE NORTHEASTWARD AHEAD OF AN APPROACHING MID-LATITUDE TROUGH THROUGH THE REMAINDER OF THE FORECAST PERIOD. BY TAU 72, THE SYSTEM WILL BEGIN TO INTERACT WITH THE BAROCLINIC ZONE, BECOME IN-PHASE WITH A MINOR SHORTWAVE TROUGH EAST OF JAPAN AND CROSS OVER COLDER WATERS, MARKING THE ONSET OF EXTRATROPICAL TRANSITION (ETT), WHICH IS EXPECTED TO BE COMPLETE NO LATER THAN TAU 96. IN TERMS OF INTENSIFICATION, THE ENVIRONMENT WILL SUPPORT STEADY INTENSIFICATION FOR THE NEXT 48 HOURS, THOUGH THE UPPER-LEVEL OUTFLOW IS EXPECTED TO WEAKEN A BIT AFTER TAU 24, AND SHOULD BUT THE BRAKES ON ANY RAPID INTENSIFICATION, WITH ALL OTHER PARAMETERS BEING GENERALLY FAVORABLE. AS THE SYSTEM ROUNDS THE RIDGE AXIS IT WILL START TO BE IMPACTED BY SOME NORTHERLY, CONVERGENT FLOW AT THE 200MB LEVEL, WHICH COMBINED WITH INCREASING SHEAR AND DECREASING SSTS, WILL LEAD TO GENERALIZED WEAKENING FROM THERE TO THE END OF THE FORECAST.

MODEL DISCUSSION: MODEL DATA IS SOMEWHAT LIMITED AT PRESENT DUE TO TECHNICAL ISSUES AT JTWC, THUS THE FORECAST IS GENERATED USING GLOBAL MODEL FIELD ANALYSIS, BOTH IN TERMS OF TRACK AND INTENSITY. THE ONLY TRACKER AVAILABLE IS THE GFS, BUT FIELD ANALYSIS OF BOTH DETERMINISTIC AND ENSEMBLE MODELS SUGGEST THEY ARE ALL IN GOOD AGREEMENT ON THE OVERALL TRACK. THE JTWC FORECAST LIES ALONG THE GFS TRACK FOR NOW, BUT CONFIDENCE IS LOW DUE TO THE LACK OF SPECIFIC GUIDANCE AT THIS TIME. SIMILARLY FOR INTENSITY GUIDANCE, JTWC IS CURRENTLY LIMITED, BUT THE DECAY-SHIPS GFS SUGGESTED A PEAK OF 65 KNOTS, WHICH IS A POSSIBILITY, BUT SEEMS UNLIKELY AT THIS TIME AND THE JTWC FORECAST CALLS FOR A PEAK OF 55 KNOTS AT TAU 48. CONFIDENCE IS LOW HOWEVER DUE TO THE LACK OF GUIDANCE.