TS 24W(KOMPASU) tracking North of Luzon and intensifying gradually, 11/09utc

JTWC IS ISSUING 6 HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON 23W AND 24W.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: UNDER THE STEERING SUBTROPICAL RIDGE, TS KOMPASU WILL CONTINUE TO TRACK GENERALLY WESTWARD INTO THE SOUTH CHINA SEA (SCS) AND ACROSS SOUTHERN HAINAN AND THE GULF OF TONKIN BEFORE MAKING LANDFALL SHORTLY AFTER 72H IN NORTHERN VIETNAM. THE MARGINALLY FAVORABLE ENVIRONMENT WILL FUEL GRADUAL INTENSIFICATION TO A PEAK OF 60KTS AT 36H IN THE SCS WHERE THE ENVIRONMENT IS EXPECTED TO BE MORE FAVORABLE. AFTERWARD, INCREASING VERTICAL WIND SHEAR WILL SLOWLY WEAKEN THE SYSTEM DOWN TO 40KNOTS AT 72H. AFTER LANDFALL, INTERACTION WITH THE RUGGED VIETNAMESE TERRAIN WILL RAPIDLY ERODE THE SYSTEM DOWN TO 20KNOTS AFTER IT CROSSES CAMBODIA INTO THAILAND.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A VERY LARGE (2040+ KM) MONSOON DEPRESSION WITH WIDE FEEDER BANDS REACHING UP TO THE EAST CHINA SEA TO THE NORTH AND DOWN TO THE SULU SEA TO THE SOUTH. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON A COMPOSITE RADAR LOOP FROM PAGASA AND TRIANGULATED FROM NEARBY SURFACE WIND OBSERVATIONS. THE INITIAL INTENSITY OF 50KNOTS IS BASED WITH MEDIUM CONFIDENCE AND OVERALL ASSESSMENT AND AN AVERAGE OF AGENCY AND AUTOMATED DVORAK ESTIMATES AND SUPPORTED BY NEARBY OBSERVATIONS INCLUDING THOSE FROM THE BASCO RADAR SITE (185KM NNW) REPORTING NORTHEASTERLY WINDS AT 35KNOTS AND SEA LEVEL PRESSURE AT 987MB, AND REFLECTS THE SUSTAINED 6-HR CONVECTIVE STRUCTURE. ENVIRONMENTAL ANALYSES INDICATE MARGINALLY FAVORABLE CONDITIONS FOR DEVELOPMENT CHARACTERIZED BY WARM SSTS IN THE LUZON STRAIT AND STRONG POLEWARD OUTFLOW ALOFT OFFSET BY MODERATE VWS AND LAND INTERFERENCE FROM LUZON AND TAIWAN. THE CYCLONE IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF THE MID-LAYER STR TO THE NORTHEAST.

MODEL DISCUSSION: NUMERICAL MODELS REMAIN IN VERY TIGHT AGREEMENT, LENDING HIGH CONFIDENCE IN THE JTWC TRACK FORECAST UP TO 72H, THEN MEDIUM CONFIDENCE AFTERWARD. COROLLARY TO THIS, THERE IS MEDIUM CONFIDENCE IN THE INTENSITY FORECAST UP TO 72H, THEN LOW AFTERWARD.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: EXTRA-TROPICAL TRANSITION IS NOW EXPECTED BEYOND THE FORECAST PERIOD, OTHERWISE, THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS NAMTHEUN WILL CONTINUE ON ITS CURRENT TRACK UP TO 48H. AFTERWARDS, A SECONDARY SUBTROPICAL RIDGE(STR) TO THE EAST-SOUTHEAST WILL ASSUME STEERING AND DRIVE THE SYSTEM POLEWARD, MAKING IT CREST THE STR AXIS NEAR 72H, THEN RECURVE AND ACCELERATE IT NORTHEASTWARD. THE MARGINALLY FAVORABLE CONDITIONS WILL PROMOTE A STEADY INTENSIFICATION TO A PEAK OF 65KNOTS/CAT 1 BY 72H AT THE STR CREST WHERE VWS WILL BE AT MINIMUM. AFTERWARD, INCREASING VWS AND COOLING SSTS WILL GRADUALLY DECAY THE SYSTEM DOWN TO 35KNOTS BY 120H.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS NO SIGNIFICANT CHANGE IN THE CONVECTIVE STRUCTURE AND DEGREE OF WRAP IN THE LAST SIX HOURS. THE LOW LEVEL CIRCULATION REMAINS PARTIALLY EXPOSED WHERE THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE HIGHER END OF AGENCY AND AUTOMATED DVORAK ESTIMATES (SEE ABOVE) AND REFLECTS THE SUSTAINED STRUCTURE OF THE SYSTEM. ENVIRONMENTAL ANALYSIS INDICATES MARGINALLY FAVORABLE CONDITIONS FOR DEVELOPMENT WITH STRONG POLEWARD OUTFLOW, MODERATE TO HIGH VWS, AND WARM SSTS. TS 23W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF AN EASTERN EXTENSION OF THE MID-LAYER OF THE STR TO THE NORTHWEST.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT WITH THE WIDEST SPREAD OF 925+ KM AT 72H, ONLY BECAUSE OF UEMN AND AFUM, THE EXTREME LEFT AND RIGHT OUTLIERS, RESPECTIVELY. IN VIEW OF THIS, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK, LAID IN THE MIDDLE OF THE MODEL CLUSTER, UP TO 72H, AND MEDIUM CONFIDENCE AFTERWARD. COROLLARY TO THIS, THERE IS MEDIUM CONFIDENCE IN THE INTENSITY FORECAST UP TO 72H AND LOW AFTERWARD.

CURRENT INTENSITY IS 45KNOTS AND IS FORECAST TO PEAK AT 100KNOTS/CAT 3 BY 13/06UTC.

TS 16E(PAMELA). TRACK AND INTENSITY GUIDANCE.

11/0930UTC.