Invest 96W: significant intensification likely next 4/5 days,approaching the Philippines//TC 03P(RUBY): forecast to reach US/CAT2 by 36H,12/09utc

12/07UTC.

THE AREA OF CONVECTION (INVEST 96W) PREVIOUSLY LOCATED NEAR 5.6N 143.7E IS NOW LOCATED NEAR 5.7N 143.2E, APPROXIMATELY 695 KM SOUTHEAST OF YAP. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS LOW-LEVEL CLOUD LINES WRAPPING INTO A DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH EXPANSIVE, FLARING DEEP CONVECTION. A 120348Z AMSR2 89GHZ MICROWAVE IMAGE INDICATES FORMATIVE BANDING WRAPPING INTO A RAGGED BUT DEFINED LLCC. A RECENT PARTIAL 112352Z ASCAT IMAGE SHOWS A 20-25 KNOT BAND OF WINDS TO THE NORTHWEST OF THE FORMATIVE CIRCULATION. ENVIRONMENTAL CONDITIONS ARE FAVORABLE WITH WARM SEA SURFACE TEMPERATURES (29-30C), WEAK VERTICAL WIND SHEAR (05- 10 KTS) AND EXPANDING RADIAL OUTFLOW. THE GLOBAL MODELS AGREE THAT THE SYSTEM WILL INTENSIFY IN THE NEXT 24 HOURS AND TRACK WESTWARD TO WEST-NORTHWESTWARD WITH STEADY INTENSIFICATION. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 15 TO 20 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1005 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS HIGH.

THE GLOBAL MODELS AGREE THAT THE SYSTEM WILL INTENSIFY IN THE NEXT 24 HOURS AND TRACK WESTWARD TO WEST-NORTHWESTWARD WITH STEADY INTENSIFICATION.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 03P WILL TRACK SOUTHEASTWARD THROUGH THE FORECAST PERIOD ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYERED STR. HOWEVER, THE SYSTEM WILL ACCELERATE AFTER 36H WITHIN ENHANCED FLOW BETWEEN THE AFOREMENTIONED STR AND A DEEP, HIGH AMPLITUDE TROUGH. THIS STEERING PATTERN IS CLASSIFIED AS A HIGH AMPLITUDE PATTERN AND IS COMMON EAST OF AUSTRALIA, AND GENERALLY PRODUCES FASTER-THAN-CLIMATOLOGICAL TRACK SPEEDS WITH HIGH CONFIDENCE TRACK CONFIDENCE. TC 03P WILL RAPIDLY INTENSIFY THROUGH 24H TO 36H WITH A PEAK INTENSITY OF 85 KNOTS/CAT 2 ANTICIPATED BY 36H. THERE IS SOME UNCERTAINTY IN THE ACTUAL PEAK INTENSITY WITH POTENTIAL FOR A HIGHER PEAK INTENSITY NEAR NEW CALEDONIA. BY 72H, THE SYSTEM WILL BEGIN TO INTERACT WITH THE SUBTROPICAL WESTERLIES AND TRACK OVER COOLER SST (25C). BY 96H, TC 03P WILL ENCOUNTER STRONG VERTICAL WIND SHEAR (30 KNOTS) WITH SIGNIFICANTLY COOLER SST (22-19C). THIS WILL SERVE TO RAPIDLY WEAKEN THE CONVECTIVE STRUCTURE AND LEAD TO SUBTROPICAL TRANSITION. HOWEVER, THE SYSTEM WILL REMAIN A STORM-FORCE SUBTROPICAL LOW AS IT APPROACHES NEW ZEALAND.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A CONSOLIDATING SYSTEM WITH A SMALL CENTRAL DENSE OVERCAST FEATURE OBSCURING THE LOW-LEVEL CIRCULATION CENTER AND CONVECTIVE BANDING OVER THE SOUTHERN SEMICIRCLE. A 120541Z SSMIS 91GHZ MICROWAVE IMAGE REVEALS DEEP CONVECTIVE BANDING WRAPPING TIGHTLY INTO A SMALL MICROWAVE EYE FEATURE, WHICH SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. THE INITIAL INTENSITY OF 45 KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE KNES AND ABRF DVORAK ESTIMATES. THIS ASSESSMENT IS CONSISTENT WITH THE FIRST APPEARANCE OF A MICROWAVE EYE FEATURE. THE RECENT RAPID CONSOLIDATION IS ATTRIBUTABLE TO FAVORABLE ENVIRONMENTAL CONDITIONS, SPECIFICALLY, ROBUST POLEWARD OUTFLOW INTO A DEEP UPPER-LEVEL TROUGH POSITIONED EAST OF AUSTRALIA, LOW VERTICAL WIND SHEAR AND WARM SST VALUES.

MODEL DISCUSSION: AS MENTIONED EARLIER, THE HIGH AMPLITUDE PATTERN TYPICALLY PRODUCES TIGHTLY-GROUPED FORECAST GUIDANCE AND, CONSEQUENTLY, HIGH CONFIDENCE FORECAST TRACKS. THIS SYSTEM IS NO EXCEPTION WITH A 185-220KM SPREAD IN SOLUTIONS FROM 36H THROUGH 96H. ADDITIONALLY, THE 120000Z ECMWF ENSEMBLE (EPS) ALSO INDICATES A TIGHT GROUPING OF ENSEMBLE MEMBERS AND A NARROW CONE OF HIGH STRIKE PROBABILITY JUST NORTH OF NEW CALEDONIA EXTENDING SOUTHEASTWARD. THE JTWC INTENSITY FORECAST IS MORE UNCERTAIN WITH A HIGH PROBABILITY FOR RAPID INTENSIFICATION OVER THE NEXT 36 HOURS AS INDICATED BY THE TRIGGERING OF THE RAPID INTENSIFICATION PREDICTION AID (RIPA). THE JTWC INTENSITY FORECAST IS PLACED ABOVE MOST OF THE RELIABLE INTENSITY GUIDANCE AND THE JTWC INTENSITY CONSENSUS (ICNW) DUE TO THE FAVORABLE ENVIRONMENTAL CONDITIONS THROUGH 48H.