TD 28W: forecast to reach Typhoon CAT 2 by 72H,approaching the Philippines// TC 03P(RUBY): peaking by 24H close to New Caledonia,13/03utc

JTWC IS ISSUING 6HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON 28W AND 03P.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY. FORECAST DISCUSSION: TROPICAL DEPRESSION 28W IS EXPECTED TO TRACK WEST-NORTHWESTWARD THROUGH THE DURATION OF THE FORECAST PERIOD ALONG THE SOUTHERN SIDE OF AN EXTENSIVE SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE NORTH. TRACK SPEEDS ARE FORECAST TO REMAIN RELATIVELY STEADY EXCEPT FOR A BRIEF SLOWDOWN BETWEEN 48H AND 72H, IN RESPONSE TO A SLIGHT WEAKENING OF THE STEERING GRADIENT DUE TO DEVELOPMENT OF A WEAKNESS IN THE RIDGE TO THE NORTH. TD 28W IS EXPECTED TO CROSS THROUGH THE SOUTHERN PHILIPPINE ISLANDS AFTER 72H, AND ULTIMATELY EMERGE INTO THE SULU SEA AND TRACK TO NEAR PALAWAN BY 120H. OVER THE NEXT 12 TO 18 HOURS, THE LLCC IS EXPECTED TO FURTHER CONSOLIDATE WHILE MOVING UNDER THE DEEP CONVECTION, ESTABLISHING A WELL DEFINED CORE. THIS WILL MARK THE START OF A PERIOD OF STEADY INTENSIFICATION TO A PEAK OF 85 KNOTS/CAT 2 BY 72H. THE BULK OF THE INTENSIFICATION IS EXPECTED IN THE FIRST 48 HOURS AS VWS REMAINS BELOW 15 KNOTS AND OUTFLOW REMAINS RELATIVELY HIGH. BY 72H, SHEAR IS EXPECTED TO INCREASE ABOVE 15 KNOTS AND THE OUTFLOW WILL DECREASE AS THE UPPER- LEVEL FLOW SHIFTS TO A MORE EASTERLY DIRECTION, CUTTING OFF THE POLEWARD OUTFLOW CHANNEL. THE SYSTEM WILL WEAKEN AS IT CROSSES THROUGH THE PHILIPPINES DUE TO INFLOW AND CORE DISRUPTION CAUSED BY INTERACTION WITH THE COMPLEX TERRAIN FEATURES. ONCE BACK OVER WATER, THE SYSTEM WILL QUICKLY INTENSIFY ONCE MORE AS THE POLEWARD OUTFLOW CHANNEL IS REESTABLISHED

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC), DISPLACED JUST SOUTH OF AN EXPANSIVE AREA OF DEEP, PERSISTENT CONVECTION. THE MOST RECENT MICROWAVE IMAGE, A 122144Z 89GHZ SSMIS IMAGE, DEPICTED THE DISORGANIZED STRUCTURE OF THE SYSTEM CONVECTIVE CORE, WITH THE LLCC DISPLACED TO THE SOUTH. THE INITIAL POSITION IN ASSESSED WITH HIGH CONFIDENCE BASED ON A SPIRAL BAND ANALYSIS OF THE EXPOSED LOW LEVEL CLOUD LINES TO THE SOUTH OF THE CENTER. THE INITIAL INTENSITY OF 25 KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE, BASED ON THE AVERAGE OF MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES. THE WIND FIELD REMAINS HIGHLY ASYMMETRIC, WITH EARLIER 121925Z SCATTEROMETER DATA SHOWING 25-30 KNOTS TO THE NORTH, WITH EVEN HIGHER LIKELY OCCURRING UNDER THE DEEPEST CONVECTION, WHILE WINDS WERE MEASURED AT 15-20 KNOTS ALONG THE SOUTHERN PORTIONS OF THE CIRCULATION. ENVIRONMENTAL ANALYSIS REVEALS DIVERGENT EASTERLY FLOW OVER TOP OF THE SYSTEM, AIDING THE CONVECTIVE ACTIVITY CURRENTLY BEING SEEN, THOUGH OVERALL OUTFLOW REMAINS RELATIVELY WEAK AT PRESENT, BOTH POLEWARD AN EQUATORWARD. SSTS ARE VERY WARM (29-30C) AND VWS IS LOW, LEADING TO AN OVERALL FAVORABLE ENVIRONMENTAL ASSESSMENT.

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH THE DURATION OF THE FORECAST WITH A 165KM SPREAD AT 48H INCREASING TO 390KM AT 120H, BUT ONLY 205KM IF THE NAVGEM TRACKER IS DISCOUNTED AS THE SINGLE MAJOR OUTLIER. THE JTWC FORECAST LIES AMONGST THE TIGHTEST PACKING OF CONSENSUS MEMBERS AND JUST SOUTH OF THE CONSENSUS MEAN WITH HIGH CONFIDENCE THROUGH 72H, AND MEDIUM CONFIDENCE THEREAFTER. INTENSITY GUIDANCE IS MIXED WITH TWO DISTINCT PEAKS WITHIN THE FORECAST PERIOD. THE ENVELOPE OF PEAK INTENSITIES RANGES FROM A LOW OF 65KNOTS TO A HIGH OF 110 KNOTS FOR THE FIRST PEAK EAST OF THE PHILIPPINES, AND 65 KNOTS TO 135 KNOTS FOR THE SECOND PEAK AT 120H. THE COAMPS-TC MODELS ARE THE MOST AGGRESSIVE THROUGH THE FORECAST PERIOD, WITH THE SHIPS GUIDANCE MARKING THE LOW END AND HWRF VERY AGGRESSIVE THROUGH 24H, BUT THEREAFTER MORE MODEST, THOUGH THE HWRF DOES NOT WEAKEN THE SYSTEM THROUGH THE PHILIPPINES. BASED ON ANALYSIS OF THE GLOBAL FIELDS, THE COAMPS-TC AND HWRF TRACKERS ARE DETERMINED TO BE TOO AGGRESSIVE WHILE THE GFS IS TOO BEARISH. THE JTWC FORECAST LIES AMONGST MOST OF THE GUIDANCE THROUGH 48H, THEN DIVERGES LOWER THAN THE MOST AGGRESSIVE MODELS THROUGH THE REMAINDER OF THE FORECAST. IN LIGHT OF THE EXTREME UNCERTAINTY EXHIBITED BY THE MODEL GUIDANCE, AT THIS TIME THERE IS LOW CONFIDENCE IN THE JTWC FORECAST INTENSITY.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. THE FORECAST DURATION HAS BEEN TRUNCATED TO 72 HOURS. FORECAST DISCUSSION: NO SIGNIFICANT CHANGES ARE EXPECTED IN THE FORECAST TRACK, AND THE SYSTEM IS FORECAST TO TRACK SOUTHEASTWARD ALONG THE WESTERN GRADIENT BETWEEN THE DEEP STR TO THE EAST AND A HIGH-AMPLITUDE TROUGH TO THE WEST. THE CENTER OF TC 03P IS FORECAST TO TRACK JUST EAST OF NEW CALEDONIA BETWEEN 24H AND 36H, THEN ACCELERATE SOUTHEASTWARD INTO THE OPEN WATERS NORTH OF NEW ZEALAND THROUGH THE REMAINDER OF THE FORECAST PERIOD. AS DISCUSSED IN SATELLITE ANALYSIS SECTION, A WEDGE OF RELATIVELY DRY MID-LEVEL AIR HAS BEGUN TO PUNCH IN TOWARDS THE CORE OF THE SYSTEM FROM THE WEST, DISRUPTING THE MAINTENANCE OF THE CONVECTIVE CORE. OVER THE NEXT 24 HOURS VWS, DRY AIR AND ROBUST POLEWARD OUTFLOW WILL COMPETE AND OFFSET EACH OTHER, AND THUS, WHILE THE SYSTEM IS EXPECTED TO CONTINUE TO STRENGTHEN THROUGH 24H,THE PEAK INTENSITY HAS BEEN LOWERED TO 80 KNOTS/CAT 1. AS THE SYSTEM PASSES NEW CALEDONIA THE SYSTEM IS FORECAST TO BEGIN TO WEAKEN AS SHEAR STEADILY INCREASES AND ESTABLISHES DOMINANCE OVER THE ROBUST POLEWARD OUTFLOW, SSTS COOL AND DRY AIR BEGINS TO SMOTHER THE CORE. BY 48H TC 03P BEGINS TO INTERACT WITH THE STRONG MID-LATITUDE WESTERLIES ALOFT AND BEGIN SUBTROPICAL TRANSITION, WITH FULL TRANSITION TO A STORM-FORCE SUBTROPICAL LOW NO LATER THAN 72H.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A VERY COMPACT TROPICAL CYCLONE WHICH HAS OVER THE PAST SIX HOURS, BECOME INCREASINGLY DISORGANIZED CONVECTIVELY. CLOUD TOPS HAVE BEEN STEADILY WARMING, ESPECIALLY OVER THE PREVIOUS THREE HOURS, WITH THE COLDEST TOPS NOW DISPLACED DOWNSHEAR TO THE SOUTHEAST OF THE ASSESSED CENTER. THE INITIAL POSITION IS ASSESSED WITH ONLY MEDIUM CONFIDENCE, AS THE LOW LEVEL CIRCULATION CENTER (LLCC) IS CURRENTLY OBSCURED BY THE CONVECTIVE ACTIVITY AND THERE HAS BEEN NO RECENT MICROWAVE OR SCATTEROMETER DATA TO ASSIST WITH ANALYSIS OF THE LOW LEVEL STRUCTURE. MODEL CROSS-SECTIONS SUGGEST THE PRESENCE OF A PULSE OF MID-LEVEL DRY AIR, WHICH IS IMPINGING THE CORE FROM THE WEST, AS SUGGESTED BY A FIELD OF STRATOCUMULUS SEEN IN THE MSI AND EROSION AND WARMING OF THE CLOUD TOPS ON THE NORTHWEST SIDE OF THE CIRCULATION. THE CROSS-SECTIONS ALSO SHOW A MODERATE AMOUNT OF DOWNSHEAR TILT TO THE VORTEX. THE INITIAL INTENSITY OF 70 KNOTS/CAT 1 IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AN OVERALL AVERAGE OF AGENCY SUBJECTIVE AND AUTOMATED OBJECTIVE DVORAK INTENSITY ESTIMATES. OVERALL THE ENVIRONMENT REMAINS FAVORABLE FOR DEVELOPMENT, BUT HAS BECOME LESS SO SINCE THE PREVIOUS FORECAST, WITH THE AFOREMENTIONED WEDGE OF MID-LEVEL DRY AIR AND VORTEX TILT SERVING TO SLOW THE INTENSIFICATION TREND.

MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN GOOD AGREEMENT THROUGH 48H, THROUGH ALONG-TRACK SPREAD INCREASES AFTER THIS POINT AS THE SYSTEM MOVES THROUGH THE SUBTROPICAL TRANSITION. THE JTWC FORECAST LIES ON THE NORTHERN SIDE OF THE GUIDANCE ENVELOPE AND MOST CLOSELY TRACKS THE GFS SOLUTION, THROUGH THE FORECAST PERIOD. CONFIDENCE IS HIGH THROUGH 36H, DECREASING TO MEDIUM THEREAFTER. INTENSITY GUIDANCE HAS SHIFTED SIGNIFICANTLY LOWER SINCE THE PREVIOUS RUN, WITH ALL BUT THE GFS SHIPS AND HWRF SUGGESTING WEAKENING FROM 00H. THE SHIPS GUIDANCE IS THE ONLY MODEL INDICATING SIGNIFICANT INTENSIFICATION AT THIS TIME. THE JTWC FORECAST CLOSELY TRACKS THE SHIPS GUIDANCE, AND IS APPROXIMATELY 15 KNOTS HIGHER THAN THE CONSENSUS MEAN THROUGH 36H AND THEN REJOINS THE MEAN THEREAFTER. IN LIGHT OF THE SIGNIFICANT RUN TO RUN VARIABILITY AND UNCERTAINTY IN THE INTENSITY GUIDANCE, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST.

13/0540UTC.