WDPS31 PGTW 100300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 03P (JASPER) WARNING NR 021// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 16.1S 154.2E INITIAL INTENSITY: 55 KTS GEOGRAPHIC REFERENCE: 486 NM EAST OF CAIRNS, AUSTRALIA MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 28 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL CYCLONE (TC) 03P (JASPER) CONTINUES TO WEAKEN, ALTHOUGH THE PACE OF WEAKENING HAS SLOWED AS VERTICAL WIND SHEAR (VWS) HAS WANED OVER THE PAST 12 HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT REGION OF DEEP CONVECTION, CONCENTRATED IN VICINITY OF THE LOW LEVEL CIRCULATION CENTER (LLCC), WHICH IS OBSCURING THE ACTUAL LLCC POSITION. HOWEVER, THE OUTER LOW-LEVEL BANDS ARE EVIDENT, PARTICULARLY IN THE DRY, CLEAR AIR ON THE NORTHERN SIDE, ALLOWING FOR THE USE OF SPIRAL BAND ANALYSIS TECHNIQUES TO DETERMINE THE INITIAL POSITION WITH MEDIUM CONFIDENCE. ADDITIONAL CONFIDENCE IS PROVIDED BY AN EXTRAPOLATION OF A LOW EMISSIVITY REGION EVIDENT IN A 092248Z AMSU-B 89GHZ MICROWAVE IMAGE, WHICH ALSO SHOWED THAT THE LIMITED CONVECTIVE ACTIVITY IS ORIENTED IN A LINEAR FASHION FROM THE VICINITY OF THE LLCC AND EXTENDING TO THE SOUTHEAST. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, HEDGED SLIGHTLY LOWER THAN THE DVORAK CURRENT INTENSITY ESTIMATES, IN LIGHT OF THE LOWER ADT, AIDT AND SATCON ESTIMATES. WHILE THE WIND RADII ARE BASED PRIMARILY ON PERSISTENCE, AT LEAST IN THE SOUTHWEST SECTOR, SURFACE OBSERVATIONS FROM LIHOU REEF AT 0100Z SHOW GALE FORCE WINDS (33 KNOTS 10-MIN) EXTENDING OUT AT LAST AS FAR AS THE STATION (APPROXIMATELY 170NM). THE SYSTEM HAS PICKED UP A KNOT OR TWO OF SPEED OVER THE PAST SIX HOURS AS THE SUBTROPICAL RIDGE (STR) TO THE SOUTH HAS STRENGTHENED. THE LATEST CIMSS ANALYSIS SUGGESTS THE OVERALL DEEP-LAYER SHEAR REMAINS MODERATE (15-20 KNOTS), PUSHING DOWN FROM THE NORTHWEST BUT THE LATEST SATELLITE IMAGERY SHOWS AN EXPANDING OUTFLOW CIRRUS SHIELD TOWARDS THE NORTHWEST, SUGGESTING THE SHEAR MAY BE A BIT LOWER, AT LEAST AT THE HIGHEST LEVELS. DRY AIR ABOVE 400MB REMAINS THE PRIMARY HINDRANCE, ESPECIALLY ACROSS THE NORTHERN HALF OF THE SYSTEM, WRAPPING INTO THE EASTERN SIDE OF THE CORE AS WELL, INHIBITING CONVECTIVE DEVELOPMENT IN THOSE SECTORS. WARM SSTS AND MODERATE POLEWARD OUTFLOW, WHILE POSITIVE, ARE NOT ENOUGH TO OVERCOME THE NEGATIVE EFFECTS OF THE SHEAR AND DRY AIR. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED NORTHEAST OF SYDNEY. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T4.0 - 65 KTS KNES: T4.0 - 65 KTS APRF: T4.0 - 65 KTS CIMSS SATCON: 56 KTS AT 100100Z CIMSS ADT: 61 KTS AT 092330Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL VWS: 15-20 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE POLEWARD OTHER FACTORS: DRY MID-LEVEL AIR ACROSS THE NORTHERN HEMISPHERE OF THE CIRCULATION. ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: THERE IS NO MAJOR CHANGE IN THE OVERALL FORECAST PHILOSOPHY FOR TC 03P, AS IT CONTINUES TO TRACK WEST-SOUTHWESTWARD ALONG THE NORTHERN SIDE OF THE STEERING RIDGE TO THE SOUTH. THE SYSTEM WILL PASS CLOSE TO LIHOU REEF WITHIN THE NEXT 18-24 BEFORE HEADING FOR CLOSE RENDEZVOUS WITH THE OTHER NORTHERN ISLANDS IN THE CORAL SEA. FROM TAU 24 TO ABOUT TAU 72, THE RIDGE IS ANTICIPATED TO REPOSITION TO A NEW POSITION NORTHEAST OF BRISBANE. THIS MOVEMENT WILL RESULT IN A SHIFT IN THE TRACK OF TC 03P, FROM WEST-SOUTHWEST TO WEST-NORTHWEST THEN FLATTENING OUT AGAIN ON A DUE WEST TRACK BY TAU 72. LANDFALL IS EXPECTED JUST AFTER TAU 72, ALONG THE EASTERN COAST OF AUSTRALIA, NORTH OF CAIRNS. IN THE EXTENDED FORECAST, THE SYSTEM WILL TRACK ACROSS THE SOUTHERN PORTION CAPE YORK PENINSULA, THEN EMERGE BACK OVER THE EASTERN PORTION OF THE GULF OF CARPENTARIA BY TAU 120. WHILE THE SYSTEM CONTINUES TO WEAKEN, THE ANTICIPATED REDUCTION IN SHEAR VALUES SHOULD RESULT IN A SLOWER RATE OF WEAKENING THROUGH THE NEXT 36 HOURS, PRIMARILY DRIVEN BY THE DRY AIR THAT IS EXPECTED TO ENGULF THE SYSTEM OVER THE NEXT 12 HOURS OR SO. GLOBAL AND MESOSCALE MODELS AGREE THAT THE ATMOSPHERE WILL MOISTEN SIGNIFICANTLY AFTER TAU 36, WHICH WHEN ACCOMPANIED BY REDUCED SHEAR AND IMPROVED OUTFLOW PROVIDED BY DEVELOPMENT OF A POINT SOURCE ALOFT, WILL ALLOW FOR A SHORT BURST OF INTENSIFICATION BETWEEN TAU 48 AND LANDFALL. INTENSITY AT LANDFALL IS EXPECTED TO BE BETWEEN 55-60 KNOTS, LIKELY TO OCCUR JUST AFTER THE TAU 72 FORECAST POINT. AFTER MOVING INLAND, THE SYSTEM WILL RAPIDLY WEAKEN DUE TO FRICTIONAL EFFECTS, ULTIMATELY DISSIPATING AS IT EMERGES BACK OVER GULF OF CARPENTARIA. WHILE BEYOND THE CURRENT FORECAST TIMELINE, IT IS VERY LIKELY THAT THE SYSTEM WILL ONCE AGAIN REINTENSIFY IN THE GULF OF CARPENTARIA AS IT MOVES AWAY FROM SHORE. MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE REMAINS IN GOOD AGREEMENT THROUGH THE FORECAST PERIOD THOUGH CROSS-TRACK SPREAD HAS INCREASED SLIGHTLY AFTER THE SYSTEM MAKES LANDFALL, NOW ABOUT 150NM BY TAU 120. CONSISTENT WITH THE PREVIOUS MODEL RUN, ALONG-TRACK SPREAD CONTINUES TO INCREASE, PARTICULARLY BETWEEN THE ECWMF AND UKMET MODELS WHICH RACE THE SYSTEM ACROSS THE PENINSULA AND FAR OUT IN THE GULF OF CARPENTARIA, WHILE THE GFS KEEPS THE REMNANT VORTEX EAST OF THE GREAT DIVIDING RANGE, NEVER REACH THE GULF, BY TAU 120. THE JTWC FORECAST IS ON THE NORTHERN SIDE OF THE GUIDANCE ENVELOPE, NORTH OF AND SLIGHTLY FASTER THAN THE CONSENSUS MEAN, WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE HAS COME INTO BETTER AGREEMENT THAT THE BOTTOM INTENSITY WILL BE IN THE 40-45 KNOT RANGE, WITH THE FOLLOWING REINTENSIFICATION PEAK BETWEEN 45-60 KNOTS. THE JTWC FORECAST IS CONSISTENT WITH THE CONSENSUS MEAN THROUGH TAU 36 THEN SHIFTS ABOUT 10 KNOTS HIGHER THAN THE MEAN, CONSISTENT WITH THE COAMPS-TC (GFS AND NAVGEM VERSIONS) THEREAFTER. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN