01W(DUJUAN) slow-moving ,35knots system, 21S(GUAMBE) 55knots, gradually intensifying over the MOZ Channel, 18/21utc updates

18/18UTC. JTWC IS ISSUING 6HOURLY WARNINGS ON 01W AND 12HOURLY WARNINGS ON 21S. 3 HOURLY SATELLITE BULLETINS ARE ISSUED FOR BOTH SYSTEMS.

CLICK TO ANIMATE. 01W(DUJUAN). WARNING 7 ISSUED AT 18/21UTC. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY REVEALS A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) POSITIONED UNDER THE SOUTHEAST EDGE OF AN AREA OF EXPANSIVE DEEP CONVECTION. UNFORTUNATELY, THERE ARE NO USEFUL MICROWAVE IMAGES TO HELP LOCATE THE CENTER, THEREFORE, THERE IS FAIR CONFIDENCE IN THE INITIAL POSITION, WHICH APPEARS TO BE QUASI-STATIONARY OR SLOW MOVING. THE INITIAL INTENSITY REMAINS ASSESSED AT 35 KNOTS BASED ON A DVORAK ESTIMATES OF T2.5 (35 KNOTS) FROM ALL AGENCIES. UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY-FAVORABLE ENVIRONMENT WITH MODERATE (20 KNOTS) SOUTHEASTERLY VERTICAL WIND SHEAR (VWS) OFFSET BY DIFFLUENT EASTERLY FLOW AND ROBUST POLEWARD OUTFLOW. SST VALUES REMAIN CONDUCIVE AT 29-30C. TS 01W IS TRACKING ALONG THE SOUTHWEST PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE IN THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 01W IS LOCATED WITHIN A WEAK STEERING ENVIRONMENT SOUTH OF A BREAK IN THE SUBTROPICAL RIDGE (STR) ASSOCIATED WITH A MAJOR SHORTWAVE TROUGH CURRENTLY OVER AND SOUTH OF JAPAN. IN GENERAL, THE SYSTEM WILL TRACK SLOWLY WESTWARD TO WEST-NORTHWESTWARD THROUGH 36H UNTIL THE MAJOR TROUGH SHIFTS EASTWARD AND ZONAL FLOW PREDOMINATES. THIS WILL ALLOW THE STR TO RE-BUILD NORTHEAST AND NORTH OF THE SYSTEM, WHICH WILL ALLOW THE SYSTEM TO ACCELERATE WEST- NORTHWESTWARD WITH LANDFALL OCCURRING NEAR 48H. WITH THE EXCEPTION OF THE UKMET DETERMINISTIC AND UKMET ENSEMBLE MEAN SOLUTIONS, NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT WITH A 325KM SPREAD IN SOLUTIONS AT 72H. TS 01W WILL INTENSIFY STEADILY TO A PEAK INTENSITY OF 50 KNOTS BY 36H UNDER GENERALLY FAVORABLE CONDITIONS, ESPECIALLY STRONG POLEWARD OUTFLOW. HOWEVER, THERE IS SOME UNCERTAINTY IN THE PEAK INTENSITY DUE TO THE PERSISTENT MODERATE VWS. AFTER 72H, TS 01W WILL CONTINUE TO TRACK ACROSS THE PHILIPPINE ARCHIPELAGO, AND BY 96H, WILL REACH THE SOUTH CHINA SEA OFF THE ISLAND OF MINDORO. INTERACTION WITH THE ISLANDS AND INCREASED WIND SHEAR WILL WEAKEN THE SYSTEM DOWN TO 25 KNOTS BY 120H. NUMERICAL MODEL GUIDANCE DIVERGES AND IS IN POOR AGREEMENT IN THE EXTENDED PERIOD WITH A LARGE SPREAD OF 980KM AT 120H (MINUS UKMET AND UKMET ENSEMBLE MEAN). THESE SOLUTIONS ARE RECURVING THE SYSTEM NORTHEASTWARD, WHICH IS UNLIKELY DUE TO THE STRONG LIKELIHOOD OF A RE-BUILDING STR AND ZONAL UPPER-LEVEL FLOW OVER THE EAST CHINA SEA. DUE TO THE QUASI-STATIONARY MOTION AND THE LARGE SPREAD IN MODEL SOLUTIONS, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK, WHICH IS POSITIONED NEAR THE MULTI-MODEL CONSENSUS.

CLICK TO ANIMATE. 21S(GUAMBE). WARNING 3 ISSUED AT 18/21UTC. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A CONSOLIDATING SYSTEM WITH CONVECTIVE BANDING WRAPPING INTO A DEVELOPING CENTRAL DENSE OVERCAST FEATURE OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC). A 181620Z MHS 89GHZ MICROWAVE IMAGE SHOWS A COMPACT CORE OF DEEP CONVECTION WITH FRAGMENTED BANDING OVER THE EASTERN SEMICIRCLE. UPPER-LEVEL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH LOW (5-10 KNOTS) VERTICAL WIND SHEAR (VWS), EXCELLENT EQUATORWARD OUTFLOW, IMPROVING POLEWARD OUTFLOW INTO THE WESTERLIES TO THE SOUTH AND WARM (28-29C) SST VALUES. THE INITIAL INTENSITY IS ASSESSED AT 55 KNOTS BASED ON THE HIGHER END OF DVORAK INTENSITY ESTIMATES RANGING FROM 3.0-3.5 (45-55 KNOTS) AND AN 181800Z ADT ESTIMATE OF 3.5 (55 KNOTS). AN 181842Z ASCAT-A PARTIAL IMAGE SUPPORTS THE INITIAL POSITION WITH FAIR CONFIDENCE. TC 21S IS FORECAST TO TRACK SOUTHWARD TO SOUTH- SOUTHWESTWARD THROUGH T48h ALONG THE WESTERN PERIPHERY OF A NORTH- SOUTH ORIENTED SUBTROPICAL RIDGE (STR) POSITIONED TO THE EAST. AFTER 48h, THE SYSTEM WILL RECURVE SOUTHEASTWARD TO EAST-SOUTHEASTWARD AS IT ROUNDS THE STR AND BEGINS TO INTERACT WITH THE MIDLATITUDE WESTERLIES. TC 21S IS FORECAST TO BEGIN EXTRA-TROPICAL TRANSITION (ETT) NEAR 72H AND WILL COMPLETE ETT BY 96H AS IT ACCELERATES WITHIN THE STRONG WESTERLY FLOW AND GAINS FRONTAL CHARACTERISTICS. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT AND SUPPORTS THE JTWC FORECAST TRACK WITH HIGH CONFIDENCE. TC 21S IS EXPECTED TO GRADUALLY INTENSIFY THROUGH 36H WITH A PEAK INTENSITY OF 85 KNOTS/CATEGORY 2 AT 36H AND 48H. STEADY WEAKENING WILL OCCUR AFTER 48H AS WIND SHEAR INCREASES AND SST VALUES COOL TO 25-24C.