Busy at JTWC! Western Pacific: 4 systems at once! Eastern Pacific: 2 systems, 05/03utc updates

JTWC ARE ISSUING 6HOURLY WARNINGS ON 13W,14W,15W AND 12W(RESUMPTION OF WARNINGS AT 04/21UTC). 3HOURLY SATELLITE BULLETINS ARE ISSUED FOR THE 4 SYSTEMS.

TS 13W(LUPIT). WARNING 10 ISSUED AT 05/03UTC.THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM 13W (LUPIT) IS NEARING LANDFALL IN CHINA, GETTING NUDGED NORTHWARD WITHIN THE MONSOON TROUGH AS IT GRADUALLY SHIFTS NORTHWARD. NUMERICAL MODEL GUIDANCE HAS HIGHER THAN NORMAL SPREAD IN THE SHORT-TERM TRACK, WITH GFS-BASED GUIDANCE TAKING LUPIT MORE NORTHWESTWARD AND DEEPER INLAND, WHILE THE ECMWF AND OTHER GUIDANCE TURNS NORTHEASTWARD AND STAYS CLOSER TO THE COAST. THE LATTER SCENARIO SEEMS MORE REASONABLE, GIVEN THAT NORTHERLY SHEAR IS EXPECTED TO CONTINUE DURING THE NEXT 48 HOURS, BIASING CONVECTION TOWARD THE SOUTHERN SIDE OF THE CIRCULATION AND TUGGING THE CENTER TOWARD THE COASTLINE. THE JTWC TRACK FORECAST KEEPS LUPIT OVER CHINA FOR ABOUT 60 HOURS, WHICH IS EXPECTED TO RESULT IN DISSIPATION BY 72 HOURS. HOWEVER, IT IS WORTH NOTING THAT SOME MODEL GUIDANCE, SUCH AS ECMWF, THE ECMWF ENSEMBLE, AND COAMPS-TC EXPECT THE VORTEX TO SURVIVE AND RESTRENGTHEN AFTER MOVING BACK OFFSHORE OVER THE EAST CHINA SEA. THIS SCENARIO COULD BE REALISTIC IF THE REMNANT VORTEX REFORMS OVER WATER WITHIN THE NEARBY MONSOON TROUGH, WHICH IS PROVIDING BACKGROUND VORTICITY. WHILE THE CURRENT FORECAST CONTINUES TO PREDICT DISSIPATION OVER LAND, THE POTENTIAL FOR REVIVAL OVER WATER WILL BE CLOSELY MONITORED.

TS 13W(LUPIT).SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED VISIBLE SATELLITE AND RADAR IMAGERY CONTINUES TO SHOW A COMPACT AND WELL-ORGANIZED INNER CORE, SEPARATED FROM THE LARGER SPIRAL BANDS TO THE SOUTHEAST. NORTHEASTERLY VERTICAL SHEAR OF 15-20 KT IS RESULTING IN AN ASYMMETRIC CONVECTIVE STRUCTURE, WITH INNER CORE CONVECTION CONFINED TO THE SOUTHERN SIDE. STRONG EQUATORWARD OUTFLOW IS OBSERVED IN THE SOUTHERN SEMICIRCLE IN ANIMATED WATER VAPOR SATELLITE IMAGERY. A BROAD SWATH OF 30+ KT WINDS EXTENDS TO THE SOUTHEAST OF THE CIRCULATION CENTER, AIDED BY THE BACKGROUND MONSOONAL SOUTHWESTERLY FLOW THAT IS NOW FUNNELING INTO THE TAIWAN STRAIGHT. THE CURRENT INTENSITY IS SET AT 45 KT BASED ON A BLEND OF AGENCY DVORAK ESTIMATES. TROPICAL STORM 13W (LUPIT) IS NOW NEARING THE CHINESE COASTLINE EAST OF SHANTOU, AND IS EXPECTED TO MAKE LANDFALL DURING THE NEXT SEVERAL HOURS.

TS 13W(LUPIT).MODEL DISCUSSION: THE JTWC TRACK FORECAST IS 6-12 HOURS SLOWER THAN THE PRIOR FORECAST DUE TO A SLOWER MULTI-MODEL CONSENSUS, AND GENERALLY FOLLOWS A BLEND OF THE ECMWF AND ECMWF ENSEMBLE. THE JTWC INTENSITY FORECAST IS CLOSE TO THE MULTI-MODEL CONSENSUS, FOLLOWING A TYPICAL OVERLAND DECAY RATE.

TD 14W. WARNING 4 ISSUED AT 05/03UTC.THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TD 14W HAS REMAINED QUASI-STATIONARY OVER THE PAST 12 HOURS WITH A BROAD, ILL-DEFINED LOW-LEVEL CIRCULATION CENTER. THUS, THERE IS SIGNIFICANT UNCERTAINTY IN THE POSITION AND TRACK MOTION. DUE TO THE COMPETING STEERING INFLUENCES, THERE IS MEDIUM CONFIDENCE WITH THE SYSTEM EXPECTED TO REMAIN SLOW MOVING AND ERRATIC. AFTER TAU 24, THE STR TO THE NORTH SHOULD WEAKEN IN RESPONSE TO AN APPROACHING SHORTWAVE TROUGH ALLOWING THE SYSTEM TO SLOWLY TRACK EAST-NORTHEASTWARD TO NORTHEASTWARD TOWARD THE KANTO PLAIN REGION OF CENTRAL JAPAN. TD 14W SHOULD GRADUALLY INTENSIFY TO A PEAK INTENSITY OF 50 KNOTS BY TAU 48 WITH GRADUAL WEAKENING AFTER TAU 72. AFTER TAU 96, TD 14W WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) AS IT INTERACTS WITH THE WESTERLIES AND THE BAROCLINIC ZONE. TD 14W SHOULD COMPLETE ETT BY TAU 120 AS IT GAINS FRONTAL CHARACTERISTICS.

TD 14W.SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS MULTIPLE MESOVORTICES ROTATING CYCLONICALLY ABOUT A CENTROID NEAR KUMEJIMA. THE TWO WESTERNMOST, EXPOSED MESOVORTICES ARE SLOWLY WEAKENING AND BECOMING LESS DEFINED. HOWEVER, ANIMATED RADAR IMAGERY REVEALS A STRONG, WELL-DEFINED MESOVORTEX, POSITIONED JUST EAST OF OKINAWA, TRACKING NORTHEASTWARD WITH 40-50 KNOT WINDS. OVERALL, THESE MESOVORTICES ARE DYNAMIC FEATURES OF THE BROAD LOW-LEVEL CIRCULATION WHICH EXTENDS FROM WEST OF OKINAWA TO EAST OF OKINAWA CONTRIBUTING SIGNIFICANT UNCERTAINTY AND LOW CONFIDENCE IN THE INITIAL POSITION AND SHORT-TERM TRACK MOTION. THE INITIAL INTENSITY OF 25 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AGENCY DVORAK ESTIMATES.

TD 14W.MODEL DISCUSSION: WITH THE EXCEPTION OF THE UKMET ENSEMBLE MEAN (UEMN), NUMERICAL MODEL GUIDANCE IS IN BETTER AGREEMENT AND SUPPORTS THE JTWC TRACK FORECAST WITH MEDIUM CONFIDENCE. OVERALL, THERE IS LOW CONFIDENCE IN THE JTWC INTENSITY FORECAST DUE TO THE COMPLEX NATURE OF THE SYSTEM, PERSISTENT MODERATE TO STRONG VERTICAL WIND SHEAR (15 TO 25 KNOTS) AND POSSIBLE INTERACTION WITH LAND AFTER TAU 72.

TS 15W. WARNING 3 ISSUED AT 05/03UTC.THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 15W WILL CONTINUE ON ITS CURRENT TRACK ALONG THE WESTERN PERIPHERY OF THE STR. AFTER TAU 18, IT WILL BEGIN TO ROUND THE STR AXIS THEN ACCELERATE NORTHEASTWARD AND INTENSIFY. AS THE SYSTEM TRACKS POLEWARD, VWS WILL INCREASE AS IT APPROACHES THE PREVAILING WESTERLIES. ADDITIONALLY, SSTS WILL BEGIN TO DROP AFTER MAKING THE TURN NORTHEASTWARD. THE ENVIRONMENT WILL QUICKLY BECOME MARGINAL BUT WILL STILL FUEL A SLIGHT INTENSIFICATION TO 50 KTS AT TAU 24. AFTERWARD, TS 15W WILL ENTER AN UNFAVORABLE ENVIRONMENT WITH HIGH VWS AND LOW SSTS THAT WILL DECAY THE SYSTEM. THERE IS A POSSIBILITY THAT THE SYSTEM WILL DISSIPATE BEFORE THE END OF THE FORECAST PERIOD SHOULD THE MARGINAL ENVIRONMENT BECOME MORE UNFAVORABLE. OTHERWISE, BY TAU 48, THE TS WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) AND TRANSFORM INTO A GALE-FORCE COLD CORE LOW BY TAU 72.

TS 15W.SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A CONSOLIDATING SYSTEM WITH BANDS OF CONVECTION IN THE WESTERN PERIPHERY WRAPPING INTO A DEFINED LOW LEVEL CIRCULATION CENTER (LLCC) WITH INDICATIONS OF OVERSHOOTING TOPS NEAR THE CENTER. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A 042158Z ASCAT-A PASS. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AND HEDGED HIGHER THAN PGTW DVORAK, ADT AND SATCON ESTIMATES. ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH GOOD EQUATORWARD OUTFLOW ALOFT, LOW (5-10 KTS) VWS, AND WARM (28-29C) SSTS. THE LIMITING FACTOR IS THE INTRODUCTION OF DRIER AIR IN THE UPPER LEVELS WHICH IS SUPPRESSING CONVECTION IN THE WESTERN PERIPHERY.

TS 15W. MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WHICH LENDS HIGH CONFIDENCE TO THE JTWC TRACK FORECAST UP TO TAU 72 ONLY DUE TO TRACK UNCERTAINTIES ASSOCIATED WITH ETT. THERE IS MEDIUM CONFIDENCE IN THE INTENSITY FORECAST.

TD 12W. WARNING 7 ISSUED AT 05/03UTC.THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TD 12W WILL CONTINUE TO TRACK GENERALLY WESTWARD THROUGH TAU 12 ALONG THE STEERING RIDGE. AFTER TAU 12, IT WILL APPROACH WITHIN 500NM OF TD 14W, COMMENCE FUJIWHARA INTERACTION AND STEER ALONG THE OUTER PERIPHERY OF TD 14W. TD 12W WILL INTENSIFY TO A PEAK INTENSITY OF 35 KNOTS BY TAU 24 UNDER MARGINALLY FAVORABLE CONDITIONS. AFTER TAU 24, TD 12W WILL ACCELERATE AROUND THE NORTHERN PERIPHERY OF TD 14W APPROACHING WITHIN 300NM BY TAU 36. TD 12W WILL DISSIPATE BY TAU 48 AS IT BECOMES ABSORBED INTO TD 14W, WHICH IS FORECAST TO REMAIN THE STRONGER, DOMINANT SYSTEM.

TD 12W.SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY-EXPOSED LOW-LEVEL CIRCULATION (LLC) WITH DEEP CONVECTIVE BANDING OVER THE WESTERN SEMICIRCLE. A 042121Z SSMIS 91GHZ COMPOSITE MICROWAVE IMAGE INDICATES SHALLOW BANDING WRAPPING INTO THE DEFINED LLC WITH FRAGMENTED BANDING WRAPPING INTO THE WESTERN QUADRANT. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE MSI. THE INITIAL INTENSITY OF 25 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON A 050055Z ASCAT-B IMAGE SHOWING 20 TO 25 KNOT WINDS ASSOCIATED WITH THE DEEP CONVECTIVE BANDING TO THE NORTHWEST.

TD 12W. MODEL DISCUSSION: NUMERICAL MODELS ARE LIMITED BUT GENERALLY SUPPORT THE JTWC FORECAST TRACK WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS LIMITED BUT ALSO SUPPORTS THE JTWC INTENSITY FORECAST.

EASTERN PACIFIC. TS 08E(HILDA). WARNING 22 ISSUED AT 05/04UTC. INTENSITY IS FORECAST TO FALL BELOW 35KNOTS WITHIN 12H.

TS 08E(HILDA). GUIDANCE.

TD 09E. WARNING 9 ISSUED AT 05/04UTC. INTENSITY IS FORECAST TO PEAK AT 40KNOTS BY 24H.