Western North Pacific: 99W is now High//Southern Hemisphere: 1st Tropical Cyclone Formation Alert of 2021/22//Atlantic updates on 16L and 17L,21/09utc

21/00utc.

INVEST 99W. THE AREA OF CONVECTION (INVEST 99W) PREVIOUSLY LOCATED NEAR 10.3N 154.6E IS NOW LOCATED NEAR 11.2N 151.5E, APPROXIMATELY 780 KM EAST-SOUTHEAST OF GUAM. A 211052Z METOP-B PASS SHOWS THAT A DISCREET LOW-LEVEL CIRCULATION CENTER (LLCC) HAS CONSOLIDATED OVER THE PAST 12 HOURS, WITH A SMALL BUT WELL-DEFINED CIRCULATION SURROUNDED BY 12-17 KNOT WINDS. A BAND OF 20-25 KNOT WINDS EXTENDS FROM SOUTH TO SOUTHEAST OF THE CENTER. ANIMATED ENHANCED INFRARED IMAGERY AND A 210811Z SSMIS 91GHZ IMAGE DEPICTS FLARING DISORGANIZED CONVECTION PRIMARILY ON THE SOUTH AND EAST SIDE OF THE ROTATION. ENVIRONMENTAL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH A COMBINATION OF STRONG OUTFLOW ALOFT WITH A POINT SOURCE OR ANTICYCLONE ALOFT DIRECTION OVERHEAD THE LLCC, LOW (10 KT) VERTICAL WIND SHEAR (VWS) AND VERY WARM (30-31C) SEA SURFACE TEMPERATURES (SST). MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 18 TO 23 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 IS UPGRADED TO HIGH.

INVEST 99W. GLOBAL MODELS ARE GOOD IN AGREEMENT THAT INVEST 99W WILL CONTINUE TRACKING NORTHWESTWARD OVER THE NEXT 24-48 HOURS HOWEVER, THEY ARE SPLIT ON THE DEGREE OF DEVELOPMENT. GFS, ITS ENSEMBLE, AND NAVGEM ARE THE MOST AGGRESSIVE, INDICATING FAIRLY RAPID CONSOLIDATION AND INTENSIFICATION, REACHING TROPICAL DEPRESSION STRENGTH WITHIN THE NEXT 24 HOURS AND TROPICAL STORM STRENGTH WITHIN THE NEXT 48 HOURS OR LESS, PRIOR TO PASSAGE THROUGH THE MARIANAS ISLAND CHAIN. ECMWF AND ITS ENSEMBLE ARE MUCH MORE RESERVED, INDICATING LITTLE TO NO DEVELOPMENT UNTIL AFTER TAU 48, WELL TO THE WEST OF THE MARIANAS. OF NOTE, THE ASCAT PASS VERIFIED THE 1200Z GFS MODEL FORECAST POSITION AND WIND FIELD WITH HIGH CONFIDENCE, LENDING INCREASED CONFIDENCE TO THE GFS FORECAST.

INVEST 90S. THE AREA OF CONVECTION (INVEST 90S) PREVIOUSLY LOCATED NEAR 9.9S 84.1E IS NOW LOCATED NEAR 9.5S 84.2E. ANIMATED ENHANCED INFRARED IMAGERY DEPICTS AN EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH FLARING CONVECTION DISPLACED TO THE SOUTH. A 1454 ASCAT- A IMAGE SHOWS WRAPPING 25 KNOT WINDS IN THE SOUTHERN SEMICIRCLE. ENVIRONMENTAL ANALYSIS REVEALS MARGINALLY UNFAVORABLE CONDITIONS WITH HIGH (30-40 KT) VERTICAL WIND SHEAR OFFSET BY PRONOUNCED RADIAL OUTFLOW AND HIGH SEA SURFACE TEMPERATURES (29-30C).MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 23 TO 27 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1007 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH.

INVEST 90S. GLOBAL MODELS ARE IN AGREEMENT THAT INVEST 90S WILL TRACK TO THE SOUTHWEST WITH THE GFS DETERMINISTIC MODEL SHOWING THE MOST AGGRESSIVE PREDICTION.

21/00UTC.

ATLANTIC. TS 16L(PETER).WARNING 11 ISSUED AT 21/09UTC. CURRENT INTENSITY IS 45KNOTS AND IS FORECAST TO FALL BELOW 35KNOTS BY 23/18UTC.

TS 16L(PETER). TRACK AND INTENSITY GUIDANCE.

TS 17L(ROSE). WARNING 9 ISSUED AT 21/09UTC. CURRENT INTENSITY IS 40KNOTS AND IS FORECAST TO FALL BELOW 35KNOTS BY 22/18UTC.

TS 17L(ROSE). TRACK AND INTENSITY GUIDANCE.

21/11UTC.