TCFA for INVEST 98P//TC 10P(NAT) update//INVEST 94P//INVEST 97P// 3 Week Tropical Cyclone Formation Probability// 0618utc

JTWC IS ISSUING 12HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TC 10P(NAT). 3HOURLY SATELLITE BULLETINS ARE ISSUED ON INVEST 94P.

HE AREA OF CONVECTION (INVEST 98P) PREVIOUSLY LOCATED NEAR 10.4S 174.4W IS NOW LOCATED NEAR 11.6S 171.9W, APPROXIMATELY 179 NM NORTH-NORTHWEST OF PAGO PAGO, AMERICAN SAMOA. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A 061452Z SSMIS 91 GHZ MICROWAVE IMAGE DEPICT A RAPIDLY CONSOLIDATING SYSTEM WITH VERY SYMMETRIC DEEP CONVECTION OVER THE CENTER AND FORMATIVE BANDING ALONG THE SOUTHWESTERN PERIPHERY. ENVIRONMENTAL ANALYSIS INDICATES THAT 98P IS IN A FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH GOOD OUTFLOW ALOFT, LOW (10-15 KTS) VERTICAL WIND SHEAR, AND WARM (30-31 C) SEA SURFACE TEMPERATURES. GLOBAL MODELS ARE IN GOOD AGREEMENT THAT 98P WILL TRACK SOUTHEASTWARD, EAST OF AMERICAN SAMOA, OVER THE NEXT 24 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1000 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO HIGH.

ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A 061452Z SSMIS 91 GHZ MICROWAVE IMAGE DEPICT A RAPIDLY CONSOLIDATING SYSTEM WITH VERY SYMMETRIC DEEP CONVECTION OVER THE CENTER AND FORMATIVE BANDING ALONG THE SOUTHWESTERN PERIPHERY.

GLOBAL MODELS ARE IN GOOD AGREEMENT THAT 98P WILL TRACK SOUTHEASTWARD, EAST OF AMERICAN SAMOA, OVER THE NEXT 24 HOURS.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC NAT WILL CONTINUE ON ITS CURRENT EAST-SOUTHEASTWARD TRACK UNDER THE STEERING INFLUENCE OF THE NER FOR THE REMAINDER OF THE FORECAST. THE MARGINAL ENVIRONMENT WILL SUSTAIN THE CURRENT INTENSITY, AT BEST, UP TO TAU 12. AFTERWARD, INCREASING VWS AND DRY AIR ENTRAINMENT AT THE LOW LEVELS WILL GRADUALLY ERODE THE SYSTEM TO DISSIPATION BY TAU 48 POSSIBLY SOONER.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH A GRADUAL AND EVEN SPREAD TO A MERE 64NM BY TAU 48, LENDING HIGH CONFIDENCE TO THE JTWC TRACK FORECAST. THERE IS ONLY MEDIUM CONFIDENCE IN THE INTENSITY FORECAST GIVEN THE POSSIBILITY OF AN EARLIER DISSIPATION.

THE AREA OF CONVECTION (INVEST 94P) PREVIOUSLY LOCATED NEAR 18.0S 159.5E IS NOW LOCATED NEAR 17.2S 159.0E, APPROXIMATELY 515 NM NORTHWEST OF NOUMEA, NEW CALEDONIA. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A 061423Z AMSR2 36 GHZ MICROWAVE IMAGE DEPICT A BROAD, PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH FRAGMENTED BANDING IN THE SOUTHERN SEMICIRCLE. A 061124Z ASCAT-B BULLSEYE IMAGE REVEALS THE BROAD NATURE OF THE CIRCULATION AND 20-25 KT WINDS. ENVIRONMENTAL ANALYSIS INDICATES THAT 94P IS IN A FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH GOOD OUTFLOW ALOFT, LOW TO MODERATE (15-20 KTS) VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA SURFACE TEMPERATURES. GLOBAL MODELS ARE IN PARTIAL DISAGREEMENT ON THE TRACK OF 94P. GFS HAS 94P TRACKING SOUTHEASTWARD OVER THE NEXT 48 HOURS BEFORE TURNING SOUTHWARD TOWARD NEW CALEDONIA, WHILE ECMWF HAS IT TRACKING SLOWLY EASTWARD OVER THE NEXT 48 HOURS BEFORE TURNING SOUTHEASTWARD, NORTH OF NEW CALEDONIA. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 20 TO 25 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 997 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS MEDIUM.

GLOBAL MODELS ARE IN PARTIAL DISAGREEMENT ON THE TRACK OF 94P. GFS HAS 94P TRACKING SOUTHEASTWARD OVER THE NEXT 48 HOURS BEFORE TURNING SOUTHWARD TOWARD NEW CALEDONIA, WHILE ECMWF HAS IT TRACKING SLOWLY EASTWARD OVER THE NEXT 48 HOURS BEFORE TURNING SOUTHEASTWARD, NORTH OF NEW CALEDONIA.

Last Updated - 02/06/24 Valid - 02/14/24 - 02/27/24 Several modes of variability continue to influence the global tropics. The low frequency El Nino footprint remains established across the equatorial Pacific, along with an active Madden Julian Oscillation (MJO), which is now slowing down across the Western Pacific (Phase 7). Increased Rossby Wave activity has also been apparent through the outgoing longwave radiation (OLR) and 200-hPa velocity potential anomaly filtering throughout the tropics during the past several weeks. Dynamical models are generally incoherent in terms of the propagation of the MJO, with many individual GEFS and ECMWF ensemble members meandering the intraseasonal signal around the Date Line (phases 7 and 8). While some members ultimately weaken the MJO back into the RMM unit circle, others maintain a healthier propagation back toward Africa and the Indian Ocean. The degree of interaction with the El Nino footprint and the high frequency Rossby Wave activity will influence the behavior of the MJO during the next few weeks. During the past week, Tropical Depression Nine developed across the southern Indian Ocean (1/31) and Tropical Cyclone Nat formed over the South Pacific (2/5), with other disturbances being monitored across both these basins for additional tropical cyclone (TC) development in the next week. The persistence of increased convection and strong low level westerlies favored across the Date Line favors at least a 60 percent chance of TC development during week-2 and 40 percent chance during week-3. Further west toward the Coral Sea and Australia, there is a bit more uncertainty as the upper-level velocity potential fields indicate a more suppressed convective pattern. However, an MJO meandering in phases 7 and 8 favors increased chances for TC development to the north of Australia and in the Gulf of Carpentaria, and this is also supported by ECMWF ensemble, which depicts elevated probabilities for TC formation. Therefore, at least a 40 (20) percent chance of TC development is indicated across this region for week-2 (week-3). Across the southern Indian Ocean, there are increased signals for continued TC formation despite a less favorable convective pattern aloft. The competing modes of tropical variability are likely to induce a series of Kelvin or Rossby Waves propagating across the region which could promote TC development, with the large scale convective environment perhaps becoming more favorable by week-3 as enhanced convection returns to the Indian Ocean. As a result of these factors along with the seasonal climatology, at least a 40 percent chance of TC development is indicated over the southern Indian Ocean to the east of Madagascar for weeks 2 and 3.