TC 07A rapidly peaked// Invest 98S up-graded// Invest 98B// GTHO maps up to 3 weeks// 15/09utc

JTWC IS ISSUING 6HOURLY WARNINGS ON TC 07A. 3HOURLY SATELLITE BULLETINS ARE ISSUED ON 07A AND INVEST 98S.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: JTWC HAS CONDUCTED A REANALYSIS OF THE PREVIOUS INTENSITY ESTIMATES FOR TC 07A, RESULTING IN A SIGNIFICANT INCREASE IN THE INTENSITY IN THE PRIOR POSITIONS, WHICH IS CARRIED FORWARD TO THIS FORECAST. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN IRREGULAR CENTRAL DENSE OVERCAST (CDO) FEATURE, WHICH IS BEGINNING TO WEAKEN AND BECOME INCREASINGLY RAGGED. THE MOST RECENT MICROWAVE IMAGE FROM 150223Z SHOWED A TITLED VORTEX, WITH THE LOW LEVEL CIRCULATION CENTER (LLCC) POSITIONED SLIGHTLY WEST OF THE CYCLONICALLY CURVED CONVECTIVE MASS DUE TO MODERATE SOUTH-SOUTHWESTERLY SHEAR. EXTRAPOLATION OF THE LLCC IN THE MICROWAVE DATA AS WELL AS THE AMBIGUITY ANALYSIS FROM A 150446Z ASCAT-B PASS PROVIDED HIGH CONFIDENCE TO THE INITIAL POSITION. AS NOTED ABOVE, THE PREVIOUS INTENSITY ESTIMATES HAVE BEEN INCREASED AND CARRIED THROUGH THIS FORECAST, WITH THE INITIAL INTENSITY NOW SET AT 45 KNOTS, IN LINE WITH THE MULTI-AGENCY CURRENT INTENSITY (CI) ESTIMATES OF T3.0 (45 KNOTS) AND CONFIRMED BY THE ASCAT-B PASS, WHICH SHOWED 40 KNOT WIND BARBS IN THE NORTHERN HEMISPHERE OF THE SYSTEM, WHICH CONSIDERING THE LOW-BIAS INHERENT IN ASCAT DATA AT THIS SPEED, EASILY SUPPORTS A 45 KNOT INTENSITY. OF NOTE, DUE TO AN UPSTREAM OUTAGE, THERE ARE NO OBJECTIVE INTENSITY ESTIMATES AVAILABLE AT PRESENT. THE SYSTEM LIES IN A MARGINALLY FAVORABLE ENVIRONMENT, FOR NOW, WITH MODERATE (15-20 KNOTS) VWS, GOOD POLEWARD OUTFLOW AND WARM SSTS. DRY AIR IN THE 500MB-300MB LEVEL IS IMPINGING THE WESTERN PORTION OF THE CIRCULATION AND BEGINNING TO ERODE CONVECTION ON THAT SIDE OF THE SYSTEM.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE INITIAL INTENSITY HAS BEEN INCREASED BY 10 KNOTS AND THE FORECAST HAS BEEN LENGTHENED BY 12 HOURS. FORECAST DISCUSSION: AS MENTIONED ABOVE, THE INITIAL INTENSITY HAS BEEN SET AT 45 KNOTS, UP 10 KNOTS FROM THE 150000Z FORECAST. HOWEVER, THIS IS NOT REFLECTIVE OF AN INTENSIFICATION BUT RATHER AN ADJUSTMENT IN THE PEAK INTENSITY FROM 24 HOURS AGO. THE ADJUSTED INTENSITY TREND IS FLAT OVER THE PREVIOUS 12 HOURS. THE TRACK HAS SHIFTED TO A BIT MORE OF A NORTHWESTWARD TRAJECTORY OVER THE PAST SIX HOURS, AS THE SYSTEM IS A BIT STRONGER AND THUS BEING STEERED BY A DEEPER LAYER OF THE DEEP STR TO THE EAST, THE PERIPHERY OF WHICH IS ORIENTED A BIT MORE SOUTHEAST TO NORTHWEST. HENCE, THE SYSTEM IS FORECAST TO CONTINUE ON A GENERALLY WEST-NORTHWEST PATH FOR THE NEXT 12 HOURS. THE RIDGE IS ANTICIPATED TO BUILD IN TO THE WEST, TO THE NORTH OF TC 07A, WHICH WILL RESULT IN A MORE WESTWARD TRACK THROUGH TAU 24. THEN AS TC 07A WEAKENS, IT WILL TURN ONTO A MORE SOUTHWESTWARD TRACK THROUGH THE END OF THE FORECAST. THE SYSTEM HAS PEAKED IN INTENSITY SOME TIME AGO AND SHOULD NOW START TO WEAKEN, AS ALREADY SEEN IN THE RAPID EROSION OF THE CDO OVER THE PAST COUPLE OF HOURS. SHEAR IS EXPECTED TO INCREASE A BIT OVER THE NEXT 12 HOURS, BUT THE REAL KILLER WILL BE THE MASS OF DRY AIR CURRENTLY LURKING OUT TO THE WEST IN THE STRONG NORTHEASTERLY FLOW. ONCE THE TC BEGINS TO INTERACT WITH THIS DRY AIR OVER THE NEXT 12 HOURS, IT WILL QUICKLY BECOME SMOTHERED IN AN AIR MASS NON-CONDUCIVE TO TROPICAL CYCLONE DEVELOPMENT, AND RAPIDLY WEAKEN, WITH DISSIPATION BELOW WARNING CRITERIA EXPECTED NO LATER THAN TAU 36.

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN MODERATE AGREEMENT, WITH A LARGE SPREAD OF 175NM AT TAU 36, THOUGH ALL OF THE CONSENSUS GUIDANCE AGREES ON THE OVERALL SCENARIO. THE JTWC FORECAST LIES CLOSE TO THE GFS AND GFS ENSEMBLE MEAN TRACKS WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS ALSO MIXED, WITH THE BULK OF THE MEMBERS SHOWING RAPID WEAKENING COMMENCING AFTER TAU 06 AND REACHING 30 KNOTS OR LESS BY TAU 36. THE ONLY EXCEPTION BEING HWRF WHICH SHOWS A VERY SLOW WEAKENING TREND, HOLDING ONTO THE SYSTEM AS A MINIMAL TS UNTIL TAU 96. THE JTWC FORECAST HAS BEEN LENGTHENED BY 12 HOURS, AS A REFLECTION OF HIGHER INITIAL INTENSITY TAKING A BIT LONGER TO WEAKEN BELOW WARNING CRITERIA, BUT OTHERWISE REMAINS CONSISTENT WITH THE PREVIOUS FORECAST AND THE BULK OF THE GUIDANCE.

THE AREA OF CONVECTION (INVEST 98S) PREVIOUSLY LOCATED NEAR 9.6S 91.3E IS NOW LOCATED NEAR 9.6S 95.5E, APPROXIMATELY 168 NM NORTH- NORTHWEST OF COCOS ISLANDS, AUSTRALIA. MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH STRONGER WINDS NOW WRAPPING AROUND THE CIRCULATION THE SOUTHERN AND WESTERN SIDES OF THE CIRCULATION, AS SEEN IN A 150305Z ASCAT METOP-B PASS. ENVIRONMENTAL ANALYSIS INDICATES LOW VERTICAL WIND SHEAR (VWS) OFFSET BY GOOD DIVERGENCE ALOFT AND WARM (28-29C) SEA SURFACE TEMPERATURES (SST). GLOBAL MODELS ARE IN GOOD AGREEMENT THAT INVEST 98S WILL CONTINUE TO TRACK SLOWLY TO THE WEST AND GRADUALLY CONSOLIDATE AND INTENSIFY OVER THE NEXT 24-48 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 27 TO 30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1008 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO MEDIUM.

MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH STRONGER WINDS NOW WRAPPING AROUND THE CIRCULATION THE SOUTHERN AND WESTERN SIDES OF THE CIRCULATION, AS SEEN IN A 150305Z ASCAT METOP-B PASS.

GLOBAL MODELS ARE IN GOOD AGREEMENT THAT INVEST 98S WILL CONTINUE TO TRACK SLOWLY TO THE WEST AND GRADUALLY CONSOLIDATE AND INTENSIFY OVER THE NEXT 24-48 HOURS.

Last Updated - 12/13/22 Valid - 12/21/22 The global tropical convective pattern appears to be dominated by two distinct modes: the ongoing La Nina across the tropical Pacific, and an active Madden-Julian Oscillation (MJO) signal crossing the Indian Ocean. Enhanced convection has persisted across both the Northwest Pacific and South Pacific Convergence Zone (SPCZ) regions since early December, which is consistent with the enhanced Walker circulation driven by La Nina though these features have not been often observed previously with this particular event due to the extent of negative sea surface temperature anomalies west of the Date Line. MJO activity during November succeeded in generating a downwelling oceanic Kelvin wave, which is reducing the extent of available cold water that the trade winds can upwell near the Date Line. The enhanced West Pacific convection may also be contributing to a fairly weak presentation of the MJO on the RMM-based index, though the intraseasonal signal is still clearly apparent in the upper-level velocity potential anomaly field. Dynamical model MJO index forecasts are generally supportive of continued eastward propagation of the signal, with many ensemble members from both the GEFS and ECWMF depicting the MJO crossing the Maritime Continent and entering the West Pacific basin over the next few weeks. Substantial differences exist during Week-1, however, with the GEFS showing substantial westward retrogression and amplification over the Indian Ocean, likely tied to Rossby wave activity and potential tropical cyclone activity over the southern Indian Ocean. Based on these recent observations and model forecasts, the MJO is favored to continue influencing the global tropical convective pattern through the Weeks 2-3 period, and the signal may teleconnect into the downstream Northern Hemisphere midlatitude pattern. During the past week, Tropical Storm Mandous formed on December 7th east of Sri Lanka, making landfall just south of Chennai, India on December 10th. The remnants of TS Mandous may redevelop into a tropical cyclone over the Arabian Sea. Tropical Storm Pakhar formed east of the Philippines on December 10th, bringing enhanced rainfall without making landfall. During the next several weeks, influence from the MJO may cause the southern Indian Ocean to become increasingly active. Dynamical models favor several regions of development during Week-2: The Mozambique Channel, the south-central Indian Ocean, and later in the period, close to Australia's Kimberley Coast. The highest forecast confidence exists over the south-central Indian Ocean, with the GEFS favoring the western portion of the hazard region and the ECMWF favoring an area west of the Cocos Islands. The precipitation forecast for Weeks 2-3 is based on a consensus of dynamical model guidance, as well as an anticipation of continued influences from the MJO and La Nina. The MJO may constructively interfere with the La Nina response as its enhanced convective phase crosses the Maritime Continent, but during the Week 2-3 period, increasingly destructive interference between the two signals becomes more likely as the enhanced phase attempts to enter the West Pacific. This interference reduces confidence overall, but enhanced convection over the Northwest Pacific and SPCZ regions remains fairly likely, as it would be supported by both signals. Across the Western Hemisphere, a significant cold air outbreak is favored over the contiguous United States during Week-2, though there is uncertainty whether significant freezes will threaten the citrus growing regions of Florida, southern Texas, and northeastern Mexico. A baroclinic zone south of the cold airmass favors enhanced precipitation for the Gulf of Mexico, Florida Peninsula, and the northern Bahamas, while an enhanced Brazil monsoon is forecast for Week-2.