Southern Hemisphere: more active: CAT 2 US TC 08S(FREDDY)//TC 12P(GABRIELLE) intensifying//Invest 94S//3 week GTHO maps//0803utc

JTWC IS ISSUING 6HOURLY WARNINGS ON TC 11S(FREDDY) AND TC 12P(GABRIELLE). 3HOURLY SATELLITE BULLETINS ARE ISSUED ON TC 11S, TC 12P AND INVEST 94S.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS A DEEP COMPACT SYSTEM THAT HAS SLIGHTLY WEAKENED AS EVIDENCED BY WARMING CLOUD TOPS IN THE CENTRAL DENSE OVERCAST. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A DIMPLED EYE IN THE 072330Z VISIBLE SATELLITE IMAGERY, ADJUSTED FOR TILT AND LINED UP WITH A MICROWAVE EYE IN THE 072232Z SSMIS 91GHZ IMAGE. THE INITIAL INTENSITY IS ALSO ASSESSED WITH HIGH CONFIDENCE BASED ON CLOSELY CLUSTERED AGENCY AND AUTOMATED DVORAK ESTIMATES AND REFLECTS THE SLIGHT 6-HR WEAKENING. THE ENVIRONMENT HAS BECOME MARGINAL WITH WARM SSTS AND MODERATE RADIAL OUTFLOW ALOFT OFFSET BY INCREASING VWS.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC FREDDY WILL CONTINUE ON ITS CURRENT WEST-SOUTHWESTWARD TRACK OVER THE NEXT 24 HOURS; AFTERWARD, IT WILL LEVEL OFF ON A MORE WESTWARD TRAJECTORY AS THE STEERING STR BUILDS AND EXTENDS WESTWARD. THE MARGINAL ENVIRONMENT, COMPOUNDED BY THE INFLUX OF DRY AIR IN THE MID-LEVELS WILL GRADUALLY WEAKEN THE SYSTEM DOWN TO 75KTS BY TAU 36. AFTERWARD, VWS WILL ONCE AGAIN RELAX AND PROMOTE A SECONDARY, ALBEIT SHORT-LIVED INTENSIFICATION TO 90KTS BY TAU 72 BEFORE REVERTING TO THE WEAKENING TREND AS VWS ONCE AGAIN PICKS UP, REDUCING TC 11S TO 85KTS BY TAU 120.

MODEL DISCUSSION: NUMERICAL TRACK MODELS ARE IN TIGHT AGREEMENT WITH A GRADUAL SPREADING TO 195NM BY TAU 120 WITH NAVGEM THE SOLE LEFT-OF-TRACK OUTLIER. UP TO TAU 72, THERE IS HIGH CONFIDENCE IN THE JTWC TRACK FORECAST THAT IS LAID JUST TO THE RIGHT OF CONSENSUS TO OFFSET NAVGEM. AFTER TAU 72, THE TRACK CONFIDENCE IS MEDIUM AS THE SPREAD WIDENS. THE INTENSITY FORECAST IS MEDIUM UP TO TAU 72 THEN LOW AFTERWARD DUE TO THE UNCERTAINTY IN THE FORECAST INTENSITY DYNAMICS IN THE EXTENDED PERIOD.

THE ENVIRONMENT HAS BECOME MARGINAL WITH WARM SSTS AND MODERATE RADIAL OUTFLOW ALOFT OFFSET BY INCREASING VERTICAL WIND SHEAR.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A BROAD CONSOLIDATING SYSTEM WITH FRAGMENTED FORMATIVE BANDS TRAILING FROM THE NORTHWEST THROUGH EAST AND A PARTLY EXPOSED LOW LEVEL CIRCULATION (LLC). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE LLC FEATURE IN THE MSI LOOP. THE INITIAL INTENSITY IS ALSO PLACED WITH HIGH CONFIDENCE BASED ON CLOSELY-CLUSTERED DVORAK FIXES FROM PGTW, ABRF AND KNES. ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH WARM SSTS, LOW VWS AND STRONG EQUATORWARD OUTFLOW ALOFT.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY. FORECAST DISCUSSION: TC 12P WILL SHORTLY TRACK POLEWARD THEN SOUTHEASTWARD TOWARD NEW ZEALAND AS IT ROUNDS THE STR AXIS. THE FAVORABLE ENVIRONMENT, ENHANCED BY INCREASING POLEWARD OUTFLOW AS THE TC TAPS INTO THE PREVAILING WESTERLIES ON THE POLEWARD SIDE OF THE STR AXIS, WILL FUEL A SIGNIFICANT INTENSIFICATION TO A PEAK OF 75KTS, POSSIBLY HIGHER, BY TAU 48. AFTERWARD, INCREASING VWS AND COOLING SST WILL GRADUALLY THEN RAPIDLY ERODE THE SYSTEM DOWN TO 50KTS BY TAU 120. CONCURRENTLY BY TAU 96, TC 12P WILL BEGIN SUBTROPICAL TRANSITION AND BY TAU 120, WILL CONVERT INTO A SUBTROPICAL SYSTEM WITH AN EXPANSIVE WIND FIELD.

MODEL DISCUSSION: NUMERICAL TRACK MODELS ARE IN TIGHT AGREEMENT, CONSIDERING THIS IS THE INITIAL WARNING, WITH A GRADUAL SPREADING TO 350NM BY TAU 120 WITH NAVGEM THE SOLE RIGHT-OF-TRACK OUTLIER. UP TO TAU 72, THERE IS HIGH CONFIDENCE IN THE JTWC TRACK FORECAST THAT IS LAID JUST TO THE LEFT OF CONSENSUS TO OFFSET NAVGEM. AFTER TAU 72, THE TRACK CONFIDENCE IS MEDIUM AS THE SPREAD WIDENS. THE INTENSITY FORECAST IS MEDIUM UP TO TAU 72 THEN LOW AFTERWARD DUE TO THE UNCERTAINTY IN THE FORECAST INTENSITY DYNAMICS IN THE EXTENDED PERIOD.

THE AREA OF CONVECTION (INVEST 94S) PREVIOUSLY LOCATED NEAR 13.3S 99.2E IS NOW LOCATED NEAR 14.2S 97.3E, APPROXIMATELY 122 NM SOUTH OF COCOS ISLAND. ENHANCED INFRARED SATELLITE IMAGERY (EIR) AND AN 071520 PARTIAL ASCAT METOP-B PASS SHOWS A LOW LEVEL CIRCULATION CENTER (LLCC) WITH 25KT WINDS IN THE SOUTHERN QUADRANT OF THE REGION ASSOCIATED WITH DEEP CONVECTION. A 061700Z OBSERVATION FROM COCOS ISLANDS REVEALS WINDS OF 21 KTS FROM THE WEST-NORTHWEST AND A MSLP OF 1005MB. ENVIRONMENTAL CONDITIONS ARE MARGINALLY FAVORABLE DEFINED BY DECENT POLEWARD AND EQUATORWARD OUTFLOW AND WARM (29-30C) SST'S OFFSET BY HIGH (25-30 KTS) VERTICAL WIND SHEAR. GLOBAL MODELS PREDICT INVEST 94S WILL TAKE LONGER THAN 48 HOURS TO CONSOLIDATE AND INTENSIFY AS IT TRACKS SOUTHWESTWARD. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 20 TO 25 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1001 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS LOW.

GLOBAL MODELS PREDICT INVEST 94S WILL TAKE LONGER THAN 48 HOURS TO CONSOLIDATE AND INTENSIFY AS IT TRACKS SOUTHWESTWARD.

Last Updated - 02/07/23 Valid - 02/15/23 - 02/28/23 A coherent Madden Julian Oscillation (MJO) signal has existed throughout January and early February. During the past week, the RMM-based MJO index indicated a slowing of the eastward propagation of the intraseasonal signal across the Indian Ocean due to increased equatorial Rossby Wave activity. This has also resulted in constructive interference with the background La Nina state, and a subsequent reemergence of a pattern typical of La Nina across the extratropics. The GEFS and ECMWF ensembles predict that the MJO will quickly resume its eastward propagation during the next week, possibly reaching the Western Pacific by week-2. Beyond week-2, model ensembles generally depict the MJO continuing to propagate into the Western Hemisphere, where it could help drive a pattern change across the U.S. during late February and early March, possibly bringing relatively cooler conditions to the eastern half of the country. The MJO centered over the eastern Indian Ocean and associated enhanced convective envelope over much of the eastern Hemisphere has led to a more favorable environment for tropical cyclone (TC) development. Cyclone Freddy formed on 2/6 to the northwest of Australia, and is expected to track west to west-southwestward posing no threat to land. Two other disturbances are being monitored for potential development, 94S over the southeastern Indian Ocean, and 99P over the Coral Sea. In addition to being climatologically active, favorable conditions for TC development are forecast to persist into week-2 along the Kimberley Coast of northwestern Australia and extending into the Gulf of Carpentaria. This supports a 40 percent chance of TC formation during the period. A 20 percent chance of TC formation is noted near the Phillipines and to the east. Although not as climatologically active, the MJO shifting into the Western Pacific may aid in TC development in that region as indicated in the GEFS and CFS ensembles. There are also some increased signals in the dynamical models for TC development across the southwestern Indian Ocean. However, given that the suppressed phase of the MJO is forecast to reach the Indian Ocean by this period, no risk area is highlighted in today’s forecast. The precipitation outlook for weeks 2 and 3 are based on a historical skill weighted blend of the GEFS, CFS, ECCC, and ECMWF models, MJO precipitation composites for phases 5 through 8, and considerations on the ongoing La Nina background state. The quick MJO propagation across the Pacific favors areas of above-average rainfall over parts of the western Pacific and northern Australia, the central equatorial Pacific north of the equator (including parts of Hawaii), and over parts of the Americas. Drier than average conditions are forecast over the Indian Ocean due to the suppressed phase of the MJO, and across the south-central equatorial Pacific due to La Nina.