TROPICAL DISTURBANCE ADVISORY NUMBER A1 ISSUED FROM RSMC NADI
Dec 250041 UTC.
TROPICAL DEPRESSION 03F CENTRE 1000HPA WAS LOCATED NEAR 08.2 SOUTH
176.0 EAST AT 250000 UTC. POSITION POOR BASED ON HIMAWARI VIS/IR AND
PERIPHERAL SURFACE REPORTS.
TD03F SLOW MOVING BUT IS EXPECTED TO DRIFT SLOWLY SOUTH LATER.
MAXIMUM 10-MINUTE AVERAGE WINDS UP TO 20 AROUND THE CENTER.
DEEP CONVECTION ASSOCIATED WITH A MOIST WESTERLY BURST PERSISTS TO
THE NORTH AND WEST OF THE SUPPOSED LLCC. OVERALL ORGANISATION HAS
IMPROVED AND OUTFLOW IS GOOD IN ALL CHANNELS. SYSTEM LIES UNDER AN
UPPER RIDGE IN A LOW SHEARED ENVIRONMENT WITH MODERATE UPPER
DIVERGENCE. CYCLONIC CIRCULATION EXTENDS UPTO 500HPA. SST IS AROUND
31 DEGREES CELCIUS.
GLOBAL MODELS ARE GRADUALLY DEVELOPING THE DEPRESSION AND MAINTAINING
A SOUTHWARDS TRACK. POTENTIAL FOR THE SYSTEM TO DEVELOPN INTO A
TROPICAL CYCLONE IN THE NEXT 24 HOURS IS HIGH.
THE NEXT TROPICAL DISTURBANCE ADVISORY ON TROPICAL DEPRESSION 03F
WILL BE ISSUED AT OR AROUND 250800UTC.
(1) THE AREA OF CONVECTION (INVEST 99P) PREVIOUSLY LOCATED
NEAR 5.5S 176.1E IS NOW LOCATED NEAR 6.8S 176.4E, APPROXIMATELY 887
NM WEST-NORTHWEST OF PAGO PAGO, AMERICAN SAMOA. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY DEPICTS A BROAD, ELONGATED LOW LEVEL
CIRCULATION CENTER (LLCC) OBSCURED BY POCKETS OF FLARING CONVECTION.
A 232034Z METOP-A PARTIAL ASCAT PASS SHOWED AN ELONGATED AREA OF
TROUGHING WITH 15-20 KT WINDS DISPLACED FROM THE CENTER. INVEST 99P
IS PASSING THROUGH A FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH LOW
(10-15 KTS) VERTICAL WIND SHEAR, VERY WARM (30-31C) SEA SURFACE
TEMPERATURES, AND POLEWARD OUTFLOW ALOFT. DYNAMIC MODELS GENERALLY
AGREE THAT THE SYSTEM WILL CONTINUE TO TRACK SOUTHWARD, CONSOLIDATE,
AND INTENSIFY OVER THE NEXT 24-48 HOURS, WITH NAVGEM PROVIDING A
SOUTH-SOUTHWESTWARD SOLUTION. MAXIMUM SUSTAINED SURFACE WINDS ARE
ESTIMATED AT 20 TO 25 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED
TO BE NEAR 1002 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A
SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO
MEDIUM.
TROPICAL DISTURBANCE 03F CENTER [1002HPA] WAS ANALYSED NEAR 07.5S
173.0E AT 232230UTC. POSITION POOR BASED ON HIMAWARI-8 VIS IMAGERY
AND PERIPHERAL SURFACE REPORTS. TD03F SLOW MOVING.
DEEP CONVECTION LIES TO THE NORTH AND EAST OF THE SUPPOSED LLCC WITH
POOR ORGANISATION. SYSTEM LIES UNDER AN UPPER RIDGE WITH GOOD OUTFLOW
IN A LOW SHEARED ENVIRONMENT. CYCLONIC CIRCULATION EXTENDS UPTO
700HPA. SST IS AROUND 31 DEGREES CELCIUS.
GLOBAL MODELS ARE PICKING UP THIS SYSTEM AND GRADUALLY MOVING IT
SOUTHWARDS WITH FURTHER DEEPENING AND INTENSIFYING TO A TROPICAL
CYCLONE.
POTENTIAL FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL CYCLONE IN THE
NEXT 24 HOURS IS LOW AND MODERATE TO HIGH IN THE NEXT 48 HOURS.
(1) AN AREA OF CONVECTION (INVEST 99P) HAS PERSISTED NEAR 5.5S
176.1E, APPROXIMATELY 824 NM NORTH-NORTHEAST OF PORT VILLA, VANUATU.
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A 231711Z SSMIS
91GHZ IMAGE DEPICT A BROAD, ELONGATED LOW LEVEL CIRCULATION WITH
FRAGMENTED CONVECTION ON THE PERIPHERY. 99P IS IN A MARGINALLY
FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH MODERATE (15-25 KNOTS)
VERTICAL WIND SHEAR, GOOD POLEWARD OUTFLOW, AND WARM (29-30C)
CELSIUS. GLOBAL MODELS ARE GENERALLY IN GOOD AGREEMENT THAT 99P WILL
CONTINUE STEADY DEVELOPMENT AS IT CONTINUES TO TRACK SOUTHEASTWARD.
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 10 TO 15 KNOTS.
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1003 MB. THE
POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE
WITHIN THE NEXT 24 HOURS IS LOW.
