WTIO30 FMEE 201221
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)
0.A WARNING NUMBER: 2/15/20242025
1.A SUBTROPICAL STORM 15 (KANTO)
2.A POSITION 2025/04/20 AT 1200 UTC:
WITHIN 20 NM RADIUS OF POINT 33.3 S / 43.9 E
(THIRTY THREE DECIMAL THREE DEGREES SOUTH AND
FORTY THREE DECIMAL NINE DEGREES EAST)
MOVEMENT: EAST-SOUTH-EAST 4 KT
3.A DVORAK ANALYSIS: NIL
4.A CENTRAL PRESSURE: 993 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 40 KT
RADIUS OF MAXIMUM WINDS (RMW): NIL
6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 215 SE: 185 SW: 280 NW: 250
34 KT NE: 150 SE: 0 SW: 0 NW: 175
7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1011 HPA / 900 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: MEDIUM
1.B FORECASTS (WINDS RADII IN KM):
12H: 2025/04/21 00 UTC: 33.9 S / 46.4 E, VENT MAX= 030 KT,
SUBTROPICAL DEPRESSION
28 KT NE: 240 SE: 165 SW: 0 NW: 240
24H: 2025/04/21 12 UTC: 34.6 S / 50.0 E, VENT MAX= 030 KT,
EXTRATROPICAL DEPRESSION
28 KT NE: 240 SE: 0 SW: 0 NW: 220
36H: 2025/04/22 00 UTC: 35.8 S / 55.1 E, VENT MAX= 025 KT,
EXTRATROPICAL DEPRESSION
2.B LONGER-RANGE OUTLOOK:
NIL
2.C ADDITIONAL INFORMATION:
SOME NEW OBJECTIVE DATA INPUT ON SYSTEM 15-20242025 HAS BEEN
AVAILABLE SHORTLY AFTER THE 06Z ANALYSIS, SHOWING THE PRESENCE OF
GALE-FORCE WINDS LAST NIGHT AND THIS SUNDAY MORNING : A 0347Z SMOS
PASS MEASURED WINDS OF 40/45 KT UNDER THE CONVECTIVE BAND CURVING
WEST OF THE CENTER, AND A 0653Z ASCAT-C PASS MEASURED WINDS OF 35/40
KT. THIS INTENSITY INFORMATION, COMBINED WITH THE CURVED BAND
CONVECTIVE PATTERN OBSERVED THIS MORNING, JUSTIFIES THE SYSTEM'S
CLASSIFICATION AS A SUBTROPICAL STORM, NAMED "KANTO" AT 10Z BY
MADAGASCAR METEOROLOGICAL SERVICE. THE BEST-TRACK HAS ALSO BEEN
REVISED AFTERHAND, UPGRADING THE 06Z INTENSITY TO SUBTROPICAL STORM
STATUS WITH WINDS OF 40 KT.
OVER THE LAST 6 HOURS, CONVECTION HAS SOMEWHAT WEAKENED, WITH CLOUD
TOPS WARMING TO -35/-40C, PROBABLY DUE TO A LACK OF INSTABILITY AND
ENVIRONMENTAL DRY AIR WRAPPING WITHIN THE CIRCULATION. ON THE OTHER
HAND, THE CLOUD STRUCTURE HAS BECOME MORE SYMMETRICAL, WITH A
PERFECTLY DEFINED VORTEX, TESTIFYING OF A SYMMETRICAL WARM CORE
EXTENDING UP INTO THE MID-LEVELS. BY INERTIA, THE SYSTEM IS LEFT AT
SUBTROPICAL STORM STAGE, WITH MAXIMUM WINDS STILL ESTIMATED AT 40 KT
IN THE CIRCULATION'S NORTHERN SEMI-CIRCLE.
IN TERMS OF TRACK FORECAST, THE LLCC'S MOVEMENT HAS TEMPORARILY
SLOWED DOWN OVER THE DAY, DRAWING A SMALL LOOP BELOW THE UPPER
TROUGH. IT SHOULD RESUME A MORE RAPID EAST-SOUTHEASTWARD MOVEMENT
FROM TONIGHT AND MONDAY ONWARDS, DRIVEN BY AN INCREASING
WEST-NORTH-WESTERLY STEERING FLOW BETWEEN A MID-LATITUDE TROUGH TO
THE SOUTH-WEST AND A RIDGE TO THE NORTH.
IN TERMS OF INTENSITY AND CONVECTIVE STRUCTURE, THE SYSTEM HAS BEEN
BENEFITING SINCE EARLY MORNING OF A NARROW WINDOW FAVORING ITS
SUBTROPICALIZATION BELOW THE UPPER TROUGH, IN A RATHER LOW-SHEARED
ENVIRONMENT AND SST NEAR 22C. THIS WINDOW IS EXPECTED TO CLOSE FROM
TONIGHT AND ESPECIALLY ON MONDAY, DUE TO INCREASING WESTERLY SHEAR,
REINFORCING DRY AIR INTRUSIONS AND MAKING THE ENVIRONMENT
INCREASINGLY BAROCLINIC, AS WELL AS DECREASING OCEAN HEAT CONTENT
(SST NEAR 20C ON MONDAY). CONSEQUENTLY, SUBTROPICAL STORM STAGE
SHOULD NOT LAST VERY LONG FROM NOW ON, POSSIBLY UNTIL 18Z. ON MONDAY,
THE SYSTEM IS FORECAST TO BECOME EXTRATROPICAL AGAIN, WHILE FILLING
IN BY TUESDAY.
THIS SYSTEM DOES NOT HAVE ANY IMPACT ON INHABITED TERRITORIES.
RSMC / TROPICAL CYCLONE CENTER / LA REUNION
TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN)
0.A WARNING NUMBER: 2/15/20242025
1.A SUBTROPICAL STORM 15 (KANTO)
2.A POSITION 2025/04/20 AT 1200 UTC:
WITHIN 20 NM RADIUS OF POINT 33.3 S / 43.9 E
(THIRTY THREE DECIMAL THREE DEGREES SOUTH AND
FORTY THREE DECIMAL NINE DEGREES EAST)
MOVEMENT: EAST-SOUTH-EAST 4 KT
3.A DVORAK ANALYSIS: NIL
4.A CENTRAL PRESSURE: 993 HPA
5.A MAX AVERAGE WIND SPEED (10 MN): 40 KT
RADIUS OF MAXIMUM WINDS (RMW): NIL
6.A EXTENSION OF WIND BY QUADRANTS (KM):
28 KT NE: 215 SE: 185 SW: 280 NW: 250
34 KT NE: 150 SE: 0 SW: 0 NW: 175
7.A FIRST CLOSED ISOBAR (PRESSURE / AVERAGE DIAM): 1011 HPA / 900 KM
8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: MEDIUM
1.B FORECASTS (WINDS RADII IN KM):
12H: 2025/04/21 00 UTC: 33.9 S / 46.4 E, VENT MAX= 030 KT,
SUBTROPICAL DEPRESSION
28 KT NE: 240 SE: 165 SW: 0 NW: 240
24H: 2025/04/21 12 UTC: 34.6 S / 50.0 E, VENT MAX= 030 KT,
EXTRATROPICAL DEPRESSION
28 KT NE: 240 SE: 0 SW: 0 NW: 220
36H: 2025/04/22 00 UTC: 35.8 S / 55.1 E, VENT MAX= 025 KT,
EXTRATROPICAL DEPRESSION
2.B LONGER-RANGE OUTLOOK:
NIL
2.C ADDITIONAL INFORMATION:
SOME NEW OBJECTIVE DATA INPUT ON SYSTEM 15-20242025 HAS BEEN
AVAILABLE SHORTLY AFTER THE 06Z ANALYSIS, SHOWING THE PRESENCE OF
GALE-FORCE WINDS LAST NIGHT AND THIS SUNDAY MORNING : A 0347Z SMOS
PASS MEASURED WINDS OF 40/45 KT UNDER THE CONVECTIVE BAND CURVING
WEST OF THE CENTER, AND A 0653Z ASCAT-C PASS MEASURED WINDS OF 35/40
KT. THIS INTENSITY INFORMATION, COMBINED WITH THE CURVED BAND
CONVECTIVE PATTERN OBSERVED THIS MORNING, JUSTIFIES THE SYSTEM'S
CLASSIFICATION AS A SUBTROPICAL STORM, NAMED "KANTO" AT 10Z BY
MADAGASCAR METEOROLOGICAL SERVICE. THE BEST-TRACK HAS ALSO BEEN
REVISED AFTERHAND, UPGRADING THE 06Z INTENSITY TO SUBTROPICAL STORM
STATUS WITH WINDS OF 40 KT.
OVER THE LAST 6 HOURS, CONVECTION HAS SOMEWHAT WEAKENED, WITH CLOUD
TOPS WARMING TO -35/-40C, PROBABLY DUE TO A LACK OF INSTABILITY AND
ENVIRONMENTAL DRY AIR WRAPPING WITHIN THE CIRCULATION. ON THE OTHER
HAND, THE CLOUD STRUCTURE HAS BECOME MORE SYMMETRICAL, WITH A
PERFECTLY DEFINED VORTEX, TESTIFYING OF A SYMMETRICAL WARM CORE
EXTENDING UP INTO THE MID-LEVELS. BY INERTIA, THE SYSTEM IS LEFT AT
SUBTROPICAL STORM STAGE, WITH MAXIMUM WINDS STILL ESTIMATED AT 40 KT
IN THE CIRCULATION'S NORTHERN SEMI-CIRCLE.
IN TERMS OF TRACK FORECAST, THE LLCC'S MOVEMENT HAS TEMPORARILY
SLOWED DOWN OVER THE DAY, DRAWING A SMALL LOOP BELOW THE UPPER
TROUGH. IT SHOULD RESUME A MORE RAPID EAST-SOUTHEASTWARD MOVEMENT
FROM TONIGHT AND MONDAY ONWARDS, DRIVEN BY AN INCREASING
WEST-NORTH-WESTERLY STEERING FLOW BETWEEN A MID-LATITUDE TROUGH TO
THE SOUTH-WEST AND A RIDGE TO THE NORTH.
IN TERMS OF INTENSITY AND CONVECTIVE STRUCTURE, THE SYSTEM HAS BEEN
BENEFITING SINCE EARLY MORNING OF A NARROW WINDOW FAVORING ITS
SUBTROPICALIZATION BELOW THE UPPER TROUGH, IN A RATHER LOW-SHEARED
ENVIRONMENT AND SST NEAR 22C. THIS WINDOW IS EXPECTED TO CLOSE FROM
TONIGHT AND ESPECIALLY ON MONDAY, DUE TO INCREASING WESTERLY SHEAR,
REINFORCING DRY AIR INTRUSIONS AND MAKING THE ENVIRONMENT
INCREASINGLY BAROCLINIC, AS WELL AS DECREASING OCEAN HEAT CONTENT
(SST NEAR 20C ON MONDAY). CONSEQUENTLY, SUBTROPICAL STORM STAGE
SHOULD NOT LAST VERY LONG FROM NOW ON, POSSIBLY UNTIL 18Z. ON MONDAY,
THE SYSTEM IS FORECAST TO BECOME EXTRATROPICAL AGAIN, WHILE FILLING
IN BY TUESDAY.
THIS SYSTEM DOES NOT HAVE ANY IMPACT ON INHABITED TERRITORIES.