迪戈加西亚西南90S - 12.6S 67.2E

大水台6

90S INVEST 260201 0000 12.6S 67.2E SHEM 15 1009

Ragasa

AWIO20 FMEE 011051
TROPICAL CYCLONE CENTER / RSMC LA REUNION / METEO-FRANCE

BULLETIN FOR CYCLONIC ACTIVITY AND SIGNIFICANT TROPICAL WEATHER
IN THE SOUTHWEST INDIAN OCEAN

DATE: 2026/02/01 A 1200 UTC

PART 1: WARNING SUMMARY



Bulletins WTIO24 013/09 and WTIO30 014/09 issued at 06 UTC sur la Depression Tropicale FYTIA. Next bulletins issued at 12 UTC.

PART 2 : TROPICAL WEATHER DISCUSSION:

The basin has a mixed configuration with a monsoon trough (MT) between 55oE and 65oE oscillating between 10S and 5S, then continuing with a near-equatorial trough over the eastern part of the basin around 5oS. Convection is moderate over the southern part of this MT around 65oE in a large low-pressure area. Moderate to strong convection is also located near FYTIA between Reunion and Madagascar and over the northern Mozambique Channel. There is also an area of weak to moderate convective activity over the far east of the basin.

Over the next five days, a succession of Equatorial Rossby waves could enhance convective activity within the TM and bring vorticity precursors within the TM over the center and far east of the basin.

Moderate Tropical Storm FYTIA :
Information at 09 UTC :
Estimated position : 19.7S / 49.8E
Movement : ESE, 8 kt
Maximum wind speed (averaged over 10 minutes) : 35 kt
Estimated central pressure : 998 hPa
For further information, please refer to bulletins WTIO24 and WTIO30 issued at 06 UTC and following.

In the center of the basin southwest of the Chagos Archipelago :
In connection with the large low-pressure area currently located around 65oE, a low-pressure system could form southwest of the Chagos Islands early next week in connection with the passage of an equatorial Rossby wave over the center of the basin. This circulation should encounter environmental conditions favorable to its development, with good surface convergence on the equatorial side, low vertical wind shear, and good divergence at altitude on the polar side of the circulation, linked to an upper-level trough circulating off the southeast of the system. In addition, the different ensemble numerical models and AI ensemble forecast models are in good agreement and forecast the development of this low-pressure system by the middle of next week.
Subsequently, the dispersion in the track forecasts for this system between the different models is too great to define the regions that will be impacted at such distant time ranges.

The risk of a moderate tropical storm forming becomes moderate from Wednesday, February 4 in the southwest of the Chagos Archipelago.

Over the far eastern part of the basin:
A low-pressure system could form over the far east of the basin over the next few days in connection with the passage of a second equatorial Rossby wave. Strong vertical wind shear and weak low-level convergence are expected to limit its development at the beginning of the week, but these conditions are likely to improve slightly by midweek. As a result, few members of the European (EPS) and American (GFS) ensemble forecast models and AI suggest that this circulation will develop from Wednesday onwards.

The likelihood of the formation of a moderate tropical storm becomes very low from wednesday february 4th.





NOTA BENE: The likelihood is an estimate of the chance of genesis of a moderate tropical storm over the basin within the next five days:

Very low: less than 10%      Moderate: 30% to 60%      Very high: over 90%
Low: 10% to 30%              High: 60% to 90%

The Southwestern Indian ocean basin extends from the Equator to 40S and from the african coastlines to 90E.

红豆棒冰冰

JTWC 21Z分析T1.0

TPXS12 PGTW 012105
A. TROPICAL DISTURBANCE 90S (SW OF DIEGO GARCIA)
B. 01/2030Z
C. 12.15S
D. 66.01E
E. FIVE/MET9
F. T1.0/1.0/INIT OBS
G. IR/EIR
H. REMARKS: 71A/PBO XTRP/ANMTN. CNVCTN WRAPS .3 ON LOG10 SPIRAL
YIELDING A DT OF 1.0. MET AND PT AGREE. DBO DT.
I. ADDITIONAL POSITIONS: NONE
   BRYANT

红豆棒冰冰

JTWC 00Z分析维持T1.0

TPXS12 PGTW 012355
A. TROPICAL DISTURBANCE 90S (SW OF DIEGO GARCIA)
B. 01/2330Z
C. 12.07S
D. 65.63E
E. FIVE/MET9
F. T1.0/1.0  STT: S0.0/03HRS
G. IR/EIR
H. REMARKS: 71A/PBO XTRP/ANMTN. CNVCTN WRAPS .3 ON LOG10 SPIRAL
YIELDING A DT OF 1.0. MET AND PT AGREE. DBO DT.
I. ADDITIONAL POSITIONS: NONE
   BRYANT

红豆棒冰冰

JTWC 03Z分析维持T1.0

TPXS12 PGTW 020318
A. TROPICAL DISTURBANCE 90S (SW OF DIEGO GARCIA)
B. 02/0230Z
C. 12.32S
D. 65.38E
E. FIVE/MET9
F. T1.0/1.0  STT: S0.0/03HRS
G. IR/EIR
H. REMARKS: 71A/PBO XTRP/ANMTN. LOOSELY DEFINED CLOUD LINES WITH
OVERCAST LESS THAN 90NM ACROSS YIELD A DT OF 1.0. BOTH MET AND PT
YIELD 1.0. DBO DT.
I. ADDITIONAL POSITIONS: NONE
   LINDGREN

红豆棒冰冰

JTWC 06Z分析维持T1.0

TPXS12 PGTW 020616
A. TROPICAL DISTURBANCE 90S (SW OF DIEGO GARCIA)
B. 02/0530Z
C. 11.40S
D. 66.24E
E. FIVE/MET9
F. T1.0/1.0  STT: S0.0/03HRS
G. IR/EIR/VIS/MSI
H. REMARKS: 40A/PBO SBC/ANMTN. LOOSELY DEFINED CLOUD LINES WITH
OVERCAST LESS THAN 90NM ACROSS YIELD A DT OF 1.0. BOTH MET AND PT
YIELD 1.0. DBO DT.
I. ADDITIONAL POSITIONS: NONE
   LINDGREN

红豆棒冰冰

JTWC 09Z分析无法找到中心

TPXS12 PGTW 020906
A. TROPICAL DISTURBANCE 90S (SW OF DIEGO GARCIA)
B. 02/0830Z
C. XX.XX
D. XXX.XX
E. N/A/MET9
F. N/A
G. IR/EIR/VIS/MSI
H. REMARKS: POSITION OF LOW LEVEL CIRCULATION CENTER COULD NOT BE
FOUND.
I. ADDITIONAL POSITIONS: NONE
   LINDGREN