SIO: FINA - Post-Tropical

[Subtrop]

97S INVEST 251113 1800 10.0S 114.0E SHEM 15 0

[StormWeather]

97S INVEST 251113 1800 10.0S 114.0E SHEM 15 0

This one is likely Tropical Low 02U from the Australian Region

[StormWeather]

TCFA from the JTWC on this

WTXS21 PGTW 171330
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 97S)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
120 NM EITHER SIDE OF A LINE FROM 10.9S 129.5E TO 8.6S 133.1E
WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 28 TO 33 KNOTS. METSAT
IMAGERY AT 171200Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 10.7S 129.7E. THE SYSTEM IS MOVING EAST-NORTHEASTWARD AT 07
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 97S) PREVIOUSLY LOCATED
NEAR 10.9S 129.0E IS NOW LOCATED NEAR 10.7S 129.7E, APPROXIMATELY 131
NM NORTH-NORTHWEST OF DARWIN. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY (EIR) AND A 170907Z SSMIS 91 GHZ MICROWAVE IMAGE DEPICT A
COMPACT LOW LEVEL CIRCULATION CENTER (LLCC) WITH POCKETS OF DEEP
CONVECTION BUILDING OVER THE CENTER. ENVIRONMENTAL ANALYSIS REVEALS
FAVORABLE CONDITIONS FOR DEVELOPMENT WITH LOW VERTICAL WIND SHEAR (10-
15 KNOTS), STRONG POLEWARD OUTFLOW ALOFT, AND VERY WARM SEA SURFACE
TEMPERATURES (30-31 C). GLOBAL MODELS ARE IN FAIR AGREEMENT THAT
INVEST 97S WILL CONTINUE TO DEVELOP WITH A SLOW EAST-NORTHEASTWARD
TRACK OVER THE NEXT 24 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE
ESTIMATED AT 28 TO 33 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 UPGRADED TO HIGH.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY
181330Z.//
NNNN

[cycloneye]

 https://x.com/VortixWx/status/1990436036401348971

[wxman57]

ASCAT pass around 00Z last evening indicates a tight circulation beneath the convection. We are calling it a TD on our advisories.

[cycloneye]

 https://x.com/BOM_au/status/1990605389088296961

[mrbagyo]

look at that cute little eye feature.

I wonder if Hector the Convector will show up before sundown to boost the CDO building process.

[cycloneye]

[cycloneye]

Remarks

Tropical Low 02U has been slowly strengthening, and is showing tighter curvature near the low level centre, improving the confidence in the low level centre position. Position was based on ASCAT passes and animated Vis and IR imagery. Dvorak pattern is a curved base of 0.5, with a DT of 2.5 +/- 0.5. A D- 24 hour trend gives a MET of 2.0, and there is no adjustment to PAT. This gives FT/CI of 2.0. Intensity set to 30 knots based on a past scatterometry pass. CIMMS is analysing 15 to 20 knots of easterly shear, which may improve over the next 24 to 48 hours and during the remainder of the week, aiding in development. However from Friday moderate northerly shear may affect the system and it may stall or weaken in intensity north of the Top End coast. TPW indicates deep moisture right near the centre. Models indicate the chance of dry air wrapping to the north but if shear remains low to moderate, the system is likely to remain pouched in moist air. Upper divergence is good but not enhanced by nearby features like an upper trough to the south. There is little in the way of external forcing. Therefore, strengthening is expected but there is some uncertainty as to how much. With there being little environmental vorticity, it is expected to be a small system which could strengthen, and weaken, quickly. Forecast peak intensity is 60 knots (category 2), and there is a chance it reaches category 3. Consensus of NWP model tracks has the system moving slowly towards the NE before recurving around to the south and then taking a SE track back towards the northern coastline of the NT.

The next bulletin for this system will be issued by: 18/1330 Coordinated Universal Time.The next bulletin for th

[cycloneye]

Remarks

Tropical Low 02U has been slowly strengthening, and is showing tighter curvature near the low level centre, improving the confidence in the low level centre position. Position was based on ASCAT passes and animated Vis and IR imagery. Dvorak pattern is a curved base of 0.5, with a DT of 2.5 +/- 0.5. A D- 24 hour trend gives a MET of 2.0, and there is no adjustment to PAT. This gives FT/CI of 2.0. Intensity set to 30 knots based on a past scatterometry pass. CIMMS is analysing 15 to 20 knots of easterly shear, which may improve over the next 24 to 48 hours and during the remainder of the week, aiding in development. However from Friday moderate northerly shear may affect the system and it may stall or weaken in intensity north of the Top End coast. TPW indicates deep moisture right near the centre. Models indicate the chance of dry air wrapping to the north but if shear remains low to moderate, the system is likely to remain pouched in moist air. Upper divergence is good but not enhanced by nearby features like an upper trough to the south. There is little in the way of external forcing. Therefore, strengthening is expected but there is some uncertainty as to how much. With there being little environmental vorticity, it is expected to be a small system which could strengthen, and weaken, quickly. Forecast peak intensity is 60 knots (category 2), and there is a chance it reaches category 3. Consensus of NWP model tracks has the system moving slowly towards the NE before recurving around to the south and then taking a SE track back towards the northern coastline of the NT.

[sasha_B]

The JTWC has this at 40 kt (1-min sustained) and 995 hPa as of 12z. The 1430z satellite bulletin from JTWC (3.0/3.0), if I'm calculating CKZ correctly, could justify something closer to 45 kt / 991 hPa. But the most recent partial ASCAT hit doesn't really support 45 kts, so 40/995 seems fine for now. The point is that the storm seems to have steadily improved since yesterday and a forecast of continued intensification seems appropriate.

[cycloneye]

Remarks

Tropical Low 02U has developed in the past six hours with stronger deep convection near the centre and stronger curved banding evident on earlier microwave imagery (GMI 0647UTC; SSMIS 0742 and 1002UTC). Position based on microwave and animated EIR imagery. Intensity 35kn with gales estimated north of centre. Dvorak: FT/CI=2.5. DT=2.5-3.0 - earlier vis imagery suggested 0.7 curved band wrap but more recent EIR banding difficult. D trend over 24h gives a MET of 2.5, no PAT adjustment. Objective guidance recently commenced: SATCON N/A; ADT: CI=3.0 45kn; AiDT: 34kn; DMINT: 39kn; DPRINT: 42kn (all 1-min means). The tropical low is a small circulation and gales are only estimated to extend 50nm to the north. Broadscale influences are generally favourable for development: High SSTs 30-31C; wind shear has eased somewhat to 10-15kn northeasterly; upper outflow is strong; abundant low-midlevel moisture (TPW) which would suggest intensification is supported in the short term. This being a small system it may fluctuate in intensity and be quick to intensify but also weaken quickly too. The intensity is capped at 60kn (category 2) as there is uncertainty in the role of potentially increasing northerly shear from Friday with some dry air impacts to weaken the system prior to any impact of the Top End coast. Should the shear remain low to moderate, the system may remain pouched in moist air. Given these uncertainties, there remains a chance it reaches category 3. Consensus of NWP model tracks has the system moving slowly towards the NE for next 36 h before recurving around to the south later Thursday and then taking a southwest track back towards the northern coastline of the NT.

[sasha_B]

Now named "Fina" by the Australian Bureau of Meteorology, making this November 2025's second named storm (after Fung-Wong).

05S FINA 251118 1800 9.8S 131.8E SHEM 45 993

H. REMARKS: 46A/PBO EMBD CNTR/ANMTN. CNVCTN WRAPS .70 ON LOG10
SPIRAL YIELDING A DT OF 3.0. MET YIELDS 3.5. PT YIELDS 3.5. DBO DT.

CKZ gives 991.6～993.6 hPa for a 45 kt TS moving at 6 kt from 9.8S with gales extending 22.5 nm from the center (depending on whether you set environmental pressure to 1004 or 1006 hPa).

[cycloneye]

Remarks

Tropical Low 02U has intensified to become Tropical Cyclone Fina. It is being analysed as a small system with gale radii less than 60 nautical miles. Position is based on animated IR imagery. Intensity 40 knots. Dvorak: FT/CI = 3.0 based on MET. DT was difficult to assign as there is no clear banding and it is too early to use EMBD centre pattern. A shear analysis would give DT of at least 3.0. Final intensity estimate is weighted to recent objective guidance (1-min winds): SATCON 47 knots, ADT 53 knots, AiDT 42 knots, DPRINT 47 knots DMINT 45 knots. Fina is a small system and gales are estimated to only extend 50nm from the centre. Broadscale influences are generally favourable for development: High SSTs 30-31C; wind shear is 10-15kn from the northeast (12Z CIMSS analysis); upper outflow is strong; abundant low-midlevel moisture (TPW) which would suggest intensification is supported in the short term. Being a small system, Fina may fluctuate in intensity and be quick to intensify but also weaken quickly too. The intensity is capped at 60kn (category 2) as there is uncertainty in the role of potentially increasing northerly shear from Friday with some dry air impacts possibly weakening the system prior to any impact of the Top End coast. Should the shear remain low to moderate, the system may remain pouched in moist air. Given these uncertainties, there remains a chance it reaches category 3. Consensus of NWP model tracks has the system moving slowly towards the NE for next 36 h before recurving around to the south later Thursday and then taking a southwest track back towards the northern coastline of the NT.

[sasha_B]

Neither HWRF nor HAFS-A are showing a 100+ kt / sub-960 solution for Fina any more, but they do both show a solid SSHWS Cat 1, in line with the JTWC's forecast. I think it'll likely get there within 24h.

[cycloneye]

 https://x.com/BOM_au/status/1990953785158512916

[cycloneye]

Tropical Cyclone Fina 02U at 0600 UTC

9.5° SouthSLatitude
132.6° EastELongitude
20 nautical miles20 nm (35 kilometres35 km)Accurate within
EastE 90°Direction of movement
5 knots5 knots (9 kilometres per hour9 km/h)Movement speed
50 knots50 knots (95 kilometres per hour95 km/h)Maximum 10 minute wind speed
70 knots70 knots (130 kilometres per hour130 km/h)Maximum 3 second wind gust
985 hectopascals985 hPaCentral pressure
T3.5/3.5/D1.5/24HRS STT:D0.5/6HRSDvorak Intensity Code
1002 hectopascals1002 hPaOutermost isobar
100 nautical miles100 nm (185 kilometres185 km)Radius of outermost closed isobar
no data available—64 knot wind radius
15 nautical miles15 nm (30 kilometres30 km)Maximum wind radius

[Hurricane2022]

No comment

[sasha_B]

Subjective Dvorak technique (CI 4.0 / FT 4.0 / DT 5.0 / MET and PT 4.0) and MW imagery from c. 06z both support an upgrade to 65 kts....ADT seems to be misidentifying the center (placing it S and E of the position on the 15z fix from JTWC) which may be a factor in its stalling around T3.5. The ASCAT hit may also be limiting the JTWC's estimate but with a storm this small and ASCAT's difficulty with storms over 50 kts it doesn't seem like enough, on its own, to rule out the presence of hurricane-strength winds somewhere in the circulation, especially with an eye starting to show up on VIS & radar & the aforementioned MW imagery.
CKZ for Vmax=65 kt, using the JTWC's most recent R(34-kt)/C/θvalues, gives P(c)=979～981 hPa for P(Env) values 1004～1006, which doesn't sound unreasonable as a current intensity estimate to me. On the other hand, the CDO seems to have started warming & losing some symmetry over the past hour or so; we might already be at or near Fina's peak. Curious to see whether improvement continues over the next 8～12h (as forecast) or no.
(As an aside, there were some recent LWIR frames with cloud tops below －105°C. Very cool!)

[sasha_B]

Satellite presentation has continued to deteriorate & intensity was held at 60 kt / 984 hPa on the 18z best track update. IMO the most recent microwave imagery (from 16:20z) corroborates the idea that intensity is levelling off or declining. I think it's plausible that Fina reached hurricane-equivalent strength at some point between 9z and 15z, which would have made it the first TC of the '25-'26 Southern Hemisphere season to do so, but it hasn't got a lot of time to recover before conditions become less favourable.