SIO: ERROL - Post-Tropical

[ChrisH-UK]

29U with its cold tops and what might be an eye starting to show up

KOMPSAT-2A Geo Proxy IR blend

[cycloneye]

REMARKS:
Tropical Low 29U has shown signs of weakening during today and has moved to the
west southwest.

Position is based on animated visible satellite imagery and observations at
Bayu Undan. The upper-level cirrus outflow is becoming more transparent,
however the low level centre may be becoming more broad and slightly weaker in
nature, so there is moderate confidence in its location. Convection to the
south of the low level centre has weakened this afternoon and become more
displaced, indicating higher shear despite CIMMS shear analysis showing low
shear.

Dvorak analysis is based on curved band with 0.2-0.4 wrap giving DT2.0-2.5 or
using a shear pattern in visible imagery of <1.25 degrees, gives a DT of 2.0.
MET is 2.0 based on 24-hr S trend. PAT 2.0. FTis 2.5 and CI 3.0. Objective aids
(all 1-min mean) at 0610 UTC: ADT 51 kn, AiDT 40 kn, DPRINT 41kn, and SATCON 47
kn. The 0107 UTC ASCAT-C pass showed 25-30 knot winds in the southern
quadrants. Intensity set at 30 knots in southern quadrants, based on the blend
of Dvorak analysis and scatterometer data.

Environmental conditions remain broadly favourable for development, with sea
surface temperatures around 30 C, a deep moist environment, and support from
upper-level divergence. However, moderate north to northeasterly shear is
currently impacting organisation, and development is expected to proceed more
slowly than typical over the next 24 hours. It is now expected to develop into
a tropical cyclone during Sunday. Some recent guidance has reacted to the
higher shear and does not develop the system into a tropical cyclone until
Monday or Tuesday.

There remains the risk of slightly faster rate of development due to the small
size of 29U, if it happens to find an area of low shear environment. Overall,
despite slow development, the system is expected to persist over somewhat
favourable waters off the WA coast to intensify in the medium to long term to a
severe category cyclone early next week.

Due to the weaker system, 29U has been recently been moving to the west
southwest. During the overnight diurnal maximum with the system likely to
strengthen again, it is likely to regain its steady track towards the southwest
under the influence of a stationary mid-level ridge over central Australia.
Around mid-next week, a sharp upper trough is expected to amplify over
southwest WA, which may then capture the system and begin to steer it towards
the WA coast. Until then, it is expected to maintain a southwest track through
the Timor Sea and move over waters well off the west Kimberley coast early next
week.

[ChrisH-UK]

29U still has decent development but it's showing signs of shear

[Hurricane2022]

 https://x.com/zeb199818/status/1911036449874756067



 https://x.com/zeb199818/status/1911036295079682335

[cycloneye]

REMARKS:
Tropical low 29U is showing signs of improvement, with deep convection
redeveloping near the system over the past few hours.

A recent ASCAT-B pass at 0116 UTC indicated an elongated low-level centre with
maximum winds of 30 knots in the southeast quadrant. Confidence in the centre
position is moderate, based primarily on the ASCAT pass. Convection has
redeveloped to the east of the centre, indicating improving organisation.

Dvorak analysis yields a DT of 2.0, with curvature improving slightly (0.2
0.3). The MET is 2.5 based on a 24-hour D trend, and PAT is adjusted to 2.0.
The final T-number (FT) and Current Intensity (CI) are set at 2.0. Objective
intensity estimates at 0530 UTC (1-minute average) are as follows: ADT 49
knots, AiDT 42 knots, DPRINT 25 knots, and SATCON 43 knots. Despite higher
objective estimates, the intensity is held at 30 knots, primarily based on the
recent ASCAT observations.

Environmental conditions remain broadly favourable for further development. Sea
surface temperatures are near 30C along the forecast track, upper-level
divergence is strong, and a deep moist layer is present. CIMSS analysis
indicates weak deep-layer shear (5 10 knots), which supports continued
development.

From Tuesday, 29U is expected to reach tropical cyclone intensity. Given the
small size of the system, rapid intensification is possible once conditions
become fully favourable. The system is forecast to intensify into a severe
category 3 cyclone, before encountering increasing vertical wind shear and dry
air from Thursday, which will likely limit further development.

Steering is currently controlled by a low to mid-level ridge to the south,
directing 29U to the west-southwest. From mid-week, an amplifying upper trough
over southwest WA may begin to influence the system s track, potentially
drawing it towards the WA coast. However, ensemble model guidance continues to
show large spread, and uncertainty in the long-term movement remains high.

[cycloneye]

Looks much better now.

[WaveBreaking]

Has that shrimp look to it now

[cycloneye]

Name: Tropical Low
Identifier: 29U
Data At: 1800 UTC
Latitude: 13.8S
Longitude: 122.8E
Location Accuracy: within 25nm (45 km)
Movement Towards: west southwest (243 deg)
Speed of Movement: 2 knots (4 km/h)
Maximum 10-Minute Wind: 30 knots (55 km/h)
Maximum 3-Second Wind Gust: 45 knots (85 km/h)
Central Pressure: 1003 hPa
Radius of 34-knot winds NE quadrant:
Radius of 34-knot winds SE quadrant:
Radius of 34-knot winds SW quadrant:
Radius of 34-knot winds NW quadrant:
Radius of 48-knot winds NE quadrant:
Radius of 48-knot winds SE quadrant:
Radius of 48-knot winds SW quadrant:
Radius of 48-knot winds NW quadrant:
Radius of 64-knot winds: nm ( km)
Radius of Maximum Winds: nm ( km)
Dvorak Intensity Code: T2.0/2.0/S0.0/24HRS STT:S0.0/06HRS
Pressure of outermost isobar: 1008 hPa
Radius of outermost closed isobar: 90 nm (165 km)
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
(UTC) : degrees : nm (km): knots(km/h): hPa
+06: 15/0000: 13.9S 122.5E: 035 (070): 035 (065): 999
+12: 15/0600: 13.9S 121.9E: 045 (085): 040 (075): 997
+18: 15/1200: 13.8S 121.3E: 055 (105): 040 (075): 997
+24: 15/1800: 13.8S 120.5E: 060 (115): 045 (085): 995
+36: 16/0600: 14.1S 119.3E: 070 (130): 050 (095): 991
+48: 16/1800: 14.3S 118.5E: 075 (135): 060 (110): 983
+60: 17/0600: 14.5S 118.5E: 095 (175): 065 (120): 978
+72: 17/1800: 14.7S 119.1E: 120 (225): 055 (100): 987
+96: 18/1800: 15.2S 120.6E: 190 (350): 035 (065): 1000
+120: 19/1800: 15.7S 121.2E: 230 (425): 030 (055): 1001
REMARKS:
Tropical low 29U is showing only gradual signs of improvement, with ongoing
deep convection east of the centre. The system is generally moving west to
southwest under the influence of a low to mid-level ridge, however movement has
slowed significantly in the last 48 hours.

System position and intensity remain difficult to estimate, with the 18Z
analysis being informed mostly by satellite and the ASCAT-C pass at 1258 UTC.
This showed maximum winds 30-35kn to the south and a somewhat NW-SE elongation.

Dvorak analysis: FT/CI=2.0 based upon a DT=2.0, curved band 0.2; MET=2.5 on a
24-hour S/D- trend and adjusted down to 2.0. Objective intensity estimates at
1630 UTC (1-minute average): ADT 45 kn, AiDT 37 kn, DPRINT 31 kn, and SATCON 39
kn.

Environmental conditions remain broadly favourable for further development: Sea
surface temperatures are near 30 C along the forecast track, upper-level
divergence is strong, and a deep moist layer is present and vertical wind shear
is low (CIMSS analysis 5-10 kn). Current guidance shows the mid-level
circulation offset from the lower level, and this fits with the lack of
significant development so far. Development is also being restricted by only
weak low to mid-level inflow from the north.

Most deterministic guidance remains muted in the short term (although there has
been an increase in the 12Z runs), with Access G, JMA, and ECMWF not developing
gales around the system until Wednesday. US GFS has been consistently showing a
stronger system than has been observed over the last few days, and further
intensifies it further during Tuesday and Wednesday. Mixed development in the
ensembles but many members showing a strong system is possible over the next
few days. Despite the lack of short term intensity in the deterministic
guidance, they do show the system becoming more vertically stacked during
Tuesday and given the favourability of the environment we expect 29U to develop
into a tropical cyclone during the day on Tuesday. A period of rapid
intensification is also possible especially given the small size of the system.
The system is expected to continue moving west to southwest under the influence
of the ridge.

The system remains vertically stacked and in a favourable environment during
Wednesday and Thursday, and therefore expected to develop further with rapid
intensification remaining a risk. The intensity forecast is largely based on
assessment of the ensemble guidance and the standard rate of development. At
this stage the forecast is for a peak intensity of a category 3 system early
Thursday. The approach of an upper trough should initially aid upper level
outflow but then will also lead to increasing vertical wind shear and dry air
ingestion, at this stage from Thursday. This will also begin to steer the
system towards the southeast later Thursday and Friday however the system will
also weaken, and is expected to drop below tropical cyclone intensity while
remaining offshore.

[cycloneye]

REMARKS:
Tropical low 29U exhibits a vigorous low level circulation on satellite imagery
with new convection forming tight convective banding segments near the centre.
Position estimated from animated visible satellite imagery with fair confidence.

Dvorak analysis: earlier curved band patterns were giving 0.5 to 0.6 wraps,
however a recent CDO-like feature has obscured this in the past hour or so. DT
has averaged 2.5 to 3.0 over the past three hours, with the pattern not clear
cut. MET is 2.5 based on a 24 hour D- trend with no PAT adjustment. FT = CI =
2.5 based on MET. Objective intensity estimates at 0540 UTC (1-minute average):
ADT 37 kn (CI 2.6), AiDT 32 kn, DPRINT 41 kn, and SATCON 39 kn. Intensity held
at 35 knots with gales analysed in the southern quadrants, verified by the 0146
UTC ASCAT pass this morning. The system is likely to achieve tropical cyclone
intensity within the next 6 to 12 hours.

Environmental conditions are broadly favourable for development. The system
lies along the axis of an upper level anticyclone and CIMSS analysed deep layer
wind shear is low at 9 kn from the east. A shortwave upper trough over Western
Australia is enhancing poleward outflow somewhat and there is reasonable upper
divergence analysed to the south of 29U. Sea surface temperatures are near 30
C along the forecast track, and deep layer moisture is in place around the
system. Development is forecast in the short to medium term, with a peak
intensity of category 3 forecast on Thursday. Given the small size of the
system and the favourable conditions, periods of rapid intensification are
possible between now and Thursday.

The system is expected to continue moving broadly westward under the influence
of a mid-level ridge to the south until Thursday. On Thursday an amplifying
upper trough is forecast to capture the system and steer it to the southeast,
towards the coast. The small system should weaken fairly rapidly under the
influence of the associated wind shear and dry air intrusion during this
process. Once fully sheared, the remnant low is expected to be steered back to
the west by low level ridging to the south. The current forecast track has this
occur just off the WA coast, however some guidance indicates the weakening
system may reach the coast first. There is still considerable uncertainty
around this scenario.

[Subtrop]

IDW24000
Australian Bureau of Meteorology
Tropical Cyclone Warning Centre

TROPICAL CYCLONE INFORMATION BULLETIN
Issued at 8:50 pm WST on Tuesday 15 April 2025

A Tropical Low (29U) was located at 8:00 pm AWST near 13.8S 121.2E, that is 475
km north northwest of Broome and 405 km west northwest of Kuri Bay, and was
moving west at 13 kilometres per hour.

Tropical Cyclone Errol is well to the north of Broome and moving west. It is
expected to continue moving west and intensify during Wednesday. From Thursday
Errol is expected to turn southeast towards the coast and weaken.

Tropical Cyclone Errol will not have any direct impact on the WA coast within
the next 48 hours.

The next Information Bulletin will be issued at 3:00 am AWST Wednesday 16 April.

[cycloneye]

Hurricane2022, Wavebreaking, ChrisH-UK, finnally it's named.

TROPICAL CYCLONE INFORMATION BULLETIN
Issued at 9:10 pm WST on Tuesday 15 April 2025

Tropical Cyclone Errol (Category 1) was located at 8:00 pm AWST near 13.8S
121.2E, that is 475 km north northwest of Broome and 405 km west northwest of
Kuri Bay, and was moving west at 13 kilometres per hour.

Tropical Cyclone Errol is well to the north of Broome and moving west. It is
expected to continue moving west and intensify during Wednesday. From Thursday
Errol is expected to turn southeast towards the coast and weaken.

Tropical Cyclone Errol will not have any direct impact on the WA coast within
the next 48 hours.

[cycloneye]

Eye will pop out very soon.

[Hurricane2022]

Eye will pop out very soon.

https://i.imgur.com/KOnsomy.gif

I was hoping that the HAFS forecasts were right and Errol would become a Super Cyclone as it wouldn't be a threat to anyone, but the system took a while to organize itself even in a good environment to gain strength. I'm still hoping that Errol will pinch a mid-C4 peak intensity before it dissipates

[WaveBreaking]

Errol is pretty small, is trying to form a small eye, and is over SSTs of at least 30°C. Barring any inhibiting factors (there seems to be a small amount of NE shear and a wedge of dry air nearby), the ceiling for intensity is very high.

[cycloneye]

Here we go.

[cycloneye]

Great pinhole eye.

[cycloneye]

TROPICAL CYCLONE INFORMATION BULLETIN
Issued at 2:42 am WST on Wednesday 16 April 2025

Tropical Cyclone Errol (Category 2) was located at 2:00 am AWST near 13.8S
120.2E, that is 510 km north northwest of Broome and 500 km west northwest of
Kuri Bay, and was moving west at 13 kilometres per hour.

Tropical Cyclone Errol is moving west over open waters well off the northwest
Kimberley coast. It is expected to continue moving west and intensify during
Wednesday. From Thursday Errol is expected to turn southeast towards the coast
and peak in intensity as a severe tropical cyclone. By Friday Errol should
weaken as it approaches the west Kimberley coast.

Tropical Cyclone Errol will not have any direct impact on the WA coast within
the next 48 hours.

[Hurricane2022]

Great pinhole eye.

Extremely small eye. We should see a brief EWRC coming soon.

[WaveBreaking]

Solid semicircle of VHTs + -80°C tops around the eye.

[Hurricane2022]

The eyewall is very small. We'll have to wait for polar passes to find out the real temperature of the eye once it fully clears.