SIO: ILSA - Post-Tropical

[Category5Kaiju]

The next name of the list is Ilsa.

Australia gets I curses too, huh? It's not just the Atlantic

[mrbagyo]

JTWC's first forecast is incredibly bullish, forecasting a C5 on day 4 and a remarkable 50kt/24hr intensification rate at one point.

https://media.discordapp.net/attachments/857017650042503178/1094345950790701196/sh182023.png

Rowley Shoal Obs link


Bedout Island obs link

[cycloneye]

TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 0104 UTC 09/04/2023
Name: Tropical Low
Identifier: 23U
Data At: 0000 UTC
Latitude: 11.1S
Longitude: 128.3E
Location Accuracy: within 30nm (55 km)
Movement Towards: southwest (221 deg)
Speed of Movement: 5 knots (10 km/h)
Maximum 10-Minute Wind: 35 knots (65 km/h)
Maximum 3-Second Wind Gust: 50 knots (95 km/h)
Central Pressure: 999 hPa
Radius of 34-knot winds NE quadrant:
Radius of 34-knot winds SE quadrant:
Radius of 34-knot winds SW quadrant: 40 nm (75 km)
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: T2.5/2.5/D0.5/24HRS STT:S0.0/06HRS
Pressure of outermost isobar: 1007 hPa
Radius of outermost closed isobar: 160 nm (295 km)
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
(UTC) : degrees : nm (km): knots(km/h): hPa
+06: 09/0600: 11.5S 127.5E: 050 (090): 035 (065): 998
+12: 09/1200: 11.8S 126.7E: 060 (110): 040 (075): 997
+18: 09/1800: 11.9S 125.8E: 065 (125): 040 (075): 997
+24: 10/0000: 12.2S 124.9E: 070 (135): 045 (085): 994
+36: 10/1200: 13.0S 123.4E: 085 (160): 055 (100): 987
+48: 11/0000: 13.9S 122.0E: 105 (190): 065 (120): 980
+60: 11/1200: 14.6S 120.9E: 120 (220): 075 (140): 971
+72: 12/0000: 15.4S 119.9E: 130 (245): 085 (155): 962
+96: 13/0000: 17.8S 118.8E: 160 (295): 095 (175): 953
+120: 14/0000: 21.6S 122.5E: 210 (390): 045 (085): 994
REMARKS:
Developing tropical low (23U) likely to become a severe tropical cyclone in the
coming days.

Low confidence in position which is suspected to be displaced to the east of
the deeper convection based on deep layer easterly shear and extrapolation of
low level cloud lines.
Dvorak: Shear pattern yields DT of 3.0. MET is 3.0 based on a 24 hour D trend.
PAT adjusted to 2.5. FT/CI=2.5 based on PAT as very low confidence in DT.
Available objective guidance is slightly higher with ADT CIs of 2.8 (CIMSS) and
3.2 (NESDIS).

Forecast track is based on a standard consensus of guidance. Steering is
dominated by a mid-level anti-cyclone to the southeast. Short term fluctuations
may occur in the next 6-12 hours as the low level centre consolidates, but a
general west-southwest to southwesterly motion is expected until Tuesday,
before a turn towards the south on Wednesday. On Thursday, an approaching upper
trough could steer it faster and to the southeast, likely as the system crosses
the coast and moves inland.

The strong wind shear constraining development is expected to gradually ease
during the forecast period. Development is also likely assisted by a Equatorial
Rossby wave moving into the area as well as an upper shortwave trough
moderately increasing outflow to the south. Forecast rate of development is
less than standard initially, increasing to standard rate of development from
early Monday morning. This has 23U reaching category 1 at 0600 UTC today, and a
forecast intensity of category 4 (100 kts) at landfall. Upper outflow could be
favourable to very favourable for a period, during Wednesday, and some sources
of guidance indicate a higher intensity is possible. Ocean temperatures are at
or above 30 degrees celsius along the length of the forecast track, reaching as
high as 32 degrees celsius in the area of forecast landfall

[cycloneye]

Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 0705 UTC 09/04/2023
Name: Tropical Low
Identifier: 23U
Data At: 0600 UTC
Latitude: 11.7S
Longitude: 127.3E
Location Accuracy: within 25nm (45 km)
Movement Towards: southwest (232 deg)
Speed of Movement: 8 knots (15 km/h)
Maximum 10-Minute Wind: 40 knots (75 km/h)
Maximum 3-Second Wind Gust: 55 knots (100 km/h)
Central Pressure: 998 hPa
Radius of 34-knot winds NE quadrant:
Radius of 34-knot winds SE quadrant: 60 nm (110 km)
Radius of 34-knot winds SW quadrant: 60 nm (110 km)
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: T3.0/3.0/D0.5/24HRS STT:D0.5/06HRS
Pressure of outermost isobar: 1007 hPa
Radius of outermost closed isobar: 180 nm (335 km)
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
(UTC) : degrees : nm (km): knots(km/h): hPa
+06: 09/1200: 11.9S 126.5E: 045 (080): 040 (075): 997
+12: 09/1800: 12.1S 125.6E: 055 (100): 040 (075): 997
+18: 10/0000: 12.3S 124.8E: 065 (115): 045 (085): 994
+24: 10/0600: 12.8S 123.9E: 070 (135): 050 (095): 991
+36: 10/1800: 13.6S 122.5E: 085 (160): 060 (110): 984
+48: 11/0600: 14.4S 121.2E: 100 (185): 070 (130): 975
+60: 11/1800: 15.2S 120.2E: 115 (215): 080 (150): 966
+72: 12/0600: 16.1S 119.2E: 130 (235): 085 (155): 962
+96: 13/0600: 18.8S 118.9E: 160 (300): 100 (185): 945
+120: 14/0600: 23.0S 124.4E: 220 (405): 040 (075): 997
REMARKS:
Developing tropical low (23U) likely to become a severe tropical cyclone in the
coming days.

The low level centre of 23U is suspected to lie east of the dominant deep
convection based on extrapolation of low level cloud lines, which is consistent
with the broad scale easterly shear analysed over the system. A second
convective bloom has developed in recent hours closer to and south of the
estimated LLCC.

Dvorak analysis is based on a curved band pattern with an 0.45 wrap giving DT
2.5. Shear pattern also yields DT of 2.5. MET is 3.0 based on a 24 hour D trend
with no PAT adjustment. FT/CI=3.0 based on MET. Available objective guidance is
slightly higher with SATCON 48 knots and ADT CIs of 3.4 (CIMSS) and 3.5
(NESDIS). The ADTs may be overestimating the intensity with an analysed
position nearer to the larger convective cluster to the SW. Intensity set to 40
knots with gales estimated to be in the southern quadrants only.

The forecast track is based on a standard consensus of guidance. Steering is
dominated by a mid-level anti-cyclone to the southeast, giving a general
west-southwest to southwesterly motion is until Tuesday. The system is forecast
to turn towards the south on Wednesday around the periphery of the mid-level
anticyclone. On Thursday, an approaching upper trough could steer it faster and
to the southeast, likely as the system crosses the coast and moves inland.

CIMSS upper wind analysis depicts the system lying near a strong deep layer
easterly shear gradient (as high as 25 knots). However, this shear is forecast
to decrease along the system's track to the southwest. Development is also
likely assisted by a Equatorial Rossby wave moving into the area as well as an
upper shortwave trough moderately increasing outflow to the south. Therefore,
forecast rate of development is less than standard initially, increasing to
standard rate of development from Monday morning. This has 23U reaching severe
tropical cyclone strength on Tuesday, and a forecast intensity of category 4
(100 kts) at landfall. Upper outflow could be favourable to very favourable for
a period, during Wednesday, and some sources of guidance indicate a higher
intensity is possible. Ocean temperatures are at or above 30 degrees celsius
along the length of the forecast track, reaching as high as 32 degrees celsius
in the area of forecast landfall.

[cycloneye]

TROPICAL CYCLONE ADVICE NUMBER 9
Issued at 9:02 pm WST on Sunday 9 April 2023

Headline:
Tropical low expected to become a cyclone during Monday with gales and heavy rainfall possibly developing along the Kimberley coast.

Areas Affected:
Warning Zone
Kalumburu to Cockatoo Island and Cape Leveque to Beagle Bay, including Kalumburu, not including Derby.

Watch Zone
None.

Cancelled Zone
None.

Details of Tropical Low at 8:00 pm AWST:
Intensity: Tropical Low, sustained winds near the centre of 75 kilometres per hour with wind gusts to 100 kilometres per hour.

Location: within 55 kilometres of 12.1 degrees South 126.0 degrees East, estimated to be 255 kilometres north northwest of Kalumburu and 770 kilometres north northeast of Broome.

Movement: west southwest at 23 kilometres per hour.

The low is likely to develop into a tropical cyclone during Monday. It is expected to intensify further over the next two days as it moves along a general west southwest track, parallel to the Kimberley coast.

There is a significant risk that this system will intensify into a severe tropical cyclone during Tuesday. It is expected the track will turn to the south during the middle of the week and a severe impact is likely along the coast between Port Hedland and Broome, during Thursday or Friday.

Hazards:
GALES with wind gusts to 90 km/h and HEAVY RAINFALL may develop between Kalumburu and Cookatoo Island, including near Kalumburu during Monday, particularly if the low moves closer to the coast. These GALES may extend westward to Beagle Bay later on Monday and on Tuesday.

Squally thunderstorms with heavy falls are expected over the northern Kimberley overnight Sunday and continuing Monday.

ABNORMALLY HIGH TIDES are expected about the Kimberley coast between Kalumburu and Kuri Bay Tuesday and Wednesday. In some locations the tide may be close to the highest astronomical tide of the year.

Recommended Action:
DFES advises of the following community alerts effective as of 9.00pm

BLUE ALERT: People in or between Kalumburu to Kuri Bay need to prepare for cyclonic weather and organise an emergency kit including first aid kit, torch, portable radio, spare batteries, food and water.

A Cyclone Advice is current for people between Kuri Bay (Not including Kuri Bay) and Beagle Bay (Not including Derby).

If you live in communities between Kuri Bay and Beagle Bay you need to prepare your home and family for a possible cyclone, with the development of a Tropical Low off the Western Australian coast.

Communities along the North Kimberley and West Kimberley Coast should start to prepare and monitor conditions and warnings.

[cycloneye]

Peak intensity reduced to 95 kt as it has delayed development because of the shear.

TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 1853 UTC 09/04/2023
Name: Tropical Low
Identifier: 23U
Data At: 1800 UTC
Latitude: 12.5S
Longitude: 125.0E
Location Accuracy: within 35nm (65 km)
Movement Towards: west southwest (250 deg)
Speed of Movement: 12 knots (22 km/h)
Maximum 10-Minute Wind: 30 knots (55 km/h)
Maximum 3-Second Wind Gust: 45 knots (85 km/h)
Central Pressure: 1002 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: T2.0/2.5/W0.5/24HRS STT:S0.0/06HRS
Pressure of outermost isobar: 1006 hPa
Radius of outermost closed isobar: 100 nm (185 km)
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
(UTC) : degrees : nm (km): knots(km/h): hPa
+06: 10/0000: 12.9S 124.1E: 050 (095): 030 (055): 1001
+12: 10/0600: 13.3S 123.3E: 060 (115): 035 (065): 999
+18: 10/1200: 13.7S 122.6E: 065 (125): 040 (075): 996
+24: 10/1800: 14.0S 121.9E: 075 (135): 045 (085): 993
+36: 11/0600: 14.8S 121.0E: 085 (155): 055 (100): 985
+48: 11/1800: 15.4S 120.3E: 100 (180): 070 (130): 974
+60: 12/0600: 16.3S 119.6E: 115 (210): 090 (165): 958
+72: 12/1800: 17.5S 119.4E: 125 (235): 095 (175): 954
+96: 13/1800: 21.5S 122.0E: 165 (300): 070 (130): 972
+120: 14/1800: 26.7S 131.9E: 245 (455): 030 (055): 1002
REMARKS:
Tropical low (23U) likely to become a severe tropical cyclone in the coming
days.

Location of 23U is proving difficult with the loss of visible imagery and no
recent microwave or scatterometer passes to assist. The position is based on
EIR and the expected motion.

Dvorak analysis: a curved band pattern with an 0.2 wrap giving DT 2.0. MET is
2.0 based on a 24 hour W- trend, PAT agrees. FT is 2.0 with CI held at 2.5.

Available objective guidance generally aligns with SATCON 39 knots (1-min),
CIMSS ADT 37 (1-min), NESDIS ADT 41 (1-min) and OPEN-AIIR about 32 knots.
Intensity set to 30 knots.

Development has been slower than initially forecast, with the influence of the
easterly shear having a more significant impact on potential for development.
CIMSS upper wind analysis depicts the system lying near a strong deep layer
easterly shear gradient (as high as 25 knots) and recent satellite imagery
shows the limited deep convection displaced to the west of the system centre.
Given this shear influence, forecast intensification has been delayed. However,
this shear is still forecast to decrease along the system's track to the
southwest. Development may also be assisted by an Equatorial Rossby wave moving
across the area. Additionally, as 23U isn't particularly large and is moving
towards a favourable region and hence once the shear eases intensification is
expected to occur quickly. Therefore, forecast rate of development is less than
standard initially, increasing to standard rate of development during Tuesday.
This has 23U reaching severe tropical cyclone strength on Tuesday, and a
forecast intensity of category 4 (100 kts) at landfall.

Upper poleward outflow could be favourable to very favourable for a period,
during Wednesday. Ocean temperatures are at or above 30 degrees celsius along
the length of the forecast track, reaching as high as 32 degrees celsius in the
area of forecast landfall. Some sources of guidance indicate a higher intensity
is possible in line with these favourable conditions.

The forecast track is based on a standard consensus of guidance. Steering is
dominated by a mid-level anti-cyclone to the southeast, giving a general
west-southwest to southwesterly motion until Tuesday. The system is forecast to
then turn towards the south during Wednesday, around the periphery of the
mid-level anticyclone. On Thursday, an approaching upper trough is expected to
steer it to the southeast and the system could begin to accelerate as it
crosses the Western Australian coast, most likely somewhere along the east
Pilbara or west Kimberley.

[/b]

[cycloneye]

Looking good as outflow improves.

[cycloneye]

TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 0117 UTC 10/04/2023
Name: Tropical Low
Identifier: 23U
Data At: 0000 UTC
Latitude: 12.6S
Longitude: 124.0E
Location Accuracy: within 30nm (55 km)
Movement Towards: west (264 deg)
Speed of Movement: 10 knots (18 km/h)
Maximum 10-Minute Wind: 30 knots (55 km/h)
Maximum 3-Second Wind Gust: 45 knots (85 km/h)
Central Pressure: 1002 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: T2.5/2.5/S0.0/24HRS STT:D0.5/6HRS
Pressure of outermost isobar: 1006 hPa
Radius of outermost closed isobar: 150 nm (280 km)
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
(UTC) : degrees : nm (km): knots(km/h): hPa
+06: 10/0600: 12.9S 123.2E: 050 (090): 035 (065): 999
+12: 10/1200: 13.2S 122.6E: 060 (105): 040 (075): 998
+18: 10/1800: 13.5S 122.0E: 065 (120): 040 (075): 994
+24: 11/0000: 13.8S 121.5E: 070 (130): 045 (085): 990
+36: 11/1200: 14.5S 120.7E: 080 (150): 060 (110): 980
+48: 12/0000: 15.2S 120.0E: 100 (180): 080 (150): 966
+60: 12/1200: 16.1S 119.4E: 105 (195): 090 (165): 954
+72: 13/0000: 17.4S 119.2E: 130 (235): 100 (185): 950
+96: 14/0000: 21.8S 123.0E: 170 (310): 050 (095): 988
+120: 15/0000: : : :
REMARKS:
Tropical low (23U) likely to become a severe tropical cyclone in the coming
days.

23U continues to show the effects of easterly shear, with the main convection
displaced to the southwest of the estimated low level circulation centre. New
convective bursts are struggling to band around the system. There is still some
uncertainty in the low level centre position with the centre obscured and no
recent scatterometer passes to assist.

Dvorak analysis: a curved band pattern with an 0.45 wrap giving DT 2.5. Shear
pattern confirms this DT. MET is 2.5 based on a 24 hour S trend with no PAT
adjustment. FT and CI are 2.5. Available objective guidance has begun to
increase again with SATCON (1715UTC) 39 knots (1-min), CIMSS ADT 43 knots
(1-min), NESDIS ADT 45 knots (1-min) and OPEN-AIIR about 35 knots. Intensity
maintained at 30 knots.

Development has been slower than initially forecast, with the influence of the
easterly shear having a more significant impact on potential for development.
CIMSS upper wind analysis depicts the system lying near a strong deep layer
easterly shear gradient (as high as 25 knots). Given this shear influence,
forecast intensification has been delayed. However, this shear is still
forecast to decrease along the system's track to the southwest. Development may
also be assisted by an Equatorial Rossby wave moving across the area.
Additionally, as 23U is not particularly large and is moving towards a
favourable region, once the shear eases intensification may be rapid.
Therefore, forecast rate of development is less than standard initially,
increasing to standard rate of development during Tuesday. This has 23U
reaching severe tropical cyclone strength on Tuesday, and a forecast intensity
of category 4 (100 kts) at landfall.

Upper poleward outflow is expected to remain favourable as the shear decreases.
Ocean temperatures are at or above 30 degrees celsius along the length of the
forecast track, reaching as high as 32 degrees celsius in the area of forecast
landfall. Some sources of guidance indicate a higher peak intensity is possible
in line with these favourable conditions.

The forecast track is based on a standard consensus of guidance. Steering is
dominated by a mid-level anti-cyclone to the southeast, giving a general
west-southwest to southwesterly motion until Tuesday. The system is forecast to
then turn towards the south during Wednesday, around the periphery of the
mid-level anticyclone. On Thursday, an approaching upper trough is expected to
steer it to the southeast and the system could begin to accelerate as it
crosses the Western Australian coast, most likely somewhere along the east
Pilbara or west Kimberley.

[cycloneye]

Not yet well organized.

[cycloneye]

TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 0712 UTC 10/04/2023
Name: Tropical Low
Identifier: 23U
Data At: 0600 UTC
Latitude: 12.6S
Longitude: 123.2E
Location Accuracy: within 20nm (35 km)
Movement Towards: west southwest (251 deg)
Speed of Movement: 6 knots (11 km/h)
Maximum 10-Minute Wind: 35 knots (65 km/h)
Maximum 3-Second Wind Gust: 50 knots (95 km/h)
Central Pressure: 999 hPa
Radius of 34-knot winds NE quadrant:
Radius of 34-knot winds SE quadrant:
Radius of 34-knot winds SW quadrant: 70 nm (130 km)
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: T3.0/3.0/S0.0/24HRS STT:D0.5/06HRS
Pressure of outermost isobar: 1006 hPa
Radius of outermost closed isobar: 120 nm (220 km)
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
(UTC) : degrees : nm (km): knots(km/h): hPa
+06: 10/1200: 13.0S 122.7E: 040 (075): 035 (065): 998
+12: 10/1800: 13.3S 122.1E: 050 (095): 040 (075): 996
+18: 11/0000: 13.7S 121.6E: 060 (110): 045 (085): 993
+24: 11/0600: 14.1S 121.3E: 065 (120): 050 (095): 989
+36: 11/1800: 14.7S 120.5E: 080 (145): 060 (110): 982
+48: 12/0600: 15.6S 119.7E: 095 (175): 080 (150): 966
+60: 12/1800: 16.6S 119.2E: 115 (215): 090 (165): 956
+72: 13/0600: 18.1S 119.2E: 135 (250): 100 (185): 946
+96: 14/0600: 22.6S 124.8E: 170 (315): 045 (085): 994
+120: 15/0600: 27.4S 137.8E: 270 (500): 030 (055): 1002
REMARKS:
Tropical low (23U) likely to become a severe tropical cyclone in the coming
days.

23U continues to show the effects of easterly shear, with the main convection
remaining displaced to the southwest of the estimated low level circulation
centre. There has been little change to the cloud pattern during the past 24
hours.

Dvorak analysis: a curved band pattern with an 0.45 wrap giving DT 2.5. Shear
pattern gives DT3.0 with 15-20nm of separation MET is 3.0 based on a 24 hour S
trend with no PAT adjustment. FT = 3.0 based on MET, CI is also 3.0. Available
objective guidance has begun to increase again with SATCON (0500UTC) 45 knots
(1-min), CIMSS ADT 49 knots (1-min), NESDIS ADT 51 knots (1-min) and OPEN-AIIR
about 44 knots. ADT based guidance may be overestimating the intensity with the
use of uniform CDO and embedded centre patterns, and positions analysed closer
to the sheared deep convection. The morning ASCAT pass (only a partial swathe)
showed maximum winds of 30 knots but captured the eastern half of the
circulation only. Intensity is set at 35 knots with gales analysed in the
southwestern quadrant only based on the distribution of convection.

Development has been slower than initially forecast, with the influence of the
easterly shear having a significant impact. CIMSS upper wind analysis depicts
the system lying near a strong deep layer easterly shear gradient (as high as
25 knots). Given this shear influence, forecast intensification has been
delayed. However, the shear along the forecast track is expected to decrease.
Upper poleward outflow is expected to remain favourable through to landfall. As
23U is not particularly large, intensification may be rapid once conditions
become more favourable. Ocean temperatures are at or above 30 degrees celsius
along the length of the forecast track, reaching as high as 32 degrees celsius
in the area of forecast landfall.

The forecast rate of development is less than standard initially, increasing to
standard rate of development during Tuesday. On Wednesday development is
forecast at slightly above the standard rate due to the potential for periods
of rapid intensification in the more favourable conditions. The forecast
intensity at landfall is category 4 (100 kts). However, given these forecast
favourable conditions, a higher peak intensity is possible.

The forecast track is based on a standard consensus of guidance. Steering is
dominated by a mid-level anti-cyclone to the southeast, giving a general
west-southwest to southwesterly motion until Tuesday. The system is forecast to
then turn towards the south during Wednesday, around the periphery of the
mid-level anticyclone. On Thursday, an approaching upper trough is expected to
steer it to the southeast and the system could begin to accelerate as it
crosses the Western Australian coast, most likely somewhere along the east
Pilbara or west Kimberley.

[cycloneye]

TROPICAL CYCLONE ADVICE NUMBER 15
Issued at 8:54 pm WST on Monday 10 April 2023

Headline:
Tropical low continues to develop slowly and is expected to reach tropical cyclone strength during Tuesday. Severe coastal impact likely late in the week.

Areas Affected:
Warning Zone
None.

Watch Zone
Cape Leveque to Broome, not including Broome.

Cancelled Zone
None.

Details of Tropical Low at 8:00 pm AWST:
Intensity: Tropical Low, sustained winds near the centre of 65 kilometres per hour with wind gusts to 95 kilometres per hour.

Location: within 45 kilometres of 13.3 degrees South 122.8 degrees East, estimated to be 520 kilometres north of Broome and 345 kilometres north of Cape Leveque.

Movement: southwest at 10 kilometres per hour.

The tropical low continues to develop at a slow rate and is expected to develop into a cyclone during Tuesday. It is then expected to intensify further over the next two days as it moves along a general west southwest track, parallel to the Kimberley coast.

There is a significant risk that this system will intensify into a severe tropical cyclone during Wednesday. It is expected the track will turn to the south during the middle of the week and a severe impact is likely along the coast between Port Hedland and Broome, during Thursday or Friday.

[cycloneye]

This will be officially a cyclone shortly.

[cycloneye]

 https://twitter.com/MikeAdcockWx/status/1645473404965748736

[cycloneye]

Details of Tropical Low at 2:00 am AWST:
Intensity: Tropical Low, sustained winds near the centre of 75 kilometres per hour with wind gusts to 100 kilometres per hour.

Location: within 45 kilometres of 13.7 degrees South 122.4 degrees East, estimated to be 475 kilometres north of Broome and 305 kilometres north of Cape Leveque.

Movement: southwest at 10 kilometres per hour.

The tropical low continues to develop at a slow rate and is expected to develop into a cyclone during Tuesday off the west Kimberley coast. It is then expected to intensify further on Wednesday as it moves southwest, parallel to the Kimberley coast. There is a significant risk that this system will intensify into a severe tropical cyclone during Wednesday.

The system is expected to track to the south and then southeast during Thursday and a severe impact is likely along the coast between Port Hedland and Broome, during Thursday or Friday.

[1900hurricane]

Still dealing with shear, but with it relaxing some over the next day and the center already propitiating downshear into the convection, we're probably on the doorstep of appreciable organization trends.

[cycloneye]

It has underperformed bigtime but it should begin to intensify according to the warning posted below.

TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 0128 UTC 11/04/2023
Name: Tropical Low
Identifier: 23U
Data At: 0000 UTC
Latitude: 14.1S
Longitude: 122.0E
Location Accuracy: within 20nm (35 km)
Movement Towards: southwest (224 deg)
Speed of Movement: 6 knots (10 km/h)
Maximum 10-Minute Wind: 40 knots (75 km/h)
Maximum 3-Second Wind Gust: 55 knots (100 km/h)
Central Pressure: 995 hPa
Radius of 34-knot winds NE quadrant:
Radius of 34-knot winds SE quadrant:
Radius of 34-knot winds SW quadrant: 70 nm (130 km)
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: T2.5/3.0/S0.0/24HRS STT:S0.0/6HRS
Pressure of outermost isobar: 1006 hPa
Radius of outermost closed isobar: 130 nm (240 km)
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
(UTC) : degrees : nm (km): knots(km/h): hPa
+06: 11/0600: 14.7S 121.6E: 040 (075): 040 (075): 996
+12: 11/1200: 15.1S 121.1E: 055 (100): 045 (085): 992
+18: 11/1800: 15.4S 120.7E: 065 (120): 055 (100): 985
+24: 12/0000: 15.7S 120.3E: 075 (140): 060 (110): 982
+36: 12/1200: 16.5S 119.7E: 090 (165): 080 (150): 965
+48: 13/0000: 17.4S 119.3E: 100 (185): 090 (165): 956
+60: 13/1200: 18.9S 120.0E: 140 (260): 095 (175): 950
+72: 14/0000: 20.7S 122.2E: 180 (335): 065 (120): 977
+96: 15/0000: 23.9S 133.2E: 250 (465): 030 (055): 1004
+120: 16/0000: 26.5S 143.2E: 185 (340): 025 (045): 1003
REMARKS:
Deep moist convection is redeveloping in the southwest quadrant to the low
level centre.
Position of 23U is based on EIR and microwave imagery at 2100 UTC. Intensity is
40 knots based off overnight ASCAT data, though recent HSCAT suggests intensity
between 30 to 35 knots. Dvorak analysis: DT = 2.5 based on a shear average over
the last few hours, though recent imagery is closer to 2.0. MET = 2.5 based on
S 24 hour trend. PAT is 2.0. FT = 2.5 based on DT. CI held at 3.0.

Cyclogenesis continues to be slow due to recently strong east to northeasterly
vertical wind shear over 23U. However, wind shear has started to decrease over
23U and at 2100 UTC, CIMSS upper wind analysis has analysed approximately 15
knots of shear. The system should begin a development cycle with favourable
shear, and intensification into a tropical cyclone is expected in the next 12
hours with high mid-level moisture and warm SSTs (30+ degrees Celsius).

Upper divergence to the south increases from mid week and the system is
forecast to develop into a severe tropical cyclone from Wednesday, likely
reaching a category 4 system during Thursday. 23U is forecast to move southwest
parallel to and offshore from the Kimberley coast during Tuesday and Wednesday
before turning south and then southeast during Thursday, with a coastal
crossing likely later Thursday or Friday between Port Hedland and Broome.

The forecast track is based on a standard consensus of numerical weather
prediction (NWP) models. This track is consistent with upper-air analyses which
show a mid-upper ridge over the NT and an approaching upper trough over
southern WA. There is relatively high confidence in this forecast track. In the
long-term, 23U is forecast to move over central Australia and begin a
transition to a deep, sub-tropical system as it interacts with the sub-tropical
jet.

Intensity forecasts are based on a standard rate of development prior to
landfall, with a landfall intensity of 95 knots (Category 4). This is
consistent with a consensus of NWP models. 23U is forecast to remain a strong
system as it moves inland on Friday.

[cycloneye]

TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 0720 UTC 11/04/2023
Name: Tropical Cyclone Ilsa
Identifier: 23U
Data At: 0600 UTC
Latitude: 14.5S
Longitude: 121.2E
Location Accuracy: within 20nm (35 km)
Movement Towards: southwest (235 deg)
Speed of Movement: 7 knots (13 km/h)
Maximum 10-Minute Wind: 40 knots (75 km/h)
Maximum 3-Second Wind Gust: 55 knots (100 km/h)
Central Pressure: 994 hPa
Radius of 34-knot winds NE quadrant:
Radius of 34-knot winds SE quadrant: 80 nm (150 km)
Radius of 34-knot winds SW quadrant: 80 nm (150 km)
Radius of 34-knot winds NW quadrant: 60 nm (110 km)
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: 20 nm (35 km)
Dvorak Intensity Code: T3.0/3.0/S0.0/24HRS STT:D0.5/6HRS
Pressure of outermost isobar: 1004 hPa
Radius of outermost closed isobar: 130 nm (240 km)
FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
(UTC) : degrees : nm (km): knots(km/h): hPa
+06: 11/1200: 14.9S 120.9E: 040 (070): 045 (085): 990
+12: 11/1800: 15.3S 120.4E: 050 (095): 055 (100): 984
+18: 12/0000: 15.7S 120.0E: 060 (115): 060 (110): 980
+24: 12/0600: 16.1S 119.7E: 070 (125): 070 (130): 972
+36: 12/1800: 16.8S 119.2E: 085 (155): 085 (155): 959
+48: 13/0600: 18.0S 119.2E: 105 (190): 095 (175): 950
+60: 13/1800: 19.5S 120.4E: 120 (225): 090 (165): 953
+72: 14/0600: 21.1S 123.4E: 145 (265): 040 (075): 994
+96: 15/0600: 23.0S 134.0E: 200 (370): 030 (055): 1003
+120: 16/0600: : : :
REMARKS:
Tropical Cyclone Ilsa has developed northwest of the Kimberley.

Good confidence in the position of 23U with visible imagery and recent
microwave passes.

Intensity is 40 knots based on recent SMAP data and development of curved band,
which gives greater confidence in Dvorak analysis of DT = 3.0. MET = 3.5 based
on D- 24 hour trend. PAT is 3.0. FT = 3.0 based on DT. CI maintained at 3.0.
Objective guidance is becoming more credible with development of curved
banding. Available objective guidance with SATCON 53 knots (1-min), CIMSS ADT
57 knots (1-min), NESDIS ADT 57 knots (1-min) and OPEN-AIIR about 35 knots.

Wind shear has decreased over 23U and at 0600 UTC, CIMSS upper wind analysis
has analysed approximately 15 knots of shear. The system should begin a rapid
development cycle with favourable shear, high mid-level moisture and warm SSTs
(30+ degrees Celsius).

Upper divergence to the south increases and the system is forecast to develop
into a severe tropical cyclone from Wednesday, likely reaching a category 4
system during Thursday. 23U is forecast to move southwest parallel to and
offshore from the Kimberley coast during Tuesday and Wednesday before turning
south and then southeast during Thursday, with a coastal crossing likely later
Thursday or early Friday between Port Hedland and Broome.

The forecast track is based on a standard consensus of numerical weather
prediction (NWP) models. This track is consistent with upper-air analyses which
show a mid-upper ridge over the NT and an approaching upper trough over
southern WA. There is relatively high confidence in this forecast track. In the
long-term, 23U is forecast to move over central Australia and begin a
transition to a deep, sub-tropical system as it interacts with the sub-tropical
jet.

Intensity forecasts are based on a rapid rate of development prior to landfall,
with a landfall intensity of 95 knots (Category 4). This is consistent with a
consensus of NWP models. 23U is forecast to remain a strong system as it moves
inland on Friday.

[cycloneye]

Looks symmetric as shear has decreased.

[cycloneye]

TROPICAL CYCLONE ADVICE NUMBER 20
Issued at 9:03 pm WST on Tuesday 11 April 2023

Headline:
Tropical Cyclone Ilsa is showing signs of rapid development and has been upgraded to category 2.

Areas Affected:
Warning Zone
None.

Watch Zone
Beagle Bay to Whim Creek, including Port Hedland and Broome, and inland adjacent areas to Marble Bar

Cancelled Zone
None.

Details of Tropical Cyclone Ilsa at 8:00 pm AWST:
Intensity: Category 2, sustained winds near the centre of 100 kilometres per hour with wind gusts to 140 kilometres per hour.

Location: within 35 kilometres of 15.2 degrees South 120.5 degrees East, estimated to be 360 kilometres north northwest of Broome and 600 kilometres north northeast of Port Hedland.

Movement: southwest at 17 kilometres per hour.

Tropical Cyclone Ilsa has intensified to category 2 and is expected to intensify further overnight and on Wednesday as it moves southwest, parallel to the Kimberley coast. Ilsa is likely to intensify into a severe tropical cyclone during Wednesday.

The system is expected to track to the south and then southeast during Thursday and a severe impact is likely along the coast and adjacent inland parts between Port Hedland and Broome, during late Thursday or early Friday.

[wxman57]

Looks like an eye may be forming. BoM has it at 50 kts (10-min winds). May be stronger than that - pushing 65 kts 1-min. It will make landfall on Eighty-Mile Beach, a rather desolate section of coastline with a wildlife preserve.