AXAU01 APRF 111348 IDW27600 TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE at: 1348 UTC 11/04/2023 Name: Tropical Cyclone Ilsa Identifier: 23U Data At: 1200 UTC Latitude: 15.2S Longitude: 120.5E Location Accuracy: within 20nm (35 km) Movement Towards: southwest (233 deg) Speed of Movement: 9 knots (17 km/h) Maximum 10-Minute Wind: 55 knots (100 km/h) Maximum 3-Second Wind Gust: 75 knots (140 km/h) Central Pressure: 985 hPa Radius of 34-knot winds NE quadrant: 60 nm (110 km) 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: 30 nm (55 km) Radius of 48-knot winds SE quadrant: 30 nm (55 km) Radius of 48-knot winds SW quadrant: 30 nm (55 km) Radius of 48-knot winds NW quadrant: 30 nm (55 km) Radius of 64-knot winds: nm ( km) Radius of Maximum Winds: 20 nm (35 km) Dvorak Intensity Code: T4.0/4.0/D1.5/24HRS STT:D0.5/06HRS Pressure of outermost isobar: 1004 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: 11/1800: 15.5S 120.2E: 040 (070): 060 (110): 980 +12: 12/0000: 15.8S 119.9E: 050 (090): 065 (120): 976 +18: 12/0600: 16.2S 119.6E: 055 (105): 070 (130): 972 +24: 12/1200: 16.5S 119.3E: 065 (120): 080 (150): 964 +36: 13/0000: 17.5S 118.9E: 080 (150): 090 (165): 952 +48: 13/1200: 18.9S 119.5E: 100 (180): 095 (175): 948 +60: 14/0000: 20.4S 121.6E: 115 (215): 070 (130): 964 +72: 14/1200: 21.8S 125.7E: 140 (255): 040 (075): 997 +96: 15/1200: 22.7S 136.8E: 210 (385): 030 (055): 1002 +120: 16/1200: : : : REMARKS: Tropical Cyclone Ilsa has developed rapidly during the past 6 hours, with bursting convection and symmetric structure evident. Good position fix based on overshooting cold tops in EIR imagery and recent microwave passes. Dvorak analysis yields FT = 4.0 based on MET/PAT and D+ 24h trend. DT not available due to development of central cold cover pattern. Available objective guidance with SATCON 55 knots (1-min), CIMSS ADT 59 knots (1-min), NESDIS ADT 57 knots (1-min) and OPEN-AIIR about 42 knots. Intensity is set at 55 knots. CIMSS upper wind shear analysed at 10-15 knots over the cyclone at 1200 UTC. Ilsa is forecast to develop at a greater than standard rate with favourable shear, high mid-level moisture and warm SSTs (30+ degrees Celsius) along the forecast track. Upper divergence is expected to increase to the south ahead of an approaching mid-latitude trough. The cyclone is forecast to intensify into a severe tropical cyclone from Wednesday, likely reaching a category 4 intensity during Thursday. Ilsa is forecast to move southwest parallel to and offshore from the Kimberley coast during Wednesday before turning south and then southeast during Thursday, with a coastal crossing likely later Thursday or early Friday between De Grey and Bidyadanga. The forecast track is based on a standard consensus of numerical weather prediction (NWP) models, consistent with 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, the cyclone 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. Tropical Cyclone Ilsa is forecast to remain a strong system as it moves inland on Friday. Copyright Commonwealth of Australia == The next bulletin for this system will be issued by: 11/1930 UTC.