AXAU01 APRF 031804
IDW27600
TROPICAL CYCLONE TECHNICAL BULLETIN: AUSTRALIA - WESTERN REGION
Issued by AUSTRALIAN BUREAU OF METEOROLOGY TROPICAL CYCLONE WARNING CENTRE
at: 1804 UTC 03/03/2021

Name: Tropical Cyclone Marian
Identifier: 15U
Data At: 1800 UTC
Latitude: 19.7S
Longitude: 92.8E
Location Accuracy: within 30 nm [55 km]
Movement Towards: east southeast [119 deg]
Speed of Movement: 8 knots [15 km/h]
Maximum 10-Minute Wind: 50 knots [95 km/h]
Maximum 3-Second Wind Gust: 70 knots [130 km/h]
Central Pressure: 984 hPa
Radius of 34-knot winds NE quadrant: 130 nm [240 km]
Radius of 34-knot winds SE quadrant: 160 nm [295 km]
Radius of 34-knot winds SW quadrant: 150 nm [280 km]
Radius of 34-knot winds NW quadrant: 130 nm [240 km]
Radius of 48-knot winds NE quadrant: 70 nm [130 km]
Radius of 48-knot winds SE quadrant: 70 nm [130 km]
Radius of 48-knot winds SW quadrant: 70 nm [130 km]
Radius of 48-knot winds NW quadrant: 70 nm [130 km]
Radius of 64-knot winds:
Radius of Maximum Winds: 30 nm [55 km]
Dvorak Intensity Code: T3.5/3.5/W1.0/24HRS STT:S0.0/6HRS
Pressure of outermost isobar: 1004 hPa
Radius of outermost closed isobar: 300 nm [555 km]

FORECAST DATA
Date/Time : Location : Loc. Accuracy: Max Wind : Central Pressure
[UTC] : degrees : nm [km]: knots[km/h]: hPa
+06: 04/0000: 20.2S 93.6E: 045 [080]: 050 [095]: 984
+12: 04/0600: 20.7S 94.0E: 050 [090]: 050 [095]: 984
+18: 04/1200: 21.4S 94.5E: 050 [095]: 050 [095]: 984
+24: 04/1800: 22.1S 94.9E: 055 [100]: 045 [085]: 986
+36: 05/0600: 23.5S 95.6E: 060 [110]: 040 [075]: 989
+48: 05/1800: 24.9S 96.1E: 080 [150]: 035 [065]: 993
+60: 06/0600: 26.2S 96.5E: 105 [195]: 035 [065]: 992
+72: 06/1800: 26.9S 96.7E: 145 [270]: 035 [065]: 991
+96: 07/1800: 28.6S 96.4E: 235 [435]: 030 [055]: 995
+120: 08/1800: 30.8S 95.9E: 310 [570]: 030 [055]: 993

REMARKS:
Marian has weakened considerably over the last 24 hours. The eye pattern that was evident 24 hours ago has been replaced by a curved band pattern. The low level centre is evident in EIR imagery and confidence in location is still fair.
There has been no high resolution microwave passes since about 1245UTC.

Dvorak analysis: DT=3.5 based upon a curved band [0.9 wrap]; adjusted MET=3.5 based on 1.0 weakening/24 hours, PAT is left at 3.5. FT set at 3.5 and CI at 3.5 consistent with a 50kn intensity. There is some variation between objective guidance: CIMSS ADT CI=2.8 41 knot 1-min wind, NESDIS is higher with CI=3.7 and 59 1-min wind, SATCON is at 54 knots 1-min. The current intensity remains at 50 knots.

Marian weakened as it backtracked across the cooler SSTs its passage produced, even though it is now moving southeast out of this environment the SSTs will only increase to around 26C and then less than 25C by Friday.

Dry air is also evident on the TPW loop wrapping around the system and towards the core. Despite that the wind shear is low with good poleward outflow. The shear is not expected to increase until Friday under the influence of mid-latitude trough to the southwest.

It is possible that model guidance is maintaining the system at too high an intensity over the next 48 hours The current forecast is conservative in that it
doesn't weaken the system as quickly would be typical given the unfavourable SSTs and dry air but is still weakening faster than the model trends.

Gale and storm radii were estimated from morning Ascat passes and an afternoon partial AMSR2 pass. The system is forecast to weaken below cyclone intensity Friday night/Saturday morning however gales are still expected on the southern flank due to a ridge to the south.

Copyright Commonwealth of Australia
==
The next bulletin for this system will be issued by: 04/0130 UTC.
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