Cyclone Warnings
at: 0643 UTC 21/03/2018
Name: Severe Tropical Cyclone Marcus
Identifier: 20U
Data At: 0600 UTC
Latitude: 14.7S
Longitude: 111.0E
Location Accuracy: within 15 nm [30 km]
Movement Towards: west southwest [256 deg]
Speed of Movement: 12 knots [22 km/h]
Maximum 10-Minute Wind: 110 knots [205 km/h]
Maximum 3-Second Wind Gust: 155 knots [285 km/h]
Central Pressure: 936 hPa
Radius of 34-knot winds NE quadrant: 110 nm [205 km]
Radius of 34-knot winds SE quadrant: 150 nm [280 km]
Radius of 34-knot winds SW quadrant: 120 nm [220 km]
Radius of 34-knot winds NW quadrant: 90 nm [165 km]
Radius of 48-knot winds NE quadrant: 60 nm [110 km]
Radius of 48-knot winds SE quadrant: 60 nm [110 km]
Radius of 48-knot winds SW quadrant: 60 nm [110 km]
Radius of 48-knot winds NW quadrant: 60 nm [110 km]
Radius of 64-knot winds: 40 nm [75 km]
Radius of Maximum Winds: 15 nm [30 km]
Dvorak Intensity Code: T6.0/6.0/D0.5 24 HRS STT:0.0/06HRS
Pressure of outermost isobar: 1006 hPa
Radius of outermost closed isobar: 300 nm [555 km]
Date/Time    : Location    : Loc. Accuracy: Max Wind   : Central Pressure
[UTC]        : degrees     :      nm  [km]: knots[km/h]: hPa
+06:  21/1200: 15.0S 109.8E:     025 [050]:  125  [230]:  919
+12:  21/1800: 15.4S 108.6E:     040 [070]:  125  [230]:  919
+18:  22/0000: 16.0S 107.7E:     050 [095]:  120  [220]:  925
+24:  22/0600: 16.7S 107.0E:     065 [120]:  110  [205]:  937
+36:  22/1800: 18.6S 106.0E:     085 [155]:  100  [185]:  946
+48:  23/0600: 21.0S 105.6E:     105 [190]:  080  [150]:  963
+60:  23/1800: 23.4S 106.1E:     125 [230]:  060  [110]:  979
+72:  24/0600: 25.5S 106.8E:     140 [265]:  040  [075]:  992
+96:  25/0600: 28.0S 107.7E:     185 [345]:  030  [055]:  997
+120: 26/0600: 30.8S 113.1E:     275 [505]:  030  [055]: 1000
Marcus was located using Visible imagery during Wednesday After a slight
weakening phase during the overnight period Marcus is showing signs of
intensification again. 

Dvorak: The eye pattern is re-establishing itself with an OW eye appearing in a
White surround giving an E number of 6.0, Eadj is now at 0.5 for an OW eye in a
CMG surround. Time averaged DT is now back at 6.0. MET/PAT is 6.0 based on D-
trend and CI is 6.0. CIMSS ADT is currently 5.7 and NESDIS ADT 6.0. Both methods
have been fluctuating between eye pattern and other patterns. There is no recent
SATCON estimate. Intensity remains at 110 kt 10-minute wind.

Marcus has begun to move to the west southwest over the last few hours as the
influence of the mid-level ridge to the south weakens. NWP is in strong
agreement that Marcus will continue to turn towards the southwest and take a
more southerly direction during Thursday.

Vertical wind shear is around 10 knots from the E. There is good upper
divergence, with dual outflow channels [poleward and equatorward]. 

Ocean Heat Content is favourable and SSTs are around 30C along the forecast
track. Shear should remain low over the next few days. 

Marcus will continue at a category 5 system during Wednesday as it continues to
track towards the west southwest. From late Wednesday the ridge will move
eastwards and an approaching upper level trough will help steer the system
towards the southwest then towards the south on Thursday and Friday. 

As Marcus tracks towards the south on Thursday and Friday it will start to
weaken with decreasing SSTs and increasing wind shear.

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The next bulletin for this system will be issued by: 21/1330 UTC by Perth TCWC.
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Severe Tropical Cyclone Marcus

Issued at 2:40 pm AWST Wednesday 21 March 2018. No Tropical Cyclone Advice is current for this system.

Community Threat

Warning Zone
Gales within 24 hours
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Watch Zone
Gales from 24-48 hours
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Past Cyclone Details

Past Location and Intensity Number
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Past Track and Movement
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Current Cyclone Details

Current Location and Intensity Number
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Very Destructive Winds
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Destructive Winds
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Gale Force Winds
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Forecast Cyclone Details
(Up to 72 hours from time of issue)

Forecast Location and Intensity Number
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Very Destructive Wind Boundary
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Destructive Wind Boundary
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Gale Force Wind Boundary
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Most Likely Future Track
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Range of Likely Tracks of Cyclone Centre
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The forecast path shown above is the Bureau's best estimate of the cyclone's future movement and intensity. There is always some uncertainty associated with tropical cyclone forecasting and the grey zone indicates the range of likely tracks of the cyclone centre.

Due to the uncertainty in the future movement, the indicated winds will almost certainly extend to regions outside the rings on this map. The extent of the warning and watch zones reflects this.

This product is designed for land-based communities; mariners should read the coastal waters and high seas warnings.


Severe Tropical Cyclone Marcus is moving towards the west southwest, well away from the WA mainland. The severe tropical cyclone may intensify further Wednesday evening before turning in a southerly direction Thursday and starting to weaken.

Areas affected:

Warning zone: None.

Watch zone: None.

Cancelled zones: None.

Details of Severe Tropical Cyclone Marcus at 2:00 pm AWST:

Intensity: category 5, sustained winds near the centre of 205 kilometres per hour with wind gusts to 285 kilometres per hour.
Location: within 30 kilometres of 14.7 degrees South, 111.0 degrees East , 1020 kilometres northwest of Port Hedland and 870 kilometres north northwest of Exmouth .
Movement: west southwest at 22 kilometres per hour .

Severe Tropical Cyclone Marcus is now tracking in a west southwest direction, well away from the WA mainland. Marcus may strengthen further during Wednesday before tracking towards the southwest on Thursday when it will start to weaken.


Severe Tropical Cyclone Marcus is well away from the WA mainland and is not expected to directly affect WA communities.


  Time (AWST) Intensity Category Latitude
(decimal deg.)
(decimal deg.)
Estimated Position
Accuracy (km)
0hr 2 pm March 21 5 14.7S 111.0E 30
+6hr 8 pm March 21 5 15.0S 109.8E 50
+12hr 2 am March 22 5 15.4S 108.6E 70
+18hr 8 am March 22 5 16.0S 107.7E 95
+24hr 2 pm March 22 5 16.7S 107.0E 120
+36hr 2 am March 23 4 18.6S 106.0E 155
+48hr 2 pm March 23 3 21.0S 105.6E 190
+60hr 2 am March 24 2 23.4S 106.1E 230
+72hr 2 pm March 24 1 25.5S 106.8E 265

Tropical Cyclone information is also available in MetEye

Next Issue

The next Forecast Track Map will be issued by 9:00 pm AWST Wednesday