Tropical Cyclone Marcus strengthened into the equivalent of a major hurricane on Monday.  At 11:00 p.m. EDT on Monday the center of Tropical Cyclone Marcus was located at latitude 15.0°S and longitude 117.7°E which put it about 340 miles (550 km) north of Port Hedland, Australia.  Marcus was moving toward the west at 18 m.p.h. (29 km/h).  The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 150 m.p.h. (240 km/h).  The minimum surface pressure was 955 mb.

The circulation of Tropical Cyclone Marcus was symmetrical and very well organized.  A very small circular eye was at the center of circulation.  A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of the circulation.  Storms in the core were generating strong upper level divergence which was pumping mass away from the tropical cyclone.  Winds to hurricane/typhoon force extended out about 60 miles (95 km) from the center of circulation.  Winds to tropical storm force extended out about 190 miles (305 km) from the center.

Tropical Storm Marcus will continue to move through an environment very favorable for strong tropical cyclones during the next two days.  Marcus will move over water where the Sea Surface Temperature is near 30°C.  It is moving under an area where the upper level winds are weak and there is little vertical wind shear.  Tropical Cyclone Marcus is likely to intensify and it could reach the equivalent of a Category 5 hurricane.  If a rainband wraps around the core of the circulation, then a second eyewall could form.  That would initiate an eyewall replacement cycle, which would cause Marcus to weaken at least temporarily.

Tropical Cyclone Marcus is moving around the western end of a subtropical ridge, which is steering Marcus toward the west.  A general motion toward the west is expected to occur for anther 24 to 48 hours.  Marcus will reach the western end of the ridge in about two days, and then the tropical cyclone will turn toward the south.  On its anticipated track Tropical Cyclone Marcus will stay north of the coast of Western Australia for the next few days.