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Tropical Cyclone Nora Strengthens Over Gulf of Carpentaria

Tropical Cyclone Nora strengthened over the Gulf of Carpentaria on Friday.  At 11:00 p.m EDT on Friday the center of Tropical Cyclone Nora was located at latitude 12.6°S and longitude 140.0°E which put it about 125 miles (205 km) west of Weipa, Australia.  Nora was moving toward the southeast at 9 m.p.h. (14 km/h).  The maximum sustained wind speed was 110 m.p.h. (175 km/h) and there were wind gusts to 130 m.p.h. (210 km/h).  The minimum surface pressure was 956 mb.  The Australian Bureau of Meteorology had issued a Warning for the portion of the coast from Karumba to Mapoon including Weipa and Mornington Island.  A Watch was in effect for the portion of the coast from Weipa to the border between the Northern Territory and Queensland.

Tropical Cyclone Nora strengthened on Friday as it entered the northern portion of the Gulf of Carpentaria.  An eye appeared intermittently at the center of circulation.  A band of stronger thunderstorms wrapped intermittently around the formative eye and the strongest winds were blowing in the band of thunderstorms.  Bands of showers and thunderstorms were revolving around the center of circulation.  Storms near the core of the circulation were generating upper level divergence which was pumping mass away from the tropical cyclone.

Tropical Cyclone Nora will be moving through an environment favorable for intensification.  Nora will move over water where the Sea Surface Temperature is near 30°C.  It will move under an area where the upper level winds are weak and there is little vertical wind shear.  Tropical Cyclone Nora could strengthen into the equivalent of a major hurricane during the next 24 to 36 hours.

Tropical Cyclone Nora is moving near the western end of a mid-level ridge which is steering Nora toward the south.  A general motion toward the south is expected to continue for another day or two.  On its anticipated track Nora could approach the coast of Queensland between Kowanyama and the mouth of the Gilbert River in 24 to 36 hours.  Nora could bring gusty winds and locally heavy rain to portions of northwestern Queensland.

Elsewhere, Tropical Cyclone Marcus was weakening off the coast of Western Australia.  At 11:00 p.m. EDT on Friday the center of Tropical Cyclone Marcus was located at latitude 25.9°S and longitude 107.5°E, which put it about 770 miles (1045 km) west of Carnarvon, Australia.  Marcus was moving toward the south-southeast at 20 m.p.h. (32 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 984 mb.

Tropical Cyclone Nora Develops Rapidly North of Australia

Tropical Cyclone Nora developed rapidly north of Australia over the Arafura Sea on Thursday.  At 11:00 p.m. EDT on Thursday the center of Tropical Cyclone Nora was located at latitude 10.0°S and longitude 136.8°E which put it about 160 miles (260 km) north of Nhulunbuy, Australia.  Nora was moving toward the east at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 986 mb.

A center of circulation organized quickly on Thursday in an area of thunderstorms over the Arafura Sea and the Australian Bureau of Meteorology designated the system as Tropical Cyclone Nora.  A primary rainband wrapped around the western and northern side of the center of circulation.  An eye appeared to be forming at the center of Tropical Cyclone Nora.  Bands of showers and thunderstorms were revolving around the core of the circulation.  Storms around the core were generating well developed upper level divergence which was pumping mass away from the tropical cyclone.  The removal of mass was allowing the surface pressure to decrease rapidly and the wind speeds were increasing in response.

The Australian Bureau of Meteorology issued Warnings for the portions of the coast from Elcho Island to Cape Shield including Cape Wessel and from Pormpuraaw to Thursday Island.  A Watch was in effect for the portion of the coast from Pormpuraaw to the border between the Northern Territory and Queensland including Mornington Island.

Tropical Cyclone Nora will move through an environment very favorable for intensification during the next 48 hours.  Nora will move over water where the Sea Surface Temperature is near 30°C.  It will move through an area where the upper level winds are weak and there is little vertical wind shear.  Nora is likely to intensify rapidly and it is likely to become the equivalent of a hurricane/typhoon within 24 hours.  Tropical Cyclone Nora could become the equivalent of a major hurricane within 24 to 48 hours.

Tropical Cyclone Nora was moving through an area where steering winds are weak and it was moving slowly toward the east.  A subtropical ridge east of Australia is expected to strengthen.  The ridge is forecast to steer Nora more toward the south in 12 to 24 hours.  On its anticipated track Tropical Cyclone Nora is expected to move over the Gulf of Carpentaria toward the coast of Queensland.  Nora could strengthen into a dangerous tropical cyclone.

Elsewhere, Tropical Cyclone Marcus continued to churn west of Australia.  At 11:00 p.m. EDT on Thursday the center of Tropical Cyclone Marcus was located at latitude 20.6°S and longitude 106.0°E which put it about 555 miles (895 km) west-northwest of Learmonth, Australia.  Marcus was moving toward the south at 13 m.p.h. (21 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 951 mb.

Tropical Cyclone Marcus Strengthens to Equivalent of Category 5 Hurricane Northwest of Australia

Tropical Cyclone Marcus strengthened into the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale as it churned northwest of Australia on Wednesday.  At 5:00 p.m. EDT on Wednesday the center of Tropical Cyclone Marcus was located at latitude 15.8°S and longitude 108.0°E which put it about 600 miles (960 km) northwest of Learmonth, Australia.  Marcus was moving toward the west-southwest at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 160 m.p.h. (260 km/h) and there were wind gusts to 195 m.p.h. (315 km/h).  The minimum surface pressure was 918 mb.

After completing an eyewall replacement cyclone on Tuesday, Tropical Cyclone Marcus began to intensify quickly again on Wednesday.  Marcus exhibited a circular, symmetrical circulation.  There was a tiny circular eye at the center of circulation.  The strongest winds were occurring in a ring of thunderstorms that surrounded the small inner eye.  Recent satellite images suggested that another eyewall replacement cycle may be beginning.  A larger, outer eyewall appeared to have encircled the small inner eye.  Bands of showers and thunderstorms were revolving around the concentric eyewalls.  Storms in the core of Marcus were generating very well developed upper level divergence which was pumping mass away in all directions from the tropical cyclone.

As frequently happens during eyewall replacement cycles, Tropical Cyclone Marcus increased in size after Tuesday’s eyewall replacement cycle was completed.  Winds to hurricane/typhoon force extended out about 50 miles (85 km) from the center of circulation.  Winds to tropical storm force extended out 180 miles (290 km) from the center.  The Hurricane Intensity Index (HII) for Tropical Cyclone Marcus was 35.0.  The Hurricane Size Index (HSI) was 18.7 and the Hurricane Wind Intensity Size Index (HWISI) was 53.7.

Tropical Cyclone Marcus is in an environment that is very favorable for strong tropical cyclones.  Marcus is moving over water where the Sea Surface Temperature is near 30°C.  It is moving through an area where the upper level winds are weak and there is little vertical wind shear.  Although Tropical Cyclone Marcus is in a very favorable environment, another eyewall replacement cycle would cause it to weaken.  The wind would begin to converge into the outer eyewall, which would cause the storms in the inner eyewall to weaken.  The wind speeds would decrease as the inner eyewall weakens.  Then the strongest winds would be found in the outer eyewall and the circulation would increase in size.

Tropical Cyclone Marcus is nearing the western end of a subtropical ridge over Australia.  The ridge is steering Marcus toward the west-southwest, but the tropical cyclone will turn more toward the south when it reaches the end of the ridge.  Tropical Cyclone Marcus will make a gradual turn toward the southeast during the next several days.  On its anticipated track Tropical Cyclone Marcus will remain west of Western Australia during the next 36 to 48 hours.

Tropical Cyclone Marcus Strengthens Into Equivalent of Major Hurricane

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.