Tag Archives: Cooktown

Weaker Tropical Cyclone Ann Nears Northern Queensland

A weaker Tropical Cyclone Ann neared northern Queensland on Monday.  At 11:00 p.m. EDT on Monday the center of Tropical Cyclone Ann was located at latitude 14.4°S and longitude 148.4°E which put it about 230 miles (370 km) east-northeast of Cooktown, Australia.  Ann was moving toward the west-northwest at 14 m.p.h. (22km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 996 mb.  The Australian Bureau of Meteorology issued a Tropical Cyclone Warning that extended from Lockhart River to Cooktown including Coen and Lizard Island.

The circulation around Tropical Cyclone Ann weakened on Monday because of a drier, more stable environment and more vertical wind shear.  Low level convergence pulled drier, more stable air closer to the center of Tropical Cyclone Ann.  The drier, more stable air caused many of the stronger thunderstorms to weaken.  Despite the drier, more stable environment stronger thunderstorms redeveloped south of the center of circulation late on Monday.  Tropical Cyclone Ann was moving near the northwestern portion of an upper level ridge.  The ridge produced easterly winds which caused moderate vertical wind shear.  The wind shear also contributed to the weakening of storms in the northern half of the circulation.

Tropical Cyclone Ann continued to have a distinct low level center of circulation despite the less favorable environment.  However, the wind field exhibited a more asymmetric structure.  The strongest winds were occurring in an area of thunderstorms south of the center of circulation.  Winds to tropical storm force extended out about 100 miles (160 km) from the center in the southern half of the circulation.  Winds to tropical storm force only extended out about 50 miles (80 km) from the center in the northern half of the circulation.

Tropical Cyclone Ann will continue to move through a less favorable environment during the next 24 hours.  Ann will move over water in the Coral Sea where the Sea Surface Temperature is near 27.5°C.  It will continue to move through a region where there is drier, more stable air and the upper level ridge will continue to cause moderate vertical wind shear.  The drier, more stable air and moderate vertical wind shear will prevent significant intensification.  Tropical Cyclone Ann could maintain its intensity during the next 12 hours, but it may weaken when it approaches the coast of the Cape York Peninsula.

Tropical Cyclone Ann will move north of a ridge which will steer Ann toward the west-northwest.  On its anticipated track Tropical Cyclone Ann will make landfall on the Cape York Peninsula in northern Queensland in about 24 hours.  Ann will bring some gusty winds, but the greatest risk will be locally heavy rain.