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CAIRNS

THE DECISION TO SORTIE OR REMAIN IN PORT

General

The Port of Cairns had developed a Cyclone Contingency Plan that establishes specific actions to be taken in a tropical cyclone threat situation. The objective of the plan is: "To have the port area evacuated at least six hours before destructive winds commence, and to have small vessels safely moored in their designated areas of shelter by that time."

The Cyclone Contingency Plan establishes three alert conditions:

YELLOW alert:  Destructive winds forecast to affect the area within 20 hours. Smaller vessels will seek shelter in the creeks adjacent to Trinity Inlet in accordance with the guidelines in the plan.

ORANGE alert:  Destructive winds forecast to affect the area within 16 hours. All large merchant vessels will be directed to proceed to sea. Naval vessels will be directed by the Base Commander. In this instance, U.S. Navy vessels in port at Cairns will be directed to proceed to sea with the large merchant vessels, as the Naval vessels addressed specifically by the Contingency Plan are those of the Royal Australian Navy assigned to HMAS Cairns.

RED alert:  Destructive winds forecast to affect the port within six hours. Port closed.

The decision on whether to sortie or remain in port is usually based on the answer to a single question: Would the vessel in question be better off attempting an evasion at sea or by remaining in port? In the case of Cairns, however, remaining in port is not an option because U.S. Navy vessels berthed at the port will be directed by harbor authorities to sortie from the port whenever the port is threatened by a tropical cyclone. Evasion rationale should include consideration of the following general factors:

1. Vessel characteristics
2. Berth and anchorage conditions
3. Most recent hurricane warning advisory
4. Tropical cyclone climatology

Individual vessel characteristics and berth/anchorage conditions are best determined by those responsible for each vessel and local port authorities. Tropical cyclone warnings are issued by the Naval Pacific Meteorology and Oceanography Center/Joint Typhoon Warning Center Pearl harbor for the U.S. Government and by the Australian Bureau of Meteorology Brisbane Tropical Warning Center. The interpretation of tropical cyclone climatology is addressed in the following sections.

Evasion at Sea

Commanding officers and ship masters with access to tropical cyclone warnings and advisories are in the best possible position to modify evasion routes and tactics, as necessary, to successfully evade the storm. Early planning is essential because the orientation of the coast of Queensland and the existence of the Great Barrier Reef limit the sortie options of ships in port at Cairns.

The timing of the sortie is affected by:

1. The time required to make preparations to get underway.
2. The time required to reach open water and gain sea room.
3. The forward speed of the tropical cyclone.
4. The radius of hazardous winds and seas that can adversely impact a vessel's ability to reach open water.

Commanding officers and ship masters with access to tropical cyclone warnings and advisories coupled with OTSR services are most capable of making the safest and most prudent decision for successful storm evasion and avoidance. In all sortie situations, OTSR services from Naval Pacific Meteorology and Oceanography Center (NPMOC), Yokosuka should be requested and utilized. The best sortie route in a specific tropical scenario is largely dependant on the location of the tropical cyclone and the forecast track. During any tropical cyclone threat there is normally one to three options available to the commanding officer and ship master. Selection of the best option is the objective of all concerned!

For Cairns the following guidelines are offered:

a. Tropical cyclone approaching from northeast or east.

Sortie as early as possible and steam northward via Grafton passage. Harbor authorities also recommend another option and that is staying in the channel between the Great Barrier Reef and the coast of Queensland on the east side of the Cape York Peninsula. They state that the route is safely navigable, but an Australian pilot should be onboard for the voyage. The route will place the vessel on the weaker (west) side of the storm, thereby mitigating the worst wind effects of the storm and creating following winds and seas. Another advantage of the route is that the shallow waters associated with the Great Barrier Reef would reduce the impact of open ocean swell waves on the evasion route.

b. Tropical cyclone approaching from north, northwest or west.

A northeastward or eastward sortie into the Coral Sea is recommended. The sortie should be started early, placing as much distance as possible between the sortieing unit and the tropical cyclone .

Remaining in Port

Remaining in port during a tropical cyclone threat is not an option at Cairns. As stated in preceding Section 5.8.1, whenever Cairns is threatened by a tropical cyclone, all ships will be directed to evacuate the port as soon as an ORANGE alert is declared.

Source: http://www.nrlmry.navy.mil/port_studies/thh-nc/australi/cairns/text/sect8.htm