Summary
APRA HARBOR
SUMMARY
Apra Harbor is not a typhoon haven. The reasons for this conclusion include:
(1) Guam is susceptible to being hit by the world's largest and most intense tropical cyclones. The maximum wind gust measured in Guam was 148 kt in Typhoon Paka, while Typhoon Karen (November 1962) was probably the most intense (estimated gust to 173 kt) typhoon to hit Guam in recent history. Note that wind-measuring equipment on Guam has historically failed in high wind events.
(2) The topography adjacent to the Port does not provide adequate protection from strong winds; all deep draft berths and anchorages are exposed and vulnerable.
(3) There is significant risk of substantial damage to vessels in the Harbor if a strong tropical cyclone would pass close to the Port. A large number of vessels that have remained in port during such passages have sustained extensive damage resulting from groundings or, in some cases, sunk in the Harbor.
(4) As stated in the 1999 Typhoon Vulnerability Study for Guam, “The seaports are highly vulnerable to winds, storm surge, coastal inundation, high seas, some hazardous surf, and flooding from the sea and from torrential rains.”
(5) Additionally, “ Apra Harbor has a single, relatively narrow deep-water channel linking the open ocean to port facilities located at the eastern end of the Harbor. Were a large ship to sink in the channel, it could take up to six months to salvage it and fully reopen the channel. This could greatly limit the use of the Port, and could produce a devastating impact to the island. For this reason, all large ships should leave the Harbor before the onset of 30.4 kt (35 mph) winds when a typhoon is expected. If winds reach strong Typhoon Category 2 intensity, they could cause a large ship to break or drag anchor, possibly endangering the channel.”
(6) As confirmed during the Site Visit in February 2006, official Naval guidance is as follows, "Due to the small size and limited natural protection of Apra Harbor, for typhoon winds, the best protection for ships capable of maneuvering at sea is to get underway early and maneuver to clear the path of the storm. Apra Harbor is not a typhoon haven or sanctuary; all ships capable of getting underway shall do so."
It is standard practice for all seaworthy U. S. Navy ships in Apra Harbor to sortie and evade at sea when a tropical cyclone threatens the Port.
About 180 ships visit Apra Harbor each year. Military Sealift Command (MSC) represents about 70% of the traffic in the Port.
Source: http://www.nrlmry.navy.mil/port_studies/thh-nc/guam/apra/text/summary.htm
