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APRA HARBOR, GUAM

THE DECISION TO SORTIE OR REMAIN IN PORT

General

Under normal circumstances, the decision on whether to sortie or remain in port is largely based on the answer to a single question: Would the vessel in question be better off attempting an evasion at sea or remaining in port? Evasion rationale should include consideration of the following general factors:

• Vessel characteristics
• Berth and anchorage conditions
• Most recent tropical cyclone warning advisory
• Tropical cyclone climatology
• Sheltering of haven qualities

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 Department of Defense assets.

Guam lies in a region prone to tropical cyclones. 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.

ANNEX H to COMPACFLT OPORD 201-06 provides guidance on meteorological and oceanographic (METOC) operations, weather response, and reporting procedures to include instances of destructive or heavy weather in the Pacific Fleet.

The criteria for setting local conditions of readiness are set forth in Commander in Chief, U. S. Pacific Command Representative Guam /Commonwealth of the Northern Mariana Islands (CNMI) Federated States of Micronesia (FSM)/Republic of Palau Disaster Preparedness Joint Plan 101 Revision 2, Ser N4/0056 dated 31 December 2005. Appendix 1 to ANNEX C to COMNAVMARIANAS Contingency Preparedness Operation Plan (Tropical Cyclone Response) provides further guidance.

Naval Pacific Meteorology and Oceanography Center (NPMOC), Yokosuka, Japan COMNAVMARIANAS Representative (Staff METOC Officer (SMO, Code N3WEA)) will provide regular or as needed heavy weather briefs to COMNAVMARIANAS. NPMOC Yokosuka will maintain cyclone tracking and forecast information on their Internet web page.

Setting of appropriate Condition of Readiness (COR) will be conducted by COMNAVMARIANAS upon recommendations by SMO (339-6141/6144) and consultation with Anderson Air Force Base Command Center and Guam Civil Defense. COR setting is normally completed during a Heavy Weather Brief in the COMNAVMARIANAS Headquarters conference room which is attended by representatives of ACOS, tenants, Navy commands on Guam, USCG, Anderson Air Force Base, and Civil Defense. Setting of COR may be conducted via available communications between COMNAVMARIANAS and the Governor of Guam. The Staff METOC Officer drafts the COR messages to all affected parties with weather watch/warning/advisory information and coordinates through COMNAVMARIANAS N1 for release. A Port Operations Heavy Weather Checklist is contained in the COMNAVMARIANAS Battle Book. COMNAVMARIANAS Operations (N3) coordinates the ship safe haven instructions for the sortie.

Tropical cyclone Conditions of Readiness are as follows:

1. COR IV: This is the normal condition for Guam. Destructive winds of 50 knots or greater are possible within 72 hours.
2. COR III: Declared when destructive winds of 50 knots or greater are possible within 48 hours.
3. COR II: Destructive winds of 50 knots or more are anticipated within 24 hours.
4. COR I: Destructive winds of 50 knots or greater are anticipated within 12 hours or are occurring.

The interpretation of tropical cyclone climatology is addressed in the following sections.

Evasion at Sea

Evasion at sea is the preferred course of action when confronted with potential typhoon conditions on Guam.

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), Pearl Harbor should be requested and utilized. The best sortie route in a specific tropical cyclone scenario is largely dependent 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!

Historically, even though there is a dominant threat axis, tropical cyclones have approached Guam from essentially all directions. Since most are in the developing stages, their movement as well as intensity and wind distribution is difficult to forecast.

Keeping in mind that tropical cyclones normally approach Apra Harbor from the east through south, the following guideline is offered for the more common “threat” situations:

1. Tropical cyclone approaching from the east or southeast and forecast to pass north or within 60 nmi south of Guam : Evasion should be southwest. The units will be in the safe or navigable semicircle with following wind and sea.
2. Tropical cyclone approaching from the east or southeast and forecast to pass more than 60 nmi south of Guam : Evasion should be northeast.
3. Tropical cyclone approaching from the south and forecast to pass east of Guam : Evasion should be west-southwest.
4. Tropical cyclone approaching from the south and forecast to pass west of Guam : Evasion should be east-southeast.

Regardless of the option chosen, the following general comments from NAVENVPREDRSCHFAC Technical Paper No. 19-75, An Evaluation of Apra Harbor, Guam as a Typhoon Haven by M. E. Brown, and S. Brand, should be noted:

• Crossing ahead of an approaching typhoon is not without hazard and must be accomplished well ahead of the typhoon. If, in attempting this track crossing, the ship is caught in the wave/swell pattern ahead of the storm, the speed of advance may be reduced to the point that the ship will be unable to maneuver clear of the storm.
• It is very possible during the peak typhoon season for rapid storm development to occur, resulting in multiple tropical cyclones co-existing in the western North Pacific Ocean. This condition exists approximately 50 days each year. This occurrence would greatly complicate the evasion problem, and should be kept in mind as evasion plans are formulated and executed.

In all cases, the timing of the evasion is affected by:

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

An analysis was performed for 50-year period 1945-1994 on those tropical cyclones that ultimately did not enter Apra Harbor's 180 nmi threat radius, but were approaching Guam from the east, and were south of 20°N when they crossed 155°E. Table II-5 shows the number of storms that crossed 155°E on generally westward tracks, the number passing north and south of Guam's 180 nmi threat radius and the number either dissipating or recurving before reaching Guam's latitude. A distinction is made between those storms that crossed 155°E while at or south of Apra Harbor 's 13.4°N latitude end those that crossed 155°N north of 13.4°N.

It can be seen in Table II-5 that 55% (27 of 49) of the westerly-moving tropical cyclones crossing 155°E at or south of 13.4°N, and did not enter Apra Harbor's 180 nmi threat radius, moved south of Guam. Forty-five percent (22 of 49) turned northward and passed north of the island and recurved or dissipated prior to reaching Apra Harbor's latitude. Of those westerly-moving tropical cyclones crossing 155°E between 13.4°N and 20°N and not entering Apra Harbor's 180 nmi threat radius, none passed south of the island. Based on previous occurrences, Table II-5 indicates that if a westerly-moving tropical cyclone were forecast to cross 155°E north of 13.4°N, and not enter Apra Harbor 's 180 nmi threat radius, a southerly evasion course would be clear of the storm's strongest winds 100% of the time.

The annual figures listed in Table II-5 are presented as track arrows in Figure II-55 and Figure II-56. The tracks shown are for illustrative purposes only, and do not represent specific trajectories of actual tropical storms. The data listed in Table II-5 and the tracks depicted in Figure II-55 and Figure II-56 are based on previous occurrences, and cannot represent what an individual storm may do in a specific situation. The current Naval Pacific Meteorology and Oceanography Center/Joint Typhoon Warning Center Pearl Harbor tropical cyclone forecast must be given primary consideration in any tropical cyclone threat scenario. The evasion options discussed above are still pertinent and should be considered as the prudent courses of action in the situations presented.

Whenever a tropical cyclone forms in the Micronesian area that poses a threat to Guam, an alert is issued. The Port Control Officer will notify all ships present of such alerts and request a current estimate of the time required to complete any repairs and get underway.

When COR III is set, all ships present should:

1. Set a continuous watch on the Harbor Net, 2716 kHz, and on VHF Channel 16.
2. Reduce boating operations to a minimum, and hoist in all unneeded boats.
3. Take on fuel as necessary.
4. Make preliminary preparations for going to sea.
5. Disabled ships should make immediate preparations to put their engineering plants in operational condition and make the ship seaworthy. Commanding officers of ships that cannot complete preparations within 24 hours should immediately report this fact to SOPA, with copy to SOPA (ADMIN).

When COR II is set, ships should be prepared to get underway on four hours notice or as ordered by SOPA.

When COR I is set, all ships capable of going to sea and evading the disturbance should sortie. Ships remaining in port should complete all securing preparations; including stationing of steaming watches and anchor details.

SOPA will promulgate a sortie plan, which will normally be executed following the setting of COR II. Ships may depart prior to promulgation of the emergency sortie plan provided that notification of such departure and the evasion intentions are made known to SOPA.

Ships will not normally enter Apra Harbor when COR II or I are set, except in emergencies and with permission of SOPA.

Remaining in Port

Because of its lack of natural protection, Apra Harbor provides no haven qualities. Apra Harbor experienced sustained winds of 150 kt during the passage of Typhoon Karen in November 1962! As a result, remaining in port is not the recommended course of action when typhoon conditions threaten. In the past, U. S. Navy ships have remained in port during typhoon conditions for various reasons, with generally poor and sometimes dire results. The U.S. Naval Oceanography Command Center/Joint Typhoon Warning Center, 1990 publication Tropical Cyclones Affecting Guam (1671-1990), with errata sheet updating data through 1994, contains descriptive data about past typhoon events, including: Typhoon Karen (November 1962) which sunk three ships in Apra Harbor and wrenched two tug boats and a huge floating crane from their moorings and forced them ashore; Typhoon Pamela (May 1976) which either sank or ran aground ten small ships and tugs which sought refuge in Apra Harbor; Typhoon Russ (December 1990) which broke the moorings of two ships and drove two ships aground on the breakwater; and Typhoon Omar (August 1992), during which two Mars class combat stores ships (AFS) that were unable to sortie were forced off their moorings to go aground in Apra Harbor

Ships incapable of maneuvering at sea will shift to designated moorings/berths assigned by the Port Control Officer. The decision is based on ship type, expected sea state, wind speed/direction, and time available for the move. Based on limited past experience it is concluded that a general rule for winds up to 50 kt would be: "Obtain an Inner Harbor berth as close to the upwind shore as possible." It is recognized that any ship subjected to high winds while moored will take some amount of beating but this rule should minimize the damage sustained. Individual unit commanders should be ready to rapidly respond to movement orders because maneuvering after the onset of heavy weather (winds 20 kt) can be extremely hazardous.

Weather warnings concerning Guam and the Trust Territories of the Pacific Islands are based on information gathered at Naval Pacific Meteorology and Oceanography Center/Joint Typhoon Warning Center Pearl Harbor. All information and warnings are then broadcast to fleet units on appropriate Fleet Broadcast channels. In addition, warnings are broadcast on Apra Harbor Control Frequency 2716 kHz and Harbor Craft frequency 3716 kHz during typhoon/tropical storm conditions. Warnings are also broadcast on NOAA Weather Radio frequency 162.40 MHz. Vessels in port having landline telephones can obtain weather information by dialing 101 on base. Information is also available by dialing 711 off base. Vessels in port without landlines can use the marine operator and telephone 477-2991 to obtain weather information. USNS ships will stand continuous guard on VHF Channel 14 that is controlled by the Port Control office, and on 2716 kHz.

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