TheDecisiontoSortieorRemaininPort
IWAKUNI/KURE
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 or 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 Maritime Forecast Center - Pearl Harbor (NMFC-PH)/Joint Typhoon Warning Center (JTWC) for Department of Defense assets.
The Port of Iwakuni is not considered a typhoon haven. An early sortie is recommended for all ships to proceed to Area "E" (Figure 1). All of the anchorages in Iwakuni may be impacted by strong winds and seas. Area "F" (Figure 3) in the Port of Kure is considered a typhoon haven but is normally crowded with merchant ships and fishing boats. The Inner Harbor is not considered safe for deep-draft ships to remain pierside. Pier "S" is considered safe for submarines in the event of an approaching tropical cyclone.
During the threat of a Tropical Cyclone (Typhoon), the Airfield Operations Department at Marine Corps Air Station Iwakuni, Japan, is responsible for the coordination and operation of the Typhoon Coordination Center (TCC) to ensure that all aircraft, personnel and essential equipment remain safe from destructive weather conditions. The TCC ensures that Station's Weather Support Division (WSD) notifies the Station Commander and Station Operations Officers of any destructive weather conditions approaching MCAS Iwakuni. The TCC shall contact Station Weather to ensure that local Television and Radio Broadcasting Stations are aware of potential threats from destructive weather conditions. The WSD shall document and forward Set Typhoon Conditions and updated Weather information to local Broadcasting Stations as it becomes available for immediate broadcast to the community.
When MCAS Iwakuni announces TCCOR-II (Destructive winds possible within 24 hours), the Typhoon Coordination Center will be assigned within the Station Weather Office. The 24 hour TCC Duty Clerk shall be posted at the weather counter on the first deck of Building# 757, Airfield Operations Department. The TCC Duty Clerk will normally be assigned within MCAS Weather Department. The TCC Duty acts as a direct liaison between the Typhoon Coordination Officer (TCO) or Station Operations Officer and all units aboard MCAS Iwakuni. Additionally, when TCCOR-II goes into effect, all small vessels are placed inside the adjacent warehouse next to the Operations Building or on the parking lot.
The interpretation of tropical cyclone climatology is addressed in the following sections.
Evasion at Sea
Evasion from the Port of Iwakuni is the recommended course of action for all U. S. Navy ships in the event of an approaching strong tropical cyclone. A sortie to Area "E" in Hiroshima Bay is considered to be the most viable option.
As stated previously, Kure is considered to be one of the best, if not the best, typhoon haven in all of Japan. As a consequence of conversations with Kure District Headquarters personnel, crowding is an important consideration and the most viable location for U.S. Naval ships would be Area "E". Area "F" is nevertheless classified as a "haven" for large vessels, including naval combatants based on weather and topographical considerations. Submarines can remain tied up at the submarine pier "S". Smaller vessels normally remain pierside or utilize the protection found in the various coves around Kure Harbor.
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 NMFC-PH 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!
Keeping in mind that tropical cyclones normally approach the Port of Iwakuni from the southwest, the following guideline is offered for the more common "threat" situations (any tropical cyclone expected to have a CPA within 180 nmi of Iwakuni):
Evasion at sea is not the recommended course of action. However, if it is desired, an evasion route to sea may be developed by the use of the NMFC-PH/JTWC warnings. In all cases, however, Optimum Track Ship Routing (OTSR) should be consulted as to the best evasion route.
There are two basic evasion tactics for ships at sea south of Japan. The most common is to place the ship south of the tropical cyclone in the left or navigable semicircle. The other is to proceed southeast or east to remain clear of the tropical cyclone track.
If a ship is in the area south of Japan and the decision is made to seek refuge in Iwakuni or Kure, then the time enroute through the Bongo Straits into Hiroshima Bay (see Figure 4) should be considered. At speeds of 10-12 kt, an enroute time of 10-12 hours could be expected upon entering the Bongo Straits.
Another option for ships south of Japan desiring refuge in a port would be the consideration of Yokosuka, Japan -- a designated good typhoon "haven." Refer to the Yokosuka port study for more details. Sasebo Harbor also provides a favorable typhoon haven for most small and medium sized ships up to and including LPD, LSD, TAE, and TAO class ships. Refer to the Sasebo study for more details.
For evasion at sea, steaming into the Yellow Sea or the Sea of Japan are the open ocean sortie options available. The choice will depend on the strength and forecast track of the approaching storm and how early in the planning process the sortie decision is made.
If evasion to the Sea of Japan is selected, the commander must be aware that the ship may be placed in the stronger, and therefore more dangerous, semicircle (the right side of the storm with respect to the storm's direction of movement).
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.
As stated during the Site Visit in October 2009, JMSDF deep-draft vessels normally sortie from Kure to Area "E" (Figure 1).
Remaining in Port
Remaining in the Port of Iwakuni is not the recommended course of action.
Iwakuni is not considered to be an adequate haven pierside or at the anchorages within the port for U. S. Navy ships in a tropical cyclone situation. These anchorages are distinct from Anchorage Area "E" in Hiroshima Bay. The reasons for not remaining in port include:
(1)The lack of protection from wind in the Inner Harbor,
(2)The vulnerability of the outer harbor anchorages (A,B,C and D) from high winds and seas.
All U. S. Navy ships capable of getting underway should sortie from the Port if Iwakuni is threatened by a strong tropical cyclone. Anchoring in Area "E" outside Iwakuni in Hiroshima Bay is the most viable option (Figure 1).
Area "F" in the Port of Kure is a safe "haven" but is normally too crowded to be used as a typhoon anchorage. Once again the best option is probably for U.S. deep-draft vessels to anchor in Area "E". JMSDF Submarines normally remain pierside in the event of a tropical cyclone.
