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YOKOHAMA

THE DECISION TO EVADE OR REMAIN IN PORT

General

Local harbor authorities at Yokohama state that U. S. Navy ships at Yokohama should move to Fleet Activities, Yokosuka in the event of a threat by a tropical cyclone. Ships moored to Mizuho Wharf at Yokohama will likely be under the operational control of the Military Sealift Command, Far East. The responsibility for overall coordination of action to be taken by Naval activities in the Yokosuka area has been assigned to Commander, Fleet Activities, Yokosuka SOPA (ADMIN) YOKOSUKA INSTRUCTION 5000.1 establishes procedures when hazardous weather is expected at Yokosuka, and the same instruction is applicable to Military Sealift Command vessels at Yokohama. The Naval Pacific Meteorology and Oceanography Facility (NPMOF), Yokosuka issues local wind warnings. As directed by SOPA, wind from any direction with expected sustained speeds of 48 kt or gusts in excess of 55 kt is sufficient to set tropical cyclone Conditions of Readiness (COR). Modified COR's may be set for different areas if wind velocities are expected to differ between different sites within the area of responsibility of Commander, Fleet Activities, Yokosuka. Typhoon conditions will be set for an approaching typhoon, i.e., expected sustained winds of 64 kt or greater. The same precautions taken for a typhoon will be taken for any tropical cyclone.

Evasion Rationale

It is of utmost importance that the commander recognize the inherent dangers that exist when exposed to the possibility of hazardous weather. A basic understanding of weather and proper utilization of meteorological products, especially the Naval Pacific Meteorology and Oceanography Center West/Joint Typhoon Warning Center (NPMOCW/ JTWC) Guam Tropical Cyclone Warnings, will enable the commander to act in the best interest of the unit, and complete the mission when the unfavorable weather subsides.

Figures V-204, V-205, through V-206, discussed earlier, address the probability of existing remotely located tropical cyclones later affecting Yokohama. Figures V-210, V-211, through V-212 have been prepared as additional aids for the commander to use when evaluating a given situation. In contrast to Figures V-204, V-205, through V-206, Figures V-210, V-211, through V-212 consider only those storms which later passed within 180 nmi of Yokohama. Approximately 50% of these storms are contained within the bounds shown by the arrow. Thus, the arrow and the associated timing arcs can be considered as an average approach scenario insofar as Yokohama is concerned. It must be stressed that the other 50% of the storms which later affect Yokohama will be outside of these bounds. Another important factor is that the actual JTWC forecast will always take precedence over the tracks and translational storm speeds suggested by Figures V-210, V-211, through V-212.

With the above restrictions in mind, the following time/action sequence, to be used in conjunction with Figures V-210, V-211, through V-212, has been prepared to aid in these actions.

I. An existing tropical cyclone moves into or development takes place in Area A with long range forecast movement toward Yokohama (recall that 40% of all tropical cyclones recurve):
a. Review material condition of ship.
b. Reconsider any maintenance that would render the ship incapable of riding out a tropical storm or typhoon with the electrical load on ship's power, or would render the ship incapable of getting underway, if need be, within 48 hours.
c. Plot NPMOCW/JTWC Guam warnings when received and construct the danger area. Reconstruct the danger area for each new warning.

II. Tropical cyclone enters Area B with forecast movement toward Yokohama (recall that prior to recurvature, tropical cyclones tend to slow in their forward motion and accelerate rapidly after recurvature):

a. Reconsider any maintenance that would render the ship incapable of going to anchor, moving to Fleet Activities, Yokosuka, or sortieing from the port.

b. Consider all options available to the ship if the tropical cyclone continues to approach Yokohama. Review Yokosuka's evaluation in Section V.2 of this manual.

c. Plot NPMOCW/JTWC Guam warnings when received and construct the danger area. Reconstruct the danger area for each new warning.

III. Tropical cyclone has entered Area C and is moving toward the Yokohama area:

a. Prepare to leave Mizuho or Shinko Wharf.

1.  If moving to Yokosuka, the transit (including bathing at Fleet Activities) should be completed before the predicted onset of 20 kt winds. Anticipate Tropical Cyclone Conditions II and I or Modified Tropical Cyclone conditions II and I to be set by SOPA Yokosuka. Take appropriate actions.

2. If remaining at Yokohama, shifting from alongside moorage to the anchorage is required if winds are forecast to reach 30 kt (15 m s-1).

b. Plot NPMOCW/JTWC Guam warnings when received and construct the danger area. Reconstruct the danger area for each new warning.

Remaining in Port

Remaining alongside Mizuho Wharf at the Port of Yokohama is not recommended and, according to local harbor authorities, is not an option. As stated above, ships should leave their berths and move to the Nakano Se anchorage if the wind is forecast to reach or exceed 30 kt (15 m s-1). Ships remaining in the anchorage during passage of a tropical cyclone should be prepared for waves of 6.6 ft (2 m) or higher, and steam to the anchor during the passage of the storm to reduce strain on the anchor chain and lessen the possibility of anchor dragging.

Instead of remaining in port at Yokohama, the ship's captain may elect to move to Fleet Activities, Yokosuka to ride out the storm. This option is, of course, dependent on the availability of appropriate berthing or anchoring space at Yokosuka. An early decision is mandatory. Harbor authorities at Yokosuka state that the large number of Japanese fishing boats that move into Yokosuka Bay for shelter prior to typhoon passage severely restricts the ability of larger vessels to enter or leave the port. A summary of port facilities and typhoon procedures for Fleet Activities, Yokosuka is contained in Section V.2 of this manual.

Evasion in Tokyo Bay

All vessels will need to make an early decision if a departure from the harbor is being considered. Boat traffic within Tokyo Bay is heavy prior to the arrival of a tropical cyclone as small craft seek sheltered positions.

Japanese Maritime Self Defense Force (JMSDF) ships use Tatayama Bay and Kisarazu Harbor (Figure V-197) as anchorages when a typhoon is expected to pass east of Tokyo Bay. Water depths in Tatayama Bay are deep enough for vessels of all sizes and the bottom offers good holding.

Merchant vessels have at times, depending on the direction of the tropical storm or typhoon CPA, anchored in the following areas identified in Figure V-197:

(1) Tropical cyclone passage to the east or south of Tokyo Bay: anchor in Chiba Harbor or Kisarazu Harbor.

(2) Tropical cyclone passage to the west or north of Tokyo Bay: anchor in Kaneda Bay.

The 3rd Regional Maritime Safety headquarters has issued a brochure titled INFORMATION SERVICE FOR VESSELS AT ANCHOR IN TOKYO BAY IN THE EVENT OF A TYPHOON APPROACHING THE MAIN ISLAND OF HONSHU, dated June, 1992. The following information has been excerpted from the brochure.

During the period when typhoons are approaching the main island of Honshu, Tokyo Bay anchorages tend to become overcrowded with vessels seeking shelter from the approaching bad weather. Overcrowding of anchorages during stormy weather can lead to the additional hazards of collisions and grounding due to anchor dragging. To prevent and reduce the risk of such accidents, the Tokyo Bay Traffic Advisory Service Center (Call sign TOKYO MARTIS) provides information services for vessels at anchor or seeking anchorage in Tokyo Bay. The center airs information services broadcasts following advisory warnings to evacuate the port or harbor due to an approaching typhoon.

Broadcasts will be in Japanese on the hour and half hour, on a frequency of 1665 kHz, and contain information on the number of vessels anchored in each of the following areas:

The brochure also makes the following recommendations to be taken during stormy weather:

(1) Maintain a listening watch on VHF Channel 16 or by radio on 1665 kHz.

(2) Listen for warnings on vessels which are dragging their anchors. The warnings will be broadcast on VHF Channel 12 following a general call on Channel 16.

(3) Keep a proper watch with sufficient lookouts. If necessary, main engines should be ready for immediate use. Power to windlasses should also be available for emergency use.

(4) Maintain a safe distance from other vessels and be alert for signs of anchor dragging either by your own vessel or others in the vicinity. Be aware that a sudden change of wind speed and direction may affect anchor holding power.

(5) Take into account the depth of water and type of holding ground in the anchorage and, if necessary, use both anchors with sufficient scope of cable laid out. Main engines should be used to back-up the anchors if necessary.

(6) Improve the vessels sea-keeping qualities at anchor in order to reduce the risk of anchor(s) dragging. For example, vessels with large sail areas should consider measures such as taking on additional ballast, altering the vessel's trim, and use of main engines to prevent the vessel from dragging her anchor.

Vessels carrying a dangerous cargo must anchor as directed by the Japanese Maritime Safety Office. Ships requiring a pilot to transit the Uraga Suido Traffic Route may be unable to secure pilot services if winds are greater than about 35 kt because pilots embark and debark from small motor launches.

Evasion at Sea

Evasion routes at sea may be developed by the use of the tropical cyclone warnings and Appendix A for the month of interest in conjunction with Figures V-204, V-205, to V-206 (tropical cyclone threat axes and approach times to Yokohama). In all cases, Optimum Track Ship Routing (OTSR) should be consulted as to the best evasion route.

If the decision is made to evade at sea, the captain should plan to get underway days in advance of the storm's arrival. It must be remembered that tropical cyclones are notoriously difficult to accurately forecast, especially in the recurvature phase. The 48-hour forecast position error may exceed 200 nmi. A storm may be closer to or farther from Yokohama than the forecast indicates, or right or left of the storm's forecast track.

A late departure from port may make the sortie difficult due to fishing boat congestion and would increase the likelihood of encountering heavy weather as the ship departs Tokyo Bay. Each tropical storm or typhoon must be considered as differing from those preceding it. The existing synoptic situation must be fully understood. To blindly establish and follow one technique or rule for avoiding the storm's danger area is not practical, and may place the ship in harm's way.

In general, a departing ship, upon entering the area of Kannon Saki (Figure V-197), will begin to feel the effects of wave/swell generated by a tropical cyclone. The waves may reduce the ship's speed of advance (SOA), thereby increasing the time required to reach open sea. If a ship is caught in the wave/swell pattern ahead of a tropical cyclone, particularly an intense tropical storm or typhoon, the SOA may be reduced to the point that the ship will be unable to maneuver to clear the danger area (see Figure I-1). If the typhoon is forecast to follow a recurving track with a CPA east of Yokohama, then a course downsea/downwind in the left (so called navigable) semicircle may be considered. Extreme caution is advised, however, due to the possibility that the storm may not recurve as forecast, and the ship may be placed in the dangerous semicircle of the storm's circulation.

Any course to the north along the east coast of Honshu is considered unwise. The possibility of being overrun exists if the storm accelerates and/or turns suddenly to the north. The average speed of advance in the higher latitudes (30ºN to 40ºN) of tropical cyclones is about 25 kt; however, they have been tracked as fast as 60 kt (see Tables V-48A and V-48B, Typhoon Tip in October 1979), and speeds of 40 kt are not uncommon. Typhoon wind intensities tend to decrease as the system moves into the northern latitudes, but nevertheless remain strong enough to be quite destructive.

Source: http://www.nrlmry.navy.mil/port_studies/thh-nc/japan/yokohama/text/sect6.htm