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HAKODATE

THE DECISION TO EVADE OR REMAIN IN PORT

General

The lack of protection from wind within the Port of Hakodate precludes any decision to remain in the Inner Harbor during the passage of a tropical cyclone. The exposure of ships to wind and waves in the anchorage west of the breakwaters makes remaining at anchor inadvisable. In a tropical cyclone threat situation local port authorities strongly recommend that all large ships leave the port. During a 1993 port visit, port authorities at Otaru mentioned that a large ferry was sunk at Hakodate during the passage of a typhoon "about 40 years ago" but they did not have specific information about the event. Hakodate harbor authorities could not provide additional information. Harbor congestion is a problem at Hakodate when the port is threatened by high winds. However, when the port is threatened by a tropical cyclone most fishing vessels and other small craft choose to go to Mutsu Bay (Figure V-170) on the north end of Honshu.

Evasion Rationale

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

Figures V-177 and V-178, discussed earlier, addressed the probability of existing remotely located tropical cyclones later affecting Hakodate. Figures V-181 and V-182 have been prepared as additional aids for the commander to use when evaluating a given situation. In contrast to Figures V-177 and V-178, Figures V-181 and V-182 consider only those storms which later passed within 180 nmi of Hakodate. 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 Hakodate is concerned. It must be stressed that the other 50% of the storms which later affect Hakodate 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-181 and V-182.

With the above restrictions in mind, the following time/action sequence aids, to be used in conjunction with Figures V-181 and V-182, are provided.

I. An existing tropical cyclone moves into or development takes place in Area A with long range forecast toward Hakodate:

a. Review material condition of ship.

b. Formulate plans for expeditious sortie from the harbor and evasion route to be taken in the event the tropical cyclone threatens Hakodate.

c. Reconsider any maintenance that would render the ship incapable of getting under way, if need be, within 48 hours.

d. 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 Hakodate (recall that tropical cyclones tend to accelerate rapidly after recurvature).

a. Reconsider any maintenance that would render the ship incapable of getting underway, if need be, within 24 hours.

b. Finalize plans for expeditious sortie from the harbor and evasion route to be taken in the event the tropical cyclone threatens Hakodate.

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 Hakodate:

a. Sortie from the harbor, taking an evasion route that will allow the unit to encounter the most favorable weather conditions during the passage of the tropical cyclone.

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

Evasion at Sea

Evasion routes at sea may be developed by using tropical cyclone warnings and Appendix A (Bi-Weekly Tropical Storm and Typhoon Tracks for the Western North Pacific Ocean) for the period of interest. They should be used in conjunction with Figures V-177 and V-178 (tropical cyclone threat axes and approach times to Hakodate). In all cases, Optimum Track Ship Routing (OTSR) should be consulted as to the best evasion route.

Two basic evasion routes are available: (1) moving west through Tsugaru Strait and entering the Sea of Japan, and (2) proceeding east through Tsugaru Strait into the Pacific Ocean and proceeding south along the east coast of Honshu. If the tropical cyclone is moving northeastward on a track that would take it east of Hakodate, remaining in the Sea of Japan would keep the vessel on the weaker, left side of the storm's circulation and thereby avoid the strongest winds of the storm. However, the ship may be exposed to relatively strong winds from the northwest quadrant as the storm passes and high pressure moves into the Sea of Japan behind the storm's circulation.

If the storm is forecast to pass west of Hakodate, moving eastward into the Pacific Ocean along the east coast of Honshu should be considered. It must be emphasized that this option has a potentially serious drawback. If the tropical cyclone should move east of the forecast track, and therefore closer to the ship's evasion route, the ship may encounter the strong winds of the storm's dangerous semicircle. In a best case situation, depending on the size of the storm's circulation the ship may still be liable to encounter strong southerly winds along the coast. However, the strongest winds should be short lived because of the historically rapid movement of tropical cyclones when they reach the latitudes of northern Japan.

Regardless of the option chosen, it is of utmost importance to begin the sortie as early as possible. The average speed of movement of tropical cyclones occurring during the 48-year period 1945-1992 is 35 kt when at CPA to Hakodate (Table V-43). Those occurring during September average a relatively rapid 38 kt, so some storms will move even faster. As an example, as shown in Table V-42 tropical storm Tip was moving at over 73 kt when at CPA to Hakodate. Several others were moving at over 50 kt.

Once clear of the harbor, an evading vessel steaming at 20 kt will take approximately 2 hours to exit Tsugaru Strait into the Sea of Japan or the Pacific Ocean. To gain an additional 200 nmi clearance from the forecast storm track will take another 10 hours. During this 12-hour period, a storm moving at only 35 kt would have moved about 420 nmi closer to Hakodate.

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 Hakodate at forecast verification time than the forecast indicates, or right or left of the storm's forecast track. Each tropical storm or typhoon must be considered as differing from those preceding it. The accompanying synoptic situation must be fully understood. blindly establish and follow only one technique or rule for avoiding a storm's danger area is not prudent and, in fact, may ultimately place the ship in harm's way.

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