TheDecisiontoEvadeorRemainatNumazu
NUMAZU
THE DECISION TO EVADE OR REMAIN AT NUMAZU
Evasion Rationale
The responsibility for overall coordination of action to be taken by naval activities in the Numazu Operating Area has been assigned to Commander, Fleet Activities, Yokosuka. The Naval Weather Service Facility, Yokosuka issues the local area forecasts for Numazu upon request.
The commander must recognize the inherent dangers that exist when exposed to the possibility of hazardous weather while operating in the Numazu Operating Area. By proper utilization of meteorological products, especially the FWC/JTWC Tropical Cyclone Warnings, and a basic understanding of weather, the commander will be able to act in the best interest of his unit and to complete his mission when the unfavorable weather subsides. The following time table (in conjunction with Figures V-29, V-30, V-31, V-32, to V-33) has been set up to aid in these actions. The orientation of the threat axis in these Figures was derived by considering the general direction from which the tropical cyclones approached to within 180 n mi of the Numazu Operating Area. The time in days to reach the Numazu Operating Area was based on average speeds of movement of tropical cyclones affecting Numazu.
1. An existing tropical cyclone moves into or development takes place in Area A with long range forecast movement toward the Numazu Operating Area (recall that about 40% of all tropical storms and typhoons recurve):
a. Review material condition of ship.
b. Plot FWC/JTWC warnings and construct the danger area. Reconstruct the danger area for each new warning.
2. Tropical cyclone enters Area B with forecast movement toward the Numazu Operating Area (recall that prior to recurvature, tropical cyclones tend to slow in their forward motion and after recurvature, accelerate rapidly):
a. Consideration should be given to ceasing operations and departing Suruga Bay. Sea state rather than wind conditions may be the governing factor at this stage.
b. Continue plot of FWC/JTWC warnings.
c. Prepare the ship for heavy weather. Ship should be alert for large long period swell and heavy surf.
3. Tropical cyclone enters Area C and is moving toward the Numazu Operating Area:
a. The decision to evade the typhoon by departing the area for Yokosuka or other known typhoon havens in the Tokyo Bay area or evasion at sea must be made.
Evasion To Yokosuka
The port of Yokosuka has been evaluated as an excellent typhoon haven for all sizes and types of vessels. In general, due to the geographical location, surrounding topographical features and harbor construction, the hazardous effects of wind and sea from a typhoon are greatly reduced. However, if crowded conditions exist within the port, which would reduce availability of pierside facilities, a Commanding Officer may elect to evade the typhoon at sea or anchor in Tokyo Bay.
Evasion In Tokyo Bay
Japanese Maritime Self Defense Force ships in the past have anchored in Tateyama Bay for typhoon passage to the east of Tokyo Bay. They also make use of Kisarazu Harbor (see Figure V-l).
Merchant vessels have, at times, depending on the direction of the tropical storm or typhoon CPA, anchored in the following areas:
(l) 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.
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
The widely held doctrine of evasion at sea rather than remaining in port for the single purpose of minimizing typhoon related damage is not generally recommended if the ship can reach Yokosuka. However, if putting to sea is desirous, each tropical storm or typhoon must be considered as differing from those preceding it. The accompanying weather situation must be fully understood. To establish one technique or rule to avoid the danger area is not practical.
In general, the effects of sea/swell generated by a tropical cyclone may reduce the speed of advance (SOA), thereby increasing the time required to reach the open sea. If a ship is caught in the sea/swell pattern ahead of a tropical cyclone, in particular 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.
If the typhoon is forecast to follow a recurving track, with a CPA to the east of Numazu, then a course downsea/downwind, in the left or navigable semicircle may be advisable.
Any course to the north along the east coast of Honshu (north of Tokyo Bay) 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 (30°-40°N) of tropical cyclones is about 25 kt; however, they have been tracked as fast as 50 kt. Typhoon wind intensities tend to decrease as the system moves into the northern latitudes but, nevertheless, can be quite destructive.
Remaining in the northern regions of Suruga Bay and riding out the storm should only be considered if the certainty of the typhoon's passage well to the east of the area can be ascertained. Some degree of protection may be offered by the mountains along the eastern side of the bay protecting the area from the northeasterly flow around the cyclone's center. Additionally, the sea state will not be as destructive because the fetch will not be as great for the northeasterly wind as it would be for a southwesterly wind.
Source: http://www.nrlmry.navy.mil/port_studies/thh-nc/japan/numazu/text/sect3.htm
