JAPAN P& I CLUBVol.45 April 2019

P&I Loss Prevention Bulletin
The Japan Ship Owners'Mutual Protection & Indemnity Association Loss Prevention and Ship Inspection Department

Marine Weather
Ship Handling in Rough Sea
Head and countering / Following Seas

INDEX§1

Introduction …………………………………………………………………………………… 1§2

Global Circulation of the Atmosphere ………………………………………… 1§3

Air Mass …………………………………………………………………………………………… 5§4

Tropical Cyclones

4-1

Extra-tropical Cyclones ……………………………………………………………………… 9

4-2

Tropical Cyclones and Typhoons ………………………………………………………… 23§5

How to Obtain Weather Information ………………………………………… 38

5-1

Surface Weather Charts ……………………………………………………………………… 39

5-2

Wave Charts ……………………………………………………………………………………… 40

5-3

Upper-air Weather Charts (Upper-air Charts）……………………………………… 43§6

Wind and Waves and Undulations (Swells) ……………………………… 47

6-1

Basic Form of a Wave ………………………………………………………………………… 47

6-2

Diﬀerences between Wind and Waves and Undulations (Swells) ………… 48§7

Ship Handling in Rough Sea:……………………………………………………………………… 6

Head and countering / Following Seas ………………………………………… 49
7-1

Ship Handling in Head and Countering Seas ………………………………………… 49

7-2

Ship Handling in Following Seas of Rough Weather …………………………… 72§8Conclusion ……………………………………………………………………………………… 98

References ……………………………………………………………………………………………………… 99
Attachment: MSC.1/Circ. 1228（11 January 2007） ………………………………………………… 100§1

Introduction

Although accidents due to dragging anchor occur during gales, in particular, most of them arecaused by typhoons. It has not been so long since a coastal tanker(after discharging jet fuel)collided with and seriously damaged a connecting bridge at Kansai Airport, in September
2018, as a result of dragging anchor caused by Typhoon No. 21 that had landed in the Kansai
region. A few months prior to this accident, we held a Loss Prevention seminar in Japan titled“Dragging Anchor - Case Studies and Preventive Measures -” (April through June 2018).
We issued our “Dragging Anchor - Case Studies and Preventive Measures - (Vol.43)” in
July, 2018, compiled from the contents of the seminar of which a large number of members
thankfully participated. In this bulletin, we discussed typhoons.
This time, we are going to introduce “Ship Handling in Head and Countering Seas”. This issomething that deserves extra attention from ship operators when navigating in rough seas.
We will focus on the generation mechanisms behind rough weather and sea conditions. Whenreading this guide, please refer to the above-mentioned bulletin No.43.

§2

Global Circulation of the Atmosphere

Although the motion (circulation) of theExtreme Easterly Wind

atmosphere is extremely complicated,

Westerly Winda characteristically large and constantmotion (circulation) can be observed from

H i g h la

NE Tradewind

M e d iu mouter space. This is known as the global
circulation of the atmosphere.
Figure 1 is a schematic view of the windt i t u d e L o w p re s s u r e z o n elatitudes High pressure zone

Equator Low pressure zone

EquatorMedium latit

patterns close to the ground (annual average)

SE Trade windcirculating in the atmosphere. The solar

Westerly Wind

energy reaching the earth consists of a

Extreme Easterly Windvisible ray (approximately half), with theNorth Poleudes High pressure zone

High latitude Low pressure zone

South PoleFig. 11

remainder consisting mostly of infra-red rays. The earth radiates the received solar energy
as infra-red rays back into space. However, the actual radiant energy remaining in theatmosphere is positive at low latitudes and negative at high latitudes. Therefore, there will bea huge temperature diﬀerence between both latitudes as a result of this radiation.
If the heat were not carried from the equator to either of the poles, the equator zone would
become too hot for any creature to live. On the contrary, if there were a large amount of snow
near both poles, they would end up being glaciers that never melt. However, in reality heatin the vicinity of the equator is carried to each pole direction and the earth temperature is
comfortably adjusted for animals and plants to survive.
It is the wind that moderately adjusts the temperature diﬀerences between the north and south
poles of the globe. Winds are generated due to the temperature diﬀerences in the atmosphereand play a role in reducing the temperature differences. In addition to regulating global
temperatures, the atmosphere serves the following three roles:
To supply oxygen necessary for living creatures and carbon dioxide necessary forphotosynthesis of plants.
The ozone layer absorbs ultraviolet rays which are harmful to living creatures.
To prevent meteorites reaching the surface of the earth. Meteorites disintegrate once
having entered the atmosphere.

Figure 2 illustrates the sizes of the sun and earth and their relative positions. While the earth
has a radius of 6,369 km, the sun has a radius of 695,508 km which is 109 times that of theearth. And, the distance from the earth is 149 million kms. The sun is 23,395 times the radius

Sun

Earth
Radius:695,508km
109 times of the earth
1
Radius: 6,369km

Distance: 149 million kms
The ratio of the distance of the earth's radius isonly 0.0004% . The distance to the sun fromthe earth is equivalent to 23,395 times theradius of the earth.
Fig. ２2

January

December 31 23: 59: 59.6 seconds

Marine pollution caused by microplastic
The earth was born

December 31 23:59:30

The birth ofmulticellularorganisms

Japan archipelago topography
31st 19:00

December 31 23:59:58

The industrial revolution
Air pollution
The sea wasformedDecemberNovember
October

19:31 December 31

Dawn of humans

SeptemberAugust
July
June
May
April
March
February
Januaryof the earth, and the ratio of the distance of the earth's radius by comparison is only 0.0004%.
Yet, the temperature difference between the equator and poles is more than 60 degrees
centigrade.
Over the recent years, issues such as global warming and environmental pollution are becoming more serious. It is said that the earth was born approximately 4.6 billion years ago. Let us
assume that this 4.6 billion years was compressed into 1 year and that the birth of the earth
was set to 00:00 on January 1. The progressive emission of carbon dioxide began during theindustrial revolution during the middle of the 18th century. Applying the compressed timeframe, human beings started air pollution around “December 31 at 23:59:58”, which can besaid to mean that a large amount of fossil fuel was consumed in only 2 seconds, which has
led to the expansion of global environmental problems giving us global warming.
Marine pollution caused by microplastic started in the 1980s; if the one-year time frame
was applied, it would have begun on December 31 at 23:59:59.6 seconds - which is only 0.4
seconds before the end of the year.
Next, on closely examining the structure of the atmosphere, the layers of the atmosphere canbe classiﬁed as follows (Fig. 3):3

Schematic diagram of each layerof the atmosphere(Scale is incorrect)

10,000km
Exosphere:

Outhside AtmosphereAs this exists in such small quantity, this is notclassiﬁed as an atmospheric layer in general.

690km
Thermosphere:
Layer from 80kms up to approximately 700 to
800kms. The higher the altitude, the greater thetemperature increases. The boundary of the
Exosphere is named the Thermopause or Exobase.
It is diﬃcult to deﬁne the boundary between the
Thermosphere and Exosphere, because there is alarge distance of 500 to 1,000kms.

AuroraThermosphere

Kármán line
(100kms up in the atmosphere):Space Shuttle

100km

Fédération Aéronautique Internationale (FAI) andthe National Aeronautics and Space Administration(NASA) deﬁne that anything outside Kármán line isouter space, as a convenient deﬁnition in order tocarry out their activities smoothly. Anything under
this line is referred to as the atmosphere in general.
However, atmospheric pressure at this altitude is
only a millionth of the ground surface.

(Kármán Line）

85km

Mesopause:

MeteorLayer from 50 to 85kms. The higher the altitude,

Middle ZoneZ

the lower the temperature. The boundary of the
Thermosphere is named the Mesopause.

50km

Stratosphere:

Stratosphere6-20kmWeather
Observation
BalloonLayer from 9 to 17kms up to 50kms. The higher thealtitude, the greater the temperature increases. The
ozone layer is found here. The boundary of the
Mesopause is named the Stratopause.

Troposphere:
Everest
AirplaneTroposphere
Troposphe
ere
0km
m

Layer from 0 ‑ 9/17 〜 20km. The higher thealtitude, the lower the temperature. Various
weather phenomena occur. The water (vapour)ratio is higher than that of the upper layer.
According to mass ratio, more than half of theatmospheric elements exist in the Troposphere.
In the vicinity of the equator, it is thick at 17km,
and at the pole, it is thin at 9km. The boundary of
the Mesopause is named the Tropopause.

Fig. 3

4

Comparing the diameter of the Earth (12,739 km)
with the Kármán line (100 km), as can be seen in

100 Km

Fig.4, it is understood that the atmosphere occupies
39

6,

a thin range (only 0.8% of the diameter of the

6

Earth).

Km

Thus, it is easy to imagine how we, humankind,
have dramatically changed the global environment,
in a very short time, and within an extremely thinrange of atmosphere that was created more than
4.6 billion years ago. Still, it is important that weunderstand the significant role of the atmosphereand continue to tackle the impending environmental issues.

§3

Fig. 4

Air Mass

Viewing the earth from outer space, there are ﬂat areas of land and sea that stretch out morethan 1,000 kms around the earth. In addition, these areas almost all look homogeneous. While
the air remains over these continents and oceans for extended periods of time (for instance,over a week), it will gradually assume particular characteristics associated with each region.
This large mass of air is referred to as Air Mass, and the area where the air mass generates iscalled the point/place of origin.
Air masses change seasonally and influence the climatic changes in the regions covered.
Figure 5 illustrates air mass by classiﬁcation.

Classiﬁcation by Humidity
Place of Occurrence

Classiﬁcation by Humidity
Continental Dry Air Mass

Tropical Air Masses
Cold Air Massess

Moist Oceanic Air Masses
in the Lower Layer

North/South Pole Air Masses
Fig. 5

5

Air masses do not originate in the vicinity of Japan. However, Japan is located in the
mid-latitude where the vast Eurasian Continent meets the Paciﬁc Ocean, thus its climate isstrongly inﬂuenced by several air masses that change seasonally.
Figure 6 illustrates air masses that very much inﬂuence the climates of Japan.
Air masses that are generated
in spring and autumn

Very Inﬂuential Air Mass

Siberian Continental Air Mass

Okhotsk Sea Air Mass
A cold and humid
polar-maritime air mass

A cold and drypolar-continental air mass

Air masses that are generated
in spring and autumn

Yangtze-River Air Mass
A warm and dry migratory
tropical-continental air mass

Very Inﬂuential Air Mass

North Paciﬁc Tropical Air Mass
A warm and humid tropical-maritime
air mass.
In Japan, the North Paciﬁc
Tropical Air Mass is also referred to as the“Ogasawara Air Mass.”

Air mass that is carried with typhoons

Equatorial Air Mass
A tropical-maritime air mass
Fig. 6 Cited from Japan Captainsʼ Association, DVD§4

Tropical Cyclones

It is a Tropical Cyclone when the air pressure in the middle is lower than that of thesurrounding air pressure. When the shapes of the isobars are vague and lack coherence, they
are simply referred to as an air pressure depression. In the northern hemisphere, winds within
low pressures blow counter clockwise into its centre, due to the rotation of the earth. This
blown wind converges to become an updraft. Because adiabatic cooling [Note 1] is caused byan ascending air current which produces clouds and consequently rain, in general the weather
is bad inside tropical cyclones.
Tropical cyclones are deﬁned as follows according to the location and cause of generation.
6

Extra-tropical cyclones are most frequently generated, and when referred to as tropical
cyclones, an extra-tropical cyclone is usually what is being referred to.
An Extra-tropical Cyclone

It is generated in middle and high latitudes andhas fronts.

A Cold-core Cyclone/
Orographic Cyclone/
Thermal low

It is generated in middle and high latitudes andhas no fronts.

Tropical Cyclones

Tropical cyclones generated in tropical waters
at low latitudes. Because these completely
differ from extra-tropical cyclones in that theirgeneration and structures are diﬀerent, these will
be covered in 4-2.

Note 1: Adiabatic cooling
Adiabatic change refers to a change in air state whereby no heat is exchanged
with the surrounding air. When gas adiabatically expands, the temperature
naturally decreases without cooling down (adiabatic cooling). On the contrary,when gas is adiabatically compressed, the temperature increases naturally (risein adiabatic temperature).
The fact that gas adiabatically expands, under the condition that energy (heat)is not transferred, and because volume increases against the external pressure,
this means that it is working against the external pressure. In other words, it
uses its own (thermal) energy which means that the temperature decreases.
Adiabatic compression is the opposite of this.
With the updraft of air mass, it will expand naturally because the nearby
pressure decreases. At this moment when it expands, there is almost no
transfer of heat between the external and internal pressure. However,
because the adiabatic expansion releases energy, the temperature drops.
The proportion is 1.0°centigrade for every 100 meters of updraft. However,the condition at this time assumes that the water vapour is still unsaturated(the temperature has not dropped to dew-point), even if the temperature of
the air mass has decreased. The way this water vapor descends, due to thehigh temperature as the air mass rises, along with water vapor that has not
yet reached saturation, is referred to as dry adiabatic lapse rate. When the air

7mass drops, the temperature rises in proportion to the dry adiabatic lapse rate
because of the adiabatic compression.

Dry adiabatic lapse rate ＝ 1.0℃ /100m
However, general air mass contains water vapour. This is when it reaches dewpoint, because the water vapour changes into water while the temperature of
the updrafting air mass has been dropping. As the water vapour contained in
the air mass condenses, ﬁne moisture is generated and clouds are then formed.
It is necessary to understand that latent heat will be released as the water
vapour condenses, when the air mass rises while clouds are being generated(air mass in which water vapour has become saturated). Because the latent heatwarms the air mass, the extent to which the air mass temperature decreases
while clouds are forming is smaller than the proportion of dry adiabatic lapse.
The moisted adiabatic lapse rate can be defined as: the temperature thathas dropped due to altitude, when the air mass rises while clouds arebeing generated (air mass in which water vapour has become saturated).
This proportion can differ depending on the conditions, but on average it isapproximately 0.5 ℃ per 100 meters of altitude. On the contrary, when air masscontaining clouds descends, it absorbs (vaporization) heat when the moistureevaporates. As the temperature does not increase in proportion with the dry
adiabatic lapse rate, it increases in proportion with moisted adiabatic lapse rate.
It is for this reason that a can of compressed gas is cold.

Moisted adiabatic lapse rate ＝ 0.5℃ /100m
Let's take a closer look at the circulation of the atmosphere. For instance,in the event that the temperature drops at the moisted adiabatic lapse rate,
while moist southeast wind blows into the Japanese islands in the summer andeven if it is raining at an updraft of 2,000 meters along the mountain range, thetemperature of the top of the mountain will be 20℃ , which is 10℃ lower, when
the temperature near the sea surface is 30℃ (moisted adiabatic lapse rate: 0.5℃
/100m x 2,000 meters).
When this atmosphere descends down the slope of the mountain, thetemperature will reach 40 ℃ (2,000 meters x 1℃ /100m) at the sea surface.
Because the temperature increases at the dry adiabatic lapse rate if there is novapour present. Foehn phenomenon on the Japan Sea side is generated by thismechanism.

8

４−１

Extra-tropical Cyclones
４−１−１

The Generation Stage

Cold airCold Front

Warm airFig. 7 Masanori Shiraki, 2007, Shin Hyakuman-nin no Tenki Kyōshitsu: Seizando

Fig. 8 Japan Captainsʼ Association,

Regarding extra-tropical cyclones with fronts, ﬁrstly, a stationary cold front (See Fig. 7) is

9generated where the cold air mass and open subtropical air mass converge at almost the sameforce. The energy needed to generate and develop an extra-tropical cyclone is the potential
energy diﬀerence between the temperatures of those air masses.
Before long, when the diﬀerence between the wind speed of the cold and warm air exceeds
a certain degree around this cold front, the wave of the front (air swell) starts to form. The
same principle is true for waves that are formed by wind blowing across the sea. In otherwords, waves are generated on the boundary surface between two ﬂuids that have diﬀerent
characteristics. Although sea waves go up and down, the wave of a front moves up and downfrom south to north. Figure 8 illustrates this.
At the point where the front swells and the warm air convects into the cold air, a depressionof pressure is generated due to a pressure drop in the surrounding air pressure. In thenorthern hemisphere, on the eastern side of the front’s bulge, because wind tends to blow ina northerly direction and the warm air rises up, seemingly creeping, over the cold air, it will
become a warm front.
On the other hand, on the western side of the front’s bulge, because wind tends to blow in asoutherly direction and the cold air rises up, seemingly creeping, over the warm air, it will
become a cold front. Other air pressure depressions other than these form at the junction of
two fronts. In addition, the axis which connects the center of the surface air pressure depression with that of the upper-air pressure depression is referred to as the “axis of pressure”.
This axis inclines to the west.

10

４−１−２The Structure and Development of Extratropical Cyclones
Warm air

CirrusAltocumulus

Nimbostratus
Altostratus

Altostratus

Cold airCold air

Ｌow

Warm region

Warm air

Cumulonimbus
CirrusWarm air

Altocumulus
Nimbostratus

Altostratus
Cold airCold airFig. 9 The structure of Extra-tropical Cyclones
Masanori Shiraki, 2007, Shin Hyakuman-nin no Tenki Kyōshitsu: Seizando

Figure 9 illustrates the structure of extra-tropical cyclones when developing. Figure (b) is abird’s-eye view of a schematic weather chart; the cloud and rain areas etc. are shaded in.
From the cyclonic central position, the warm front stretches out to the southeast and the cold
front extends out to the eastwest. Dense isobars generate an air circulation which constitutes

11even stronger low-pressure air, and the winds blow counterclockwise into the centre of thecyclone. Figure (a) is a cross-sectional diagram taken from ﬁgure (b) where A-A’ is in the
direction of east-west and to the north from the centre of the Tropical Cyclone.
Figure (c) is also a cross-sectional diagram taken from (b) where B - B ‘ is in the direction ofeast-west to the south from the centre of the Tropical Cyclone.
Westerlies and the jet stream’s core are located on the upper layer of a developing
extra-tropical cyclone (see Fig.8), where the lowest centre of the pressure is on the west sideof the surface cyclone and where wave amplitude (degree of meandering) remains large. This
structure is a common characteristic of developing extra-tropical cyclones. Another featureis that there is upward motion on the east side of the upper-level pressure and a downward
ﬂow on the west side.

Fig. 10 The structure of Extra-tropical Cyclones
Masanori Shiraki, 2007, Shin Hyakuman-nin no Tenki Kyōshitsu: Seizando

Due to the upper-level pressure trough that moves eastward, the front undulates dramaticallyand unstably. The extra-tropical cyclone passes in the vicinity of Japan as it continues todevelop (Fig.11).

12

Fig. 11 Japan Captainsʼ Association, DVD

４−１−３

The Mature Stage of Extra-tropical Cyclones

The central air pressure of the extra-tropical cyclone reaches its lowest in the sea east ofJapan. At this stage, the front begins to be occluded and forms the occluded front. This iswhen the force of the extra-tropical cyclone reaches its peak (Fig. 12).

Fig. 12

Japan Captainsʼ Association, DVD

13

The Rapid Development of Extra-tropical Cyclones at the Nojimazaki
Point (on the southern tip [at the southern extremity] of the Boso
Peninsula in Chiba prefecture) in WinterIn winter, it should be noted that extra-tropical cyclones may rapidly develop in the region
between east of the Nojimazaki Point and the western North Paciﬁc Ocean. In this sea area,
the Kuroshio Current raises the seawater temperature. Isotherm lines extend from west to eastand the seawater temperature is higher in the southern area, more so than in the northern area
where it gets colder (Fig.13).

Fig. 13

Japan Captainsʼ Association, DVD

The upper-level cold air protrudes southward like a “wedge” or “tongue” toward the cold
front of the surface low and travels from west to east along with the easterly migration of thecyclone (Fig. 14).

Fig. 14

14

Japan Captainsʼ Association, DVDWhen upper cold air flows southward like a wedge over the waters off Nojimazaki Point,where water temperatures are high and the temperature difference between the cold air
and warm seawater becomes greater as the cold air moves southward, ocean waves tend toincrease in height. Because of the signiﬁcant temperature diﬀerence between seawater andthe cold air in the area behind the cold front and presence of additional water vapour, the sea
waves oﬀ Nojimazaki Point are prone to be larger than usual.
In the event that a swell from a diﬀerent direction collides with the low pressure passing before
it, irregular waves such as pyramidal waves may be formed, and this may cause extremely
dangerous waves for vessels. Please pay extra attention to high-wave sea areas (Fig. 15).

Fig. 15

Japan Captainsʼ Association, DVD

On 5 January, 1969, bulk carrier “Boriba Maru” (33,814GT, Loa: 223m) sank, then on 9
February, 1970, another bulk carrier “Califorunia Maru” (34,002GT, Loa: 218m) sank. Twoother vessels in the same area and at around the same time became distressed and sank: tanker “Sophia P.” (details unknown) on January 5, 1970, and a cargo ship “Antonio Demades”(details unknown) on February 7 in the same year.

15４−１−４ The Attenuation Stage of Extra-tropical Cyclones
On approaching or almost reaching the waters around the Aleutian Islands, and the frontof the cyclone has completely occluded, at this point, the lowest centre of the upper-levelpressure is almost above the centre of the surface cyclone causing the axis of pressure (SeeFig. 8) to become vertical, and the cyclone becomes an isolated air-eddy without fronts andis completely merged with a cold air mass. The extra-tropical cyclone begins to attenuate andﬁnally decays (Fig. 16).

Fig. 16

Japan Captainsʼ Association, DVD

However, in more recent years, during the winter season in the North Paciﬁc Ocean, cyclones
have been crossing east to south of the Aleutian Archipelago while maintaining full force tofrequently land in North America where they dissipate, after having peaked in force in thevicinity of Alaska bay. Therefore, in the winter season of the North Paciﬁc Ocean, especiallywhen navigating en route North America to Japan, it is always diﬃcult to choose from thefollowing routes: 1) through the rough sea area: North America ⇒ Umnak Strait ⇒ Bering
Sea ⇒ Ats Island ⇒ Kinkasan (or Inubozaki) ⇒ Tokyo (total distance is 4,610 nautical
miles) or 2) via a longer southernbound route (total distance is 4,890 miles) which avoids therough sea area, that will add an extra 280 nautical miles to the distance.
16

The author has also frequently experienced winter season operation of a container ship via a
North American route. However, during the Paciﬁc West Coast voyage, taking into accountthat the ports of departure would be in the North America, namely, Vancouver, Seattle andPortland, I decided on taking the northbound route, but would be preoccupied with roughsea countermeasures. Meanwhile, given that the ports of departure, San Francisco and Los
Angeles, were located in the south, I was closely checking the weather chart until the very
last minute of departure, and also discussed the recommended route in a straight-forwardmanner with a weather information provider i.e. a weather routing service arranged by thecharterer.
As mentioned above, when operating a container ship between San Francisco and Tokyo,
if one is to choose the southernbound route, it means that the total distance will be longer
than that of the northernbound route via the Bering Sea by 280 nautical miles. In addition, it
would take an extra 14 hours when navigating at 20 kts, meaning that one would be behindTrans Pacific Route（example）
4,610 Miles Bering Sea Route

4,560 Miles 44N Rough Sea RouteTokyo

4,890 Miles 34N Line South Route

San Francisco

San Francisco 〜 Tokyo
Rough Sea
Route4,560 Miles

Bering Sea

4,610 Miles

Distance difference

50 Miles
330 Miles
280 Miles

South Route

4,890 Miles

Fig. 1717

on schedule because of the incurred extra distance, compared with taking the northboundroute to avoid rough seas. One is left with no choice but to increase speed in order to makeup for the delay. This in turn results in a large amount of fuel being consumed, which makes
it a truly painful decision for the Master to select the southernbound route (Fig. 17).
One day in February, the author conﬁrmed via AIS that a container ship chartered by anothercompany set sail from San Francisco at around the same time, and that it was also boundfor Tokyo. After the pilot disembarked, the author decided to take the southernbound route.
However, since the other container ship set course for the northenbound route, the author
asked the other Master why he had decided to take that particular route. His response was asfollows.

“I have no other choice but to take the recommended route arranged by thecharterer. But, I personally believe that the best choice is the southernboundroute, the same route on which you are headed!”
Actually, the recommended route according to the weather route was a northernbound routefor our vessel as well. However, in my experience of weather and sea conditions, as predicted, a cyclone developed in Alaska Bay and passed their front which was to later become anorthwest head wind. There would also be a huge swell from several different directions.
Thus, the author knew that the vessel would be forced to signiﬁcantly reduce speed.
Also, when navigating in rough sea area affected by a cyclone in Alaska Bay, as thefollowing low pressure moving north east after passing the Ats Island is often experienced,
in the event of operating towards the south of a cyclone there, the vessel will be forced to
face a southwest head wind, which often means that it will not be possible to steer towards
Kinkasan. Again, deciding whether or not to take this route is also a tough choice. Thanks
to the charterer agreeing with my decision, eventually, we set course for the southernboundroute this time.
Later, via AIS, I enquired as to how the container ship’s northbound voyage went once they18

had reached the coast of Chiba. The following had occurred:
In Alaska bay, the cyclone passed in front of the ship andthe height of the wave was 12 meters, which was greatly
diﬀerent to the originally predicted 5 meters as recommended.
Because of such a high wave together with swell, the Master
was forced to reduce speed down to 8 kts.
The Bering Sea was calm, however, once passing Ats Island,
the ship encountered a cyclone which came about as a resultof a blocking anticyclone (discussed below in 4-1-5). The
Master was obliged to return to North America on a course of<150> navigating southward at 36 north latitude. Then, theMaster headed for Tokyo.
The Master noted that he should have taken the southboundroute similar to me at the time of setting sail from San Francisco.
As a result, the navigation detour and considerable reductionin speed caused by the cyclone, meant that in order to makeup for the delay, the Master had no choice but to navigate at
the highest possible speed after having set sail southward at
36 north latitude, and consequently, the amount of fuel thatwas consumed ended up being far more than that used by thesouthbound route.

When navigating the North Paciﬁc Ocean en route North America to Japan during the winterseason, it is important that the safest and most suitable route be selected. This example
illustrates the importance of a mutual agreement between related parties: consideration of
the Master’s judgement and in-depth pre-meetings with the ship management company andcharterer are paramount.

19