The learning objectives for this chapter
is to gain a basic understanding of what
weather routing is and how the voyage
plan can benefit from this statistical
data based on long-term accumulation of
data combined with up-to-date whether
routing information whether routing of
ships has been effectively used for some
time several different systems and
philosophies have been developed and
used the advantages which may be gained
from a weather routing system are
quicker sailing between two points
reduced risk of damage to Holland cargo
more accurate prediction of arrival
times the savings can sometimes be
considerable not only by reducing damage
due to heavy sea but also quicker
sailing times and avoiding unnecessary
risks the shortest distance between two
points is along the great circle passing
through these points however the weather
seas and currents experience along this
route will influence the time taken and
result in this route not always being
the quickest current wind and
particularly the waves will influence
the ship's speed considerably and may
cause permanent structural damage such
as pounding damage the unexpected
presence of severe storms such as
tropical revolving storms TRS may
require moderating the voyage plan and
taking avoiding action this type of
weather may be unpredictable but it is
essential that the voyage plan is
adjusted to avoid excessive danger and
damage
similarly unpredicted reduced visibility
will require reassessment of desired
speed and possible deviations
the statistical mean values for current
and sea conditions often show variations
that make it advantageous to depart from
the great circle track on this basis
recommended roots are calculated for
different trades the roots may apply to
a season a month or even shorter periods
statistically based recommended roots
which take into account likelihood of
ice fog high winds etc should be used as
a reference when considering the
advantage of whether routing to give a
rough estimate of whether routing
savings in sailing time for a given ship
in a given trade with a certain loading
condition and with a certain captain is
very difficult not to say impossible
possible savings in the short term and
avoiding damage in the long term should
be considered while it may be that the
captain would have selected the same
route anyway there is ample evidence
that the additional information provided
by the weather routing services
generally contributes to an optimal
route selection with today's improved
weather forecasts the number of ships
using where the routing services is
increasing during a voyage
it's most important that a good
understanding is established between the
captain and the weather routing
organization the captain must have full
confidence in the weather routing system
and its organization
otherwise the service is not likely to
be used
new knowledge about the forces acting on
a ship during various weather conditions
together with expensive damage with loss
of lives and money has led to a better
understanding of the need for a more
accurate way of measuring the forces
acting on a ship while underway an
increasing number of ships are today
sailing with a weather monitoring system
the information from which is included
when estimating the forces acting on the
ship
this allows the master to determine the
optimal speed which is the highest
possible speed without causing damage to
the ship