During the last 15 years, meteorology has made remarkable progress in terms of forecast accuracy, directly impacting the shipping sector and more specifically, route planning. With a significant increase in the range of weather models used, we can now predict the conditions of wind, waves and currents 7–16 days in advance. Furthermore, next generation satellite platforms (i.e. Metop A and B) act as “observing eyes” above the ocean—providing us with measurements for isolated oceanic areas. Routing Advisory Services (RAS), previously viewed as dispensable by captains, are now understood to be a critical tool for every captain. To understand why these services are so crucial, we must look into what exactly they entail, as well as their advantages in situations when a vessel can lose time while en route.
When a vessel departs from Port A to destination Port B, there are two main factors that cause delays: distance and weather. Let us consider that
A vessel departs from Le Havre (Port A) with the destination being New York (Port B). If she sails across the Great Circle, the LTD will be equal to zero because the Great Circle is the shortest course in terms of nautical miles.
During winter, however, the ship is very likely to encounter adverse weather conditions when traveling through the Great Circle, forcing a remarkable reduction in its speed. For this example, we will assume that LTW equals 12 hours along the Great Circle (GC). This means the total time lost will be:
Loss Time (GC) = LTD + LTW = 0 + 12 = 12 hours.
If the same vessel chooses to sail along the rhumb line with a turning point in 40N / 40W, it will be a longer distance but with a greater chance of sailing in better weather conditions.
In this case, the LTD may be 6 hours and the LTW only 2 hours, decreasing the total time lost to 8 hours. This second course, although longer in miles, is not only the safest but also the shortest time-wise.
This exemplifies why the captain should seek to find a balance between the LTD and the LTW, or the distance of a voyage and the weather conditions that may be encountered.
There are three options to reach this balance:
Advantages of Route Advice Services:
The below figure depicts three alternative routes for a Transatlantic western passage during winter where NaviPlanner BVS is used.
The results show that the negative effect of the weather is greater in the southern course (-2.15 KT), although one would expect the opposite. The same applies to currents, where across Track 2, the current factor is -0.28 KT.
We can see that the southern passage has not only the largest LTD but also the largest LTW, which can often occur in a transoceanic passage during winter.
Between the Track 1 and Track 3, we see that Track 1 is shorter by 11.3 hours, but the negative effect of weather is almost the same (-1.8 KT and -1.9 respectively). However, the cost of Track 1 is $5916 higher as the ship travels longer within the U.S. ECA.
Thus, we can conclude that Track 2 is not only the safest but also the most economical, with a potential savings of $26,932.