For ship routing the shortest route is not necessarily the safest or fastest route, so optimising routes for weather and currents is an important step in voyage planning as adverse weather and currents can have a considerable negative impact on a vessel’s speed resulting in significant increases in costs, fuel consumed, emissions, etc. Whether the priority for a voyage is least cost, least fuel, fixed ETA, fastest, etc. our prevoyage brief (PVB) is designed to help clients make the right choice.
The Fleetweather PVB consists of a table comparing different variables for various routing options for an upcoming voyage. These variables include distance through water, speed through water, total voyage time, and current and weather factors. This format helps clearly show the difference between routing options depending on the priorities set (fastest, safest, least cost, fixed arrival time, etc). The shortest route (distance over the ground) is not always the most optimal, and does not always lead to the earliest arrival time. This blog provides some recent examples where savings of 10% or greater were possible.
Minimising Adverse Currents
One recent voyage in early August 2021 from Corpus Christi to Buenos Aires offered a number of routing options as outlined in Fig. 1 primarily based on current factors as the weather factors were all identical assuming a directed speed of 14.0 kts.
The corresponding PVB table at Fig. 2 details the three route options as described in Fig. 1.
- Route Alt-1 was provided by the Master, and is the shortest route in distance over the ground via the Yucatan Channel at 6396 nm. After factoring weather and currents this increases to 6774 nm distance through water (DTW) and a total voyage time of 484.1 hrs. Even though this is the shortest route, it does not have the earliest estimated time of arrival. Alt-1 encounters adverse current in a portion of the Loop Current and the Yucatan Channel.
- Alt 2, using the Old Bahama Channel saves approximately 50nm distance and exploits some helping current from the Loop Current, SW of Florida, as seen in Fig. 3.
- Alt-3, using the Old Bahama Channel and the Mona Passage saves 259 nm DTW and arrives about 18.4 hours sooner. The main savings factor comes from avoiding the strong Guiana Current. This equates to about a 4% in savings solely based on currents since the weather factor for each route above is the same at minus 0.09 Kts.
Speed change options
Speed reduction to 11.5 kts was also an option to reduce fuel consumption as indicated in Fig 4. This resulted in differing weather factors coming into play as the trade winds fluctuate.
Alt-1 now experiences a more negative weather factor (-0.26 kts) than Alt-2 & Alt-3 (-0.18 & -0.17 kts). This is due to the increased time spent in the opposing fresh to strong SE’ly trade winds and associated sea and swell as depicted in Fig 5.
Alt-3 via the Old Bahama Channel & Mona Passage is still the shortest DTW, saving approximately 36.7 hours. This equates to about a 6% savings when factoring in both weather and current factors.
While 6% savings is significant, routing in general between the Gulf of Mexico to off NE Brazil can yield even higher savings in excess of 10% depending upon the time of year and actual weather/current patterns at the time. The same analogy applies to other regions of the world too.
Furthermore, a saving of some 36 hrs can add up significantly when one includes savings in fuel, hire and emissions, etc. The vessel taking this route was a 74,000 DWT Panamax tanker. By taking the Old Bahama Channel and Mona Passage, and minimizing currents, fuel and hire costs savings would be about $32,000 and $26,000 respectively (based on the latest data at time of publish for this vessel type/size). Also, our optimized route saved 176 MT of CO2, 5.06 MT of NO2, and 0.56 MT of SO2 for a total savings of 181.34 MT in emissions.
Our PVB tool provides the ability to determine the best route for any given voyage, depending on the circumstances whether these be least cost, least fuel, fixed ETA, fastest, environmental or Time Charter Equivalent (TCE), etc. while keeping safety as the utmost priority. We use a number of global and regional (weather, wave and ocean current) models and climatological data to help recommend optimal routing in line with client wishes.
Overall, optimal routing via prevoyage planning is a net benefit service, which need not be cross ocean in nature. In general the savings that can be accrued by clients far outweigh the cost of the service by many orders of magnitude. As part of this service, Fleetweather can track cumulative savings (time, distance, fuel, emissions) at either single voyage, vessel or fleet level for clients and so help track total savings.
Stay connected and safe.