AWT Weather Routing/Routeing: Applied Weather Technology

What Other Sources Say About the Benefits of Weather Routing

Various studies by the IMO and its consultants from 2000 to 2009 have reported that significant gains in fuel and emission reduction can be achieved by weather routing. The range reported is 2-4 percent while AWT data suggest typical savings of 4-8% on trans-ocean passages and smaller savings for near-shore voyages. The IMO values were first published in the 2000 study, “Study of Greenhouse Gas Emissions from Ships,” (Martinek, et al) and contrasted and compared a number of different technical and operational measures.

Here is the breakdown of individual operational measures in the 2000 report:

Operational Measures for Fuel Reduction in Ships
Operational Measures	Fuel saving potential	Combined	Total
Planning and Speed Selection			1-40%
Fleet Planning	5-40%	1-40%
“Just in Time” Routing	1-5%
Weather Routing	2-4 %
Miscellaneous Measures
Constant RPM	0-2%	0-5%
Optimal Trim	0-1%
Minimum Ballast	0-1%
Optimal Prop Pitch	0-2%
Optimal Rudder	0-.3%
Reduced Time in Port
Optimal Cargo Handling	1-5%	1-7%
Opt. Berthing, Mooring, Anchorage	1-2%

The weather routing estimates are actually based upon the post-graduate research of the Norwegian scientist, Arve Lepsøe, and reflected in his thesis: “Use of Computer Aided Weather Routing System on Ships” (in Norwegian only), Norwegian University of Technology and Science, Faculty of Marine Technology, Trondheim 1997.

According to the 2000 report, “It is clear that total effect from combination of different measures is difficult to predict or identify.” This is reflected in the range of reported values. The authors make no specific distinction between vessel type and voyage characteristics, including season, weather patterns, route selection, vessel speed, currents, and transoceanic versus near-shore voyages. Data from AWT suggest these can be critical in determining fuel savings as well as emission reductions.

Also unclear in the original IMO report is how various technical and operational factors interact, potentially reinforcing one another--for example, the link between advance knowledge of sea conditions and speed.

IMO reports demonstrate as much as 23.3% in gains from speed reduction, but researchers have long been aware that vessel speed on different legs of a journey is influenced by the captain's desire to arrive on schedule and his perception of potential risk along the way that might cause delays. The terms of charter define the limits here. Because of uncertainty, captains commonly “hurry up” on the early portion of a voyage to maintain adequate cushion should they encounter foul weather.

Accurate and effective weather routing diminishes this and the need for cushions. In fact, AWT data show that with better weather routing and a clearer picture of likely sea conditions, captains can smooth out their own speed regimen and capture fuel savings in the process.