Figure #1: Henry the Navigator's
"Volta do mar" technique.

(click to enlarge)

Ocean surface currents have always been a factor of great importance and curiosity in the world of shipping. From techniques such as "Volta do mar" developed by Henry the Navigator in order to quickly and efficiently travel from mainland Portugal to the Canary Islands and Azores during the fifteenth century (see Figure #1 - the phrase in Portuguese literally means turn of the sea), to the current high-tech applications involving satellites and numerical modeling, mariners have always been trying to find ways to save time and bunkers at sea by taking advantage of the natural movement of wind and water at the ocean's surface.

In the recent past, satellite measurements have resulted in a leap forward in the understanding and prediction of ocean currents in the scientific community. For example, in 2008 scientists announced the discovery of a previously unknown current pattern called the North Pacific Gyre Oscillation, which answered long standing questions regarding changes in salinity and chlorophyll that have been observed over the Northeast Pacific. These same satellite measurements have also contributed to the development of the Hybrid Coordinate Ocean Model (HYCOM) and the Real-Time Ocean Forecast System (RTOFS) by a collaboration of scientists at Florida State University, NOAA, and the U.S. Navy. These models produce both an analysis and an accurate ocean current forecast covering nearly the entire globe that can be used in a variety of applications ranging from hydrographic and biological research to efficient ship routing.

Figure #2 - Current eddy over the
Alboran Sea as pictured on
www.wridolphin.com

(click to enlarge)

These models have proven to be highly effective in not only predicting the strength and location of well-known currents such as the Gulf Stream and Agulhas Current, but also the small scale eddies that typically separate from these larger scale streams. Unlike the large scale currents, these eddies can vary significantly in size/strength and location on a day-to-day basis, and this would be nearly impossible to predict without the assistance of satellites and forecast models. Figure #2 shows a current eddy that is often present over the Alboran Sea in the western Mediterranean. When this eddy is present, westbound vessels approaching Gibraltar Strait will transit more efficiently when following a southern route, avoiding the strong head currents present along the northern periphery of the eddy.

WRI provides RTOFS and HYCOM data to our clients through our Dolphin Fleet Management website (www.wridolphin.com) and Dolphin Voyage Planner, and in our detailed forecast advisories. Dolphin users can simply adjust the charts to any location at any zoom level with our dynamic "zoomable" map interface, with your ships current and future positions plotted on the charts.

Figure #3 - The Guiana Current

(click to enlarge)

WRI ingests the full RTOFS ocean current forecasts into our system, and always take this data into account when analyzing and recommending routes for ships worldwide. Figure #3 demonstrates the importance of ocean currents with regards to efficient ship routing. Ship captains often prefer a shorter more coastal route toward Cabo de São Roque from Galleons Passage, however significant time savings can be gained when following an offshore route and avoiding strong the adverse Guiana Current. A more coastal route would be preferred for northbound vessels in order to benefit from a strong following current.

We also ingest RTOFS current data into our high resolution wave model, in combination with high resolution wind forecasts from the WRF-ARW model. This produces highly accurate wave height forecasts in areas where strong semi-permanent ocean currents meet opposite swell, locally amplifying the waves. These areas are also known to be particularly favorable for rogue waves, and can be dangerous for small or sensitive vessels.

Figure #4 - WRF-ARW winds, RTOFS currents, and the resulting model forecast significant wave height.

(click to enlarge)

Figure #4 demonstrates this concept in two areas (highlighted by white circles) where the Mozambique and Agulhas Currents flowing southward meet seas/swell propagating northward, increasing the forecast wave heights.

The use of high resolution current data allows WRI to always recommend the most efficient route possible, avoiding dangerous conditions for safety of the vessel and crew, and keeping our clients better informed and prepared for the conditions they will encounter at sea. Our innovative tools and detailed advisories will provide your fleet and operations with the information required to ensure safe and efficient transits. Contact WRI today to discuss how our services can be customized for your fleet!