An Investigation of the Weather Impacts to Ships Transiting the Gulf Stream in Winter and Early Spring

The Gulf Stream is an ocean current transporting warm water along the Southeastern U.S. coast before turning east-northeastward off Cape Hatteras and continuing well south of the Canadian Maritime Provinces. The Gulf Stream velocity can reach speeds up to 5 knots, and sea surface temperature gradients along its northern boundary can exceed 15 degrees C in late winter and early spring. Mariners have used or avoided the Gulf Stream to gain efficiency for centuries. However, wind, wave, and current interactions within the Gulf Stream system are complex and can produce localized hazardous seas, extreme waves, and enhanced winds.

To better understand the impacts and the associated conditions on safe and efficient passage by commercial ships, Automated Identification System (AIS) data was queried over a three month period using the Department of Transportation’s Seavision 2 web application. Ship track data from transits with speed reductions and course alterations in the Gulf Stream were downloaded for further investigation. A 20% speed reduction from the observed average and at least a 15 degree heading change were considered significant. Roughly two thirds of the 120 ship tracks displayed significant speed reduction and/or heading changes. The environmental conditions at the time of these significant events were further analyzed using Advanced SCATterometer data (METOPS-A and B), satellite altimeter data, archived OPC Atlantic Surface Analysis Loops, and archived Wind Wave Analysis charts. In addition, point data from numerical analyses, hindcasts, and short term forecasts from the NOAA Global Data Assimilation System (GDAS), WAVEWATCH III wave model (NWW3), and Global Real-Time Ocean Forecast System (GRTOFS) were examined to better understand the larger scale wind, wave, and current conditions occurring during each event. The results of these investigations will be presented. Existing gaps in both observing capabilities and prediction tools will also be discussed.