22 to VII-29 (appendix VII). A major positive factor affecting performance 

 in forecasting limits was the daily oil surveillance flights from December 17 

 to December 27. Data from these flights permitted accurate correction of 

 initial oil position each day, 



2.3.2 U.S. Coast Guard Research and Development Center 



The usee R&D Center began to forecast the movement of the oil on Decem- 

 ber 15, 1976, at the request of the Marine Safety Office (MSO) in Boston. 

 The forces that transport the oil were examined by R&D Center personnel. It 

 was found that the magnitude of the wind vector determined from predicted 

 values of wind speed would move the oil at a rate of 0.5 to 1.5 knots in a 

 downwind direction; that the magnitude of the tidal currents would move the 

 oil at 0.5 to 1.3 knots; and that the magnitude of the permanent currents in 

 the area are approximately 0.1 to 0.2 knots. After comparing the magnitude 

 of the forces that move the oil it was decided that for the short-term pre- 

 dictions (24 hours) the tides and winds would control the movement of the 

 oil. For long-term predictions, the winds alone would dominate. The method 

 used for predicting the movement of the oil was a simple vector addition of 

 the tidal vector and 3.5 percent of the wind speed on an hourly basis. The 

 lateral movement of the oil was determined to be the magnitude of the tidal 

 movement. This combined with the hourly vectoral movement of the oil showed 

 the "worst case" estimate of the areal extent of the oil. 



On December 16, at 0930, MSO, Boston, requested the R&D Center to fore- 

 cast the movement of oil should the tanker rupture. At 1135, MSO was in- 

 formed that the oil would move southeast for the next 24 to 48 hours, and 

 would continue to move southeast-to-east through the weekend of December 18 

 and 19. This forecast was based on the tides and the predicted winds sup- 

 plied to the R&D Center by the National Weather Service (NWS). MSO, Boston, 

 was also informed that the oil would continue to move offshore as long as the 

 winds were offshore. 



Figures VII-9 through VII-12 in Appendix VII depict the long-term pre- 

 dicted movement of the oil using predicted winds and net tidal currents. 

 These figures were the basis for the information that was transmitted to MSO, 

 Boston. The long-term movement is based on the predicted winds as supplied 

 by NWS. Figure VII-9 shows the predicted limit of the slick as of 1900, 

 December 17. This figure includes the effects of the predicted winds used 

 for the forecast as well as the total movement of the oil caused by previ- 

 ously predicted winds. From 1600, December 16, the west-northwest winds and 

 tides moved the oil 8 miles to the east-northeast. From 0700 to 1300, Decem- 

 ber 16, the northeast winds moved the oil toward the southwest, a distance of 

 6 miles. The spill was treated as a continuous leak, and the oil movement 

 was therefore predicted continuously from the site of the Argo Merchant. 

 This is the reason for two vectors being labeled 0700-1300, December 16. One 

 of these shows the transport of the oil that moved northeast prior to these 

 wind conditions. The other vector shows the movement of oil from the site of 

 the Argo Merchant during the period 0700-1300, December 16. This process was 

 used for the entire period. Thus, the boundaries of the oil spill limits as 

 shown in Figures VII-9 through VII-12 are, in essence, an estimate of the 

 limit of the oil slick. 



43 



