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Trajectory

Date: March 20, 2001
  To: NOAA SSC Steve Thumm  
FROM: NOAA/Hazardous Materials Response Division
      Modeling and Simulation Studies
      Seattle, WA 98115
      
SUBJECT: Main Pass Block 310

FOR ADDITIONAL INFORMATION, PLEASE CONTACT Debra Simecek-Beatty
MODELING AND SIMULATION STUDIES, NOAA, SEATTLE, WA 98115.
PHONE (206) 526-6317.
_______________________________________________________
Per your request we have looked at trajectory implications of the crude oil that
has been released from a platform. These notes are based on the following
information:

On March 20, 2001 at 1240 CST, a platform located at 29° 10'N, 88° 41'W (Main
Pass Block 310) released approximately 3, 300 gallons Louisiana Sweet crude oil.
 At this time, the platform is not leaking any product. If any of this initial
information is incorrect, please let us know ASAP as it would affect any
trajectory implications.
_______________________________________________________
1) Weather Forecast
Tonight, the winds are expected to be from the NW at 25 knots and gusty. 
Wednesday, NW winds at 20 knots are predicted to decrease to 15 knots by the
afternoon hours.  Wednesday night, N-NW winds at 15 knots are forecast to shift
and be from the NE at 5-10 knots by the late evening hours.

2) Trajectory Analysis
Real-time current meter observations, to the east of the incident, (from the
Northern Gulf of Mexico Littoral Initiative) indicate weak offshore flow. 
On-scene observers report winds from the west-northwest at 20 to 30 knots. Given
these environmental conditions, we would expect the winds to dominate oil
movement.  The forecast strong northwest winds will likely move much of the oil
further offshore and to the southeast.  We would not anticipate shoreline
contact in the next 24 to 36 hours.  Forecast onshore winds for Thursday through
Saturday may eventually bring some oil ashore in the form of tarballs.  

3) Oil Weathering
Louisiana Sweet is a light crude with a typical API of 34.5. Initially, the oil
would spread into a thin film, however, the high sea state will tend to overwash
the slick making visual observations extremely difficult.  Using the rough
estimates for the amount spilled and environmental conditions, we would expect
the oil to rapidly emulsify with 50 to 70% of the oil evaporated or dispersed
into the water column in the first 12-hours of the release.  Over the next
couple of days, the remaining oil will eventually form coin sized tarballs which
will be very difficult to observe on visual overflights and with remote sensing
techniques, particularly when the tarballs are widely dispersed.  Tarballs are
very persistent and can travel hundreds of miles.