Storm Avoidance: Maximum Distance

You are underway on course 050°T and your maximum speed is 13 knots. The eye of a hurricane bears 100°T, 120 miles from your position. The hurricane is moving towards 275°T at 25 knots. If you maneuver at 13 knots to avoid the hurricane, what could be

Storm Avoidance: Maximum Distance

Given:    Own course = 50°T
               Own speed = 13 knots
     Hurricane bearing = 100°T
      Hurricane course = 275°T
       Hurricane speed = 25 knots

 What is asked: Maximum distance

Solution:

We have to solve first for the course to steer to have the maximum CPA before we can solve for the maximum distance.

1. We are going to divide own speed by the storm speed. 
2. And then press inverse cosine. 
3. Answer in #2 shall be added or subtracted the storm course. (Rule: + if storm bears quarter, - if storm bears bow)

         13 ÷ 25 = 0.52 inv cosine = 58.67° + 275° = 333.67°

We can now proceed in solving for the maximum distance in avoiding the storm.

1. We have to add 180° to the course to steer, and then minus 360°.
2. The answer in #1 will be subtracted by the storm bearing.
3. Multiply the cosine of your answer in #2 times the distance of the hurricane from your position.

333.67° + 180° = 513.67° - 360° = 153.67° - 100° = 53.67° and then 120 miles × Cos 53.67° = 71 miles is the final answer.


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