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Re: Avoiding Wx Problem
From: Robert Owens
Date: 2000 Dec 15, 10:18 AM

```Thanks, that makes sense to me, now for another that confuses me. You
suggest a right angle course away from the hurricane. So....Try this one:
You are underway on course 050T 12knots max. The hurricane eye bears 080T ,
100 miles. The hurricane is moving 265T at 22knots. If you maneuver at 12
Knots to avoid, what course would you steer to have the max CPA.     The
Working out the CPA as you suggest is correct at 63 NM.
Bob Owens
TUGLY

----- Original Message -----
From  "Smith, Peter"
To:
Sent: Friday, December 15, 2000 8:50 AM
Subject: Re: Avoiding Wx Problem

>
snip> Construct a geographic plot with your initial position and the
hurricane
> bearing 120dT at 110mi. Draw the hurricane's projected track of 285dT and
> extend it for 150mi (6 hours into the future). Since the test expects you
> to "maneuver at 12 knots to avoid the hurricane", construct a new course
> line from your initial position on a course of 015dT (perpendicular to
> the hurricane track) and extend it 72 miles (6 hours at 12kt).
>
> To find CPA distance:
>
>  1. Lay your ruler along your new 015dT track and draw a line back along
>     195dT until it crosses the hurricane track. This is the CPA.
>
>  2. Measure the distance from the CPA back to the hurricane's initial
>     position. Divide that distance (in miles) by 25 (hurricane's speed in
>     knots) to get the time of CPA (hours in the future).
>
>  3. Multiply that time by 12 (your speed in knots), giving the number of
>     miles you will travel before CPA.
>
>  4. Mark that distance on your 015dT track. The distance from there to
>     the CPA point on the hurricane track is the CPA distance.
>
> I just tried this using the cheep protractor and compass at my desk and
> came pretty close to the book's answer of 77 miles.
>
>  -- Peter
```
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