I'm not sure I understand your question, but if you are looking for how to find out when the Moon is due south, I believe that you need to find the Moon's azimuth when it is 180 degrees East of North. The following calculator will help you with that:
http://aa.usno.navy.mil/data/docs/AltAz.php
Just select "Moon" and put in your location, and it will give you the azimuth in intervals that you've selected for one day. For example, for Boston, Massachusetts, on November 14, the Moon's azimuth at 5:34 am EST is 180.1 degrees East of North, which means it is about due South for that location.
As to the relationship between the tides and when the Moon is due South, it is a general guideline that when the Moon is due South, there will be the time of high tide in coastal locations. Keep in mind that different coastal locations, due to the layout of the coast etc, may experience 1 or 2 high tides, and if 2, some places will have 1 very high tide and 1 not-as-high tide, while others have about equal high tides. So, the "high tide occurs when the Moon is due South" is a very general guideline. The Moon's position plays a large role, but so does Earth's topography etc.
Hope this helps!
I'm not sure I understand your question, but if you are looking for how to find out when the Moon is due south, I believe that you need to find the Moon's azimuth when it is 180 degrees East of North. The following calculator will help you with that:
http://aa.usno.navy.mil/data/docs/AltAz.php
Just select "Moon" and put in your location, and it will give you the azimuth in intervals that you've selected for one day. For example, for Boston, Massachusetts, on November 14, the Moon's azimuth at 5:34 am EST is 180.1 degrees East of North, which means it is about due South for that location.
As to the relationship between the tides and when the Moon is due South, it is a general guideline that when the Moon is due South, there will be the time of high tide in coastal locations. Keep in mind that different coastal locations, due to the layout of the coast etc, may experience 1 or 2 high tides, and if 2, some places will have 1 very high tide and 1 not-as-high tide, while others have about equal high tides. So, the "high tide occurs when the Moon is due South" is a very general guideline. The Moon's position plays a large role, but so does Earth's topography etc.
Hope this helps!