The Distant Future of Montevideo

For my consideration of Uruguay 100 million years into the future, I consider two climactic possibilities. 
It is important to note that for both considerations I will assume that the Milankovitch cycles will have returned to the status they are today due to difficulty in predicting their interactions to such a future date. Secondly I will assume that by this time anthropogenic influences will be minimal either due to catastrophic extinction of humanity or an enlightenment of the human race coupled with advances in technology that allow them to live harmoniously with natural ecosystems.  


The first shall be represented by this map:

http://www.youtube.com/watch?v=pGACbD4zbWs

 According to this simulation Uruguay will still remain in the Southern Hemisphere but it will have moved much closer to the equator. My approximation of latitude will be 10 degrees South with Longitude at about 18 degrees West. At this new more northern location, the sun's angle will be much more perpendicular to the ground year round and will result in higher temperatures. Additionally, this location will be right below the ICZN and the subsolar point. As the sun warms the region, the hot air will rise and give off its moisture resulting in heavy rains. Given that Montevideo will still be off the coast, it is likely the air will be saturated.

Predicted climograph for Uruguay 100 million years into the future.
Temperature in burgundy and precipitation in purple.

Seasons will remain during the same time of year but given the proximity to the equator, it is unlikely much of a difference will be seen from month to month. With the location near an ocean and given the now limited amount of land in the southern hemisphere, I do not expect a lot of air mixing and therefore I feel temperatures in the area will remain constant. Any air circulation will most likely be influenced by the Doldrums.

Notice the location of Uruguay just south of the low pressure system

Tectonic activity throughout South America will be limited over the next 100 million years so it is unlikely a mountain range should develop anywhere near Uruguay and thusly eliminate the potential for a rain shadow or other orographic interferences with climate. Montevideo's location on a passive margin makes it unlikely that any geologic lake formation should occur either. The only fluctuation in lentic and lotic systems should depend on increased precipitation and sea level fluctuation.

http://www.globalchange.umich.edu/globalchange1/current/lectures/evolving_earth/evolving_earth.html
Uruguay is located on a passive margin that will experience little tectonic activity. Montevideo indicated with pink dot.

Air masses will no doubt change globally but given the northward migration of South America and its relative isolation, I expect only maritime equatorial and continental tropical influences. 

Maritime equatorial in red, Continental tropical in pink

Vegetation in Uruguay will likely change from grass lands to tropical rain forest. Average relative humidity will be high year round but the foliage should keep the suns rays from striking the ground directly and keeping the heat more moderate.

http://www.britannica.com/blogs/wp-content/uploads/2009/09/monkey-costa-rica.jpg

For the second simulation I consulted this map:

http://www.educatedearth.net/video.php?id=4943

As you can see, temperatures would still be high as Uruguay migrates to the equator but a rise in sea level with no potential tectonic uplifting would mean that Montevideo would exist only as an underwater ancient city.