Vine split tomatoes

Tomatoes can  over-ripe or, in this case, probably had too much watering, if not a fungus.  Pick them a little on the early side and let them ripen further on a windowsill.

 If the plants get really dried out and then soggy with water and then dried out again, this may cause the tomatoes to split.

Or, you may have a case of sour rot. This is a fungus that leads to wide, deep cracks in tomatoes near the stem end. This can be correctred with a standard fungicide found in your local garden centers. Spray it on the plant according to the manufacturer's directions and tomatoes should be fine. To avoid fungal problems in the future, do  not water the tops of the plants.

Good luck.