As stated, weather occurs everywhere and no way to predict weeks or months in advance. Ships try to steer clear of storms. We have 19 transatlantics behind us with 3 more scheduled. We don't get seasick and were basically raised on water. All the TA's have been great, choppy seas in the Mediterranean and Gulf of Mexico, but nothing extraordinary. Just like flying, there is no way to predict turbulence.
In regard of medical evacuation, if the ship is relatively near a port, it will circle back. In the middle of the ocean, the medical staff will do all they can. We have found medical care is
to be excellent. They not only serve passengers, but all the staff.
I believe if one is so concerned about seas and medical, cruising is not the ideal vacation,