There is a stretch along the Gulf of Mexico that is known to be very rough.
Gulf of Tehuantepec.
The strong winds are known as "tehuantepecers", and caused by the north flow of air funneling thru the gap in the mountains at the north head of the gulf. Effects can be felt up to 100 miles from the coast. The winds can occur any time of the year, but, are more frequent from Nov. - Feb, - up to 5 times/month.
I can remember doing a cruise on the Pacific Princess & the ship was really rockin' thru the gulf. On the larger ships it is not as noticable.