MADRID, Oct 25 (Reuters) - Relatively high inflation rates are likely to be observed over coming months, even though their underlying causes are mainly transitory, Bank of Spain governor Pablo Hernandez de Cos said on Monday Rising energy prices could last through the winter as demand generally increases because of cold weather and oil and gas storage levels are relatively low, he said, warning that the longer the transitory inflation pressure lasts, the likelier high inflation will become persistent. Nevertheless, de Cos added the general perception is that the European Central Bank will keep its expansive tone for a “dilated period of time”. He added the current supply chain disruptions, higher energy prices and other recent developments are likely to prompt a “significant downward” revision of the bank’s outlook for 2021. (Reporting by Jessica Jones, Editing by Inti Landauro and Andrew Cawthorne)