TOKYO (Reuters) - Japan’s weather bureau said on Tuesday that it estimated that a La Nina weather pattern has emerged and that there was a 60 percent possibility that the phenomenon would last through the winter months December to February.

But there was a 40 percent chance that it would return to normal conditions during the winter, it added.

La Nina, which tends to occur unpredictably every two to seven years, is characterized by unusually cold temperatures in the equatorial Pacific Ocean.

The outlook is in contrast to a U.S. government weather forecast, which said last month that La Nina conditions were no longer likely to develop during the Northern Hemisphere fall and winter of 2016/17, saying neutral conditions were more likely.