A long-awaited La Nina has finally appeared, but the periodic cooling of Pacific Ocean waters is weak and unlikely to cause as many weather problems as usual, meteorologists said Thursday. La Nina, the flip side of the better-known El Nino, is an irregular rising of unusually cold water in a key part of the central equatorial Pacific that changes weather patterns worldwide. The last El Nino was declared finished June 2024, and National Oceanic and Atmospheric Administration (NOAA) forecasters have been expecting La Nina for months. Its delayed arrival may have been influenced by the world's oceans being much warmer than the last few years, said Michelle L'Heureux, head of NOAA's El Nino team. It's totally not clear why this La Nina is so late to form, and I have no doubt it's going to be a topic of a lot of research, L'Heureux said. In the United States, La Ninas tend to cause drier weather in the South and West. They tend to make weather wetter in parts of Indonesia, northern ...