Signs of a historically strong El Niño global climate pattern became obvious in recent weeks — including deadly fires in South America and deluges in California. Yet scientists are now predicting that the regime could disappear within months. Forecasters at the National Weather Service issued a La Niña watch Thursday, projecting that there is about a 55 percent chance that this pattern — which is the opposite of El Niño — will develop by August. The development of La Niña would have major consequences for weather around the world. It could also temporarily slow the rapid global warming that began about nine months ago, when El Niño first took hold. …It also tends to subdue global temperatures. While it won’t turn back a decades-long rise in planetary warmth, it could moderate the extreme levels of warming scientists have observed as of late. …Climate scientists … suspect that the frequency of strong El Niño and La Niña events is likely to increase throughout the next century.