How a mix of natural and human-caused factors cooked up Tropical Storm Hilary’s soggy mess

By SETH BORENSTEIN
AP Science Writer

Scientists figure a natural El Nino, human-caused climate change, a stubborn heat dome over the nation’s midsection and other factors cooked up Hilary’s record-breaking slosh into California and Nevada. Cooked up is the key phrase because hot water and hot air were both crucial in growing Hilary quickly and then steering the storm on an unusual path that dumped 10 months of rain in just one weekend in some normally bone-dry places. Nearly a foot of rain fell along a couple of Southern California mountains while cities easily exceeded summertime records.