Hurricane Polo reached Category 5 strength three times this week in the eastern Pacific, the first storm there to do so, prompting some analysts to discuss an unofficial Category 6 as it threatens Mexico this weekend. Warm waters near 90 degrees Fahrenheit, several degrees above mid-September norms and above the 82-degree level needed, plus weak upper winds and good outflow, drove the rapid growth, NASA and SUNY Albany scientists said after viewing satellite images of its large clear eye.

Forecasts show it nearing Baja California Sur early next week with unclear landfall, and remnants possibly bringing rain, flooding and winds to Arizona, New Mexico and Texas. Mexican officials opened shelters, evacuated southwestern coastal beaches and deployed 15,000 security staff while residents stacked sandbags and left some homes from Thursday. Hurricane-force winds reach just 40 miles from the center and tropical-storm winds 125 miles, the National Hurricane Center reported.