A NOAA Hurricane Hunter aircraft measured winds near 180 mph and a central pressure of 892 millibars Tuesday afternoon. Only Hurricane Patricia in 2015 had a lower pressure. By 5 p.m. PDT, Polo had eased slightly to 175 mph and 900 millibars, but was still a Category 5 storm. 

Polo went from a minimal tropical storm to a Category 5 in just 33 hours, which would be the fastest such development recorded in the eastern Pacific.

That 120 mph jump in less than 36 hours was fueled by exceptionally warm ocean water, abundant moisture and little wind shear, the disruptive winds aloft that can tear hurricanes apart. Surface water off southwestern Mexico reached 88 degrees, among the warmest on record for mid-September. The anomalously warm ocean temperatures are being boosted by a very strong El Niño, which continues to set daily ocean temperature records in the equatorial Pacific.