Prolonged El Niño Conditions in 2014-2015 and the Rapid Intensification of Hurricane Patricia in the Eastern Pacific
A deepening of the thermocline because of sustained El Niño conditions and increased salinity stratification from river discharge near the Mexican coast caused the explosive intensification of Hurricane Patricia in the eastern Pacific.
Hurricane Patricia, the most powerful hurricane in the western hemisphere in recorded history, devastated the west coast of Mexico in October 2015. Scientists from Atlantic Oceanographic & Meteorological Laboratory of NOAA and the Department of Energy’s Pacific Northwest National Laboratory performed an analysis of the prevailing oceanic state at the time of Patricia to understand the ocean’s role in the intensification of the hurricane. The team found that a deepening of the thermocline due to sustained El Niño conditions and enhanced salinity stratification due to river discharge near the Mexican coast caused the explosive intensification of Hurricane Patricia.
Researchers used the framework of Dynamic Potential Intensity (DPI) to understand the impact of oceanic conditions on the intensification of Hurricane Patricia. Using monthly-mean sub-surface oceanic temperature and salinity data, monthly-mean atmospheric profiles of temperature and humidity along with sea-level pressure data, the DPI was computed using sub-surface oceanic conditions from 2015, 1997, and weather conditions over time. The team also evaluated the role of upper-ocean salinity stratification. The team found that the warming of the upper-ocean and the deepening of the thermocline along with increased salinity stratification because of the freshwater discharge from Rio de Grande and Balsas Rivers reduced the ocean’s vertical mixing and sea-surface cooling for Hurricane Patricia and boosted its intensity. Using satellite altimeter data, they showed that the cause of the heat build-up in the eastern Pacific was the prolonged and persistent El Niño-like state that persisted in the tropical Pacific beginning in 2014. Finally, they performed a heat budget analysis to rule out the role of the warming in the northeastern Pacific as an anomalous heat build-up in the Hurricane Patricia region.