An Investigation of the Formation of Hurricane Patricia (2015)

Patricia (2015) was a late-season hurricane in 2015 identified as the strongest hurricane on record in the eastern North Pacific and North Atlantic basins. According to NOAA National Hurricane Center (NHC) analysis, Patricia’s development was slow and complicated, involving the interaction of multiple weather systems. It started as a tropical disturbance on 11 Oct entering the eastern Pacific and later merged with another tropical wave. Meanwhile a Gulf of Tehuantepec gap wind event was occurring and provided an injection of cyclonic vorticity to the merged disturbance, forming an elongated area of low pressure system. Deep convection associated with the large cyclonic gyre increased substantially on 17 October, possibly due to more favorable large-scale conditions associated with the passage of the rising branch of a strong Madden-Julian Oscillation moving eastward across the eastern Pacific. The occurrence of a second gap wind event combing with deep convection finally led to a small well-organized circulation on 20 Oct.  An Air Force Hurricane Hunter aircraft recorder a maximum sustained winds of 180 kt and a minimum central pressure of around 879 mb around 0600 UTC on 23 Oct. The unusual rapid intensification of Patricia poses a great challenge for real-time prediction by dynamic models.

To understand the intrinsic dynamic and thermodynamics processes associated with the formation and rapid intensification of Patricia, we simulate the storm using the U. S. Navy operational tropical cyclone prediction system, COAMPS-TC, and analyze dropsondes from the ONR TCI field campaign. The study focuses on the interactions of multiple scale circulations and the relative importance of them. Sensitivity of the terrain, SST gradient, and cloud microphyscis will also be presented.