On October 11, 2015, an area of disturbed weather traversed Central America and emerged over the eastern Pacific Ocean. The disturbance moved slowly over the next few days, later merging with a tropical wave on October 15. The merger of these systems and the effects of a concurrent Tehuantepec gap wind event spurred the formation of a broad area of low pressure. This feature gradually consolidated and became a tropical depression shortly after 00:00 UTC on October 20; at this time the depression was situated roughly 205 mi (335 km) south-southeast of Salina Cruz, Mexico. A mid-level ridge to the north steered the depression generally west and later pulled it north along an arcing path.
Development was initially slowed by locally cooler sea surface temperatures and dry air, and the depression became Tropical Storm Patricia later that day. Once clear of the unfavorable region, Patricia traversed anomalously warm waters within an environment exceptionally conducive to rapid intensification. Dramatic strengthening began late on October 21 and continued through October 23. Patricia reached hurricane strength shortly after 00:00 UTC on October 22, featuring prominent outflow, well-defined banding features, and a developing eye. Data from Hurricane Hunters investigating the cyclone indicated Patricia to have reached Category 4 status on the Saffir–Simpson hurricane wind scale by 18:00 UTC.
Satellite animation of Patricia weakening considerably before making landfall on October 23
By the early hours of October 23, a clear northward turn took place followed by acceleration northeast. A solid ring of −130 °F (−90 °C) cloud tops surrounded the hurricane's 12 mi (19 km) wide eye and signaled its intensification into a Category 5 hurricane. In a 24-hour time span, Patricia's maximum sustained winds increased by 120 mph (195 km/h), the fastest such intensification in any hurricane observed by the National Hurricane Center (NHC). The hurricane achieved its peak around 12:00 UTC on October 23, with estimated winds around 215 mph (345 km/h) and a barometric pressure of 872 mbar (hPa; 25.75 inHg); these values are based upon continued intensification after a Hurricane Hunter mission into the storm six hours prior. In the NHC's report on Patricia, it is noted that the hurricane may have surpassed Typhoon Tip as the strongest tropical cyclone ever observed, but lack of direct observations at the time of its peak prevent analysis of such.
Later on October 23, rapid weakening ensued as an eyewall replacement cycle took shape and wind shear increased. In the five hours up until landfall in Mexico, Patricia weakened at an unprecedented rate while still over water. However, upon moving ashore around 23:00 UTC near Cuixmala, Jalisco, it remained a strong Category 4 hurricane, with sustained winds of 150 mph (240 km/h) and an analyzed pressure of 932 mbar (hPa; 27.49 inHg). This made Patricia the most intense landfalling Pacific hurricane on record. Once onshore, the high terrain of the Sierra Madre mountains accelerated Patricia's weakening. The low- and mid-level circulations of the tropical cyclone decoupled, with the latter accelerating northeast, and Patricia dissipated on October 24 over central Mexico, less than 18 hours after moving ashore.
Hurricane Patricia set multiple records for maximum strength, rate of intensification, and rate of weakening throughout its relatively short existence. With maximum sustained winds of 215 mph (345 km/h) and a minimum pressure of 872 mbar (hPa; 25.75 inHg), Patricia is the most intense tropical cyclone ever observed in the Western Hemisphere. In terms of central pressure, it is also the second-most intense tropical cyclone ever recorded worldwide, just shy of Typhoon Tip in 1979 which had a minimum pressure of 870 mbar (hPa; 25.69 inHg). Patricia's one-minute maximum sustained winds ranked as the highest ever reliably observed or estimated in a tropical cyclone, surpassing Typhoon Haiyan of 2013. The magnitude of Patricia's rapid intensification is among the fastest ever observed. In a 24-hour period, 06:00–06:00 UTC October 22–23, its maximum sustained winds increased from 85 mph (140 km/h) to 205 mph (335 km/h), a record increase of 120 mph (195 km/h). During the same period, Patricia's central pressure fell by 95 mbar (hPa; 2.81 inHg). Despite record over-water weakening prior to striking Mexico, Patricia became the most intense Pacific hurricane to make landfall, with a pressure of 932 mbar (hPa; 27.52 inHg).