page_title: Tropical Storm Patricia (2009)
section_title: Meteorological history
hierarchical_section_title: Tropical Storm Patricia (2009) / Meteorological history
caption_attribution_description: English: Track map of Tropical Storm Patricia of the 2009 Pacific hurricane season. The points show the location of the storm at 6-hour intervals. The colour represents the storm's maximum sustained wind speeds as classified in the Saffir–Simpson scale (see below), and the shape of the data points represent the nature of the storm, according to the legend below. Saffir–Simpson scale Tropical depression≤38 mph≤62 km/h Category 3111–129 mph178–208 km/h Tropical storm39–73 mph63–118 km/h Category 4130–156 mph209–251 km/h Category 174–95 mph119–153 km/h Category 5≥157 mph≥252 km/h Category 296–110 mph154–177 km/h Unknown Storm type Tropical cyclone Subtropical cyclone Extratropical cyclone / Remnant low / Tropical disturbance / Monsoon depression
context_page_description: Tropical Storm Patricia was a short-lived tropical cyclone that briefly affected parts of Baja California Sur before rapidly degenerating over water. Developing from a tropical wave that traversed the Atlantic Ocean during September 2009, Patricia was first classified as a tropical depression on October 11 several hundred miles south of the Baja California Peninsula. The system quickly intensified into a tropical storm as it tracked in a general northward direction. By October 12, Patricia attained its peak intensity with winds of 60 mph and a minimum barometric pressure of 996 mbar. The following day, increasing wind shear and unfavorable conditions caused the storm to rapidly weaken. By the morning of October 14, Patricia had degenerated into a non-convective remnant low pressure area near the southern coastline of Baja California Sur. The remnants of the storm persisted until October 15, at which time they dissipated over open waters.
  Although the center of Patricia did not impact land, the outer bands caused significant rainfall in portions of western Mexico. In Sonora, up to 240 mm of rain fell, leading to significant flooding that left 600 people homeless.
context_section_description: Tropical Storm Patricia originated from a tropical wave that moved off the west coast of Africa on September 23. Two days later, Tropical Depression Eight developed from the wave over the eastern Atlantic Ocean. The depression tracked northwestward, while the wave continued a steady westward track. By October 6, the system crossed Central America and entered the eastern Pacific Ocean. Gradual development took place over the following several days with widespread, scattered convection consolidating around a developing area of low pressure. On October 11, a well-defined circulation had formed and the National Hurricane Center (NHC) estimated that it developed into a tropical depression roughly 405 mi (650 km) south-southeast of the southern tip of Baja California Sur.
  Several hours later, the system further strengthened into a tropical storm and was named Patricia. The low-level circulation became embedded within very deep convection and further intensification was anticipated. Patricia tracked north-northwest in a region of low to moderate wind shear, under the steering currents of a strong ridge of high pressure to the east and a trough located northwest. Although over warm sea surface temperatures, relatively stable air aloft prevented substantial intensification. By the late morning of October 12, the overall extent of cloud cover had increased but the center became less defined. Later that day, Patricia attained its peak intensity as a moderately strong tropical storm with winds of 60 mph (95 km/h) and a minimum barometric pressure of
  996 mbar (hPa; 29.41 inHg).
  The storm maintained this intensity for several hours as its central dense overcast remained intact despite increasing wind shear. However, the NHC stated that there was a 20% chance of the storm becoming a hurricane within 24 hours based on climatological factors and the average forecast intensity errors. However, this did not take place. The combination of moderate wind shear and a stable environment caused Patricia to rapidly weaken on October 13. The storm's cirrus outflow became weak in all directions and convection diminished. Later that day, convective developed ceased to occur as the storm neared the south tip of Baja California Sur. Early on October 14, Patricia degenerated into a remnant low pressure area, bypassing tropical depression status, roughly 30 mi (50 km) south of the Baja California Peninsula. The remnant low turned westward and tracked over open waters before dissipating on October 15.
caption: Map plotting the track and the intensity of the storm, according to the Saffir–Simpson scale
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