| Category 4 hurricane (SSHS) | |
|---|---|
| Hurricane Dora at peak intensity on July 21 | |
| Formed | July 18, 2011 |
| Dissipated | July 24, 2011 |
| Highest winds | 1-minute sustained: 155 mph (250 km/h) |
| Lowest pressure | 929 mbar (hPa; 27.43 inHg) |
| Fatalities | None |
| Damage | Minimal |
| Areas affected | Baja California del Sur, Colima, Guerrero, Jalisco, Michoacán, San Benedicto Island, Socorro Island |
| Part of the 2011 Pacific hurricane season | |
Hurricane Dora was a very powerful and intense hurricane and the second of four Category 4 hurricanes during the 2011 Pacific hurricane season. The fourth tropical depression, named storm, hurricane, and second major hurricane of the season, Dora developed a from a tropical wave on July 18. Quickly intensifying, the new tropical depression became a tropical storm just three hours after formation. The storm began to explosively intensify on July 20, strengthening from a minimal hurricane to a category 4 in only 17 hours. Dora reached its peak strength during the early morning hours of July 21 with maximum sustained winds of 155 mph (250 km/h) and a minimum central pressure of 929 mbar, just 1 mile per hour short of Category 5 status. However, as quickly as Dora strengthened, it weakened. Cooler waters and wind shear began to weaken the hurricane, and by the end of July 22, Dora had already weakened to a tropical storm and soon dissipated on July 24, just west of the Baja California Peninsula.[1][2]
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In the early morning hours of July 14, a tropical wave had moved off the Colombian coast.[3] The wave gained convection as it moved into the Southwestern Caribbean Sea, and the National Hurricane Center (NHC) began to monitor the disturbance, giving it a 10% chance of development into a tropical cyclone.[4] Over the rest of the day, the storm continued to move westward until it moved ashore on the Nicaragua/Costa Rica border the next day.[5] The tropical wave emerged into the Pacific Ocean on July 16 under favorable conditions for development. The system strengthened and became better organized the next few days as the once disorganized system of thunderstorms began to collect towards the center.
At 1500 UTC July 18, the disturbance was designated as Tropical Depression Four-E. By the time Four-E was designated, well-defined bands of convection and a tight inner wind field were observed.[6] Despite modest northerly upper-level winds, the depression strengthened into a tropical storm, receiving the name Dora.[7] Dora began to move west-northwestwards under the influence of a strong high pressure system. Gradual intensification ensued, and an eye began to form in Dora the next day.[8] Late on July 19, Dora attained hurricane status with hurricane-force winds extending up to 35 miles (55 km) from the center as the eyewall contracted.[9][10] Dora continued to gradually strengthen early on July 20. However, in the afternoon, Hurricane Dora rapidly intensified to a major hurricane, the second of the season with winds of 115 miles per hour (185 km/h) and higher gusts. The inner core solidified and eyewall mesovortices were hinted.[11][12] Dora continued to quickly intensify, becoming a category 4 hurricane just hours later with maximum wind speeds of 135 miles per hour (217 km/h) and a hurricane-force wind field extending to a 40 miles (64 km) radius.[13][14] The next day, Dora began to take on the appearance of an annular hurricane, with an eye similar to those seen in Hurricane Isabel.[15] Continuing to rapidly intensify, Hurricane Dora attained peak intensity later on July 21 with winds of 155 miles per hour (249 km/h) and a central minimum pressure of 929 mbar (hPa; 27.43 inHg) while 445 miles (715 km) south-southeast of Cabo San Lucas, Mexico.[16]
However, Dora began to traverse colder waters and encountered unfavorable wind shear. The eye abruptly dissipated and convection became much less organized.[17] Within 12 hours, Dora already weakened into a category 3 hurricane.[18] On July 22, the low-level circulation center became exposed as convection shifted to the southern semicircle.[19] Dora continued to be sheared by strong northwesterly wind shear as it quickly weakened. Dora's satellite signature deteriorated along with much of its convection.[20] The hurricane was downgraded to a tropical storm late on July 22 as it moved into hostile atmospheric conditions and cooler water. Based on data from Hurricane Hunters, the NHC issued its last advisory for Dora on the evening of July 24.[21] As a remnant low, the circulation began to curve around the high-pressure area that had steered Dora for much of its existence on July 25.[22] Early on July 26, the remnants of Hurricane Dora dissipated completely, over Central Baja California. [23]
On July 19, a tropical storm watch was issued for portions of the coast of Southwestern Mexico as Dora strengthened into a category one hurricane. The watch was continued until late on July 20, after Dora moved further away from the mainland.[24] Another watch was soon posted on July 21 for the coasts of Baja California del Sur before it was upgraded into a warning the same day.[25] The watch was discontinued two days after.[26]
Dora caused strong rip currents and rain to Southwest Mexico's coastline. In Acapulco, Mexico, police advised swimmers about the dangers of the strong waves.[14] Dora's storm surge toppled a lighthouse and swept about 60 thatch-roofed restaurants on the coast.[27] In the Los Cabos Municipality, four elementary schools were converted into emergency shelters in preparation for any potential flooding. Boat tours and other tourism services in Los Cabos were suspended.[27] As a remnant low, Dora enhanced a monsoon southerly flow into Arizona, producing showers across the state.[28]
