page_title: Hurricane Sergio (2006)
section_title: Meteorological history
hierarchical_section_title: Hurricane Sergio (2006) / Meteorological history
caption_attribution_description: For the first time since 1961, two tropical storms formed in the month of November in the Eastern Pacific. The first was Tropical Storm Rosa. On November 13, 2006, Tropical Storm Sergio became the second tropical storm of the month. Sergio, unlike Rosa, continued to build in power to reach hurricane status, making it the tenth hurricane of the 2006 Eastern Pacific storm season. While the hurricane season officially runs until the end of November, late storms are unusual. Only five other storms on record have formed later in the season than Sergio. It is also unusual for tropical storms that form this late in the season to intensify all the way to hurricane strength as Sergio had done. This data visualization shows Sergio while it was a Category Two strength hurricane early in the morning of November 16. The image depicts wind speed in color and wind direction with small barbs. White barbs point to areas of heavy rain. The data were obtained by NASA’s QuikSCAT satellite on November 16, 2006, at 12:29 UTC (5:29 a.m. local time). Sergio appears to be have a well-defined and circular core, with a long apostrophe-shaped tail streaming out from this mature well-formed core. However, the wind-direction barbs do not spiral around the center of the storm as they would in a classical strong hurricane, hinting that winds are not symmetrical around the storm and that they may be pulling apart the storm. QuikSCAT employs a scatterometer, which sends pulses of microwave energy through the atmosphere to the ocean surface, and measures the energy that bounces back from the wind-roughened surface. The energy of the microwave pulses changes depending on wind speed and direction, giving scientists a way to monitor wind around the world. This technique does not work over land, and hence the lack of measurements over the mainland of Mexico shown here.
context_page_description: Hurricane Sergio was the third strongest Pacific hurricane in the month of November on record. The nineteenth named storm and eleventh hurricane of the 2006 Pacific hurricane season, Sergio developed from a tropical wave on November 13 about 460 miles south of Manzanillo, Mexico, and steadily intensified as it tracked southeastward. It reached peak winds of 110 mph on November 15, and subsequently began to weaken due to increased wind shear as it turned to the north. Sergio later turned to the west, remaining well off the coast of Mexico, and dissipated on November 20 about 320 miles west-northwest of it originally formed.
  Sergio produced light rainfall along the coast of Mexico, though its effects were minimal. The formation of Sergio marked the 2006 season as the busiest in 12 years and the first season in which more than one tropical storm formed in November. Sergio, in addition to being the strongest hurricane after November 1, was also the longest-lived Pacific tropical cyclone in November, lasting a total of seven days.
context_section_description: A tropical wave crossed Central America and entered the eastern Pacific Ocean on November 7. An area of convection along the wave tracked westward to the south of Central America and Mexico, and became more concentrated on November 12 while located about 400 miles (645 km) south of Acapulco. Later that day, Dvorak classification began on the disturbance, and the convection continued to organize. Early on November 13, the National Hurricane Center indicated the possibility of the system developing into a tropical depression. Thunderstorm activity briefly decreased, though late on November 13 the system acquired enough circulation and organized convection for it to be designated Tropical Depression Twenty-One-E while located about 460 miles (740 km) south of Manzanillo, Mexico. Operationally, the depression was not upgraded until eleven hours later.
  Initially, the tropical depression tracked to the northwest, and was forecast to peak as a 50 mph (80 km/h) tropical storm while continuing on a northwest motion. Located within an area of weak wind shear, deep convection increased near the center, and banding features became more pronounced. Anticyclonic flow aloft and a moist troposphere allowed the depression to intensity into Tropical Storm Sergio on November 14. Shortly after becoming a tropical storm, Sergio turned to the southeast, believed to be due to the flow associated with a mid- to upper-level trough to its northeast. It steadily intensified, and Sergio attained hurricane status on November 15 while located about 420 miles (675 km) southwest of Acapulco. With a small, distinct eye located in the center of the deep convection, Sergio rapidly intensified to attain peak winds of 110 mph (175 km/h) about 6 hours after becoming a hurricane.
  Upon reaching peak strength, forecasters at the National Hurricane Center predicted Hurricane Sergio to intensify further to reach winds of 120 mph (195 km/h). Shortly after peaking, the hurricane turned to the north and gradually weakened as wind shear from an upper-level trough to its northwest increased. By early on November 17, the low-cloud circulation became partially exposed on the west side of the deep convection, and it is estimated that Sergio weakened to a tropical storm later that day. A ridge to its north and northeast turned the storm to the northwest and later to the west as Sergio gradually weakened. Deep convection reformed near the center on November 18, resulting in a slight increase in winds, though vertical shear quickly weakened it again. Later that day, the storm made its closest approach to land, about 225 miles (360 km) southwest of Michoacán. Early on November 20 it degenerated into a tropical depression, and later that day Sergio dissipated about 360 miles (580 km) southwest of Manzanillo, Mexico, or about 320 miles (515 km) west-northwest of where it originally formed. The remnants of Sergio continued westward for about a day before the minimal amount of convection diminished.
caption: QuikSCAT image of Sergio on November 16
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