Tropical Storm Odile (2008) - Meteorological History

Meteorological History

A tropical wave emerged off the west coast of Africa on September 23, and merged with the southern end of a decaying frontal system over the Caribbean Sea. The combined disturbance gradually split, with the northernmost section eventually become Tropical Storm Marco. The southernmost end moved into the eastern Pacific, which then immediately showed signs of organization. The system stalled just south of El Salvador throughout October 5, where it came under the influence of strong vertical wind shear. The circulation slowly drifted east-northeastward and became absorbed by a neighboring tropical wave, with the broad resultant low re-curving to the west-northwest. In response to relaxing shear aloft, convection redeveloped around the newly formed center of circulation. It subsequently acquired a sufficiently organized structure and post-analysis found that a tropical depression formed at around 1200 UTC on October 8. Upon developing, the depression was designated as Sixteen-E about 120 mi (195 km) south-southwest of San Salvador, El Salvador, and operationally, advisories were initiated at 2100 UTC — 9 hours after post-analytic estimates of formation.

Despite being in an area with favorable conditions, lack of inner core organization proved difficult for rapid deepening to occur, and initially, model guidance did not forecast any significant strengthening. Contrary to expectations, satellite imagery showed a gradual increase in organization later that evening. Bands of convection deepened in the southern quadrant, indicating that the storm was steadily strengthening. Located just to the south of a large mid-level ridge over Mexico, the system was steered toward the west-northwest, proceeding within a favorable environment. Based on the improved appearance on satellite imagery, it is estimated the depression intensified into Tropical Storm Odile at 0600 UTC on October 9 about 330 mi (530 km) southeast of Puerto Ángel, Mexico. Shortly after attaining tropical storm status, Odile began to develop a small area of central dense overcast, and upper-level cirrus outflow became well-defined within the western semicircle of the storm. Convective banding organized to the south and southwest of the circulation, leading Dvorak T-numbers to estimate an intensity of at least 50 mph (80 km/h). Based on this estimate, the NHC noted a high chance of further intensification into a minimal hurricane. Odile maintained its intensity, as upper-level outflow of the circulation was reduced to the northeast. Although wind shear initially dislocated the circulation from the main convection, a large burst of convection allowed Odile to intensify slightly further to peak winds of 60 mph (95 km/h) at around 0600 UTC on October 10.

Odile closely paralleled the Mexican coastline. The intensification did not last long, in fact, the convection associated with Odile diminished in the afternoon and its rainbands became rather distorted. Another cluster of convection sprung up that evening, this time with cloud tops colder than −80 °C (−112 °F). The circulation center was well embedded within the convection. As a consequence of the slightly improved organization, Odile had a stronger interaction with the easterlies aloft, therefore increasing forward movement speed. Later that day, an reconnaissance aircraft passed through Odile and observed a rather weak and disorganized tropical cyclone, resulting in meteorologists at the NHC to change it's forecasts. Early on October 12, Odile made its closest approach to coastline of Mexico, only about 50 mi (80 km) offshore of Guerrero, Mexico. Increasing southeasterly vertical wind shear took toll on the system. Furthermore, around 0600 UTC, NHC confirmed that Odile weakened into a tropical depression. The last advisory regarding Odile was issued later that day stating that it has subsequently degenerated into a remnant low-pressure area, a swirl of low-level clouds. The remnants of Odile meandered slowly south-southwestward before completely dissipating on October 13.