Tropical Storm Aletta (2006) - Meteorological History

Meteorological History

On May 21, 2006, a tropical wave crossed Central America and entered the East Pacific. The wave drifted westward, and after several days began to interact with a low-level trough near the Gulf of Tehuantepec, and as a result deep convection increased. By May 25, a large area of low pressure formed several hundred miles south of Acapulco, Mexico. Wind shear inhibited development initially, though conditions became slightly more favorable after a number of days, and at 0600 UTC on May 27, a tropical depression formed about 190 mi (305 km) south of Acapulco.

Moving very little, the depression was disorganized due to continued shear, leaving the center of circulation west of the convective activity. By later in the morning hours of May 27, the system began to show overall signs of organization, primarily related to a burst of convection in the eastern semicircle. At the same time, the center of circulation either reformed or began to move farther north, possibly north-northeast. Embedded within the steering currents of a ridge, most forecasts anticipated the storm would drift northward for several days, though some computer models predicted the storm would eventually move inland near Acapulco. At 1800 UTC on May 27, the depression organized into a tropical storm, and as such was named Aletta by the National Hurricane Center.

With continued forecasting difficulty, a burst of new convection formed east of the center early on May 28, as the storm began meandering southward. At 0600 UTC, Aletta attained peak winds of 45 mph (72 km/h) while nearly stationary in forward movement. Later in the afternoon, the storm's center was obscured, thus subjecting the exact location to speculation. In addition, the circulation fluctuated in organization with the alternating intensity of the wind shear, and at the time maintained elongated cloud patterns, rather than the typical circulatory shape. As the storm drifted to the west and executed a small cyclonic loop by early on May 29, increased shear and dry air became entrained in the system, causing it to weaken to a tropical depression at 1800 UTC. Little convection remained afterward, and the storm struggled for several days, becoming a remnant low by May 31. The low dissipated shortly thereafter.