PRELIMINARY REPORT
TROPICAL STORM ALETTA
16―21 JUNE 1988
by
Dr. Harold P. Gerrish
INTRODUCTION
The eastern Pacific hurricane season got off to a rather slow start in 1988 with Aletta, the first named tropical storm, forming on June 17, 1988. The median date for the first storm during the 22-year period 1966-1987 was June 2. Although the intertropical convergence zone (ITZ) had been moderately active with what appeared on satellite pictures to be favorable localized upper air support, the circulation embryos had difficulty in developing perhaps due to poorly organized low-level inflow.
SYNOPTIC HISTORY
Aletta, pronounced A-LET-A, had its origin as a tropical wave that moved off the coast of Africa around the 1st of June 1988. The weak wave was difficult to track across the tropical Atlantic but the convection became more distinct as the system passed over the Windward Islands on the 10th. The convection essentially disappeared while in the Caribbean but based on persistence and continuity, the wave passed over Central America on the 13th and emerged over the warm waters of the eastern Pacific on the 14th.
Deep convection started developing north and south of a poorly defined low-level center late on the 14th and the system first met the Dvorak classification criteria for indications of development (T1) at 0000Z on June 15th. Even though satellite pictures revealed the presence of substantial outflow at the upper levels, development progressed slowly with poor cloud banding. On the 16th the broad diffuse center became better organized near deep convection to the northeast. As a result, it is estimated that the system reached tropical depression (Two-E) status 200 miles southeast of Acapulco, Mexico by 1800Z on June 16, 1988.
Development continued as Tropical Depression Two-E moved northward toward the southwest Mexican coast and it is estimated that the system reached tropical storm strength by 0000Z on June 17th. Ship ZCKP had 35-knot sustained winds near the center at 0300Z and 47 knots at 06002 on the 17th...the latter being the highest sustained surface wind observed during the storm's history.
Tropical Storm Aletta drifted north northwestward for the next 36 hours and then gradually turned westward while maintaining a distance of about 75 miles parallel to and off the rugged Mexican coastline. The system began losing its convection on the 19th and became Tropical Depression Aletta by 18002 on June 19, 1988. Aletta appeared primarily as a low-level swirl of stratocumulus clouds from then until marine advisories were terminated at 1500Z on June 21, 1988.
