Hurricane Calvin (1993) - Meteorological History

Meteorological History

Satellite imagery on July 2 revealed that an area of disturbed weather, characterized with scattered deep convection, developed south of the Gulf of Tehuantepec. That same day, the system was classified using the Dvorak Technique, although the disturbance was not yet classified by the National Hurricane Center (NHC) due to a lack of concentrated convection. However, during the morning hours of July 14, banding features became visible, notably on the southern semicircle of the disturbance, and is estimated that the system attained tropical depression status at 1200 UTC, while centered approximately 275 mi (443 km) southeast of Acapulco. Intensifying within a favorable atmospheric environment, the depression attained tropical storm status at 0000 UTC July 5, receiving the name Calvin. A period of rapid intensification ensued shortly thereafter, and banding-type eye formed in association with Calvin later that day. Thus, the system was upgraded to a hurricane at 0000 UTC July 6, the second hurricane of the season. Embedded within the northeastern portion of a large, monsoon-like deep-layer-mean cyclonic circulation that stretched from the Intertropical Convergence Zone to the southwest Mexican coastline, Calvin's size significantly increased. Subsequently, 35 mph (55 km/h) surface winds were reported nearly 200 mi (320 km) from the storm's center.

A change in the storm's movement occurred shortly thereafter, when Calvin briefly slowed down before quickly accelerating to the northwest, bringing Calvin's center of circulation 90 mi (140 km) south-southwest of Acapulco. At 1200 UTC July 7, Calvin reached its peak intensity of 95 mph (153 km/h) and a minimum barometric pressure of 966 mbar (28.5 inHg). Shortly thereafter, Calvin made landfall, approximately 40 mi (64 km) west-northwest of Manzanillo, Mexico. At 0000 UTC July 8, Calvin re-entered the Pacific, but as a weakening tropical storm as a result of land interaction with the mountainous terrain of Mexico. Despite Calvin's drastic weakening, seas in excess of 12 ft (3.7 m) were generated as far as 300 mi (480 km) to the south of the system's center. Calvin weakened to a tropical depression late on July 8 as it made a second, and final, landfall on the Baja California Peninsula, and dissipated roughly twelve hours later over cold sea surface temperatures.