Hurricane Stan - Meteorological History

Meteorological History

Hurricane Stan originated from a tropical wave that was first identified by the National Hurricane Center (NHC) off the west coast of Africa on September 17, 2005. Traveling westward, the wave remained weak, barely being notable. By September 22, before convection began to increase; however, wind shear in the region prevented this development from lasting. The system entered the Caribbean Sea several days later, a region with more favorable conditions for cyclonic development. Intermittent convection formed around the wave as it moved west-northwestward before the development maintained itself. On October 1, the system had become sufficiently organized for the NHC to classify it as Tropical Depression Twenty, with the center of circulation situated roughly 135 mi (215 km) souhteast of Cozumel, Mexico.

Located to the south of a low to mid-level tropospheric ridge, the depression tracked towards the west-northwest. Within a few hours of being warned upon, the system further intensified into Tropical Storm Stan. This followed the development of a strong convective banding feature to the southeast of the storm's center. Around 1000 UTC (5 a.m. CDT) on October 2, Stan made its first landfall near Punta Hualaxtoc, Mexico, roughly 35 mi (55 km) south of Tulum, with winds of 40 mph (65 km/h). Over the following 18 hours, the weak storm traversed the southern portion of the Yucatán Peninsula. Upon entering the Gulf of Mexico on October 3, Stan had weakened to a tropical depression; however, convection began to redevelop over the storm's center, allowing the system to re-attain tropical storm status.

A strong area of high pressure over the western Gulf of Mexico forced the storm to turn southwestward, back to the Mexican coastline. Increasingly deep cloud cover formed over the storm in response to a favorable environment over the Bay of Campeche. Late on October 3, forecasters at National Hurricane Center noted a statistical rapid intensity index indicating a 49% chance of Stan undergoing rapid intensification before its final landfall. This intensification did take place within 12 hours before the hurricane moved onshore. Overnight, the structure of Stan rapidly improved, with a banding eye-feature developing within unusually deep convection with cloud-top temperatures measured at −90 °C (−130 °F) by infrared satellites. Following this development, National Hurricane Center upgraded the storm to a Category 1 hurricane on the Saffir–Simpson Hurricane Scale. Around 1200 UTC on October 4, Stan made landfall near Punta Roca Partida, with winds of 80 mph (130 km/h). The storm also attained its lowest barometric pressure of 977 mbar (hPa; 28.85 inHg)at this time. Not long after moving over the mountainous terrain of central Mexico, Stan rapidly weakened to a tropical depression and fully dissipated early on October 5 over the state of Oaxaca.