[1] The origins of Tropical Storm Sonia can be traced to a well-defined active phase of the Madden–Julian oscillation (MJO) that traversed eastward from the Central Pacific during late-October 2013.

A tropical wave located several hundred miles to the south of Acapulco gradually entered the cyclonic circulation late on October 26, producing deep convection.

[2] In advance of Sonia, a Tropical Storm Watch was ordered for the coast of Sinaloa from Topolobampo to La Cruz, late on November 2.

[10] Sonia made landfall near El Dorado, Sinaloa as a rapidly weakening tropical storm on November 4, causing heavy rainfall over portions of Mexico.

[1] Several inches of precipitation was recorded in Cabo San Lucas along with winds of around 30 mph (50 km/h), as the storm passed close to the resort city.