Sonia (2013)

A broad area of low pressure south-southwest of mainland Mexico organized into a tropical depression about 280 nautical miles southwest of Manzanillo on 1 November 2013. The system became Tropical Storm Sonia early on 3 November as it turned north-northeast, accelerated, and passed just south of the southern tip of the Baja California peninsula. Sonia reached its peak late on 3 November and then moved northeast toward the mainland, making landfall and dissipating over the Sierra Madre Occidental on 4 November.

Sonia made a single confirmed landfall near El Dorado in the state of Sinaloa around 0500 UTC on 4 November 2013 while still at tropical storm strength. After landfall the cyclone moved inland, weakened to a tropical depression by 0600 UTC, and dissipated later that day over the high terrain.

The maximum sustained winds reached 40 knots (about 46 mph) and the lowest estimated central pressure was 1002–1003 mb, making Sonia a tropical storm at its peak (below hurricane strength). Best-track estimates list the peak wind at 40 kt (≈46 mph) on 3 November with the minimum pressure near 1002 mb.

Storm effects included coastal flooding and heavy rains. In Mazatlán water rose as high as 5 ft (about 1.5 m), prompting evacuations; roughly 1,000 people were evacuated in the region and the Culiacán–Navolato highway was closed because of flooding. Watches and warnings had covered areas from Mazatlán to Altata and from Topolobampo to La Cruz prior to and during landfall.

Two direct deaths were reported in Mexico: one fisherman reported missing at sea (Sinaloa) and one fatality in Nayarit from a lightning strike. The main impacts were localized flooding, road closures, and the evacuations noted above, primarily affecting Sinaloa, Mazatlán, and nearby coastal areas.

Notable aspects include that Sonia was one of only three eastern North Pacific tropical storms on record to make landfall in November during the satellite era (since 1966). Forecasters captured the system’s formation reasonably well in the short range and the official intensity forecasts performed better than typical five-year averages, while track forecasts tended to show larger along-track timing errors at longer lead times though the landfall location was well predicted.