Ivo (2013)

A small tropical cyclone formed from a tropical wave in the eastern Pacific and became Tropical Depression Nine-E about 1200 UTC on 22 August 2013, roughly 430 nautical miles west-southwest of Manzanillo, Mexico. The depression moved generally north-northwestward, its center briefly reformed during interaction with another nearby disturbance, and it strengthened to Tropical Storm Ivo around 0000 UTC 23 August. Ivo stayed well offshore of mainland Mexico while moving parallel to the southern and central Baja California peninsula, weakened over cooler waters, became a remnant low late on 25 August, and dissipated a few days later.

Ivo did not make a direct landfall on mainland Mexico. The tropical-storm warning area and later watches covered parts of the southwestern Baja California peninsula because of the storm’s large wind field, and the center of the system passed within a few hundred nautical miles of the southern Baja California peninsula on 24–25 August. Socorro Island and Cabo San Lucas experienced the closest approaches and the strongest local effects from the circulation and outer bands on 23–24 August.

The storm’s peak intensity was 40 knots (about 46 mph) with a minimum central pressure estimated at 997 mb, reached around 0000 UTC 24 August. That intensity kept Ivo in the tropical storm range; it never reached hurricane strength.

Storm-related water impacts included coastal and inland flooding from heavy rain. Reported rainfall totals driven by Ivo’s moisture over the U.S. Southwest included 4.42 inches (112 mm) near Julian, California, and 4.26 inches (108 mm) at Grapevine Springs, Nevada. Socorro Island reported a minimum pressure near 997.0 mb and tropical-storm-force gusts on 23 August; Cabo San Lucas recorded 1-minute winds up to 34 kt with gusts to 51 kt at 1500 UTC 23 August. In Loreto on the southern Baja California peninsula, overflow of San Telmo Creek flooded about 200 homes and led to temporary water-supply loss and damaged roadways.

There were no confirmed direct deaths from Ivo. One indirect fatality was reported in the United States: a 77-year-old woman in San Bernardino County, California, was killed when flash flooding associated with Ivo’s moisture swept away her vehicle. In Loreto, six people were reported injured (including injuries from a weather-related car accident), about 400 residents were evacuated, and multiple roads were damaged. Flash flooding in the southwestern United States caused numerous vehicle strandings, 18 swift-water rescues, and localized damage (Las Vegas suburbs reported at least $300,000 in damage).

Noteworthy items include that forecasters successfully predicted the storm’s genesis well in advance and that official intensity forecasts for Ivo were generally more accurate than recent averages. Short-term track errors were larger than recent means—partly because the initial center position changed during the interaction with the nearby disturbance—while guidance models and consensus forecasts sometimes outperformed the official track.