Posted on 14 Oct 2011
According to catastrophe modeling firm AIR Worldwide, after striking a sparsely populated stretch of Mexico’s Pacific coast on October 11 as a Category 2 hurricane, Jova weakened as it traveled inland towards the north, dissipating late last night over the state of Nayarit. Because it was a small storm and weakened to tropical storm strength within 12 hours of landfall, damage from Jova’s winds has been limited. AIR estimates insured losses from flood-induced damage, as well as from some isolated wind damage along southern coastal areas, to be less than $52 million.
"Heavy rainfall, which began as Jova’s outer rain bands approached the coast prior to landfall and is finally subsiding after the storm’s dissipation, has caused serious flooding and landslides in parts of Colima and Jalisco," said Dr. Tim Doggett, principal scientist at AIR Worldwide. "Mexico’s coastal mountains enhanced precipitation on the north and east sides of the storm. As the slow-moving storm came ashore, its counterclockwise flow of air was forced over the mountainous terrain, cooling in its ascent and forming clouds and precipitation."
The highest recorded wind speed was a 74 km/h (46 mph) gust in Manzanillo. However, this was located outside Jova’s 15-mile radius of maximum winds. It thus does not reflect the true maximum winds that were located in a very limited area around the eye of the storm at the time of landfall, which according to the National Hurricane Center was around 100 mph.
Initial reports from the Mexico National Weather Service indicate up to 37 cm (14.5 in) of rainfall in parts of Colima, and 10–12 cm (4-5 in) in other impacted areas, including parts of Chiapas, Jalisco, and Michoacán. These rainfall totals fall within the forecast range.
Dozens of towns—including Cihuatlán, La Huerta, Villa Purificacion, and Cuautitlán de García Barragán—have been isolated by floodwaters, which are several feet deep in some places. The Marabasco River, which forms the border between Colima and Jalisco, and ten of its streams have overflowed.
Significant flooding has also been reported in Manzanillo in Colima state, about 60 miles southeast of the Jova’s landfall location. Yesterday, streets in the busy port town remained impassable, and highways that connect Manzanillo to southern Jalisco were closed. Nearby, streets in the coastal towns of Zihuatlan, Melaque and Barra de Navidad were reported to be inundated as well.
Dr. Doggett continued, "Jova passed within 15 miles to the east of Puerto Vallarta, a popular resort city with a population of more than 250,000. Because of its reduced wind speeds by that point (maximum sustained of 65 mph, which put it at tropical storm strength), and the fact that Puerto Vallarta was on the weaker, left side of the storm, the city was spared from significant wind and flood damage."
According to AIR, most insured residential structures on Mexico's west coast—including those in Manzanillo and Puerto Vallarta—are made of confined masonry, which performs better than plain masonry under lateral wind loads because of its use of bond beams and columns. However, masonry is characterized by weak connections between building elements and the material itself is pervious to water. Furthermore, a large percentage of houses built every year in Mexico are constructed without a building permit, perhaps as large as 50%. Take-up rates (the percentage of properties actually insured) for residential properties are very low in the region, estimated at around 5%.
Commercial properties in this region are typically constructed of confined masonry or reinforced concrete and usually have stronger foundations than residential buildings, making them less vulnerable than residential structures. Concrete buildings are less vulnerable to flooding than masonry, but may suffer cracking and rebar expansion. Commercial/industrial insurance penetration is estimated at around 70%, and automobiles at 100%.
Dr. Doggett concluded, "In summary, the storm hit a relatively sparsely populated region of the coast, and strongest winds from the storm were highly confined. Furthermore, rainfall accumulations were moderate, but not extreme, in the more populated regions of Jalisco where there are higher concentrations of exposure."