Mexico Hurricane: A Tale of Two Coastlines

It has been a brisk start to the Pacific Hurricane Season. Within the first two weeks of June, there have already been two hurricanes off the Pacific Coast of Mexico recording Cat 4 maximum sustained winds on the Saffir-Simpson Scale. On June 7, Hurricane Aletta, tracking far off the coast of southern Mexico, saw a period of rapid intensification with winds doubling to 140 miles per hour (220 km/h) within 24 hours before weakening and dissipating. The second named hurricane, Hurricane Bud had a similar intensification, going from 50 miles per hour (80 km/h) on June 10, to 132 miles per hour (212 km/h) some 24 hours later. Bud’s legacy now looks to be a weekend of heavy rain over the Baja California peninsula. For the North Atlantic Hurricane Season, the hurricane tally stays at zero.

So, lots of activity already in the Pacific, but overall, how different is storm activity on the Pacific compared to Mexico’s Atlantic Coast? RMS estimates that for Mexico, around 40 percent of the annual average loss from wind comes from the Pacific. To evaluate the complete hurricane risk for Mexico, the upcoming Version 18 release of the RMS® North Atlantic Hurricane Model will model both the Atlantic and Pacific coasts.

Pacific vs Atlantic

According to the National Hurricane Center (NHC) HURDAT database for the Pacific Coast (1971–2015) and the Atlantic Coast (1900–2014), on average there are more hurricanes annually on the Pacific Coast than the Atlantic Coast. If you look at hurricanes per 100 kilometers of coastline, activity is higher on the Atlantic Coast because the Pacific coastline is longer. With regards to the number of extreme intensity events, the Atlantic Coast also wins out.

As Aletta and Bud shows, for many Pacific Coast hurricanes affecting Mexico this pattern of rapid intensification, followed by rapid weakening is a signature trait. And when RMS considered expanding modeling to cover the Pacific Coast, two hurricanes in particular provided the motivation — these were Hurricane Patricia in 2015, and Hurricane Odile in 2014.

Record-breaking Patricia

Hurricane Patricia remains the strongest hurricane in either the Eastern Pacific or the Atlantic, recording maximum sustained winds of 200 miles per hour (320 km/h) building peak intensity just offshore the Pacific Coast of Mexico. Patricia took the record from Hurricane Allen in 1980, which achieved maximum sustained winds of 190 miles per hour (305 km/h) as the first named storm of the 1980 Atlantic Hurricane season.

Patricia has become a storm of record for RMS. A fierce Cat 5 storm, it had increased its maximum sustained winds by 125 miles per hour in a 24-hour period during October 22-23, 2015, with a peak at 215 miles per hour. But it also experienced rapid weakening, it made landfall as a Cat 5 near Cuixmala, a 25,000-acre private estate of beach, jungle, and nature reserves. It was the strongest recorded hurricane to hit Mexico’s Pacific coast since records began in 1949.

Hurricane Patricia weakened even faster than it strengthened as it came into contact with the mountainous terrain of the Sierra Madre Occidental mountain range. By 09:00 UTC on October 24, maximum sustained winds had dropped to 75 miles per hour (120 km/h), equivalent to a weak Category 1 hurricane, and 12 hours later, maximum sustained wind speeds reached only 30 miles per hour (45 km/h).

In September 2014, Hurricane Odile also meandered off Mexico’s southern Pacific Coast, before rapidly intensifying on September 14, moving from a Cat 2 to a Cat 4 event in the space of just six hours. It made landfall on September 15, near Cabo Saint Lucas on the southern tip of Baja California Sur with winds at 125 miles per hour (205 km/h). It caused over a US$1 billion in economic losses.

Coast-to-coast Challenge

Through the reconstruction of these events, together with the available event set, and using the components from the North Atlantic Hurricane Model, we can now get a combined view of the hurricane risks for both coasts. There were many challenges — data availability and reliability for Pacific Coast events, especially in terms of intensity varies greatly pre-1970. Data goes back to 1851 for the North Atlantic, but only back to 1949 for the Eastern Pacific. Understanding whether a storm is extratropical is very important, and new research from the University of Arizona questioned extratropical flags within HURDAT covering the eastern North Pacific. Many HURDAT storm points were located to the south, but research from Kim Wood shows that many extratropical storms track further to the north that first thought.

What does our modeling show when looking at both coasts? As an example, when looking at 50-year return period winds the highest winds are in the Yucatan peninsula on the Atlantic Coast, but also along the Pacific Coast from Sinaloa to Michoacán, and for Baja California Sur.

Looking at the highest loss cost overall, the state of Quintana Roo on the Yucatán Peninsula, with a mix of high hazard and coastal exposure leads the way, with a similar picture for Baja California Sur with relatively high hazard and coastal exposure.

With the RMS North Atlantic Hurricane Model providing a combined event set for the Pacific and North Atlantic, clients will now be able to deliver combined analyses, to compare with areas within the U.S. For instance, when looking at loss costs, the Southeast U.S. is similar to Baja California Sur and Sinaloa to Michoacán; the southwestern coast of Mexico is more similar to the U.S. Northeast.

As a final note, I would also like to thank everyone who has helped RMS to win accolades such as the “2018 Latin America Risk Modeler of the Year”, and RMS reassures its commitment to innovation across the Caribbean and the Latin America region.