by Hurricane warnings are in effect from Playa Perula to El Roblito, including Puerto Vallarta, a popular vacation destination. The Islas Marías, a group of islands off the coast, are also in the warning zone. To the north of the warning, a hurricane watch extends to Mazatlán, while tropical storm watches cover both that area and the area south of the hurricane warning to Manzanillo.
The storm is increasingly likely to make landfall as the strongest to impact that region since Kenna in 2002, which made landfall at the mouth of the Rio Grande de Santiago near Boca de Asadero as a Category 4 storm with winds of 140mph It had been a Category 5 storm just 10 hours before landfall.
Roslyn’s Quick Intensification
Roslyn came after a cluster of thunderstorms off Mexico’s west coast froze into a tropical depression and eventually a named storm on Thursday. It wasn’t until 11:00 p.m. ET on Friday that Rosslyn became a hurricane, but it quickly intensified into a major hurricane, defined as a Category 3 or higher, just six hours later on Saturday morning.
Rapid intensification, defined as a storm’s maximum sustained winds peaking at 35 mph or more in 24 hours or less, is more likely due to warmer waters and calm upper-level winds. Links are emerging between human-induced climate change and the frequency and severity of rapid intensification.
As of mid-morning eastern time on Saturday, Roslyn had 120 mph winds and was located just over 150 miles southwest of Manzanillo, Mexico. It was moving northwest at 7 mph at the time, but was beginning a north-northeast curve. It will head toward the western coast of Mexico as it begins to feel the effects of an approaching shortwave trough, or a pocket of cold, low-pressure, twisting air, near the Baja California peninsula.
The expected impact of Roslyn
On her current course, Roslyn is looking to make landfall in the same area that Kenna did. That would put rural areas on the Narayit coast in line to experience the eyewall, or the ring of raging winds surrounding the calm eye. While Roslyn will be in the midst of a gradual weakening trend, wind gusts near 120 mph are still possible off the immediate coast. Communities like San Blás, Matenchén and Aticama can experience the strongest winds. Winds will decrease exponentially outside the eyewall, although tropical storm force strikes are still possible as far south as Puerto Vallarta.
The largest increase will occur just south of where the center of Roslyn makes landfall. That’s because the storm, like all large-scale low-pressure systems in the Northern Hemisphere, rotates counterclockwise; that means the winds south of the eye will be heading towards the coast. That will efficiently push the water towards the shore.
The National Hurricane Center writes that “a dangerous storm surge is expected to produce significant coastal flooding near and to the east of where the center makes landfall.”
They also warn of “large and destructive waves” near the coast, which according to computer models could reach 25 feet in height.
The risk of storm surge is generally lower on the west coast of Mexico than on the Gulf coast because the slope of the continental shelf is steeper. That makes it more difficult to get large volumes of water up the coast on the Pacific side.
The storm is also forecast to produce 4 to 6 inches of rain, with maximum totals around 8 inches, along the upper coast of Colima, Jalisco, southeastern Sinaloa, and western Nayarit, including the Marias Islands. .
“This rain could lead to flash flooding and mudslides in areas of rough terrain,” the Hurricane Center wrote.
