Sandra to Continue Flooding Rain Potential in Western Mexico

By By Kristina Pydynowski, senior meteorologist
November 29, 2015, 6:25:39 AM EST

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Tropical Rainstorm Sandra will continue to bring the risk of flooding rainfall to portions of western Mexico into Saturday night.

After not moving much on Friday night, Sandra will likely make landfall on Saturday night, local time, as a tropical rainstorm in the Mexican state of Sinaloa, near or in between La Cruz and Mazatlan. Sandra, however, will not be a repeat of dangerous Hurricane Patricia.

Strong wind shear caused Sandra to rapidly weaken after it became the latest major hurricane on record on Wednesday afternoon.

Wind shear is the rapid change of direction and speed of air flow at different layers of the atmosphere. When wind shear is strong, these changes are very great and can shred apart tropical systems.

Satellite images early on on Saturday morning showed very little rain and thunderstorm activity around the center of the storm, a classic sign of a sheared system.


Winds could still gust to around 55 km/h (35 mph) for a time on Saturday around the site of landfall, potentially causing tree damage and sporadic power outages. Surf will also remain rough along the coasts of Sinaloa and Nayarit as Sandra approaches.

Sandra will also threaten western Mexico with flooding rain despite weakening.

Mexico Weather Center
Latest Statistics on Sandra
Detailed Forecast for Mazatlan

The main risk for flooding into Saturday will center on southern Sinaloa and neighboring parts of northern Nayarit and southwestern Durango.

“Rainfall amounts of 75-150 mm (3-6 inches) are possible in these areas with local amounts up to 200 mm (8 inches),” stated AccuWeather Meteorologist Eric Leister. “The biggest concern will be heavy rainfall that can cause flash flooding and mudslides.”

The heaviest rain totals will be measured in the mountains.


Sandra’s moisture will stream far enough to the north in the United States to contribute to an extensive period of ice in the southern High Plains and the risk for flooding elsewhere in the South Central states.

Sandra is turning to the northeast quick enough to allow Cabo San Lucas to escape the worst of the storm. A couple of outer rain bands will swing through on Friday, but AccuWeather Senior Meteorologist Rob Miller does not expect flooding or winds to gust to tropical storm force.

Rough surf, however, will still create hazards for swimmers and operators of small craft.

“The impacts from Sandra in Mexico will quickly wind down later on Saturday as it will get ripped apart by the mountains and dissipate,” stated Miller.

The demise of Sandra will close the chapter on the latest major hurricane on record to form in the central/eastern Pacific or Atlantic oceans, a status Sandra achieved on Wednesday afternoon. The equivalent of hurricanes that develop west of the International Date Line are called typhoons or cyclones.

An unnamed hurricane from 1934 in the Atlantic previously held the record when it was a major hurricane on Nov. 23 of that year. In the eastern Pacific Basin alone, the last latest major hurricane was Kenneth from Nov. 22, 2011.

There have now been nine major hurricanes in the eastern Pacific this year, a record for the basin.

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