Hurricane Sandra remains on track to target northern Mexico Friday and Saturday, but it should be much weaker at landfall than the major hurricane status to which it is currently strengthening.
Sandra is on track to become the latest major hurricane on record to form in the eastern Pacific Ocean on Thursday. Kenneth from 2011 currently holds this record when it strengthened into a Category 4 hurricane on Nov. 22 of that year.
Sandra should set the record on Thursday as it continues on its northwest track.
Despite its current movement, a landfall in Mexico is expected on Saturday as a storm system located over the western half of the United States will pull Sandra to the north, then northeast later this week. Sandra, however, will not be a repeat of dangerous Hurricane Patricia.
Sandra will be well past its peak intensity as it approaches Mexico. Instead, strong wind shear will lead to rapid weakening later this week.
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.
Sandra will be a tropical storm as it makes its closest approach to the southern tip of Baja California Sur Friday night before moving into mainland Mexico, likely in southern Sinaloa state near or in between Culiacan and Mazatlan, on Saturday. It is even possible that Sandra comes onshore as a tropical depression.
Despite weakening, Sandra will still threaten parts of northern Mexico with flooding rainfall Friday into Saturday. Around the point of landfall, southern Sinaloa faces the greatest risk of widespread flooding.
"Rainfall amounts of 75-150 mm (3-6 inches) are possible in these areas with local amounts up to 250 mm (10 inches)," stated AccuWeather Meteorologist Eric Leister. "The biggest concern will be heavy rainfall that can cause flash flooding and mudslides."
Similar rain amounts will graze the southern tip of Baja California Sur, including Cabo San Lucas.
Locally damaging winds of 65-95 km/h (40-60 mph) will also accompany the rain in these two areas.
The threat for flooding will not be confined to places near Sandra's path. The storm pulling Sandra to the north will also draw its moisture and downpours much farther to the north across more of southern Baja California Sur and into Chihuahua later Thursday into Saturday.
"[In these areas,] there will be pockets of 25-50 mm (1-2 inches) with locally 100 mm (4 inches)," continued Leister. "The moisture is getting strung out, so that limits the torrential rain. Instead, there will be a 24-hour period of soaking rain with localized areas getting downpours that result in flooding."
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.
After reaching the Mexico coastline, the weakening tropical cyclone will dissipate over the higher terrain of northern Mexico later in the weekend.