By: Capt. Pat Rains
To read more travel articles, visit http://travel.fyicenter.com/
How to Predict a Norther in the Sea of Cortez
February can be the crowning glory of cruising season in Mexico, but it’s also time to keep a lookout posted for Northers in the Sea of Cortez. Here’s how it works:
This year’s fleet of cruising boats (yates) was the largest ever. Whether powerboater or sailor, we’re all called “yatistas” down here. Last November and December, some yatistas immediately scooted south down the Mexican mainland to warmer destinations such as Barra Navidad, Zihuatanejo and Huatulco, where they made a U-turn. So by now they’re gunkholing back north at a leisurely pace. Other yatistas spent the holidays in Los Cabos or La Paz and are just now beginning to explore the lower and middle reaches of the Sea of Cortez.
Most of the winter-spring cruising season is blessed with benign sea conditions all along Mexico’s Pacific side. Our day-hops up and down the Gold Coast are driven by social needs, rather than the weather, and we can ping-pong around the Sea of Cortez pretty much like the free spirits we’ve always wanted to be.
But it’s those pesky Northers that we want to watch out for. Depending on where we are and how strong the Norther becomes, we might get no more than a pleasant two-day breeze that keeps the no-see-ums away. Yet some Northers carry such strong winds that they raise the sea surface into a short, steep chop for which the Sea of Cortez is notorious.
Mariners should seek a good snug shelter if a Norther is predicted. (See my list “Handy Hideouts for Northers.”) If a Norther is already blowing, you’ll want to hunker down and stay put.
Screaming Blue Norther
If the winds develop into what I call a “Screaming Blue Norther,” all vessel traffic can be pinned down in safe ports for a week or more. During a regular Blue Norther, the humidity is very low, the wind blows colder and the air over the water may appear milky blue from all the spume, so visibility may be reduced.
During a regular Blue Norther, everyone on board has been cooped up belowdecks for days on end, bundled in every shred of warm clothing available, listening to the wind howl through the rigging, with their lips turning blue and snapping irritably at one another ... that’s when a regular Blue Norther turns into a Screaming Blue Norther.
Well, maybe that distinction has more to do with the emotional impact than with anything meteorological. But irritability is commonly reported.
How to Predict a Norther
During winter cruising season, the conditions that generate Northers in the Sea of Cortez are similar to those that generate Santa Ana winds or gales along Southern California waters.
Here’s what to watch for:
After the passage of a low-pressure system over the Pacific coast of the U.S., the ocean air that has quickly pushed in behind it then slows down as it rises over the land. This air mass sometimes gets stranded inside a huge mile-high plateau basin that lies east of the Sierra Mountains and west of the Rockies. Here the accumulated air mass mounds up and is referred to as the “Plateau High.”
The Plateau High may accumulate and build for days, like a balloon, but eventually it must burst and go somewhere. When it does, this mass of high pressure flows outward at a level just above the ground surface. Gravity initially draws it downward, sucking it through the lower mountain passes, where a Venturi effect may amplify the wind velocity.
Taking the path of least resistance westward into Southern California, this cold wind blows down through the Cajon Pass, into the Santa Ana River Valley and out into the Pacific (see illustration) In Southern California waters, we know it as a “Santa Ana.”
How does it get to Mexico? When the Plateau High is centered in the eastern part of the plateau, this cold, dry mass of air similarly rushes downward and outward. But this time it flows south through the Salton Sea Trough and the Colorado River Valley, then out onto the northern end of the Sea of Cortez. The areas first affected are San Felipe, Puerto Peñasco and Desemboque.
Channeled between Baja’s mountainous spine and the Sonora Mountains on the mainland, the Norther continues flowing down the Sea of Cortez, northwest to southeast, drawn like a magnet toward the areas of low pressure at the equator.
A strong Norther can blast down the entire 700-nautical-mile length of the Sea of Cortez and be felt at Los Frailes on the Baja side, at Isla Isabela off the mainland Nayarit side and even by yatistas making the 275-mile crossing between Los Cabos and Puerto Vallarta.
... to read more travel articles, visit http://travel.fyicenter.com/article/