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Merit McCrea – WHEELHOUSE SCOOP

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Tuesday, December 05, 2017
Dropping the hint
Tuesday, December 19, 2017
Cods from isolated high spots okay?


Northeast Santa Ana winds
The past week we saw our first really strong, extended northeast conditions. It was dry, and winds ripped offshore. Fires that started, barreled downwind toward the coast, taking out everything in their path and sending thousands running for refuge.

At sea, it's a complete role reversal. In most areas, the places known for glassy weather were the roughest, while outer


islands and offshore banks had halcyon conditions, greasy-flat calm. While our prevailing westerly winds rip hardest in the afternoon, dying down at dawn, these easterly Santa Ana winds crank up at night, rip through the morning hours and die down in the afternoon.


How does this work? Why does this happen? And what do you do about it at sea? Well, the natural ebb and flow of highs and lows across the Pacific tends to kick start changes, but it's really the local conditions that are the primary drivers. It's these that cause one or the other scenario to persist or intensify.


The first thing to wrap one's mind around is the three dimensionality of atmospheric air flow. Mostly, surface wind patterns flow like water over land and sea. They go around mountains and islands when they can, and over them when they can't. Cresting ridges, air/wind cascades down-canyon.


Lower air layers are more dense, heavier than those above. It's a function of their temperature and air pressure mostly. When this fails to be the case it rains, storms form, and at its worst, cyclones and tornadoes, too.


Normally we have northwesterly winds, especially in late spring and early summer. This is because waters offshore are considerably cooler than inland deserts, and these deserts are heating up way faster than the water. Water not only holds more heat than land, but it circulates around, forcing the sun to heat a lot of it to raise the temperature even just a little. The air temperature above the ocean matches the water. In the desert, the sun heats just the top inch or so and the air temperature soars.


Warm air is lighter than cold air. The cool, heavy and moist marine air offshore wants to flow ashore into the void. Along the way, the spinning earth twists its trajectory to the south some, causing the wind to blow from the northwest rather than directly ashore. This onshore effect is strongest in the afternoon as inland areas heat.


Typically, when winds blow, in the lee of the islands an eddy of calm water forms. But sometimes, when wind really rips, it can come straight over the top of low lying islands like San Miguel, San Nicolas and even Santa Rosa, accelerating to cover the extra distance and landing on the water with tremendous force. Yet, without fetch there is no sea. Waves are small but vicious and getting the hook to hold can be a chore.


Santa Anas are exactly the opposite situation from westerlies. The land holds less heat than the water, and cools faster as the autumn nights get longer. The air spills off the land as it cools in the night, and by dawn the flow is maxed. Yet, it's offshore momentum continues until the land heats enough to stem the flow.


Moisture – moisture, or lack thereof, is another reason Santa Anas get going. Normally it takes just a calorie per gram of water to heat it a degree centigrade. But to vaporize a gram of water, it takes 540 calories. So when a gram of water condenses as dew, it dumps off this hill of heat along the way.


What does this mean? It means, if the air is moist and cooling, the dew falls and this keeps the air temperature from dropping much below the "dew point" temperature.


Marine air is moist, keeping offshore areas relatively warm after sunset. Desert air is dry. Although it heats easily during the day, the temperature drops like a rock after dark. Air density skyrockets as it cools and this dense air spills toward the coast, taking the lowest path possible, but the sheer volume of it fills the canyons and passes, screams over mountain tops and buffets the waters to leeward.


Geographically speaking, this means the air spilling out of the high desert, from as far away as the Four Corners, careens around the south end of the High Sierra, screams through the Antelope Valley, bounces down the I-5 corridor, and through the passes and canyons of the San Gabriels.


From there, winds splash down the Santa Clara River Valley, smash into and over the Santa Monicas and spill out to sea, blasting Anacapa Island and screaming up the backside of Santa Cruz Island. Northeasters typically run out of steam out towards Santa Rosa Island.


Most recently, our Santa Ana conditions were so strong and gathered from so far, deep into the deserts of the Southwest, winds whistled through passes as far south as northern Baja.


Evening Santa Anas can be warm along the coast. As this extremely dry air falls to sea level, it compresses and heats (following Lussac's law).


When Santa Ana winds blow, you'll want to run for calm waters. But the usual hiding places can offer no shelter at all. Boats at Avalon have been ripped from their normally peaceful moorings and cast ashore. Areas out of the wind include the normally challenging San Miguel and north Santa Rosa islands. San Clemente and San Nicolas islands are usually out past the buffeting breeze, as are the outer banks. It's a boon for those who fish up west, far offshore or along the Central Coast.


If you are pinned into a hole, hiding somewhere along the west side of an inshore island with winds blowing from the east, hunker down until early afternoon, when Santa Ana winds will typically die down as deserts heat up. It's quite the opposite of hiding from our prevailing westerlies, staying overnight in some named anchorage, waiting for the calm of morning to boogey on home.


While northeasters typically skirt the Santa Barbara coastline, sometimes they blast straight up the Channel. If you're wrong in reading the forecast, you can find yourself facing a 20- or 30-mile uphill nightmare, with nowhere to hide. Instead, I'd opt for the epic fishing off Santa Rosa's Talcott Shoals, or Simonton at San Miguel. Fish there until at least 1 p.m. and amble in after the wind has died for the day.


* * *


Merit McCrea is saltwater editor for Western Outdoor News. A veteran Southern California party boat captain, he also works as a marine research scientist with the Love Lab at the University of California at Santa Barbara’s Marine Science Institute. He can be reached at: merit@wonews.com.


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