West Paso Robles Wind Flow, the Templeton Gap and the Adelaida Climate

As I've said before, it's great to have interesting friends.  I got a question from one of them (Kelly Bobbitt of Mike Bobbitt Associates, vineyard mappers here in San Luis Obispo County) asking about a model that he'd created to show the incursions of fog into the Paso Robles AVA.  He was looking at his model and wondering how fog (and an afternoon sea breeze) got out to where we are.  Why he was wondering is explained by the below map (again, thanks, Kelly; click on it for a full-size version):

Elevations are noted by color; lowest-lying areas are pale blue, then white, then green, yellow, orange and brown.  White marks ridgetops over 3000 feet.  You can see that the Santa Lucia Range to our west is nearly at its highest point, and that Tablas Creek is protected on nearly every side.  The area around us, with its north- and west-draining watersheds, historically formed the community of Adelaida.  It was close enough to the coast to receive enough natural rainfall for grain and nut tree farming.  Areas farther east, which were drier, were used for ranching.  

I often get questions from people who assume that because we're west of town, we must have direct ocean influence, or it must be cooler.  Looking at the topography shows why this isn't necessarily true.  The unbroken ridgeline to our west shunts air flow southward, through the Templeton Gap, which isn't really a single gap at all, but instead a series of passes through which air flows cumulatively before ending in the Jack Creek, Paso Robles Creek and Santa Rita Creek valleys.  We do get some eddies of cooler air flowing up our way, but as you can see from the map, they are very far from their source and flowing uphill without an outlet.  Our waterway, Las Tablas Creek, opens to the west, and we see negligible air flow up the creek's valley.  All this is a long way of saying that we don't get a sea breeze very often. 

You can see the action of the air outflow in a post I wrote last summer showing time-lapse satellite images of fog in Paso Robles.  The fog, which pushes down from Monterey Bay and in from the Pacific, surrounds the Adelaida area but doesn't cover us.   The topography illustrated so well in the map in today's post explains why.  This sheltering effect of the ring of mountains discourages fog formation  in the mornings, which allows us to allows us to warm up more quickly.  The days stay warm longer than they do in the Templeton Gap, although the proximity to the ocean means that the nights are just as cold -- and often, due to the lack of fog cover, even colder.  The cumulative effect is enough to allow us to reliably ripen Southern Rhone varietals.  Wineries in the Templeton Gap, just a few miles south, struggle to ripen Mourvedre and Grenache and tend to be more focused on Syrah or even Pinot Noir.

The climate of the Adelaida area is remarkable.  It is relatively wet; we get on average 50% more rainfall than the weather station at Summerwood (in the Templeton Gap, at the eastern edge of the map in the same cluster of vineyards as Treana and JanKris) and double what the town of Paso Robles receives.  It is relatively high elevation, which makes it lower in humidity and increases the intensity of the sun.  It is relatively warm during the day, which facilitates ripening, but cold at night, which keeps acid levels strong late into the growing season.  And it happens to have one of California's nicest bands of calcareous soils underneath it.

We didn't know all of this when we bought the property, although we did know about the soils, and felt that the climate would overall be good.  It has been wonderful to find that our site has turned out to be even better than we had expected.