Tuesday, April 23, 2013
The Banana Belt of Brookings, Oregon
The Pacific Northwest has lots of weather oddities and one of my favorites occurred yesterday at Brookings, Oregon, located on the southern coast of Oregon. Here are the high temperatures yesterday (Monday) over the Northwest from a National Weather Service summary chart. Lots of 60s, but wait! ON THE COAST, right near the California border temperatures jumped to 80F, while temperatures were in the 60s to the north and south! To an experienced NW weather watcher this means only one thing: the "Brooking's Effect" has again revealed its power. There is a reason this area is called the "Banana Belt" of southern Oregon!
A closer-in view reveals more detail (see below). Low 80s in Brookings and 60s to the north and south along the coast. 70s inland. What is the origin of this weird effect, one that can brings 70s or higher to the coast near Brookings during ANY MONTH OF THE YEAR?
To understand what is going on, we must start with a terrain map (see below). There is something unique and special about Brookings: it is just west of the one location along the coast where high terrain extends all the way from the coast to way inland (known as the Klamath Mountains/Siskiyous). It also is a place where the coast is oriented SE-NW.
In situations where the winds are from the east or northeast, air descends the terrain east of Brookings and is compressed as it moves downward. Compression results in warming. We know this was happening for many reasons, including the availability of a radiosonde (balloon-lofted weather instrument) upstream at Medford (see below). This figure show temperature, dew point, and winds from the surface to roughly 10,000 ft (700 is pressure in hPa). We can see the easterly and northeasterly flow through the layer.
One final curiosity...while the minimum temperature last night at Brookings was 62, while at Burns in eastern Oregon it dropped to 13F. Nice to live in a region with some contrasts.
Posted by Cliff Mass at 12:29 PM