September 10, 2013

The Banana Belt Ripens

One of my favorite local anomalies is the Brooking's, Oregon hot spot and the cool temperatures that are inevitably a few miles away.    Brookings is a coastal town just north of the Oregon/CA border that is famous for occasionally enjoying wacky warm temperatures.  It is known as the Oregon coast's banana belt.

Today, Brooking, Oregon got to 100 or 101, depending on which station you looked at, while just offshore temperatures were in the mid-50s! (see map).  A few files south of the border, upper 60s and mid-70s were the rule.   But even there, a few miles inland temps can to 104F!

These amazing hot temperatures were associated with northeasterly flow descending the Klamath/Siskiyou Mountains.   The air was fairly warm to start with, but got superheated by compression as the air sank along the western slopes of the terrain.  This is supported by the 850 hPa level (around 5000 ft) forecast map for 2 can see the strong offshore (northeasterly flow).  This northeasterly flow was the result of resurgent high pressure over the eastern Pacific and a thermal trough over California.

There is a radiosonde (balloon-launched weather instruments) at Medford, located to the east of Brookings.  The 5 AM sounding shows the northeasterly winds aloft, and relatively weak wind near the surface. The line to the right is temperature, to the left dew point.

Brookings is unusual in having high terrain to its west that extends virtually to the coast (see map). That sets it up for temperature spikes when offshore flow occurs.

 Brookings really has bipolar weather.  Most of the time they are heavily, marine influenced and cool, but occasionally offshore flow causes temperature to soar.   Take a look at the temperatures over the past 6 months you will see what I mean.  Almost ANY time of the year temperatures can spike when there is offshore flow there. Must be unsettling for the natives.

By Wednesday, you won't even have to go the Brookings for warm temperatures.   The thermal trough will move north to Puget Sound, with offshore flow extending across the Cascades.   (see  surface map that shows winds, pressure, and lower atmosphere temperature) Expect temperatures close to 90F over the eastern side of Puget Sound!

1 comment:

  1. Local weather wallahs have dubbed this the "Brookings Effect".

    Notably, it is prominent even in the Winter, when Brookings can warm up to the low-mid 70's while the Willamette Valley struggles with the 40's and low 50's.

    In our region, the Brookings Effect is probably the best demonstration of Foehn (Chinook)(Sirocco)(Mistral) winds and their warming effects.


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