As many of you know, the jet stream is a current of strong winds---much narrower than its length--that is often found in the upper troposphere--typically between 25,000 and 35,000 ft--in the midlatitudes (generally 35-50N). The jet stream (a.k.a, the jet) is associated with major weather systems-- the wind and rain storms that strike the region-- particularly in the winter. Jet stream winds can reach over 200 mph, and can greatly accelerate or retard the motion of jet aircraft, depending whether they are heading east (fast trip) or west (long trip). Midlatitude jet streams can meander north and south in a wavelike manner.
The jet stream was first described by German meteorologists in the 1930s and this feature become very obvious to pilots on bombing missions during World War II. The jet stream is generally strongest in the mid-Pacific and some missions directed at Japan found themselves making little headway to the west at times.
During a typical year the jet stream core is north of the Northwest in late summer and then slides down into our area in late October and November. Think of the jet stream as an atmospheric hose and we are on the receiving end during November through January. When is the hose most predictably and intensely over us? The last week of November. The wettest and stormiest week of the year climatologically. In December the jet actually heads south of us more frequently and the weather actually improves in our area...believe it or not.
Today and Saturday the jet stream will dip down close to us... let me show you. The following charts present the wind speed (in meters per second, roughly double for knots or mph, by colors) at a pressure level of 300 mb (roughly 30,000 ft). Here is a forecast for today at 2 PM. Strong jet over the Pacific that is approaching northern Washington, with values well over 100 kts.
Here is the 24-h predicted rainfall charts end Saturday, Sunday, and Monday at 5 AM.
Ending 5 AM, we see modest amounts over western Washington reaching 1-2 inches on the western slopes of the northern part of the State.
Dawg Dash Forecast
And talking about outdoor activities, the annual Dawg Dash will take place on Sunday at the University of Washington at 9:30 AM (http://www.promotionevents.com/dawgdash/). It will probably be cloudy with a few sprinkles, but nothing compared to the deluge of last year!
Seattle School Board Race
My next blog will discuss in detail, but I believe that supporting the challengers is critical for turning around this district.