Monday, January 18, 2010
Its 9 PM and Its Getting Warmer Out!
Something very strange is going on right now (9 PM). It is getting warmer! I was just down in Kent and the temps felt nearly 60 (and there were modest winds from the east). As a drove through downtown Seattle it was 57F. Here is the temperature and wind trace (plus other goodies) at the UW. It has gotten warmer!
The sun is down..why is it getting warmer?
The east winds know!
The next major low system is moving up the coast right (see satellite image and forecast sea level pressure for 10 PM tonight).
Pressures are dropping (in fact they are really very low tonight...lower than last night). A fairly good pressure difference has developed across the Cascades and there is easterly flow at crest level. The result...easterly flow is moving through and down Stampede Gap (a weak area in the Cascades). Here is a model simulation of the winds at 10 PM. Some strong winds in the foothills and to the immediate west (sustained 20-35 mph, gust to 50 mph). One NWS spotter near Enumclaw clocked 80 mph.
There winds are influencing mainly the east side of the Sound from roughly Tacoma to north Seattle. (see graphic). Note how much colder it is northeast of Seattle (click on image to enlarge).
As the air sinks it is compressed by higher pressure and warms (see my book for more on this). So we are warming right now due to air compression.
I am a little tired now so I won't talk about all the exiting weather coming up with mega-deep lows passing off the S. Oregon coast bring storm-force winds there. Or the huge rainfall totals that will hit California and Arizona. That is why we have the NWS. Those folks are there three shifts a day, every day of the year. Their contributions are important and often unrecognized...but they are very good.
Posted by Cliff Mass at 9:13 PM