|GFS 500mb analysis from 12Z, Sept. 6, 2011. Annotations by LM.|
|GFS precipitable water analysis at 12Z, Sept. 6, 2011.|
Further to the southeast and just coming onto the map is Hurricane Katia. As far as Katia goes, it may be a powerful category three storm right now, but ensemble track forecasts don't show it making landfall.
|ECMWF ensemble track forecast (50 members) for Katia as of 12Z, September 5, 2011.|
Get familiar with this overall synoptic pattern, though--it's going to stick with us. Particularly with respect to the idea of a large ridge over the western US and a trough over the Mississippi and Ohio River valleys. Here's the GFS 500mb forecast for Thursday morning:
|GFS 54 hour forecast of 500mb heights and winds, valid 12Z, Thursday, Sept. 8, 2011.|
|GFS 48 hour forecast of precipitable water valid 12Z, Sept. 8, 2011.|
Meanwhile, out west, things look pretty dry. Being under a ridge, general subsidence will prevail everywhere and we should see lots of clear skies, warm temperatures, and little chance of rain.
Let's fast forward to Sunday. Here's the 500mb forecast from the GFS again.
|GFS 120-hour forecast of 500mb heights and winds valid 12Z Sunday, Sept. 11, 2011.|