It’s always wise to jump off of something solid and real versus a computer model. So what does that mean exactly might you ask? Well, in the world of weather forecasting there’s both real and simulated data, the later which is often referred to as “the models”, in weather office lingo. The above map is a real sampling of the atmosphere at a pressure level of 500 millibars (mb). This correlates to about 18,000 feet. We’ll start here with the real.
Near the Gulf of California there are two closed isobars or lines of equal pressure that make a circle. This feature is the “cut-off closed low” that Drew highlighted on both the five and six o’ clock shows, and also our chance of a little rain and snow late on Saturday. The numbers on the isobars on the whole map correlate with the height at which the pressure is 500mb. The two around the Gulf of California Low happen to be 558 and 570. These numbers are listed in decameters, so for the 570 height contour we would give this a height of 5700 meters (m). After a little quick math, this correlates to a height of 18701 feet (ft).
Looking upstream or to the West, the next feature of interest is a Low that just about has a closed contour around it off the coast of Northern California. It is this storm system that is prognosticated to move through our area by the second half of next week. The dip in the isobars just above this Low, to the east of Alaska, represents a shot of cold air that will spill in here early on Sunday. This is a precursor for any hopeful snow event. The more cold air we have the better and the way things are looking a few successive shots will be moving in.
Back to the Low off the coast of California. Long range models have this system (music please) spinning and spinning and not moving much and then spinning some more and then finally breaking up somewhat in a few pieces that look to scoot through the central plains next week. There is a reason for this. Back to the 500mb map. The east coast is presently within a deep trough of Low pressure. The central Atlantic is dominated by a strong ridge of high pressure and lastly the Mediterranean has a strong Low pushing in. This pattern of Low, High, and Low is a blocking pattern known as an Omega block. An Omega block thwarts westward movement and with this present set-up a building of cold air over much of the country can be expected.
So with assumed cold air place, finally things can get interesting! The map in color above is a simulated state of the atmosphere for Friday February 2nd at noon. It’s cold, snowy and very much a picture of winter across much of the country. This latest run of the GFS (18Z) at this time, already had a system that passed through our area late Wednesday into Thursday but this image highlights a Low forming south of Colorado with yet another push of cold air. This one will have jet stream energy to work with and just may be the one to watch out for!
Will things change? You bet! Will the models continue to hint at a legitimate winter scenario? Say your prayers!
But, will it be turning COLD? Bank on it!