Thursday, December 01, 2011

The Talked About Cold's Slow Ooze

Much like "The Blob", the upcoming mass of cold air that is poised to slip into Canada and the northern portions of the US over the next week will ooze like a slow-moving morass that means business for a good chunk of the Midwest and Northern Plains.  There is now some uncertainty about how much of that cold actually moves east and when it does so as computer modeling from both the GFS and Euro are suggesting that a developing storm system that will organize in the Plains this weekend and lift northeast will take a while to clear the coast.

To show you how slow it might take to clear the East Coast, I've highlighted the GFS computer model from Sunday afternoon (above) and also show the Euro computer model for Wednesday morning (below).  Yep, it takes the better part of two to three days for this front to move from Detroit to Central New York, which isn't a terribly long flight as the crow flies.  The GFS is slightly faster with clearing the front, having the front near I-95 on Wednesday morning but the Euro and GFS show a very slow progression...having a 100-150 mile difference this far out isn't out of the norm in computer modeling.

The cause of this uber slow movement is the building of another ridge of high pressure out in the Atlantic Ocean.  These stronger mid atmospheric ridges of high pressure block the movement of storm systems from the west to east.  They instead ride along the front as the front slowly grinds into the ridge and tries to break it down.  These type of ridges are sometimes regular features in La Nina years and can wreak havoc with East Coast temperatures depending on the strength of the ridge, especially if the North Atlantic Oscillation is not in a negative phase (supporting a trough in the Eastern US).   As a result, the colder air is delayed...it will get here later next week than what was earlier projected and it also may not be as cold...the latter is still very much to be determined.  What isn't different is that the brunt of the cold will continue to focus itself on the Midwest and Plains, where some rather cold air will dive down next week.