Pattern Change or not??? Where is Winter????

Continuing from my last post, the sharp trough that I anticipated to take place this week did form. Temperatures dropped into the teens with high temps in the 20’s and 30’s for one day, but the trough was not deep/sharp enough and tilted enough to form the cutoff upper level low the European model was forecasting. The result was rain followed by sharply cold temperatures for a couple days, with a light coating of snow in North Georgia and snow in the Appalachians.  Since then, the mild Winter of 2011/2012 continues…………why, and where do we go from here??

A strong vortex of low pressure continues to dominate the Alaskan landscape, bringing them bitterly cold air. Typically, if Alaska is cold, we aren’t. Why? That means the cold air is bottled, and has no way to be steered in our direction due to the counter clockwise flow around the strong vortex. In order to have that air transported our way, we need a strong area of high pressure, with clockwise flow, to get in place in or near Alaska.  That would funnel the cold into the United States. Also, Greenland has stayed very cold for similar reasons.  The latest European and GFS models are showing high pressure building into or near these areas in the next 7-10 days. With continued +PNA(roller coaster) setting up a ridge in the western US, this will eventually funnel the cold into the United States. The Arctic Oscillation, which basically tells us how cold the Arctic regions are at upper levels(+AO) is trending downward, and there are signs of a strong negative index very soon.  This would warm the stratosphere there and bring the cold down into the United States, as the upper level warm air presses the lower level cold out and to the south.  The NAO is trending negative to neutral, which could slow any systems that come through our area in the next 7-10 days(see attachments for AO, PNA and NAO courtesy of CPC).

What all this means is that IF the models are to be trusted(and after being locked in this pattern since November the likelihood is high for change), we should see very cold weather come into our picture for the SE US the end of next week(Thursday) following the strong upper level low that may give us up to 2 inches of rainfall Tuesday-Wednesday.  This cold air should be reinforced after a brief warmup, and IF the atmospheric setup changes as noted, we can expect a potentially bitterly cold arctic outbreak around January 20th. 

The Canadian model(see attached, courtesy of CMC) is showing an area of low pressure developing in the Gulf of Mexico next Thursday, moving to the Mid-Atlantic coast next Friday, possibly bringing us snow and ice, following the passage of the upper level low and an associated Arctic front, next Wednesday.  The European showed this low pressure area on last night’s run.  The setup supports this, and I will follow this over the next few days, and keep you advised. Hopefully our first “real” snow threat looms soon.

Ensemble Mean AO Outlook

Ensemble Mean NAO Outlook

Ensemble Mean PNA Outlook





About snoah47

Weather lover, that completed my Bachelor's degree in Operational Meteorology from Mississippi State University in 2011. Now working on a Master's degree in Applied Meteorology from Mississippi State University.
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