Cold, Cold, Cold. Will It Ever End? Omega Block and Winter Weather

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The forecast for Wednesday night. The cold air has pushed off the coast except in Florida. An Alberta Clipper is over Lake Superior.

The forecast for Wednesday night. The cold air has pushed off the coast except in Florida. An Alberta Clipper is over Lake Superior.

Mother Nature is a football fan. How else can we explain the break from the unrelenting cold of winter 2014 for a few days around the Super Bowl?

Well, we could try the jet stream, or the omega block, or the polar vortex — not to mention the anomalous water temperatures in the northeast Pacific Ocean.

This Winter’s Weather: The Omega Block

Much of this winter has been characterized by high pressure in the upper atmosphere over the eastern Pacific and west coast.

Shaped like the greek letter omega, this pattern prevents the normal west-to-east progression of short waves in the jet stream.

To the east of the block, northwest winds stream into the United States and arctic air plunges far to the south.

This Winter’s Weather: Computer Models Keep Getting it Wrong

Just before Super  Bowl week, a low latitude branch of the jet stream undercut the omega block and weather systems started moving. Rain fell in California and the jet stream flattened out to allow warmer air to reach East Rutherford, New Jersey just in time. Numerical model forecasts continually believe that the more normal zonal (west to east) flow will be re-established on a more permanent basis. But the omega block re-appears every time.

This Week, Another Trough Will try to Break the Omega Block

The omega block and associated trough in the jet stream and southward-displaced polar vortex will bring frightfully cold temperatures to the upper midwest and cold elsewhere east of the Rockies with the lone exception of Florida. Extreme drought will be exacerbated in the west, then a new trough will try to plow through the block. Indications are that it will bring rain to all of California. But can it kick out the cold air in the east and force the polar vortex back to its normal position?

The Battle For the Midwest and East

The Polar Vortex and the zonal flow will wage war for the next week and a half. Either side could gain the upper hand, but the smart money is taking the under on air temperatures east of the Rocky Mountains.

The high sea surface temperatures in the northeast Pacific Ocean are providing an anchor for the omega block and it is likely to return. There could be a warm spell in early March, but a return to cold in the eastern United States is a good bet for much of the month.

A Respite From Storms. Will It Last?

As the cold air pushes into the Gulf of Mexico and Atlantic Ocean, the frontal boundary that spawns winter storms has moved out to sea. Alberta Clippers may drop a little snow on parts of the midwest, but these storms will be moisture-starved. However, the warm ocean water makes the formation of a new front along the coast a strong possibility. Some computer models forecast a decent nor’easter by the end of the week.

At Least Some Areas Will Have Spring

Cold air covers the eastern two-thirds of the U.S., and warm air dominates the west.

Cold air covers the eastern two-thirds of the U.S., and warm air dominates the west.

Though astronomical spring doesn’t begin until March 20 (the vernal equinox), meteorological spring starts on March first. This year spring will come in like a very cold lion in the eastern United States, and residents will notice no change from winter. However, in the west, shielded from the cold air by the Rockies, temperatures will be well above normal. This map shows the average high temperature anomaly (departure from normal) forecast for Feb. 27-Mar. 3.

The extreme temperature gradient along the Rockies will be the battleground between zonal flow and the polar vortex. Cold air is denser than warm, so the cold air at the surface east of the mountains will not easily be displaced — several more weeks of winter are a good bet.

Punxsutawney Phil was wise to crawl back into his cave.

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