An end to the drought?

 Well, an end to the drought doesn't apply for the High Country, due to the nitro charged storm track we had from this winter. This winter, we had a very strong anomalous low over Alaska and another over Greenland. The low over Alaska induced a more zonal flow across the United States, and the low over Greenland aided in keeping a ridge over the Southeast. In fact, except for a two week break, this same pattern held up all winter.

January - March 2012 Geopotential height anomalies. Red = higher heights (warm areas) blue = lower heights (colder areas).

This bears no resemblance to the 2010-2011 and 2009-2010 winters. A supercharged jet stream entering into the Pacific Northwest means a very flat, zonal storm track across the United States. The few times there were short waves embedded within the flatter track, they would detach from the track as a cutoff low and drift towards the southwest U.S. That is really the only reason why we do not see as strong of a positive anomaly across the southwest United States.

The strong ridge across the Pacific and the strong trough over Alaska induced a strong pressure gradient, strengthening the jet here (due to the steeper gradient change).
 

The mean jet stream from January 2012 to March 2012. Notice the anomalously strong jet over the Pacific Northwest, and how it penetrates across the northern states. The jet actually isn't weaker across the central United States. Rather, it is descending down to another level. Across the east coast it rises back up to that level. See how the highest values are well off the east coast and do not pass over the Southeast? Lets look at the prior winters.

 The Armageddon winter of 2009 - 2010. The storm track has been pushed much farther south, to the point where the Southeast was almost always in a perpetual trough. Also look at the absence of a strong jet stream entering into the Pacific Northwest.

 The much more benign winter of 2010-2011, which had a brutal start but a slow finish. The jet stream entering the Pacific Northwest is stronger but not nearly as strong as this prior winter. Most of the strong values over the Southeast are from December 2010 alone. That's how far south the trough was during that winter.

We can see how strong the current negative phase of the North Atlantic Oscillation is right now. The stronger it is, the more zonal the flow is across the Atlantic.


Enough reminiscing about the past, lets get to the meat of the forecast. A split in the primary jet stream will put the High Country in between the storm tracks. A building upper level ridge this weekend will keep the area sunny to partly cloudy and displace the trough that has been keeping the High Country in unseasonably cool weather. The polar and subtropical jet stream are both defined, unlike last summer where the subtropical jet stream was heavily suppressed. The subtropical jet stream is weaker, and found at a higher height level due to the warmer (and thicker) atmosphere. The end result of a trough of the southerly jet is below.

The next 3 figures are winds at the 250mb level.

Friday winds. The backside of the trough will funnel in remnant cold air in the morning but I am expecting a wind shift tomorrow. Rainfall is confined to the eastern Gulf Coast and Florida.

Saturday winds. Notice the slight colors at the bottom of the figure. This is actually the southern branch of the jet, augmented by the lack of a strong zonal flow into the Pacific Northwest. Notice the building trough across the southern jet. At this point the rainfall will be confined to the Gulf Coast, due to the close proximity of the descending portion of the northern jet stream.

Sunday winds. Stronger southern jet flow and building trough in the southern jet will support slight synoptic ascent across Florida, Georgia, and southeast South Carolina. Rainfall will be here.

Positive geopotential heights over Greenland and the Arctic are inducing the expansion of cooler weather across the East Coast. Weaker polar jet is allowing for a southerly branch to have some weight in this forecast.

We have a retreat of the higher pressure over the Arctic, and with that the cooler weather retreats as well. We start to see a building ridge across the Great Lakes Region. This is not a deep ridge nor is this ridge linked to the Bermuda high but is an upper level ridge.

I am actually looking up at the sky thanking God for this ridge having no connection to the Bermuda High. The Bermuda high has been confined to the eastern Atlantic, and thus has confined what made last summer brutally hot. With an expanded Bermuda High (called a "Death Ridge"), the storm track is shunted well to our north and a ring of convection forms along the western periphery of the ridge. The High Country and the rest of the southeast are stuck in a very warm, humid weather pattern that remains in a steady state for weeks at a time and only isolated convective activity provides rainfall.

Looking ahead, I see an expansion/contraction of the Bermuda High but no sign of there being a steady state Bermuda High extending over the Southeast. Rather, a welcoming southerly jet will keep Florida and the Gulf Coast in a wetter weather pattern, and this may occasionally encompass Georgia and the Carolinas with it. The northerly branch will not envelop the High Country with NEARLY as much frequency but it's proximity, along with the southern branch, will keep the High Country in a more consistent temperature pattern than last summer.

Verdict: The next several weeks continue the wet and mild weather pattern. Hot weather will not be able to get a foothold over the Southeast and precipitation will be abundant.