What Are The Models Saying This Winter? - CMC1 Model

This model examination will focus on the long range CMC1 model.

The image above shows predicted 200 millibar contour lines and anomalies. We're going to focus on the contour lines for right now. We start in East Asia. Looking closely at the image, we see tightened contour lines in the area around Japan. Considering there is a 6-10 day gap between storm systems in the East Asian area and storm systems in the East US, a tightening of contour lines could suggest an increased number of storm systems. This, in turn, may suggest a stormy East US this winter. We see a large ridging pattern across the Alaska/western Canada. This ridging could then provoke a colder than normal pattern to evolve across the Midwest and East US, as cold air flows southeast along the ridge. If the ridge extends far enough into Alaska, a cross-polar flow situation could set up, which would transport Siberian air to the States. A cross-polar flow is one of the situations that brings the coldest air possible to the US- another situation would be the cold air displaced to the surface as a result of a stratospheric warming. Enhancing the probability of a stormy Midwest and East Coast is the presence of lower than normal heights offshore of the Southwest. This suggests a stormy subtropical jet stream, which could lead to some snowy events for portions of the Central and East US.

The temperature forecast for the winter from the CMC1 model shows a very warm nation. We see consistently above normal temperature anomalies stretching from the West to the East. Much warmer anomalies are found in northern Canada towards Greenland, and this could be suggestive of upper latitude blocking. However, whether than actually happens remains to be seen, as temperature anomalies can be deceiving. Negative temperature anomalies are found in western Alaska, which may or may not suggest troughing in that area. Again, temperature anomalies can be deceptive, and I'm not willing to speculate beyond that.

Precipitation anomalies suggest a very wet Midwest and Northeast for this winter, with a dry Southeast. Considering the prospect of a Southeast Ridge, storms would tend to be directed north into the Midwest and Great Lakes. I would not be too surprised to see the precipitation pattern along the eastern half of the nation verify- it is in line with my current thinking for this winter. As far as the West, I would expect to see dry precipitation anomalies further to the north due to the idea of some ridging closer to the Pacific Northwest and western Canada. But this is only one model's take, and we are still months away from winter.

Andrew

Persistent Stratospheric Warming Setting Stage for Winter

Stratospheric warming currently ongoing throughout this past summer and now is beginning to set the stage for this winter.

This graph shows observed temperatures in the 70 millibar region of the stratosphere from the latitudes of 65N to 90N. The red line illustrates the actual observed temperatures, while the green line shows average temperatures for that time of year. The light gray lines depict the minimum and maximum temperatures observed to this date for any certain time of year. Looking at this past summer, where the red line begins to arch up, we see the observed temperatures were consistently above the green line, meaning the stratosphere has been above normal for a while. It then tapered off for a little while, but as the zoomed-in portion on the bottom right shows, stratospheric temperatures have been on the rise for a bit, to the point where they are above normal.

The temperatures have been above normal for good chunks of the last few months, but the question now is: What is causing these above normal stratospheric temperatures?

An examination around the solar activity reveals daily sunspot trends may be at fault. This chart shows many things at once, but we want to focus on the red line, which shows daily sunspot values. Take a look at the red line after the big spike in the middle of the chart. After that spike, sunspot values take a dive, and stay in slightly below normal territory for a while. This big drop-off happens in the month of June and into early July. Taking a second glance at the stratospheric temperatures, the 70 millibar level was constantly above normal throughout this period of low sunspot numbers. A second example can be found in the time during and right before the big spike on the sunspot graph. These above normal sunspot numbers happened between April and late May. Examination of the temperature chart shows consistently below normal values in this same time frame, meaning there may be a negative correlation between daily sunspot numbers and stratospheric temperatures.

All of that said, if we continue to see the current sunspot numbers stay at unusually low values (circled in blue), the stratosphere should continue to warm. Further warming may set the stage for a warmer than normal stratosphere this winter, which would then encourage a cooler than normal winter.

Andrew

Preliminary 2013-2014 Winter Storm Tracks

This is my preliminary 2013-2014 winter forecast. Bear in mind this is all VERY preliminary, and certainly not set in stone. There are four storm tracks we will analyze here- from the top of the image to the bottom, we will analyze the Alberta Clipper, the Colorado Low, the Panhandle Hook, and the Nor'easter.

Alberta Clipper
The Alberta clipper involves a relatively low-amount snow system that originates in the Canadian province of Alberta and swings down into the US, leaving howling winds and biting cold in its wake. The clipper system is moisture-starved, leading to its usual 2-5'' snowfalls it puts down. This winter, I anticipate the Alberta Clipper to be a little less prevalent than usual, but due to a still-unknown pattern just offshore of Canada, confidence in that outlook is low.

Colorado Low
The Colorado Low is a storm system that originates from the West US and passes in or close to Colorado, depending on its eventual track downstream. The Colorado Low then moves northeast, and can bring rather significant snows to the Plains, Midwest, Great Lakes and even the Ohio Valley. This winter, I expect we will see more Colorado Lows than usual, as ridging in the West and a stormy pattern offshore the Southwest should lead to a more active storm track.

Panhandle Hook
The Panhandle Hook is essentially the motherlode storm system for the Midwest and Plains. It comes from the West US and does a hook around Oklahoma (hence the PANHANDLE Hook) before coming north and east. The Panhandle Hook is relatively rare, but when it happens, under the right conditions, over a foot of snow can hit areas affected by this system. I anticipate an above normal number of Panhandle Hook systems, as stormy conditions are expected in the region where Panhandle Hook systems originate.

Nor'easter
The Nor'easter is quite possibly the most intense winter storm that can hit the United States. Its cousin, the Panhandle Hook, will be rather active this winter, and it's no surprise that the Nor'easter should be either normal or slightly above normal for this winter as well. It will depend on the presence (or lack) of ridging in the Southeast, which, if it were to be present, would discourage Nor'easters. I'm not sure which way I'll lean as far as if these storms will be normal or above normal. That should become clearer by October.

Andrew

Long Range Lookout: Warmth Displaced North as Omega Block Evolves

The recent warm weather that many across the nation have experienced has ended for the next several days, as a new Omega Block pattern begins to set up over the northern part of the nation.

Shown above is the long range projection of 500 millibar height anomalies across the Northern Hemisphere from the American GFS Ensembles. This is valid around the September 26th period. On this forecast map, we see deep troughing along the western coast of Canada and into the Pacific Northwest. This provokes high pressure to develop in the Central US in a situation that would typically bring hot weather back to the nation. However, the body of high pressure will be displaced further north into Canada, which will spare much of the north central US from getting in on another hot spell. As long as the stormy pattern along the western North America coast continues, the threat of warmer weather easing into the US again is not out of the realm of possibility. I do not believe that the US will end up warmer than average in the next week or two due to this high pressure being displaced north, and those who sweated out several 90+ degree days in the last week will catch a well-deserved break.

The European ensemble set takes this idea of the heat being displaced north to another level, showing the evolution of an Omega Block across the United States and Canada. The Omega Block involves a body of high pressure being sandwiched between two areas of negative height anomalies. If you look closely at the height contours, you may be able to see what looks like the Greek letter Omega (Ω). The Omega Block pattern typically brings hot weather to those in the positive height anomaly region, and cool temperatures to those in the negative height anomalies. The Northeast, Ohio Valley and Plains will likely receive the negative height anomalies, while Canada and Greenland are inundated by positive height anomalies. Should this pattern stay in place for a prolonged period of time, it would not be impossible that we see a cooler than normal September over portions of the country that would be affected by this Omega Block.

Andrew

What Are The Models Saying This Winter? (9/13/13)

This post will show the GFDL model's long range forecast for the December-January-February 2013-2014 period. Additional models will be shown on here in the future.

The image above shows predicted 200 millibar contour lines and anomalies. We're going to focus on the contour lines for right now. We start in East Asia. Looking closely at the image, we see tightened contour lines in the area around Japan. Considering there is a 6-10 day gap between storm systems in the East Asian area and storm systems in the East US, a tightening of contour lines could suggest an increased number of storm systems. This, in turn, may suggest a stormy East US this winter. We see a large ridging pattern across the Alaska/western Canada. This ridging could then provoke a colder than normal pattern to evolve across the Midwest and East US, as cold air flows southeast along the ridge. If the ridge extends far enough into Alaska, a cross-polar flow situation could set up, which would transport Siberian air to the States. A cross-polar flow is one of the situations that brings the coldest air possible to the US- another situation would be the cold air displaced to the surface as a result of a stratospheric warming.

Temperature anomalies are pretty much in line with the 200mb forecast- strong warming trends in the Alaskan/west North American regions, and significant warming in eastern Canada into Greenland. The cause of this more significant body of warming is not immediately evident on the 200mb map, other than a slight ridge signal in that region. I would like to wait for another month or so to see if the GFDL corrects this east Canadian warming in the event it is incorrect. The split between the two warm air masses is where the coldest air of the season would be focused- central Canada into the Midwest.

The precipitation forecast from the GFDL suggests a very wet Pacific Northwest and southern Midwest/Ohio Valley. I'll start off by saying I am most skeptical of precipitation forecasts in the long range because they seem to be the most vulnerable to sudden change. That said, this forecast does look good for a stormier than average Ohio Valley. The trend has been for a dry Midwest and lower Ohio Valley with my analog years, but if the eastern Pacific waters begin to warm up in coming weeks, my analog years will require change that could then see a different precipitation prediction. In any case, this forecast lines up with many that believe cold weather will enter the Midwest, Great Lakes and East US due to western North America ridging, among other things.

More of these posts will come out as we dive into fall and closer to winter.

Andrew