What Are The Models Saying This Winter? - GFDL_FLORb01 Model

In the next part of this series, we're going to analyze yet another version of the GFDL model, named the GFDL_FLORb01 model. It's quite a mouthful, so we'll just refer to it as another version of its parent GFDL model.

This version of the GFDL model shows a pretty cold start to winter. As the image above shows, the December 2014 forecast calls for widespread below normal temperatures, concentrated in the Plains, and spilling east across most of the land east of the Front Range. This cold also extends into southeastern Canada, but from there, warmth dominates to the north. We see intense warm temperature anomalies concentrated near the Arctic Circle, which may indicate the negative phase of the Arctic Oscillation. The negative phase of the Arctic Oscillation (AO) can be defined by warm weather over the Arctic Circle, which can lead to a weakening of the polar vortex. The polar vortex then releases vast quantities of cold air to lower latitudes, which can include North America. We have yet to see if this is the case, but if this forecast were to verify, we would see potentially a repeat of last winter's cold.

The precipitation forecast from the GFDL_FLORb01 model shows anomalously dry weather spread out across the Pacific Northwest and into British Columbia, with wetter than normal conditions located in the Southwest, especially in California, and into Arizona. This wetter than normal trend continues across the Southern Plains, into the Ohio Valley, and on to the Mid-Atlantic. From there, we see spots of dry conditions extending from the Midwest into the Great Lakes, as well as some dryness in the Southeast. This goes strongly against the expected El Nino's typical winter precipitation pattern, and for that reason, I am a bit skeptical.

This is likely an experimental model not intended for operational use, so confidence is already low. However, the somewhat-odd precipitation pattern lowers my confidence further.

Additional models will be analyzed in coming days.

Andrew

What Are The Models Saying This Winter? - GFDL_FLORa06 Model

Today, we will be taking a look at the GFDL_FLORa06 model, which we'll shorten to call another version of the GFDL model.

This version of the GFDL model has a rather neutral start to winter in the temperature department. We see that this forecast has an abundance of warmer than normal temperatures in Canada, partially extnding down into the upper Midwest and New England areas. This sort of temperature pattern resembles the El Nino pattern, where one typically sees above normal temperatures in the North and cooler weather in the South. However, that is where the similarities end. This version of the GFDL model then produces cooler than normal weather across the Rockies, pushing south into Texas as well. Normal temperatures are then projected across the remainder of the nation, going against typical El Nino winter temperature patterns.

The precipitation forecast from this particular version of the GFDL model is also somewhat different from a typical El Nino winter. In normal El Nino winters, we tend to see wet weather in the Southwest, dry in the Northwest, and continued drought-esque precipitation patterns in the Ohio Valley. Wetter than normal conditions are then observed across the East Coast. In this model projection, we do see a dry Pacific Northwest and wet Southwest to kick off winter, but then an area of above normal precipitation is observed across the Plains and Midwest. The tell-tale dry signal is then forecasted in the south central Plains into the Ohio Valley, but rather than see wet conditions along the East Coast, we see dry conditions. Anomalously above normal precipitation is forecasted in the Southeast, but it does not extend into the East Coast.

Because this appears to be an experimental derivation forecast from the parent GFDL model, confidence in this forecast is low.

Additional models will be analyzed in coming days.

Andrew

What Are The Models Saying This Winter? - CMC2 Model

This is a continuation of this series of posts, where we are analyzing long range climate model projections for the beginning of the winter of 2014-2015. This post will feature the CMC2 model.

The temperature forecast from the CMC2 model is a toasty one. We see warmer than normal conditions prevailing across the heavy majority of the country, especially around the Midwest and Northeast regions. There is a slight cooler than normal projection in the Southern Plains, but warmth definitely triumphs here. This forecast is very reminiscent of a typical El Nino temperature pattern, where warm weather stays in the North US and cooler than normal temperatures prevail in the South US. It would definitely be a welcome turn-around from what we experienced last winter.

The precipitation forecast for December 2014 from the CMC2 model is not as similar to an El Nino precipitation pattern. We see more or less neutral precipitation anomalies across the West Coast, but the real story is the shifting of drought-esque precipitation anomalies from the West to the Central US, as the CCM2 model predicts would happen to kick off the winter of 2014-2015. Typically, these dry anomalies would be centered in the Ohio Valley for an El Nino winter, not so far west. The El Nino pattern does briefly show itself as a wet start to winter in the East, but i'm not sold. I believe this model needs more time to solidify its forecast; I am not investing much confidence in it.

Lastly, we see the forecast of z200 anomalies for December 2014 from the CMC2 model. We're going to focus on the contour lines over the northern Hemisphere. In this forecast, we see the contour lines arching northward over the west coast of North America, signifying ridging/high pressure in that area. Typically, this would mean a chilly winter for the East US, but the arching of these contour lines extends east into the Central US, meaning high pressure would be favored over low pressure for that part of the country. This map does support the warm temperature forecast we saw earlier in this post, and such a forecast would be nearly a complete-180 from this past winter.

Additional model forecasts will be discussed in the near future.

Andrew

What Are The Models Saying This Winter? - CMC1 Model

This is a continuation of this series of posts, where we are analyzing long range climate model projections for the beginning of the winter of 2014-2015. This post will feature the CMC1 model.

The temperature forecast from the CMC1 model, valid for December 2014, shows a very chilly winter for many in this country. This model suggests we will see an abundance of warm air overspreading Alaska and the west coast of North America. This is likely the result of high pressure, which then forces mid-level troughing to the east. This mid-level troughing, which will be discussed more later in this post, results in below normal temperature anomalies over the Central and East US, extending as far north as upper Canada. If you follow the weather closely, you may recognize this pattern as a positive Pacific-North American (PNA) index pattern. Like last winter, the Pacific pattern looks to have a grip on the downstream weather here in the US, resulting in a cold start to the winter.

The precipitation forecast from the CMC1 model shows a pattern almost identical to a traditional El Nino winter precipitation pattern. We first see anomalously wet conditions along the West Coast, a telltale El Nino signal due to the subtropical jet stream's natural enhancement due to the aforementioned El Nino. This enhanced subtropical jet stream then leads to more storm systems hitting the West Coast, and then more precipitation. We then see significantly below normal precipitation across the Central US, hitting the Ohio Valley the hardest. Once again, this is an El Nino signature. The El Nino is evident yet again in the CMC1 model's forecast for a very wet start to winter on the East Coast. This all strikes me as odd, since the temperature forecast does not reflect an El Nino temperature pattern, but given how this past winter went, you really have to expect the unexpected.

Lastly, we see the forecast of z200 anomalies for December 2014 from the CMC1 model. We're going to focus on the contour lines over the northern Hemisphere. In this forecast, we see the contour lines arching northward over the west coast of North America, signifying ridging/high pressure in that area. We discussed the likely presence of high pressure along the west coast earlier in the temperature forecast, and now we are seeing that theory come to fruition. We then see the contour lines plummet south over the Central US, which is how we got that cold December forecast at the top of this post. Oddly enough, we then see ridging in the Southeast US, which would typically divert storm systems north through the Ohio Valley. However, the precipitation forecast for the Ohio Valley is very dry, as shown above. This is likely the long range model up to its antics, which means confidence is similarly low.

Additional models will be discussed in coming days.

Andrew

What Are The Models Saying This Winter? - NASA Model

This is a series of posts that I have made in previous years, in which I display a specific long range model and its prediction for the upcoming winter. Based on its success in past years, I have decided to kick off the multi-month series early, to give you an early heads up on the upcoming winter.

Today's model will be the NASA model.

The above image shows the NASA model's forecast of 200mb wind speed anomalies across the world, with 200mb pressure contour lines superimposed. We want to mainly pay attention to the contour lines for today's analysis, since it seems to be the easiest for many to decipher over the anomalies. If we look at North America, we see the contour lines arching up across the West Coast, likely indicative of the presence of high pressure/ridging. This ridging over the western portion of North America then leads to a depression in the contour lines, where cold air would funnel southward into the central and eastern portions of the continent. This cold air would be helped along south by that troughing/depression in the contour lines. In other words, going solely by this image from this single model, we would be looking at a very similar set-up as last winter, with warmth over the West and cold over the East.

If we look at the North American temperature forecast for December 2014, the same timeframe as the image above, we see a similar story to my analog package which I posted about earlier this week. We see cold weather present across the South US, with warmth prevailing over Canada and the North US. This temperature forecast looks very similar to a textbook El Nino event, which is expected to form this summer and result, possibly, in a temperature pattern similar to the one above for this winter.

Lastly, the temperature forecast from the NASA model, valid December 2014, confirms the idea of a textbook El Nino pattern. We can recognize this El Nino pattern by viewing the below-normal precipitation across the Great Lakes and Ohio Valley, with a very wet precipitation pattern swallowing the Southeast and East Coast. These two features are common during an El Nino winter, and may very well appear this winter. On the West Coast, in accordance with the ongoing drought, we see well-below-normal precipitation values extending from California to Washington. All in all, even though this is a long range forecast, this solution is indeed a plausible one from this model.

To summarize, the NASA model is predicting the following conditions to begin the winter of 2014-2015:
• Cool South US
• Warm North US
• Wet & Stormy East Coast, Dry West Coast
• Very similar to a typical El Nino pattern

Andrew

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

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