Updated JAMSTEC Model Supports Cold, Snowy Winter

The latest run of the JAMSTEC long range model came in last night, and it's still calling for a heavy-duty winter for millions across the country.

JAMSTEC

The graphic above shows the temperature anomaly forecast for the December-January-February period of 2014-2015. In this image, focusing on North America, we see an outlook very similar to what I had been pondering a handful of weeks ago. In this outlook, much of the south half of Canada is inundated with below-normal temperatures, which then intensifies and extends into the Northern US.

Interestingly enough, these below normal anomalies only hit the Plains, Great Lakes, Midwest, and eastern Rockies. For all other areas, save for the Southeast, temperature anomalies are actually above normal. The projection for the Eastern Seaboard includes a warmer than normal winter, though not a "blowtorch" winter, per se. The Western US also looks to see a warm winter, according to this outlook.

JAMSTEC

For precipitation, zooming in on North America, we do see a well-above normal precipitation trend over the Ohio Valley. This trend continues into the Northeast and Mid-Atlantic, even backtracking through the Great Lakes and Midwest. Such a wet forecast is also observed in the Southwest, where rain would certainly be welcome. The Pacific Northwest may then see slightly below normal conditions.

The piece that puzzles me (pun intended) in this forecast is the swath of above-normal precipitation anomalies across the Ohio Valley. The West US is exhibiting typical El Nino characteristics, with dry conditions in the Pacific Northwest and wet conditions in the Southwest. However, more La Nina-like conditions are observed in the East, with the above-average precipitation forecast over the Ohio Valley. It remains to be seen how reliable this outlook is, since this is the minority opinion out of the global forecast models right now.

To summarize, the new JAMSTEC is supporting a cold and snowy winter for much of the Central and East US, possibly spoiled by a warm winter in the Eastern Seaboard.

Andrew

Long Range Lookout: Warm End To September, Chilly Start To October

Model guidance is hinting at the idea of a warm end to October, before a chilly October opener enters the scene.

ECMWF

The two-panel image above shows 500mb height anomalies over North America on the left, with the spread among individual ensemble members on the right. For the image on the left, depressions of contour lines, as well as normalized standard deviations in the shaded areas. On the left panel, darker shades of purple indicate higher and higher uncertainty among ensemble members for what will happen in a given area.

According to the graphic above, valid September 28th, a strong trough looks to be pushing into the Western US, forcing high pressure to build in the Central and East US. Warm and dry weather can be expected from this event, while the West may experience its first period of cold and stormy weather in some time. This ridging of high pressure over the Central and Eastern US should allow for warmer than normal conditions to persist through the end of the month.

NAEFS

By the first week of October, the story changes. The image above shows another ensemble "spread" forecast over the 500mb level, now comprised of multiple North American model guidance systems, and now valid for October 1st. In this forecast, we see 500mb contours collapsing south over the Plains and Rockies, as this trough tries to push east. The ridge we discussed earlier is now weakened and suppressed to the south, as it begins to lose control of the Central and Eastern US.

While all of this is playing out, there's a very interesting story playing out in the Pacific. If we take a look at the northeast Pacific region, in the top-left part of this graphic, we see a large swath of yellows and reds, meaning high uncertainty over the area. The ensemble average for this area shows stormy weather in the Bering Sea, but those red colors mean not all ensemble members agree with this prognosis. The downstream effects of this uncertainty in the Pacific are shown in the Western US, as the stormy weather in the Bering Sea/Northeast Pacific produces high pressure over the Rockies, where some uncertainty is shown by the swath of green colors in that region.

To summarize, a warm end to September is expected, but model guidance is indicating a return to cold weather may be expected to kick off October, when a strong trough tries to push into the Central US.

Andrew

JAMSTEC Model Predicting Harsh Winter Ahead

A popular weather model, the JAMSTEC climate model, is forecasting a harsh winter ahead... but will it verify?

JAMSTEC

The image above shows the December-January-February temperature anomaly forecast for the winter of 2014-2015, with the forecast made in August 2014. This forecast is made up of 27 ensemble members, which can enhance its credibility, so long as the forecast is within reason.

In this image, we can see strong below-normal temperature anomalies across nearly the entire United States. Canada and Alaska look to see above to well-above normal temperature anomalies, with the anomalies maximized over the far northern reaches of the country. Last winter, the core of the cold was displaced in the north-central US, but if this model is correct, it would be shifted into the Southern Plains.

JAMSTEC

On the precipitation side, the JAMSTEC model is forecasting a swath of above-normal anomalies to affect the Southeast US, even stretching west into the Texas/New Mexico region. These wet conditions look to extend up the East Coast, almost in typical El Nino fashion. The Pacific Northwest would see a rather dry winter if this solution were to verify, while the Southwest would see slightly below-normal to average precipitation anomalies.

Even though this model certainly is painting an ominous picture, is it a realistic one?

JAMSTEC

The graphic above once again shows an outlook for the December-January-February period, but now depicts sea surface temperature (SST) anomalies . In this image, I can identify two areas of concern, as far the forecast potentially not verifying.

First off, we see a moderate to borderline-strong El Nino evolving in the Pacific. SST anomalies of 1.2 to 1.5 degrees Celsius above normal might be a bit too strong for this winter, as I'm currently expecting only a weak to possibly-moderate El Nino. It would be quite a stretch for a strong El Nino to hit this winter.

Second, we see a pool of deep negative SST anomalies in the waters just south and west of Greenland, while well above-normal anomalies flourish on either side of the land mass just north of the cold pool. There isn't as much reasoning behind this one as there is a gut feeling; the alignment of SST anomalies looks odd to me, and I'm not so sure I would put stock in this forecast.

To summarize, the JAMSTEC model is indeed forecasting a very ominous winter to once again hit the United States. However, concerns with the sea surface temperature anomaly forecast for the coming winter could mean the forecast may be flawed.

Andrew

New LRC Winter Pattern Projected To Be Snowy

Long range climate models are in agreement that the month of October may feature above-normal precipitation in the North and East US, which could play into a very snowy pattern later on in the winter LRC cycles.

Wxcaster

What we'll do first is analyze four precipitation forecasts, each one slightly different from the other based on their initialization and model foundations, from the CFS model. Shown above is the first member of the CFS suite, showing precipitation accumulated over the next 45 days. The end of this forecast period puts us at the very end of October, on Halloween night.

In this forecast, we see a swath of substantial precipitation values extending from the Plains into the Upper Midwest, giving the Great Lakes some of those wet conditions as well. A very dry forecast is noted in the southern Midwest, Ohio Valley, and into the Gulf Coast. We then see somewhat-dry conditions into the Mid-Atlantic, with wet conditions again present in the Northeast.

Wxcaster

The next 45-day precipitation forecast from the CFS ensemble members shows a pretty similar story across the board as the first forecast image. In this new projection, we see what appears to be a swath of wetter-than-normal conditions extending from the Southern Plains and into the Midwest, once again hitting the Upper Midwest and Great Lakes the hardest. In a twist, we now see the Eastern Seaboard receiving similarly-heavy precipitation totals, quite a difference from the first ensemble member. Overall, once again, it appears a wet end to September and most of October would be expected for the Upper Midwest.

Wxcaster

This third ensemble member from the CFS once again retains a similar projection as the first two members for the next 45 days, but differs in the East. For the Central US, heavy precipitation values are displaced across most of the Midwest and west-central Great Lakes, extending back into the Plains. In this forecast, the Mid-Atlantic is dry, in a similarity to the first ensemble member. The Northeast then appears very wet, all in all looking like a combination of the dry scenario from the first member and wet scenario from the second member.

Wxcaster

This fourth member I specifically saved for last, since it appears to be most radical with its forecast in the Midwest (that should be taken as a caveat as well). In this final forecast member, we see very heavy precipitation values over the month of October and late September in the entire Midwest and most of the Great Lakes, stretching down south into the Plains, and even hitting the Ohio Valley in the process. The Eastern Seaboard is forecasted to be predominantly dry, save for the New England region. This could mean that the wet-East projection from the second member we analyzed may be a false forecast, but that's not something we'll investigate right now.

So, why should we care what these four members say about precipitation in the next month and a half?

Because we could be staring right at our winter precipitation pattern.

Something I've discussed on here more than a few times is the concept of the Lezak Recurring Cycle, or LRC. The LRC was developed by meteorologist Gary Lezak, and discusses the idea that weather patterns which develop in October leave a 'footprint' of sorts that is repeated in a regular interval, between 40-60 days through the winter and following spring. In other words, the weather patterns that develop in October repeat themselves for the better chunk of the next year.

So, if we take the four members above to be true (which is NOT something I'd advise to do; I'm showing them in collaboration with additional forecasts below), the Upper Midwest, Midwest, Great Lakes, Plains, and other parts of the East could be in for a very snowy winter.

CPC

In the image above, we see an average of precipitation anomalies over the month of October, compiled from eight global forecasting models. In this graphic, we see a familiar trend. The Plains are projected to receive above normal precipitation, leading directly into the Midwest and Great Lakes, as well as the New England area. Does this look familiar? Because it's nearly identical to some of the projections we were viewing earlier in this post.

Based on the average of these eight global model projections, as well as the four CFS ensemble members we dissected earlier, it's safe to say the current trend favors a very wet October for the Midwest (particularly the Upper Midwest), portions of the Great Lakes, Plains, and Northeast. If these projections end up verifying (again, there are many long range caveats associated with this), then the aforementioned areas may want to prepare for a pretty snowy winter, so long as the LRC cooperates.

Since we don't have as many projections for temperature as we do for precipitation, I won't discuss temperature projections for the LRC in-depth right now. However, based on the average of the eight climate models, October could be a warm month, which might then transfer over into a warm winter. I personally don't agree with the diagnosis for now, but the possibility will be re-examined later on this fall.

Andrew

The Story Behind The Polar Vortex

Ever since last winter, the polar vortex has taken over as the go-to thought as soon as the prospect of cold weather is brought up. Let's take this time today to go over what the polar vortex actually is, and disprove some inaccuracies I've seen swirling around the world.

1. The Polar Vortex Exists Year-Round
The phrase 'polar vortex' is used to describe a strong low pressure system (vortex) that is semipermanently placed over the Arctic region (polar). In the summer, the vortex significantly weakens, and is replaced by high pressure. During the fall months, however, the vortex gains strength yet again and low pressure dominates the Arctic as the polar vortex gears up for winter.

2. The Polar Vortex Extends into the Stratosphere, Not Just the Troposphere

NCEP

The image above shows the 10-day forecast from the GFS model in the stratosphere, at the 30 millibar level. That's pretty high up the sky when you consider us humans are at the 1000 millibar level. In this forecast, we see relatively weak low pressure establishing itself over the Arctic Circle, with weak high pressure surrounding it. That low pressure body is the "birth" of the polar vortex for this cold season, as it begins to come back to life and strengthen for the winter.

Some people assume the polar vortex is no different than your average storm system that brings snow to your neighborhood. The vortex is actually quite different. In order for it to be the polar vortex, it must exist at both the tropospheric and stratospheric levels. That's how big and controlling it is in the atmosphere.

3. There is only ONE Polar Vortex

This is something I've been hearing ever since January 2014, when this polar vortex business really took off. The belief is that there is more than one polar vortex in the atmosphere. This might stem from the aforementioned idea that some believe the polar vortex is no different than your average storm system, but regardless of its origins, the belief is false.

ESRL

Take a look at the image above. In this image, we see a view of 500mb height anomalies across the Northern Hemisphere on January 7th, 2014. Warm colors correspond to high pressure, which brings warmth and generally quiet conditions. Blues and purples indicate the presence of low pressure, which permits stormy and chilly weather. Just taking a glance over this map, we see one strong upper level low that seems to be the strongest one in the entire hemisphere. That upper level low, seen scraping the northern US and inundating Canada, is the tropospheric version of the polar vortex. As you can see, there is only one low as strong as the one in North America, hence there is only one polar vortex. Those other low pressure systems are just disturbances compared to the polar vortex.

ESRL

To give you a better idea of how there's only one polar vortex, let's take a look at the stratosphere on January 7th, 2014. In this image, we see what appears to be two strong areas of negative height anomalies, being pinched by two bodies of ridging/high pressure on either side of the globe. If you thought that this image shows two polar vortexes, you are incorrect!
What's actually happening is the two bodies of high pressure are trying to tear apart the polar vortex, something that happens rather often each year. The difference between other years and this past year is that the ridging forced the main part of the polar vortex into North America; that other area of negative height anomalies in Asia is just a weaker part of the single polar vortex that was torn off of the main body. Some of you more experienced weather enthusiasts may know this type of set-up as Wave-2 stratospheric activity, as two bodies of high pressure push into the Arctic.

To close out this post, here's a stellar graphic made by the folks at the National Weather Service office in New York in early January, when the hype over the polar vortex was in full swing.

NWS

To summarize:

• The Polar Vortex exists year-round, varying in strength. It does not (and will not) "come back" for the winter, as it's already present and cannot "come back".

• The Polar Vortex exists across both the troposphere (where we live) and the stratosphere (where Felix Baumgartner jumped from his capsule in October 2012); it does not exist at the surface.

• There is only one polar vortex; our world would be much different if more than one polar vortex existed.

Additional points of summary are included in the NWS graphic above.

Andrew