Winter 2011-2012 Outlook

Overview

After a Strong La Nina last winter, it’s likely we will re-enter the La Nina threshold again this winter, but the La Nina won’t nearly be as strong as last year. After a rapid warming period this past spring, the La Nina has struggled to gain any strength over the summer. Currently, we have a MJO wave forecasted to move across the West Pacific (Phase 6/7), which is not typical of a La Nina. This is usually observed during El Nino events, such as 2009-2010. Current cooling continues at a very slow pace, which I expect to continue for several weeks as we head into winter. Some strengthening is also likely during November/December, before a peak around early January.

            

A look at the global pattern shows a bit of a mixed situation. A well defined –PDO is evident in the Pacific, but the GLAAM has risen into positive territory over the past couple weeks, along with the GWO in phase 6. As mentioned earlier, a robust MJO wave is currently moving into phase 6 as well. Current SST anomalies remain weak across the equatorial Pacific, with subsurface SSTs slowly diminishing over the past month. The coldest SST anomalies are located in the East Central ENSO Region. This suggests that any La Nina stronger than moderate territory is unlikely to develop for this winter.

So: What does this really mean?

The answer: A lot. I’m forecasting a weak La Nina to develop this year, which is shown by almost all seasonal forecasting models (see ECMWF, CFSv2 Below). A typical La Nina favors areas west of the I-95 corridor (which has seen the brunt of the last 2 winters). The QBO plays an interesting role this year. With a 50mb positive, 30mb slightly negative, and building negative anomalies at 10mb, the QBO will be very interesting to watch. What happens during the winter could greatly affect the overall winter pattern, so it’s worth watching closely during the next six to eight weeks. That being said, here’s my ENSO forecast month by month:

            Let’s take a look at a typical east/central based La Nina, going back approximately 100 years:

East-based to basin wide La Ninas have below normal temperatures extending from the Pacific Northwest across the Plains, Midwest, parts of the Ohio Valley, and into the Northeast United States. Slightly above normal temperatures are located in the southeast United States, due to a ridge commonly referred to as the “Southeast Ridge”, which almost always shows up during a La Nina episode. The strength and location of the ridge can greatly affect storm tracks, along with temperature gradients, especially in the Northeast.

Looking at previous La Ninas, specifically my analogs, you get this end result:

There’s a deep trough over the West Central U.S., with a –NAO signature in Greenland (Positive 500mb Heights). This image also appears to be “missing” something a typical Nina contains- the ridge in the southeast. It is there- but very weak. This keeps temperatures down slightly, especially in the Mid Atlantic and Southeast. However, with a ridge still there, this will “push” the storm track west of the coast, especially with the mean trough located towards the Plains. This suggests an active track through the southern plains into the Midwest/Ohio Valley this year.

Analogs

This winter may end up being better than last winter in the Ohio/Michigan/Southern Ontario area. Here is my analog list for this winter:

·         1950-51

·         1964-65

·         1966-67

·         1967-68

·         1970-71

·         1973-74

·         1984-85

·         2007-2008

·         2008-2009

Of those nine analogs, eight featured above average snowfall for Toledo, Ohio. This included 5 winters of over 45” (1950, 1964, 1967, 2007, 2008). Of the 9 total analogs used, two had distinctly strong blocking in the previous two winters (’66-67, ’70-71), and only two did not have a –AO during the winter (’07-08, 08-09). However, the strength of the –AO was much weaker during my analog years then in winters preceding them. This is why I expect a weak  to neutral –AO during the winter. While a –AO favors a trough position favoring the east coast, a neutral to slightly positive AO is more favorable for the Midwest (as long as other telleconnections are also supportive). I expect this occur fairly often during this winter, with a very active storm track through the eastern third of the country. Frequent Colorado lows, panhandle hooks, gulf lows will be the primary storm tracks, especially during December, and again in February and March.

If we see a continuation of an active MJO in the West Pacific (Phase 6-7), we could see a more active Subtropical Jet (STJ) during the winter, after a “non-existent” STJ last winter. Even with a northern stream dominated winter like last year, you can still have an active pattern, but the STJ and “Pineapple Express” will only add more fuel to the fire. I don’t think that the STJ will be too active- which is why I have my precipitation maps looking like they do.

The Forecast

So, this is probably the reason you clicked on this anyways: the actual forecast. I’m sure most of you will skip through this text and look at the maps, and then may go back and actually read. If you do read this before you look at the “pretty” maps, then kudos to you.

Using the analogs mentioned above, this is the DJF composite you are left with:

And Precip:

Looking at these maps, you could not print out a better looking composite for the Great Lakes. As you can tell, the tendency is for below average temperatures and above average precipitation, especially centered from STL to Chicago, extending towards the Appalachains.

This is similar to what I expect during the this winter. Snowfall will also be above average in the Great Lakes, with below average snowfall in the Mid-Atlantic coast and south. Precipitation will be well above average in the Pacific Northwest this winter, with slightly below average precipitation in Oregon/No. Californina, with below average precipitation across the Arizona/New Mexico/Texas, along with slightly below average precipitation in the gulf states.

Individual Months:

November: Winter does not officially begin until Dec. 1^st, but I expect that late November will feel more like winter than fall. My analogs show a cold eastern US for November, and some early season snowfalls (November ’66 anyone?) wouldn’t be surprising. I believe winter starts after the 15^th, and continues into December. Temperature Forecast:

Precipitation Forecast:

December: I’m a bit skeptical about this month in general. I do think early December will be cool, but I think a brief warm up towards the middle of December is possible. Although temperatures end up near average, along with above average precipitation, I don’t think anybody east of Grand Rapids gets anything higher than slightly above average snowfall. However, one big storm could ruin that forecast, and if we do get a big storm during one of the active periods of the month, above average snow is likely across the Great Lakes. I do believe that after Christmas, most of the Great Lakes and Plains are back to below average temperatures, while the south and parts of the I-95 corridor stay a bit above normal. Temperatures:

Precipitation:

January: This is probably the toughest call on any month this winter. While the majority of winter forecasts I’ve seen call for a brutal month of cold and snow, again, I’m skeptical that this will occur. It’s not that I don’t think we’ll have below average temperatures for almost all of the country (especially central/west U.S.), I don’t think it will be nearly as cold as many are predicting. I do feel that late January into February will be an active period; see February’s discussion for that.

Temperatures:

Precipitation:

February: This is where I think the best part of winter will be. If you live in Michigan or Ohio you probably have fond memories of February ’08 (or if you live in D.C. or Philly, not so much), and something similar is possible again this winter. This is my “big” month in my forecast, and this is the time that could make or break the winter, especially west of the Appalachians. The temperature/precip composites for my top 9 analogs are suggesting a cold/snowy Midwest, and I’m not going to doubt it. Even in strong La Ninas (see last year), February and March can end up showing impressive snow totals in the Great Lakes Region. With a slightly more active STJ, along with a pretty tight thermal gradient, there could be some big storms during this period. Will we see another record setting February in the Midwest/Great Lakes? It’s definitely possible.  

Temperatures:

Precipitation:

March: Another toss-up here. My analogs are pretty much split down the middle, some extreme anomalies showing up. I don’t want to say anything about this month right now, because there are too many questions to answer at this time. When I release an updated outlook sometime in late October or early November, I should have more details on this month. For the time being, I won’t have any maps for this month.

Summary:

The active winters will continue in the eastern third of the country. Extreme cold, snowstorms, and even the possibility of ice storms in parts of the Mid Atlantic/Ohio Valley will be widespread for the majority of winter. If you didn’t get a great winter last year, this may be your year. We start off winter cold and stormy, then have a bit of a break in December. January starts off a bit slow, but quickly becomes more active, especially in the later portion of the month. February could be the heart of the winter, with cold and snowy conditions likely across the Midwest and Ohio Valley. An active storm track will stay further west of last year’s, which isn’t good for the I-95 corridor to hear. With winter about 10-12 weeks away, it’s time to get ready for a very exciting winter!

Video:

Having technology troubles. Will be ready tomorrow!