My Winter 2010-2011 Outlook

Winter 2010-2011 Forecast

As fall starts to peak and winter starts to approach, it’s time for many forecasters to issue a final winter outlook. At this time we are currently already in a moderate to borderline strong La Nina. This La Nina should peak by November and slowly weaken by the heart of winter. This current Nina coupled with a very +SOI, -GLAAM, and –PDO should create very interesting weather conditions across the U.S. and Canada. Before I get into the forecast, let’s see what is going on with the current La Nina.

With MEI bimonthly values of -1.9, the La Nina is currently the lowest on record at this point in time. This makes we want to believe that it will run out of steam by winter, with a weakening La Nina as winter starts. Currently our La Nina is Basin-Wide, but it appears it is trying to transition more to an east based La Nina. Current SST anomalies across the Equatorial Pacific reach -2.0 in the easternmost regions (Region 1.2 and 3), with higher anomalies in the more western regions. Although this may be temporary, many of the Long Range forecast models keep the La Nina central to east based, which may save the winter for parts of the Northeast and Ohio Valley regions.

As of late we have seen a complete switch in the GWO/GLAAM/MJO phases compared to where we were for the majority of this season. We just saw a strong MJO wave with a move to Phase 6 over the last week or so… and the GWO is starting to propagate towards Phase 8. The GLAAM, which remained positive for almost the entire summer, has also suddenly switched back positive. However, this is should be fairly short lived, and I expect the GLAAM to be fairly negative throughout winter, with a “lag effect”- where the overall GLAAM remains negative for a few months after the La Nina peaks (Which I expect by November). This is based mostly on a hunch—but with such a strong La Nina, the GLAAM/GWO/MJO seem to be well coupled with the ENSO phase. The SOI is extremely positive, with some of the highest Monthly SOI values recorded in history. There is some of a correlation with high SOI years with a cooler than average North/Northeast compared to a typical Nina during this type of event, and I believe this may also be the case again this year.

The QBO also has taken a switch positive since the spring… coming off a long –QBO regime. A +QBO features positive Zonal Wind anomalies from 30mb-50mb (Although some places use up to 70mb, etc.) along the equator. As you can see in the image below, positive anomalies are starting to develop in the QBO regions, although it isn’t greatly positive yet. A +QBO in the winter tends to give a stronger Polar Vortex, which is harder to displace and cause those record breaking –AO values like last year. However, I still expect the northern 1/3 of the CONUS and Canada to be slightly cooler than average to very cold in the Northern Plains and PNW. +QBO’s aren’t typically associated with La Ninas, but the winters of ’71-72, ’73-74, ’75-76, did.

The 70s are gaining my interest, as they occurred during a –PDO phase just like we are starting now, although they occurred in a –AMO phase. With so many variables different about each ENSO event, I try to stay fairly far away from using analogues too heavily, although you could make an argument to support the use of them. As of now my primary analogues are ’73-74 and ’07-08. ’73-74 is my top one as it came off a strong El Nino… and had a -1.9C peak off the MEI. As I mentioned earlier, the current MEI value is already -1.99… .24*C lower than ’73… but it’s one of the closer fits that I could find. ’07-08 came off a moderate La Nina (+1.3C on the MEI scale) and progressed into a Moderate La Ninas. A –PDO/+AMO regime favors a –NAO pattern, but with a strong La Nina a Southeast Ridge is imminent this Winter. However, I feel that any arctic outbreaks that do make it to the northern U.S. should be very intense, and a storm or two during this timeframe could lead to a large snowstorm for many people.

Above is the image of my top 3 analogues (I also threw in 1964-1965 although it’s not my favorite analogue). I was also tempted to add 1903-1904 as an analogue but I can’t get accurate data as far as QBO/PDO/AMO go… but adding that does give a somewhat cooler average look, which I will mention later on. As you can see it will pretty much go along with my thoughts: Cold north, warm south and east. The Great Lakes is right on the edge of where the cold and warm collide-leading to several events that could create a tight rain/snow line, also giving the area many ice storms (although each storm should have a different area affected). This winter will have very steep total snow gradients highly affected by each storm. I also think that this winter will be slightly cooler than the analogues above, although it’s more of a hunch than anything else. Some strong blocking periods with a –NAO/-AO will be possible this winter, leading to some brutal cold snaps, as I mentioned previously.

Precipitation Anomalies should be fairly positive as indicated by my top 3 analogues above. Both rainfall and snowfall should be above normal, so long-lived snowpacks could be less frequent due to some warm-ups (Especially in January, where the Southeast Ridge strengthens), but snowfall should still end up above average. This does not mean a record breaking season like last year was for the Mid-Atlantic states, but respectable totals should be seen across the Great Lakes, Midwest, Northeast, Pacific Northwest, and Northern Plains regions. Elsewhere across the south precipitation and snowfall should be below average, with some droughts possible in the deep South.

With Nino Regions 1.2 and 3 continuing to strengthen despite this, I’m favoring an East Based La Nina, with its’ peak coming relatively soon, at least a few weeks before the start of the Winter Season. However, we will still feel the affects of the Southeast Ridge, and the worst of this should happen in January, with February and March to a lesser extent. I feel like The last few weeks of February into early March could really add on to snow totals, especially in the Great Lakes and Interior Northeast regions. Take a look at this image below:

Look at how cold it is for much of the Northern U.S. in these 4 years (All Moderate-Strong La Ninas) in February and March. With Precip. Anomalies looking like this:

It’s hard to not have above average snow in the Great Lakes and Midwest. I’m leaning towards one of the snowier 4 week periods recorded for the last half of February into the first half of March. Even if you take out 1903-1904 the results are very similar… so it supports my thinking of a Cold/Snowy end to winter.

The Forecast:

I’ve explained my reasoning very thoroughly above, and it’s time to get into the actually forecast.

The Winter should really get kicking by the second half of November… with cooler than average temperatures extending into the Northern US for much of November into Mid December. A big storm or two for the Midwest is possible during this timeframe, and it could be quite snowy for the Northern Plains and Great Lakes. Somewhere after the Christmas timeframe I think the SE Ridge starts to develop and hold strong across the southeast, making a real struggle against cold and warm air in the Ohio Valley and Great Lakes regions. Panhandle Hooks and “Bowling Ball” systems that track through the Eastern US should be the predominant storm track along with Alberta Clippers—which can produce several small accumulations that add up quickly. Most of the Southeast and Eastern Coast should end up 1-3 degrees above average while the Interior Northeast, Great Lakes, and Midwest end up at average or slightly below average. Precipitation should be above normal in the Great Lakes, Midwest, and PNW with average to below average precip. in the southern half of the country, along with the East Coast.

February should have the Ridge Collapsing in the east, leading to colder than average temperatures to take a hold of the Midwest and Great Lakes, along with the Ohio Valley and Northeast. This month should be one of the colder months along with March, and above average precipitation and snowfall is likely for much of the Midwest, Great Lakes, and Ohio Valley regions. March should also be fairly similar to February, but after the first 15 days or so the pattern should slowly start to break down.

Winter Temperature Outlook:

Winter Precipitation Outlook:
Winter Snowfall Outlook:
Winter Snowfall Outlook:

This should be an entertaining winter for many of the folks that were disappointed by last year’s winter.