THIS FORECAST IS OLD
CLICK HERE FOR THE NEW FORECAST
This is the update to the 2012-2013 Preliminary Winter Forecast. We will start off with an ENSO update and go from there.
|(Refresh page if it stops looping)|
An El Nino Watch was issued just over a week ago by the Climate Prediction Center, as seen in this post. An El Nino Watch is issued when conditions are at least 50% favorable for an El Nino to form in the 2nd half of 2012. As a recap, an El Nino is warming of ocean waters in the Pacific Equatorial region.
The next thing we can see indicating an El nino is something called Outgoing Longwave Radiation, or OLR. Basically, a negative OLR value means more thunderstorms, which signifies an El Nino, whereas a positive OLR index tells of less convection than normal, AKA a La Nina. Let's take a look at the last 5 months of OLR observation.
Something I really want to share with you is the relation of the Pacific Decadal Oscillation to this winter.
source). Considering that we are in and will be staying in a negative PDO, it can be expected that a generally warmer body of water than usual will be sitting in the areas off the Asian coast.
I decided to put in another set of analogues, but this time trying to pinpoint the scenarios that may happen for us. I used years with El Ninos and Negative PDO values (source 1) (source 2).
|Temperature Anomalies in El Nino and Negative PDO Years|
|Precipitation Anomalies in El Nino and Negative PDO Years|
Now we get into the analogues that I am using to make a much better determination of this winter's potential.
Now, let's check out years that followed two La Ninas in a row. The years I used were:
It should be noted that while some of these years could be called neutral, I was looking to see if they were still in negative territory and it seemed that the two years in question remained connected by the same La Nina event, by one way or another.
|Temperature Anomalies in December - February for the years mentioned above|
|Precipitation Anomalies in December - February for the years mentioned above|
What we see as the result are basically El Nino conditions, which is a given, considering an El Nino is expected this winter. It should be noted that the strength of the El Nino was not taken into effect this time around for these years. Looking at temperature anomalies, we see warmer than normal conditions in the northern US, with cooler than normal temperatures and wetter conditions along the Southern US. Dry conditions prevailed in the Ohio Valley.
Now, let's take the same years listed above and pick the ones with weak to moderate El Ninos (classified as +0.5 to +0.9 for a weak Nino, and +1.0 to +1.4 for a moderate El Nino).
As a result, we have:
•1963 (Moderate El Nino)
•1976 (Weak El Nino)
•1986 (Iffy Moderate El Nino)
•2009 (Can Pass for a Moderate El Nino)
1972 was thrown out as it was a very strong El Nino, as was 1997. I did include 1986, which was classified as a strong El Nino. I included 1986 because it was a moderate El Nino in December -February. 2009 was a tough choice. i did decide to include it, despite the fact it was a strong El Nino, because it was borderline strong, and it is one of the analogues that is being buzzed around the weather world recently.
Putting the 4 years listed above, we have these results:
|Temperature Anomalies in weak or moderate El Nino's following a double dip La Nina|
|Precipitation Anomalies in weak or moderate El Nino's following a double dip La Nina|
Let's discuss analogues in specific. 1976 is a good one, in my eyes, because I compared charts for Chicago, Illinois, from this year and 1976, and found both years to have well above average late winters and springs. Towards fall and winter of 1976-77, the temperature sharply dropped and averaged below normal for those seasons.
1986 was a little less on the ball. 1986 involved temperature swings that seemed to equal themselves out, with no defined above average phase or below average phase. However, there are some sharp spikes in Chicago temperatures from 1986 in the first half of the year, and that could correlate with the upcoming winter.
2009 was a curveball. There were small phases of above normal temperatures, and small phases of below normal temperatures throughout the year in Chicago. The first half of the year involved a mainly below normal temperature phase, but the first few months eventually brought a nice, warm temperature swing. This analogue could be a fair one.
1963 had a fairly similar situation as 1976, but 1963 began cool and stayed warm throughout the year before completely tanking in the last month or so of the year. They both follow a cool-down in the last part of the year, but 1963 began a little too cool for my complete satisfaction.
It should be noted that the 1950-1980 timeframe involved a negative PDO, whereas the 1980s were in a warm PDO. That said, I think I will discount it. 2009 was a pretty neutral PDO, on its way to a negative phase, where we are now, so I want to keep it in the game.
As if this wasn't long enough, let's make up one final analogue set using 1976-77, 2009-10, and 1963-64.
|Temperature Anomalies for Weak/Moderate El Nino years following a double dip La Nina in a -PDO|
Something else I am watching is an index called the Quasi Biennial Oscillation, or QBO. It involves wind patterns in the stratosphere. When the QBO is negative, winds are going in a westward direction. A positive QBO leads to winds going in an eastward direction. Now, last winter there was a lot of hype over sudden stratospheric warmings, or SSW's. An SSW happens when the QBO quickly changes from positive to negative, leading to intense and sudden warming.
Now, I decided to look around and see if I could find a relationship between the QBO and equatorial convection. I did find an interesting article, and I was able to determine from the information provided that tropical convection is deeper, or stronger, in the Negative QBO than in the Positive QBO. That said, it would be logical to find a negative QBO in an El Nino situation, due to the fact that El Ninos are characterized by abnormally high levels of convection. This is also logical, as a negative QBO contributes to a Negative NAO, which in turn combines with the El Nino to produce intense Northeast snowstorms.
I also found a correlation between Outgoing Longwave Radiation (OLR) and the Quasi-Biennial Oscillation (QBO). When there is enhanced convection in the equatorial region, the OLR becomes negative. That said, a negative OLR is more tilted to be indicative of an El Nino. Deep convection is characterized by a low OLR, as stated earlier. If the Negative QBO supports deeper convection, then it would only make sense that both the QBO and OLR have a relationship with each other and the ENSO pattern. However, not all of these will definitely happen, but they do have an increased likelihood of happening in correlation with each other.
Right now, we are in a neutral ENSO situation that appears to be heading towards an El Nino, and this has been reflected by a very weak negative OLR anomaly. However, the QBO has recently been tanking to very low levels in recent months. I find that this is not a surprise, as I showed above the upwelling of warmer waters in the ENSO region. Since the QBO is negative, I would expect at least one ENSO region to be in an El Nino state of warmer than normal waters. To be quite honest, I have a feeling that the eastern ENSO areas could pass off having an El Nino right now. If the QBO is negative, I would expect the OLR to become negative soon, as warmer waters at the surface increase convection, keeping the QBO and OLR in negative territory.
Keep in mind that just because the QBO and/or OLR are negative, an El Nino is not guaranteed to form. It is just in the favor that these align with an El Nino.
All of that said, here is my forecast for winter 2012-2013.
-Weak to Moderate El Nino will be here for winter.
-Cool temperatures have the potential to take the eastern US by storm this winter.
-Precipitation could be on the below normal side in the Ohio Valley, but that is not for sure just yet. A weak El Nino can bring above average precipitation to the eastern US, while a stronger Nino does not.
-Considering we may be heading into an El Nino, I am liking the idea that the South US and East Coast will get above normal precipitation. Yes, that means more snow for the East Coast.
-Cold shots ought to reach across much of the Eastern US, so some crops in the Southeast may be at risk.
Thank you so much for reading.