This yearâ€™s winter outlook once again took many hours of research and many factors were considered. Unlike last year when we had a La Nina in the Pacific Ocean, this year we will have a weak to very weak El Nino. Here's just a small part of the items I considered this year and how I think they will play out with our winter of 2012-2013.
El Nino: When looking at the El Nino, you must look at how strong it is, when will it peak, how fast will it fade and where in the Pacific Ocean is it strongest. This year's El Nino is forecast to be weak to neutral. Here's a chart of the forecast of the El Nino and as you can see it is forecast to stay weak at best.
Pacific Decadal Oscillation ( PDO ): I'm a firm believer in the Pacific Ocean having a major impact on our winter weather. Let's face it, oceans cover about 3/4 of the earth so we must pay close attention to what certain ocean currents and sea surface temperatures are worldwide when doing long term seasonal forecasts. This oscillation as the name implies, tends to last for a decade or longer, actually around 20 - 25 years. We were in the "cool" phase of the PDO from about the middle 1940's till the late 1970's. We then went into the "warm" phase of this oscillation from the late 1970's until about 2000. Since around 2000, we have gone back into the "cool" phase and this had to be factored in when looking at the El Nino. El Ninos of the 80s and 90s will not act the same as current El Ninos because of the change in the PDO. I believe this is going to keep us in colder winters for probably the next 1015 years. To give you an example, during the decade of the ‘90s all our winters were above normal. Since 2000, we’ve had 12 winters and 8 of those have been colder than normal. There’s an obvious change that has happened since 2000. Here's a graph of the PDO trends since 1900:
Atlantic Ocean and Gulf of Mexico temperature profiles: Depending on what the temperature profiles look like in these areas will help determine where storms may be more likely to form and where the will track. Will a high pressure be more likely to form in the southeast or will low pressure be more likely there during the winter, this can greatly impact temperatures and storm tracks for us in this area. This year it does not look favorable for a â€œridgeâ€? of high pressure to set up over the southeast part of the country for any long period of time. In the graphic below notice lots of warm water in the Gulf of Mexico and in the Atlantic. The cool area off the southeast coast was colder water churned up by hurricane Sandy in late October.
North Atlantic Oscillation ( NAO ): Just like the PDO, this also will oscillate but on a much shorter time period. The NAO is very difficult to predict much more than a couple of weeks in general and then it's not always predicted well. When the NAO goes into a negative value, we generally have colder than normal temperatures and when it's positive, we normally have warmer than normal weather. The NAO has been mainly running mainly negative the past few months ( it was positive much of last winter ) so the question here is, will that trend continue. My feeling is that we will remain in a negative phase much of the time but there will be swings to positive and this will give us some pretty large temperature swings from cold to warm. Here's the NAO chart since 1950. Notice the very positive values for last winter but very negative for the two winters before that and those winters were cold.
Arctic Oscillation ( AO ): This works similar to the NAO and when negative, we have colder weather and positive brings warmer weather. It was running mainly positive until around October 1st and then went negative and stayed there for the entire month and we ended October 3 degrees colder than normal. It has been bouncing around the last few weeks as you can see from the chart. Once again, I think we are looking at mainly a neutral to negative value here. When the AO and NAO are both negative, we should experience some pretty cold weather and look for that for some of the winter.
Atlantic Multidecadal Oscillation (AMO) This is based on the sea surface temperatures mainly in the northern Atlantic Ocean. It’s currently in the “warm phase” and is running the warmest we’ve seen since back in the 1950s. We are still learning about the AMO but we tend to see more of a “blocking” pattern when it’s in the warm phase and this brings shots of colder weather into the eastern part of the United States during the winter months.
Snowpack in Canada and the US: This helps to show how much modification air masses will have when coming down from the cold far northern reaches of Canada and Alaska. The snowpack here in late November is a little more than normal and about 30% more in southern Canada as compared to this time last year. Notice the difference in snow cover from November 2011 to this November. Lots more snow cover in southern Canada and less in the Rockies this year.
Volcanic activity worldwide: You may say what does a volcano half way around the world have to do with our weather? That's a good and reasonable question but remember that the "weather" travels worldwide and is impacted by things many thousands of miles away ( such as La Nina way out in the Pacific Ocean ). Let me give you an example: On April 10th, 1815 there was a major eruption of the volcano Tambora in Indonesia. The year that followed ( 1816 ) is known as "the year without a summer." That summer there was frost here in the Midwest and even snow in the Great Lakes and New England and this was caused by a volcano eruption thousands of miles away. We did have a couple of notable eruptions in the last three years. One was in Iceland back in 2010 and then later in 2010 a pretty major eruption happened in Indonesia. I believe a volcano eruption in the southern latitudes such as in Indonesia will have a bigger impact on weather patterns than one in the more northern latitudes. Depending on the amount of ash being thrown into the atmosphere and depending on how high into the atmosphere it reached, will determine any impact on weather patterns. The impacts from those eruptions can be felt for around 3 â€“ 5 years so this needed to be factored into the outlook.
Sun activity: The sun had been pretty inactive for a few years but as become much more active recently. There are still many questions on what impact we see with long term temperature predictions and solar activity but another factor looked at again this year. Here's a chart of the solar activity since 2000 and as you can see we reached a low around 2009 and we've seen an increase in the last couple of years but has seen a drop in the last several months and is running lower than forecast and closer to what we had in 2003 and 2004 and both of those years were used in the winter outlook.
Fall trends: I look at how weather patterns in October and November from the past compare to this year and how past winters in those years turned out. Many times we find that a warm November brings a warmer than normal winter and a colder November will many times bring on a colder than normal winter. After taking all those things into consideration along with a few others, I came up with what we call "analog years." These are years when things like El Nino, PDO, hurricane season, volcanic activity and so on are similar. I came up with the following analog years that I used: '51-’52, '76-’77, '78-'79' , '79-’80, '90-’91, '93-'94, '94-'95, ‘03-’04, '04-'05, '06-'07, '09-'10. Some of you may have noticed something in those years and that being 1976-1977 and 1977-1978. Those are the two coldest winters ever on record in this area and produced the last blizzard for the area back in January of 1978! I’m not expecting a winter that extreme but it was the first time in all the years of doing a winter outlook that those years came up in my analog years. I then give each analog year a weight value based on how close I think it is and come up with a formula to produce some numbers to be used in my winter outlook.
So after much work on it this year, here is my winter outlook.
Walker's Winter Outlook 2012-2013 1. Colder than last winter YES...36.1 degrees last winter/34.3 so far this winter 2. More snow than last winter YES...9.4” last year/11.3” so far this winter 3. Colder start to winter than last year YES...1st 1/2 last year was 36.3 degrees/1st 1/2 this winter was 34.8 degrees 4. First measurable snow not till after December 15th YES...Happened on December 26th 5. More windy days this winter YES...21 days so far with winds of 25mph or grater (almost every other day!) 6. Large temperature swings this year (60+ degree swings) YES...66 degrees so far 7. The coldest part of the winter will be the second 1/2 YES...34.8 for 1st 1/2...29.0 so far in second half and won’t get as high as 34.8 degrees 8. There will NOT be a white Christmas (at least 1 inch of snow on the ground Christmas morning) YES...NO white Christmas this year 9. There will be 4 sub zero days (we had 0 last year!) None yet... 10. December will be ABOVE normal temps YES...was + 6.2 degrees 11. January will be BELOW normal temps NO...was +1.6 degrees 12 .February will be BELOW normal temps Don’t know yet 13. Slim chance of any major ice this year YES...Nothing major so far 14. At least 1 record or near record high temperature YES...on December 3rd and January 28th 15. At least 1 record or near record low temperature None yet 16. Biggest snowfall will be from middle January to early February Not looking likely but too early to say for sure
17. “Snow Days” (days with 1”+ snow) will be below normal with less than 9 YES...only 3 through January and we will not reach 9 18. Temperature will be BELOW normal Forecast is 29.5 This is my coldest forecast ever! Normal is 31.2 Don’t know yet 19. Precipitation will be BELOW normal Forecast is 9.25" Normal is 8.88" NO...has been above normal already 20. Snowfall will be BELOW normal Forecast is 15.5" Normal is 16.5" Don’t know yet but so far only 11.3” at the TV station
Record so far is 12-2 86%