Sunday, November 10, 2013

FINAL WINTER 2014 OUTLOOK

Welcome to the final 2014 winter outlook. In this post I will update the original outlook I posted originally in September and briefly summarize the factors behind this forecast and take a more speculative approach for Month to Month temps and snowfall. So lets start off with the assumptions I am using in this forecast: Click all images to make bigger

*For those of you who do not want the details you can skip down to the maps following these bullet points that are derived from the variables below. This area will be marked with a page break*

1. Neutral ENSO signal

  • ENSO stands for the El Nino Southern Oscillation and is basically measures if the temperatures off the coast of South America are colder or warmer than normal. If they are noticeably warmer than normal we are in an El Nino and noticeably colder than normal a La Nina. If there is a very weak negative or positive anomaly then we are in a La Nada. This effects the pattern of the Jet Stream. This year based on observations and model projections we will be in a La Nada which will not be a dominant climate signal, thus we have to look at the other factors below. Here are model projects for the ENSO this winter



2. Above normal snowfall in Eurasia (4th most on record)
  • Eurasian snow cover. Research by Judah Cohen at MIT suggests that if October snow cover in Eurasia is above normal then that results in a negative phase of the Arctic Oscillation. In its negative phase the polar vortex weakens and cold air bleeds into the USA from Canada. October was ranked 4th most since they started recording snow cover in 1967. (For those who know about this I realize the SAI is not favorable for a negative AO but I am still impressed with the large anomaly).  Below are historical anomalies with 2013 being the last bar. 


3. A westerly QBO (Quasi-Biennial Oscillation) that will lower into a more neutral phase
  • QBO is basically a wind pattern in the high levels of the atmosphere near the equator. The winds will cycle from propagating downward (westerly) and upwards (easterly). In its positive phase high pressure over Greenland (-NAO) and Arctic (-AO) are not favored. However I expect this index to go into its neutral range which will again not have a major influence on the overall pattern. If anything moving into a neutral phase from strong positive or negative can promote blocking. 
4. A weak negative PDO (Pacific Decadal Oscillation)
  • This is a water temperature pattern in the northeast pacific. In its negative phase water is warm along the  west coast of Canada and colder out to sea. A negative PDO usually indicates we will see a southeast jet stream ridge present this winter. 
5. A very warm Atlantic ( positive AMO signal) 
  • A warm Atlantic ocean favors blocking over higher latitudes and gives a good barrier for storms to form off the east coast. Image below shows the ENSO, PDO and AMO/Atlantic tripole


6. A Sunspot cycle that is peaking at very low levels compared to other sun cycles
  • The sun goes through multi year cycles of intensity. The currently cycle is very low compared to historical standards as measured by sunspots. Speculation has begun that it is similar to the mini-ice age of the 1700's but that's a topic for a different time. Research suggests high solar activity strengthens the polar vortex and does not promote blocking. Solar activity as recently been very low despite the spike in sunspots in Oct. Although this is a concern, the spike is much less than other spikes we have seen in the fall such as back in 2011 and 2001. Image below compares past cycles to current cycle 24


7. Long range climate models 
  • Mixed signals in this category, but they all favor Southeast ridge. Below are some example for the Dec Jan Feb period:
CFSv2 Major USA Climate model















GFDL Model


NMEE Model


Japanese Model


As you can see there is a model spread and in general the models have not been consistent especially the CFSv2. Joe Bastardi at Weatherbell.com has been a big advocate of the Japanese models consistency and this is the most progressive of the mix.Regardless they all seem to be catching onto the idea of a SE ridge as a result of the negative PDO. 

8. Storm tracks in the fall:
  • There are many that support a theory called the Lezark Recurring Cycle that suggests a storm track pattern establishes itself in the fall and then repeats its cycle after anywhere from 30-60 days. I am not a huge proponent of this theory, however it is important to recognize that many storms have affected the Midwest and lakes regions. We have seen no big Nor'easters which does concern me. 

To sum this all up, if you want a cold stormy winter we have the Eurasian snow cover, AMO, neutral ENSO and decent model support promoting blocking in the high latitudes. However, the westerly QBO, recent spike in sunspots (in a very low cycle) and negative PDO promoting that SE ridge do suggest the contrary. In my opinion the most dominant variable this season will be that very large October snow cover anomaly over Eurasia. It would be a lot different if we had a strong El Nino or Strong La Nina signal or were in an intense sunspot cycle. That is simply not the case so I am looking for a variable to tip the scale which I think is the warm Atlantic and snow cover which favor a cold and stormy winter.


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So here is my graphical forecast based on all these above variables followed by an explanation :

Winter 2014 Temperature Outlook (compared to average winter temps for that region)


Winter 2014 Snowfall Outlook (compared to averages for given area)




Winter this year will be categorized by very cold polar air invading the northern plains and lakes regions from northwest to southeast. At times this very cold air will make it over to the Mid-Atlantic and Northeast giving us colder periods than we have seen last two years. As with any colder winter, it will come in waves. The Southeast will experience above normal temps due to a stubborn jet stream ridge frequently developing over this area. This ridge can also produce some ice storms for the mid-Atlantic at times when it runs into the cold air coming in from Canada. 

In terms of snowfall, I expect three major storms (over 10 in) to effect the eastern third of the country this year, one coming possibly early December,  early to mid January and mid to late February. The warm Atlantic ocean combined with an active southern jet stream will assist in providing a nice baroclinic zone for these storms to develop. In between we will see the central part of the country get big storms (as seen this fall), which will give them the most snowfall relative to averages this winter . The Great Lakes regions will experience many lake effect outbreaks as cold air rushes over the lakes putting them well above their averages for the year. Ski season out west and up in Vermont and New Hampshire should be one of the better ones of the last 5 years. 

Now although more speculative here is a month by month breakdown of temps and snow for the Mid-Atlantic and Northeast

December: 

December will start off relative cold and stormy this year but quickly snap into a more mild weather pattern. I think a storm will develop early and effect areas east of the Mississippi. 

January:

Cold weather will arrive once January is underway and I believe we will see our first big storm of the season during this time frame most likely before mid month.

February:

February should be the most active month this year with overall cold and storminess centered on our forecast area. It is at this time I expect the strongest -NAO. and any potential slow start to my winter forecast to be made up for. 

Risks and overall forecast confidence to my forecast:

Biggest risks to a forecast bust this year will be a lack of blocking developing over Greenland and the Arctic due to recent solar activity strengthening the polar vortex and a QBO that does not drift towards a neural phase. Based on these two wildcard variables I give this forecast a 3 on a scale of 1-5 in confidence. 

Hope you enjoyed reading my insight on this winter. I will cut a video as well this week to verbally discuss this outlook.

@weatherwilly 






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