Hi it's Rebecca here with the third and final part of my winter outlook for 2012-2013. I might refer to two other parts. This outlook will look at the overall pattern and try to give a overview of what the upcoming winter will be like in terms of precipitation and temperature.. The outlook will not tell you how many individual nor'easters, lake effect snow storms, or daily temperatures across the Northeast. I will have a summary at the end. So, if you don’t want to read all through the entire thing, you are allowed to skip ahead. I won’t take it personally. But I will encourage you to read the whole discussion so you can get an idea of what my reasoning was and that goes into making seasonal weather outlook.
Link to part one of this years outlook.
Link to part two of this years outlook.
The ENSO (El Nino Southern Oscillation):
Back during the summer of 2012, I pointed out how most of models were pointing towards an El Nino year. Most of the ensembles were showing a weak to moderate El Nino. CFS v1 and CFS v2 showed a long duration weak El Nino. The SST charts backed this up by showing warm water temps off of Peru and extending well into the central equatorial Pacific. Because of this the National Weather Service issued an El Nino Watch.
However, During the fall the warm sea surface temperature anomaly from the central to eastern equatorial Pacific started decaying, It will in all likely hood disappear by early winter. which means instead of a weak El Nino, it will be neutral.
It's a fact that no two ENSO winter seasons are ever exactly the same, and weak El Nino winters in particular can be very different from each other. Because of this it makes it more difficult to make a long-range outlook. The Summer of 2012 is quite unique. They have been keeping records of the ENSO state for the last 63years. In those 63 years we have never seen an El Nino form in summer and fade in September. I have a very good feeling this is one of the reasons for the 2012 Atlantic Hurricane season being so active.
This will have a big impact on our weather in the Northeast and northern Mid-Atlantic states. Generally when the equatorial Pacific is in a neutral state, the polar jet slide south of us into the Mid Atlantic states. It can also cause an increase in the number of Nor'easters that impact New England. One only has to look back at Sandy and the recent Nor'easter a few days ago, to see this is already happening.
Map with data from the National Oceanic and Atmospheric Administration showing the typical effect on North American winters from ENSO El Nino.
Map with data from the National Oceanic and Atmospheric Administration showing the typical effect on North American winters from ENSO La Nina.
Map with data from the National Oceanic and Atmospheric Administration showing the typical effect on North American winters from a ENSO Neutral .
You can see the jet streams all interact differently with each other during the three ENSO phases. All of which has a profound impact on our weather in the Northeast.
NAO (North Atlantic Oscillation):
This oscillation was the main cause for so much cold air in 2010-2011 but also the reason why last winter was so warm. The NAO is a very good indicator of cold air in the Northeast coast. Only problem is the NAO can only be forecasted out 2-3 weeks at the most.
The NAO has been very persistent in staying negative over the Sumer and Fall. The negative NAO produced a dry flow over New York and New England this Summer, while keeping us away from the searing heat they saw in the Midwest and the incredible drought in the Plains and Midwest. It did cause the Summer in the Northeast to be very dry.
What a negative NAO leads to is blocking over Greenland. During the winter this type of blocking pattern can lead to more storms moving up the East Coast and more arctic air outbreaks in the Northeast. One only has to look at Sandy to see what a negative NAO can cause, the block helped push Sandy back toward New Jersey.
In past outlooks, I've talked about sea ice. The amount of sea ice had been thought to have reached a low in 2007. However back in August of this year. It reached a new low point. Over the last few months it's been coming back. We didn't see a lot of ice melt in 2010-2011 that could have been what lead to the positive NAO last winter.
There is some evidence that supports the idea, of when the polar vortex isn't strong enough to keep the cold air in place over Greenland it leads To a negative NAO. Nature likes to balance things out, so if the arctic is warmer, the temps in United States are gererally lower. The way things are trending we could see a return of a little cross polar flow. But in spite of all this I don't see enough evidence for calling for a mostly negative NAO , As I pointed out in August this will be a mostly positive NAO this year, and I will stick with that.
AO (Arctic Oscillation):
This oscillation is also very hard to predict, it only looks out 2-3 weeks like the NAO. But based on many of the same factors that are working on the NAO. It looks like the AO will predominately negative this winter.
Like the NAO, the AO has a huge impact on winter in the Northeast. One only has to look at the two most recent winters to see the impact. We've been tracking the phases of the AO for the last 62 years. During that time, the winter of 2009-10 was the most negative on record. Whereas the winter of 2011-2012 saw the most positive AO on record. So clearly the AO and NAO are going to be big wild cards
PDO (Pacific Decadal Oscillation):
The PDO, like ENSO, consists of a warm and cool phase which alters upper level atmospheric winds. It's normally a 20 to 30 year cycle. The PDO is currently in a cool phase, with the ENSO going into a neutral and a cool PDO, this would lead Near-normal precipitation. Near-normal to a little below-normal temperatures in the Southeast.
With the polar jet dipped down over the Mid Atlantic states, the storm tracks would favor storms moving over the Southeast and then moving up the eastern seaboard. The conditions in the Southeast could intensify those storms a bit more.
There have been two full PDO cycles in the past century: During 1890-1924 and again from 1947-1976, saw cool phases. Whereas from 1925-1946 and from 1977 through the mid-1990's, the PDO was in warm phase. A look at those decades would show you how winters turned out on average. For instance, the East Coast saw several years of hard winters during the 50's and 60's. Also, a Study by Rodionov and Assel in 2003 showed a direct correlation between weak to neutral ENSO and a cold PDO. The Data showed cold air outbreaks and snowstorms are more frequent around the Great Lakes.
PNA (The Pacific/North American):
This is one of the most recognized, influential climate patterns in the Northern Hemisphere. The PNA is also a short term forecast. So like the NAO and AO it is difficult to forecast. The GFS ensemble has been handling the PNA very well this year. The ensemble Index Forecast indicated the PNA would be weakly Negative in the November 8-15 timeframe, as you can see that is just what we have. It is forecasting the PNA to go neutral to weakly positive very soon.
Although the PNA pattern is a natural internal mode of climate variability, it is also strongly influenced by the ENSO. The positive phase of the PNA pattern tends to be associated with El Niño (Pacific warm episodes), and the negative phase tends to be associated with La Nina (Pacific cold episodes).
I'm forecasting the PNA to be mostly positive for the upcoming winter. With ENSO El Nino being very weak or most likely neutral this will have an impact on our winter in the Northeast.
When the PNA is positive you normally see ridging over the western U.S., and deep toughing over the east. This results cold arctic air in Canada being forced southeastward, which results in below normal temperatures over the eastern U.S. It also can lead to more winter weather events in the Southeast.
Lake Erie and Lake Ontario water temps:
I put this in for those who live in and around the lake effect snowbells. The Big Lakes saw surface water temps that were very high this Summer. However in spite of that , the lakes cooled off very quickly, thanks to the cooler than average fall temperatures. Now there is no correlation between warm lake water temps and the amount of lake effect snow in the winter. Because if there was last winter would have been a bonanza for the lake effect snowbells.
The surface temps for Nov 10 2012 is 50 degrees Fahrenheit. Here is a chart that shows the average water temps from 1992-2010, by month for Lake Ontario. You can see on the bell curve, that the 50F (10C) reading is right where it's suppose to be for this time in November.
As most of us know, there is nothing carved in stone or certain about a seasonal outlook. There are many variables which impact seasonal weather that are not completely understood. So as you read the results of my research keep that in mind. If there is anything we've learned is that there are several bellwether things that can affect our climate and in turn the weather. As I said earlier there has never been a recorded instance when the a Summer El Nino turned back around into a neutral ENSO. So, I'm sure it will throw curves and cause surprises. The winter of 2012-2013 will be an interesting one to watch unfold.
If you take a look at the ENSO diagrams, in the ENSO section above, see how in El Nino and La Nina years, the subtropical and polar jet streams tend to be further apart and interact less. whereas, when the ENSO is neutral subtropical jet and polar jet converge over the northern Mid Atlantic states. Because the two jets are fighting for the same real estate, there are frequent outbreaks of cold air from Canada as well as frequent warm and wet intervals.
Ok with all that said, here is my precipitation and temperature outlook for the winter of 2012-2013. Temperature: It will variable and swing back and forth. We will see moderately long warm spells followed by moderately long cold spells. Because we're still transitioning into a neutral ENSO, I think the first 1/3 of the winter will see average to above average temperatures. Then we will see more in the way of cold air outbreaks with more in the way of below average temperatures. The temps should turn colder than normal during February. So over all, I think the temps in the Northeast will be slightly below average.
Precipitation: As I said, the first part of winter will start off a bit above normal. Therefore, the cold most likely won't phase with the big storms until later in the winter. Some of these storms will make the headlines, since the big cities would be getting impacted by the winter storms. However, the NAO will be a fly in the ointment. So it should a variable, but interesting winter. Time will tell how it all turns out.
Because of increased Nor'easters, the eastern US will see snow from Alabama into New England. Above-normal snowfall for parts of the Northeast and mid-Atlantic. Up here in the Northeast New York City, Philadelphia , Boston, and Albany will be in the corridor to see above average snowfall. While areas in Central NY, Western NY and PA, and the Tug Hill see more in the way of average snowfall. We will see more clipper like systems this winter, but they typically aren't big snow makers. Therefore, I think based on the pattern that the snow belts will see near average snowfall, when the lake effect machine kicks in.
As I said, during an ENSO neutral year generally the storm track moves storms across the Southeast, it will be a wet winter for portions of the Gulf Coast and the Southeast. There will be some severe weather worries for those along the Gulf and parts of the Southeast, especially in Alabama and Florida.
The reason I feel the Mid Atlantic and Northeast will see above average snowfall is an higher than average number of Nor'easters that will track up the coast. Southern New England could do well…A SW flow is often good to them during the winter.
Ok here are my predictions for snowfall in some of the major cities in the Northeast.
Albany...... 60-75 inches.
Boston....... 45 -60 inches.
Buffalo, NY ........ 90 -105 inches
New York City...... 32-38 inches
Rochester, NY....... 95-110 inches
Syracuse....... 120-135 inches
Utica...... 90-110 inches
I want to close by saying, I can’t tell you the number of snowstorms, for it to snow it has to be cold. since there will be warm spells and cold spells. The timing will depend on a storm moving through when there’s a cold outbreak.
That’s it…..hope you enjoyed reading the outlook.
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