The Official Winter Outlook For 2012-2013 In The Northeast

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.      





Summary:  

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.




Rebecca

Lake Effect Snow

Hi it's Rebecca again, I've been mentioning lake effect snow lately; so I thought I would post an blog entry about it. I'm sure some of you living outside of the snowbells are curious about what it is. This blog entry will give you a broad overview of what lake effect snow is, how it forms, and where it can occur. As well as the difference between a lake effect snow storm and a synoptic scale snow storm.

Before I get into lake effect snow amounts I want to give you a broad overview of the Tug Hill Plateau. Nestled in the ‘North Country between Lake Ontario and the Adirondacks, Tug Hill is a region of unbroken northern hardwood forests and pristine wetlands drained by a vast network of coldwater streams. The Tug Hill region is located in four Upstate New York counties: Jefferson, Lewis, Oneida, and Oswego. The top of the plateau is relatively flat compared to other areas in New York State.  The most outstanding characteristic of the Tug Hill region is its undeveloped state. There are some small, scattered hamlets and villages along the outer edges of the region, but the core area is heavily forested and relatively unpopulated. In spite of the region being sparsely populated (for some strange reason), a few  places like Boonville, Barnes Corners, Redfield, and Montague occasionally make the news during the winter. Many old timers up here think Tug Hill got its name sometime  around the 18th and 19th centuries. in this time span the term "tugging" was use to describe  areas that were reached by horses or oxen pulling a wagon up a long road to get to a high area.  H.E. Krueger in an article "The Lesser Wilderness - Tug Hill" he claims the Tug Hill was named by two early settlers, Isaac Perry and a Mr. Buell when traveling up the hill west of Turin The Tug Hill covers an area of 2,100 square miles with an elevation from about 350 feet on the west to over 2,000 feet in the east. The area because of its location on the east-end of Lake Ontario, along with the combination of winter winds blowing over almost 200 miles of Lake Ontario waters, and the 2,000-foot rise of Tug Hill creates these heavy lake snows. These storms are responsible for the majority of the over 200 inches of snow the Tug receives annually, turning the region into a winter wonderland. The heavy snowfall is one of Tug Hill’s greatest recreational assets.

            Several towns in the region hold impressive records. An out of the way place called Hooker (near Barnes Corners) recorded 466.9” of snow in the winter of 1976-77. The monthly record for snow accumulation belongs to Bennet Bridges and is 192” in January 1978. The official record for a one day snowfall in NY State belongs to Montague NY. The hamlet had 77” of snow in 24 hours on the 11th/12th of January 1997. Montague also holds the single storm record for snowfall in NY with 95” from January 10th-14th in 1997.  Not to be outdone, Redfield received 141 inches during the 12 day lake effect event of February, 2007. Well that tells you a little bit about this fascinating area...now on to lake effect snow.

Just what is Lake Effect Snow?

Lake effect snow, also called snow squalls, results from cold, arctic air traveling over a relatively warm body of water. The cold, dry air picks up the water moisture and deposits it, in the form of snow, over land areas in- lee of the warmer water. In the case of the Northeast lake effect snows can occur around Lakes Ontario and Erie and to a lesser extent around Lake Champlain and the Sound off of Long Island.  After the passage of a cold front the relatively warm waters of the Great Lakes often create convective instability in an otherwise stable, arctic continental airmass. Therefore, while areas in eastern New York and the rest of New England are clearing up after a recent cold front or storms passage, The Great Lakes communities hold their breath waiting for the lake effect snow machine to awaken. Lake-enhanced snow is different from lake-effect as it is part of an already present system.

How does Lake Effect Snow form?

The first two ingredients

These come under the heading of temperature contrast. The temperature between the lake surface and overlying air promotes "convective instability" that provides the basic energy source for lake effect snow. Ideally, the ambient air temperature at 850mb should be at least 13°C cooler than the surface water temp. Heat and moisture from the warm lakes rises into the "modified" arctic air where it then cools and condenses into snow clouds.   The intensity of the lake effect snowfall also depends upon how far the wind moved over the  lake surface (the fetch) . The longer the fetch, the more moisture the air can obtain and more snow it can form. One reason that mid-lake bands are so impressive is that the fetch is maximized. In the case of Lake Ontario the band can be 150 miles or longer. Major storms rarely develop unless the fetch is at least 50 miles. If the lake has a lot of ice cover; the band intensity is greatly reduced. This is because the ice cuts down on evaporation. Therefore the fetch can't pick up much moisture. This is the reason Lake Erie normally only has lake effect snow during the early winter. Lake Erie is the most likely of the Great Lakes to freeze because it is by far the shallowest. whereas, Lake Ontario is the least likely due to its vast depth and southern location compared to the upper Great lakes.  

The wind speed determines how far inland and the horizontal spreading of lake-effect snow. With relatively light winds, the snow maximum will be closer to the shore. Strong winds tend to blow the snow further inland and produce a snow maximum which is more than 10 miles inland. The heaviest snows rarely occur right at shoreline. Wind speed needs to be light enough across the lake in-order for moisture convergence to occur. The moisture content of the air depends on the previous dewpoint of the air moving over the lake and the moisture acquired through evaporation over the lake. If winds are too strong ( over 50 miles per hour), enough moisture may not be able to evaporate to produce heavy lake effect snow. The best combination is cold arctic air moving between 10 and 40 miles per hour.

The third ingredient

Forecasting lake effect snow can be a huge challenge. Therefore knowing the wind direction is vidal. Wind direction is measured in degrees, as on a compass where 360 degrees is north, 90 degrees is east, 180 degrees is south, and 270 degrees is west. Since Lake Ontario is elongated west-east, and since the Tug Hill is on the eastern end of the lake. Winds with a 270 flow will often bring in a single extremely intense snow band that dumps huge amount of snow. Sometimes the Capital District will be affected by snow off of Ontario this usually occurs when winds 30 to 40 mph set up on a 280-290 flow.

The forth ingredient       This is the topography around the lake.  Elevation plays a major role in lake effect snow production  ( this is called orographic lift ).  This occurs when the wind comes over the flat, nearly frictionless (somewhat ice covered) Great Lakes and then plows into the shore and over the land. This creates friction as well as lift when it hits the land and elevation change. When the air is lifted, you get clouds and eventually lake effect snow showers. For the Great Lakes this would include locations such as the Keewenaw Peninsula of Michigan, the Bruce Peninsula in southern Ontario, the Tug Hill and Allegheny Plateaus of upstate New York; It is estimated that annual snowfall increases by 65 cm (25 1/2 inches) per 100-meter  (slightly more than 328 feet) in elevation gain leeward of the Great Lakes.

 There are other factors as well. Some of these are wind shear, thermal convergence, and  frictional convergence. I will not go into these. However, if you want to know about them. Drop me  an Email and I would be happy to answer any questions you may have.

Where can it Occur?

The lake effect I've been discussing has been on the Great Lakes. However,  these types of snowstorms can occur anywhere cold air moves over a fairly large area of relatively warmer water during the winter.

Below are a few maps that show some of these places.

                                                                   Pictures courtesy of NWS Buffalo

The  difference between a synoptic scale snow storm and a lake effect storm

The main difference between a lake effect snow and a synoptic scale snow storm, is that lake effect snow storms are not low pressure system storms. Instead it is cold, dry air  moving over the  Lakes that brings the snow. Another major difference is a winter storm may last a few hours to a day or so with on and off snow, Where-as a lake effect snow storm will often produce snow continuously for 48 hours or longer in a particular area. Lake effect snows can precipitate as much as 76 inches  of light-density snow in 24 hours with snowfall rates as high as 6 to 8 inches per hour. In fact in 2007 a lake snow band lasted over 10 days; when it was over anywhere from 100 to 141 inches had fallen. The good news was that the band meandered around a lot during that time. Imagine what the snow amounts would have been if the band had more or less stayed in one place.

                        Here are a few pictures of the Tug Hill. To give you an idea what it looks like.

The Winteridge near Lowville run by the Northrup family

There is always a wind on the Tug. So wind skiing can be a lot of fun

One of the windmills outside of Lowville.

A good way to get around in winter

Well that's about it. I hope you enjoyed reading this post. Again I will be happy to answer any questions you may have.

Rebecca