Tim’s 2010 – 2011 DC Winter Outlook

For Tim’s  2011-2012 Washington DC Area Winter Outlook please click here.

Nobody will forget “Snowmaggedon” or the “Snowpocalypse” that crippled the National Capital region during the winter of 2009 – 2010.  The pattern that created the ‘parade of blizzards’ across the Mid-Atlantic region from Washington to Philadelphia was unprecedented. A southern storm track was expected given the strengthening El Nino in the Pacific ocean but the consistent feed of cold air spilling into the region out of Canada was quite impressive.  The North Atlantic Oscillation and Arctic Oscillation remained extremely negative for much of the winter months creating the perfect set up for a parade of Nor’easters to ride up the Mid-Atlantic coast.

NASA’s GOES project put together an amazing satellite time-lapse of the unprecedented pattern which left the Nation’s Capital, Baltimore and Philadelphia buried in snow. Click here to see NASA’s time-lapse depicting the very active southern branch of the jet stream (high clouds moving west to east from Baja California to the Gulf coast) responsible for the active storm track cutting across the Gulf coast and up the Mid-Atlantic coastline.

Source: NOAA Climate Data 1887 – 2010

After the snowiest winter on record in Washington followed by the hottest summer since 1980 what will the Winter 2010 -2011 season bringLa Nina conditions have replaced the strong El Nino pattern of last winter.

According to NOAA, a moderate to strong La Nina will persist through much of Winter 2010 – 2011 (Image below depicts the cooler sea surface waters along the equatorial pacific, circled in red).

La Nina conditions have developed and are expected to persist through Winter 2010 – 2011

La Nina winters are typically mild with below average snowfall. However…The La Nina winter of 1995 -1996 was one of the snowiest winters of the past 20 years when the Blizzard of 1996 (January 7, 1996) crippled the Washington Area with 17 to 30″ of snowAnother La Nina winter in 1999-2000 brought a poorly forecast snowstorm out of North Carolina dumping 2 feet of snow on Raleigh and over 18″ of snow in Washington’s southern and eastern suburbs.

 

The storm track this winter will vary and will be highly dependent on the cyclical behaviors of the Pacific North American (PNA) ridge, North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). The graphic above shows why a positive North Atlantic Oscillation (NAO) or “progressive/zonal flow” between the Azores and Greenland keeps the arctic air across Canada and the storm track to the north and west of Washington (along the northern branch of the jet stream). If you enjoy mild, snow-less winters you had better hope that the NAO remains positive.

  • Summer 2010 featured a pattern of “blocking” as stubborn ridges of high pressure kept much of the United States (southern plains, southeast and Mid-Atlantic) and eastern Europe (Russia) baking in triple digit heat.

 

  • If high latitude ‘blocking’ occurs during the upcoming winter, one Nor’easter could bring a decent snowfall to the Washington Area. The jet stream that travels around the globe is like a fast-moving stream of water. Think of “blocking” as  large rock thrown into the middle of the stream.  The jet stream is diverted around the ‘block’ creating a highly ‘amplified’ pattern that you see in my graphic below.

 

  • The Greenland high or “Greenland Block” causes the jet stream to ‘buckle’ or drop drastically far south unleashing arctic air into the continental United States.  The trough, or ‘buckle’ in the jet stream (U-shaped dip) causes cold air to clash with the warmer Gulf Stream off the southeast US coast.  These ingredients along with disturbances riding the jet stream (river of fast-moving air) produce the powerful Nor’easters that give the Washington Area its snow storms.

 

Bottom Line: A negative NAO can throw a wrench into an overall mild pattern as it did a week before the Blizzard of 1996 when temperatures in the Washington Area were in the 70s in early January!

My Prediction for 2010 – 2011

I spent a great deal of time digging through DC climate data and found similarities between the current pattern (hot, dry summer), active hurricane season, negative PDO, positive AMO, SST anomalies/ENSO cycle/strength and here is what I think:

Temperatures:

  • Based on the analogs I used temperatures may run 2 degrees above average (December, January and February).  However, before you pack away your winter coats, La Nina winters feature a jet stream which can vary greatly… there will likely be several arctic outbreaks.

Snowfall:

  • On average, the storm track will stay north and west of Washington for much of the winter as storms enter the Pacific northwest and traverse the mid-west before exiting off the New England coast.  However, throw in some blocking (negative NAO, positive PNA, negative AO) and a Nor’easter could deliver a decent snowfall to the area. Within the Northeast Megalopolis – I think New England has the greatest chance of receiving above average snowfall .

Bottom Line: I expect slightly below average to near normal snowfall in the Washington Area.

Average Seasonal Snowfall for the Washington DC Region:

washington_dc_region_average_snowfall_dcstorms-com

Average Snowfall for the Washington DC Metropolitan Area:

washington_metro_average_seasonal_snowfall_dcstorms-com

 


20 thoughts on “Tim’s 2010 – 2011 DC Winter Outlook

  1. Pingback: Tim’s 2009-2010 DC Winter Outlook « Storms and Rumors of Storms

  2. Pingback: DC Area Weather

  3. Christian

    Nice read….seems pretty much in line with a lot of forecasts i have been reading.
    What about the shot of a raging +EPO…causing a milder winter for areas including the Midwest through southern New England….or maybe even further north. It seems like there is a decent shot for a strong + EPO and less blocking….causing a warmer winter for a large part of the lower 48…although there will be an arctic outbreak or two. Also your average snowfall map needs a lot of help regarding the areas on the NW side of your map…..western Maryland (Garrett county) gets over 100 inches on average. Also the western VA/West Virginia mountains above 2500 ft do better than 60 inches a year.

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    • Tim

      The oceanic cycles have a huge influence with a “general” pattern (PDO, EPO, AMO, NAO, AO, ENSO etc). The problem is there are always outliers that are impossible to predict. That is why I have two maps… one showing a general zonal flow and then the outlier of what blocking would bring. There are similarities to the general pattern that we are in that match up pretty well with the analog years that I used. As far as my average snowfall accumulation map, you are right, Garrett County MD does ‘average’ 100 inches of snow. My map doesn’t show Garrett County. The map only goes as far west as Allegany… which averages between 30 and 36…. got to get west of Piney and Haystack Mountains, west of Cumberland, to get the orographic enhanced snows.

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    • Tim

      Thanks for your question. Due to the tendency for La Nina winters to produce storm tracks to the north and west of Washington, the likelihood of an over-running event (warm, southwest flow aloft, gliding on top of sub-freezing/near freezing air at the surface) becomes more likely. Areas most prone to severe icing during any over-running WAA (warm air advection) event is the Shenandoah Valley because the cold air gets trapped between the Allegheny mountains and the Blue Ridge mountains. When? Computer models can’t predict with 100% accuracy when an ice storm will hit more than about 5 days in advance.

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  4. Christian K

    Hi, I’m really liking the thorough information you have put out. It seems accurate and in line with a La Nina winter season. I’m not from around the Mid-Atlantic but I’m just to the north in New England specifically NH. We typically experience years between 60-100 inches of snow. Last year though, those big storms that would bring our total to say 80 inches were stopped by that infamous Greenland Block, therefore the Mid-Atlantic would get those big snows. I’m hoping that those two tracks come into play properly so that without the block on the first track snowstorms may miss you down in DC but hit us with a vengeance. The second track seems the most potent because with the jet stream being pushed down your area and my area we be hit hard more or less your area. My main question was, How do you think my winter here in northern New England will pan out? (Above Average or below average snowfall and how much of it this winter)

    -Thanks

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    • Tim

      Thank you for your comments and question. New Hampshire, in particular northern New England has the highest probability of receiving or exceeding their normal snowfall during a typical La Nina pattern. So to be more specific, northern New England could see 100 to 175% of their normal snowfall. This is because the storms tracking out of the mid-west will likely push east through PA/NJ exiting off of the southern New England coast or heading up into the Gulf of Maine. So you are well north and west of this storm track delivering northern New England (VT, NH and ME) some good snowstorms.

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  5. Christian K

    Thanks Tim! I really appreciate you giving me that helpful information. Living in northern New England you have to like the snow or you won’t be happy and being a snow lover I’m glad to hear that the upcoming winter might fufil my expecations of a “good” winter.

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  6. MIKE PAULOCSAK

    Hi Tim. Do you think Ohio will have above normal snowfall for the winter of 2010-2011? I’m pretty confused with what the almanacs are predicting. I live in Holmes county in northern Ohio.

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    • Tim

      Hi Mike. Thanks for your question. Northern Ohio will get some decent snows from two sources this year: the Lake Effect Snow Machine as well as an active northern branch of the jet stream. With that said, I would expect 125% or greater of your normal snowfall this season.

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    • MIKE PAULOCSAK

      Hi Tim. Do you think that there will be several low pressure systems that will travel along the Ohio river up through Pittsburgh? This setup usually produces heavy snow in my region. Also, how many snowstorms do you think will occur in Ohio?

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    • Tim

      Northern Ohio will be north of the average trough axis for a good portion of the winter. There is no way of knowing exactly how many storms will follow a specific track however since arctic air will be clashing with milder air over the mid south that raises the potential for some good storms for your area. Your average snowfall is 30 to 40″. I see that you have had some below average snowfalls during 07-08 and 08-09.

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  7. Tim

    Generally speaking southern Illinois will be very near the average jet stream found during a moderate to strong La Nina. That being said, I would expect a much more active winter than last with near normal snowfall. Ice storms could play a roll in this winter as well as arctic air masses collide with over-running mild air out of the mid-south. All in all I expect a more active winter this year across the Midwest.

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