Friday, October 21, 2011

Winter Outlook 2011

 A story to begin...

It was October and the Indians on a remote reservation asked their new Chief if the coming winter was going to be cold or mild. Since he was a Chief in a modern society he had never been taught the old secrets. When he looked at the sky he couldn't tell what the winter was going to be like.

Nevertheless, to be on the safe side he told his tribe that the winter was indeed going to be cold and that the members of the village should collect firewood to be prepared. But being a practical leader, after several days he got an idea. He went to the phone booth, called the National Weather Service and asked, "Is the coming winter going to be cold?"

"It looks like this winter is going to be quite cold," the meteorologist at the weather service responded.

So the Chief went back to his people and told them to collect even more firewood in order to be prepared. A week later he called the National Weather Service again. "Does it still look like it is going to be a very cold winter?"

"Yes," the man at National Weather Service again replied, "it's going to be a very cold winter."

The Chief again went back to his people and ordered them to collect every scrap of firewood they could find. Two weeks later the Chief called the National Weather Service again. "Are you absolutely sure that the winter is going to be very cold?"

"Absolutely," the man replied. "It's looking more and more like it is going to be one of the coldest winters ever."

"How can you be so sure?" the Chief asked.

The weatherman replied, "The Indians are collecting firewood like crazy."

Winter weather forecasting is not so easy.  This is a topic that always gets quite the buzz this time of year.  What will this winter be like?  Will there be lots of cold and snow?  The easy answer is Yes.  But remember that's winter in Northwest Ohio and Southern Michigan!  It is also easy for some to say this to generate hype, and offer no explanation for the reasoning.  I hope you enjoy reading my outlook and explanation, which is based on scientific analysis, forecasting knowledge of our local area and important pattern recognition for weather that impacts our area. 

The Outlook for Precipitation:

 

 The Outlook for Temperatures:

 

 Forecast Discussion:

This forecast is based on probability and is not an exact representation of daily weather.  Rather it is a likelihood or chance that the winter may be above or below average based on temperatures and precipitation for given areas.

 The reoccurrence of the ocean and atmospheric phenomena termed La Nina factored greatly into this forecast for the winter.  La Nina occurs in the equatorial Pacific Ocean waters, but can impact global atmospheric flow world-wide.  Last winter was classified as a moderate to strong La Nina, this winter will have a repeat of La Nina.  Typically what occurs is a northerly shift to the Polar jet stream focusing an onshore flow into the Pacific Northwest part of the United States.  This results in an abundance of Pacific moisture with heavy mountain snows across the northern Rockies and into the Northern Plains.   Typically, most of this Pacific moisture is lost over the Rocky Mountains and does not directly impact our area.  However, this pattern does promote a more “active” storm track into the Great Lakes Region.  The more active jet stream is associated with a higher frequency of storms that impact our area.  These storms typically regenerate over the central and northern plains, drawing up additional gulf moisture to the Great Lakes and Northeast.  The atmospheric trend during La Nina years has been consistent to this fact and has been noted to focus heavier precipitation over the Ohio River Valley. 

 Last year, a La Nina year resulted in 49.7” of snow in Toledo which was +12.3” above normal.  I expect snowfall will again be above normal this winter.  The months of December and January look particularly favorable for higher amounts of snowfall. 

 This active, more northerly flow of the jet stream has consequence to the southern tier of the United States.  With the favored storm track to the north, much of the nation’s southern periphery regions from Texas through the gulf coast and into Florida will be below normal.  This is dire news for locations across the Southern Plains including Texas and Oklahoma that are dealing with one of the worst droughts in decades. 

 Temperature trends tend to mirror that of the precipitation.  Cooler than average temperatures are expected across the northern half of the country while warmer than average temperatures are expected across the southern third of the country.  It is my belief that the La Nina phenomena will have these consistent characteristics for much of the country.  However the East Coast and Great Lakes region has a far greater relationship with other factors that influence our temperatures to a greater degree. 

 The Arctic Oscillation (AO) is an atmospheric teleconnection with greater interseasonal variation on the order of one to two weeks.  It has much to do with the strength and weakness of high and low pressure system over the Arctic.  The fluctuation of this indicator to a negative state typically means that a flush of colder air is headed into the Great Lakes and Northeast.   It is my expectation that our winter will be near normal with respect to overall temperatures, but will experience multiple, shorter duration cold snaps which will be better predicted a few weeks in advance by this Arctic Oscillation. 

 The North American Oscillation (NAO) is a similar measurement that impacts the position of the jet stream and storm tracks of developing and travelling mid-latitude cyclones, particularly over the eastern third of the country.  It is another measurement of semi-permanent pressure areas over the Atlantic Ocean. A strong NAO through the winter of 2009-2010 resulted in all time record breaking annual snows up the East Coast.  Here are a few snow totals:

Baltimore: 77.0”

Washington, D.C: 73.2”

 Philadelphia: 71.6”

 Interestingly enough, during this winter the negative NAO phase was present during January of 2009 which resulted in the 2nd snowiest January on Record for Toledo with 30.7” of snow.    

 
Final Assessment:

 I expect this winter to be above average with snowfall and near normal with temperatures.  However, I believe there will be greater impact from short term indications will need to be monitored more so than La Nina.  These shorter term changes in the atmosphere better measured by the Arctic Oscillation and the North American Oscillation will have my attention on a regular basis over the course of the winter.   It was my goal was to introduce to you and stress the importance of understanding there are many other factors in play here besides La Nina.