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MANY FACTORS FOR THE WINTER FORECAST


Hey Folks,

As mentioned in the previous post... this past 6 months can't be beat. Only the Spring/Summer of 1999 (or 2006 for Labrador) rivals this past "warm season". So what does that mean for the rest of the Fall and into the Winter Season?

There are a number of factors you can examine when looking for clues as to what the upcoming season will look like. Climatologists are obviously the experts when it comes to this type of thing... and we'll dive into their long range prediction models in a minute. First, a look at the many factors which will no doubt influence this upcoming cold season.
 
Sea Surface Temperatures

As far as Newfoundland goes and even coastal Labrador, this is a very important factor. Our warmer than normal Spring and Summer has sea surface temperatures running 2° to 6° above normal off the coast of the Island!
 
SSTAnom.PNG
I believe this will be a key factor and will no doubt, help to keep the Island warmer than normal into the Fall & early Winter period. Over the past few Winters, we've witnessed first hand what warmer than normal sea surface temperatures can do. Snow storms can become mixed storms, with huge differences in Snow amounts depending on how close you are to the coast. Remember this storm in January 2011?
 
Lack of Arctic Sea Ice

SeaIce.PNG
Back in September, sea ice in the Arctic dropped to the lowest level ever recorded! What does that have to do with our Winter? Well with the lack of sea ice, the Arctic will take longer to cool down this Winter. Some research suggests, a warmer Arctic & less Arctic sea ice can lead to a weaker Polar Jet, which tends to creep further south into most of North America. This is known as a the Negative phase of the "Arctic Oscillation". More on this below.
 
Arctic Oscillation (AO)

Without getting into too much scientific mumbo jumbo. The Arctic Oscillation Index is a measurement of pressure levels in the Arctic. When pressure is lower than normal in the Arctic, the Polar Jet tends to move from West to East, keeping the coldest air "contained" over the Northern Latitudes. This is know as the Positive phase of the AO. When this happens, NL tends to be colder than normal.
 
AO.PNG
When the pressure is higher than normal in the Arctic, the polar jet is weaker. This is known as a negative AO, which allows more Arctic outbreaks into continental North America. However, here in NL we tend to stay warmer than normal. Our warmest Winters of the past 10 (2010-2011) (2009-2010) (2005-2006) have all been during mostly Negative phases of the Arctic Oscillation. There are of course exceptions. The infamous Winter of 2000-2001, was during a Negative AO phase :) Unfortunately, the long term AO is almost impossible to predict this far out, but I'll be watching it closely.
 
 
North Atlantic Oscillation (NAO)

This is a measurement of pressure levels in the North Atlantic Ocean. When we get into a Negative NAO, or higher than normal pressure (the good old blocking High) over Greenland/Iceland, it can cause systems to sit and stall over NL for days. It ruined much of last Spring & Summer, but it can actually help to keep Winter months warmer than normal. Again, we were primarily in Negative NAO phases during those Winter seasons I mentioned above, especially 2010-2011. A positive phase leads to colder than normal conditions.
 
nao_wintertime.jpgThe trend so far in 2012 has certainly been negative. However like the AO, the long term NAO is also extremely difficult to predict this far out. Stay tuned. 
 
WEAK EL NINO

The forecast is calling for a weak El Nino through the Winter months. An "El Nino" is present when surface ocean temperatures in the equatorial Pacific are warmer than normal. Here is how Canada is typically influenced by a weak El Nino.
 
ElNinoWeak.PNG
HISTORY SAYS...

As we've been saying, this was the 2nd warmest Spring Summer combo (April 1st-Sept 30th) on record for most of Newfoundland, second only to 1999. So what kind of Winter did we have? 
1999 Temps.PNGThe Winter of 1999 was slow to start and went on to be warmer than normal for most of the Island. Eastern and Central had plenty of mixed storms in December January and even into February. But despite the warmer than normal temps, the West Coast ended up with a lot of Snow! About 500 cm from November to April! No huge storms, but a little snow each day. The warmer than normal water temps in the Gulf of St. Lawrence must have helped dump plenty of sea effect Snow in the West. That's definitely something to watch for this year as well. In Labrador, temperatures were slightly warmer than normal and snowfall was close to average.
 
THE FORECASTS

Haha, I can hear you now... get on with it Snoddon! So what do the experts and long range climate models say? Well, the long range ECMWF (European) model is predicting a warmer than normal Fall and Winter for Newfoundland, with wetter than normal conditions for Eastern Nfld. Environment Canada of course, releases a forecast of their own. Their October-November-December climate forecast is calling for warmer than normal temperatures for most NL. The probability of warmer than normal temperatures across most of the Island is in the 80-100% range (image on the right). For more on how these maps and how they are developed, click here.
 
Temperatures: October-November-December.          Forecast Probability: Oct-Nov-Dec

TempsFallWinter.PNGTemperatures:  November-December-January           Temps: January-February-March
 
Temps-Winter.PNG
 Precip: October-November-December.                       Precip: January-February-March

PrecipWinter.PNG
SUMMARY
 
The purpose of this blog wasn't just to pass along the Fall/Winter Outlook, but instead give you a taste of just how many factors are at play here. So much can happen, the atmosphere is a crazy beast!!! Having said that, it certainly seems this warmer than normal trend will at least carry us through the rest of the Fall and early Winter. 
 
It's important to remember that warmer than normal doesn't necessarily mean no Snow, or no cold outbreaks. It means that OVERALL, conditions will be warmer than normal during this period. However, that certainly brings a better possibility of mixed Snow/Rain storms, (especially in Newfoundland) snowfall that melts after a few days/weeks and most of all, a delayed start to Winter... again.
 
As always, I'll keep you posted!
 
Ryan

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