View all posts »
MANY FACTORS FOR THE WINTER FORECAST
October 4, 2012 8:10 PM
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
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!
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
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
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.
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.
The 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
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?
The 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.
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
Temperatures: October-November-December. Forecast Probability: Oct-Nov-Dec
Temperatures: November-December-January Temps: January-February-March
Precip: October-November-December. Precip: January-February-March
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...
As always, I'll keep you posted!
View all posts »