A background first.
An El Nino is warmer-than-normal sea water in the Pacific.
La Nina is cooler than normal Pacific sea surface water.
In an El Nino the warmer waters flow towards the east, in
other words towards the United States west coast.
The opposite happens in an La Nina.
IT IS NOT A STORM. This misconception seems to have
been made recently so lets clear that up now.
It is simply a variable of the earth's climate, not some
gigantic demon (or Godzilla as some national media outlets have described it)
coming to ravage the country.
It's warm water, pure and simple, but it DOES have an effect
on the country and on us here in Michigan.
Why? Simple, Jet stream.
The Jet moves around north and south and fluctuates from
season to season.
It can also fluctuate day to day and these fluctuations are
what help systems track our way and help to fuel us with moist, warm, or cold
air.
The warmer waters in the Pacific change the way the Jet
behaves and increase its temperature which then moves over the Jet like a
conveyor belt.
It can change some seasonal things so lets dive right in and
see what could happen.
EL NINO'S EFFECT:
In strong El Nino years the weather is characterized by
increased moisture in some areas and warmer than normal temperatures.
It is no secret that the weather and atmospheric
circulations depend a lot on the ocean temperatures and circulations.
So if you take a system moving over warm Pacific waters, it
is pretty certain it will be on the warmer side of things.
Plus, warm moist air rises so now you add a lot of moisture
to the air that has to come down somewhere.
That somewhere first is California.
I expect there to be a lot of rain coming to the west coast
and that is both very good, and terribly bad.
A lot of rain at once can cause massive mud slides which has
happened in a past El Nino year I will talk about in a second.
BUT, it will do a lot to replenish their reservoirs and add
water to the mountains there in the form of snow.
They need water, badly, so our best hope is the added
moisture comes in a gentle wave instead of a deluge all at once.
FOR MICHIGAN: A strong El Nino year means warmer
winter on average and more just plain wet conditions and less snow.
So depending on who you are you'll either be far more
excited for less shoveling and extra heat, or be the other end of the spectrum
and wish you could be sledding.
PAST STRONG YEARS-EXAMPLES COMPARED TO CURRENT STRENGTH
AND TREND:
There are 2 big years to focus on as potential benchmarks:
winter 1982-83 and winter 1997-98.
Our average snowfall for a winter season is around the 44 to
45 inch mark, give or take a couple tenths of an inch of snow.
In 1982-83 we got only 26.5" of snow, and in 97-98 we
got only 28.3" of snow.
PLUS, in 1982 we were in the 60's for Christmas!
In 1997-98 we had one of the warmest January's on record
here with Detroit seeing days in the 60's.
HOWEVER, winter and seasonal outlooks in general are awfully
difficult to come up with accurately. Look at last winter where the original
outlook was for a warmer than average winter and we froze.......again.
But El Nino gives a huge confidence boost as meteorologists
because the actual, tangible data is there. You can see it, feel it, measure
it.
We base the measure for the winter off of a guess the trend
will continue but it sure doesn't look like it's stopping.
Before anyone says to me months from now while standing in
half a foot of snow "You said it was going to be warm!" you have to
remember, it is still winter.
Michigan will still see snow, and the season total may be
made of 1 or 2 larger storms and a couple small bursts.
But the overall season would be much warmer with more warm
days, less overall snow, and a lot of sunshine.
