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Meteorologist Jim Woodmencey |
The comments and questions are starting to come more often now, about the current El Nino and how it will affect our winter. I blame the bigger media outlets for creating this hype, by attaching monikers to their headlines like: “Super El Nino”, “Strongest El Nino Ever”, and my personal favorite, “The Great Godzilla of an El Nino”.
It makes me
want to throw-up when I read these headlines, especially since nothing
extraordinary is actually happening yet.
To help
squelch some of the hype, by way of plain-old scientific explanation, in this
week’s column I am going to tell you what El Nino is, what the current and
forecasted state of the El Nino is, and what affects this El Nino might have on
weather patterns this winter. In particular, what it might mean for snowfall in
Jackson Hole.
El Nino
Defined
El Nino is
not a monster storm, nor is it a series of monster storms that guarantee copious
amounts of snow. I will guarantee you though, that every single major weather
event that happens between now and next spring will be blamed on El Nino.
El Nino is
part of a larger phenomenon that has to do with the Sea Surface Temperature (SST)
in the equatorial Pacific, collectively known as “ENSO”, or the El Nino
Southern Oscillation.
ENSO comes
in three different flavors: 1) El Nino, when SSTs are warmer than average. 2)
La Nina, when SSTs are cooler than average. 3) Neutral (No-Nino), when SSTs are
near average.
The
strength of an ENSO event is measured by how much warmer or cooler those SST’s
are getting, and how far across the Equatorial Pacific they are spreading. This
in turn creates differences in pressure across the Equatorial Pacific. Sometimes,
in the case of an El Nino, a complete reversal of the normal wind flow pattern may
occur.
Ocean temperatures
down near the equator are relatively warm to start with, but during an El Nino
they may get 1 or 2 degrees warmer. This creates more thunderstorm activity
over the ocean, and the effects of that extend up into the upper atmospheric
circulation, as well. And voila, we have
a disruption of the “normal” atmospheric circulation, which translates to a
change in the weather patterns both north and south of the Equator.
El Nino
2015
I don’t
know if you remember back to May of 2014, but NOAA scientists then were
predicting that a “Super El Nino” would develop for the fall and winter of
2014-15. That never materialized. El Nino conditions (warmer SSTs) never showed
up until March of 2015, too late to disrupt winter weather patterns in the
northern Pacific.
May-June-July
2015 average SSTs warmed up to 1-degree (Celsius) above the average in some
portions of the ocean. Winds were not reversing yet, but they were slowing
down, and more convection was noted; that is, more thunderstorms were showing
up on the satellite photos.
All of that
has led NOAA forecasters to predict: “This El Nino will peak in the late
fall/Early winter with 3-month average SSTs near or exceeding 2-degrees C above
normal. IF this forecast comes true, it will place the 2015 event among the
strongest El Ninos in the historical record (1950-2015).”
The strongest
El Nino winters on record were 1997-98, which peaked at 2.3 –degrees above
normal, and 1982-83, which peaked at 2.1 degrees above normal, for their three
month average SSTs in November-December-January.
What’s
Expected?
If this
does develop into an El Nino of those proportions, then what should we expect
to happen? Usually during El Nino winters the jet stream, or storm track, tends
to dip further south in the Northern Pacific, moving over California and the
Southwestern United States, then cruising across the Southeastern U.S., keeping
those locations wetter than normal in winter.
In both
1997-98 and 1982-83 the Sierra Nevada Mountains in California had huge winter
snowfalls, both were attributed to the strong El Nino.
The Pacific
Northwest and northern Rockies are a bit too far north of the storm track
during strong El Nino’s to reap the same benefits. The opposite though is true
during strong La Nina winters, when the storm track usually does favor the Pacific
Northwest and Jackson Hole, and leaves California and the Southwest dry.
In Jackson,
during the strongest El Nino Winter of 1997-98 we had average snowfall in town
and just above average snowfall in the mountains. In the El Nino Winter of
1982-83, we had below average snowfall, both in town and in the mountains.
When I take
into account all the El Nino years, weak & strong, it’s a 50/50 proposition
for Jackson Hole. Half the El Ninos ended up with above normal snowfall around here,
half had below normal snowfall.
Given all
that info, I wouldn’t get too hyped-up about this “Giangundous El Nino 2015”
just yet for Jackson Hole, it might make for a bigger snowfall winter here or
it might not. Unless you live in Tahoe, then it’s going to be HUGE, for sure,
dude!
Jim is the
chief meteorologist at mountainweather.com and has been forecasting the weather
in Jackson Hole and the Teton Range for almost 25 years.
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