Ticker for April 6, 2012

                
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April 6, 2012      April 6, 2012      April 6, 2012      April 6, 2012


El Nino chances on the rise

First a bit of housekeeping (no, we don't do windows). A statement I made
yesterday concerning the sun's downwelling radiation was misleading. Two
statements, actually.

"The energy (ultraviolet) received by the sun is at a maximum in the
summer."

"... allows the sun's rays(ultraviolet energy) at their most intense
to get converted almost entirely to heat energy (infrared)."

Now obviously the earth receives energy from the sun in a broad spectrum of
wavelengths, and mainly from the ultraviolet and visible wavelengths to the
near infrared. Thanks to the gentle reader that sent us an "Ummmm, that looks
a bit off" instead of the big old fat "DUH" that it deserved.

The heat energy emitted from the earth is definitely infrared, however. Partial
credit!

*********************************

With La Nina quickly growing smaller in our rearview mirror, thoughts now turn
towards next fall and winter, and what might be in store for us ENSO-wise. ENSO
(El Nino/Southern Oscillation) can have an impact on our weather, sometimes
significantly and sometimes not-so-significantly. The three phases, determined
by the sea-surface temperature anomalies in the equatorial pacific are El Nino
(warm anomalies), La Nina (cold anomalies), and ENSO-Neutral (normal).

As we've talked about many times, a La Nina tends to give us, on average, drier
and warmer weather in the cool season, that sometimes lasts into the warm
season. The impacts tend to be more important for points south of here, and
also northeast, but we do see the impacts nonetheless.

Now on the opposite side of the anomaly scale, El Nino weights Oklahoma's
climate dice towards a cooler and wetter cool season.

Here is a pretty good diagram detailing the impacts to the U.S. for both. Notice
that Oklahoma is on the periphery of the impacts for both.



We're currently still in the so-called "spring barrier" (March-June) that is
well known as the period of lowest skill for forecasting ENSO conditions. That
does not mean that the skill is zero, however, as noted by the folks at IRI,
one of the leading ENSO knowledge bases in the world.

http://iri.columbia.edu/climate/ENSO/background/prediction.html#barrier

"While ENSO forecasting is most difficult through the late northern
spring, the spring barrier is not impenetrable. Signs of changes in
the ENSO state, such as increased heat content in the western equatorial
Pacific Ocean, are available, so that at least a probability forecast
can be made through the spring barrier. As April, May and June come
along, such probabilities normally become more robust."

The latest predictions have all been trending more and more towards developing
an El Nino episode later this fall after entering ENSO-Neutral conditions this
month. For the first time that I've seen this go-round, the CPC/IRI ENSO
forecast officially has El Nino as the most probable between the three
possibilities as we head into the November-January time period.



The actual odds for each by the November-January time frame are as follows.
These are consensus forecasts, meaning they are basically the average of quite
a few models.

La Nina - 22%
Neutral - 38%
El Nino - 40%

One of the models out of that consensus has been identified by research done
at IRI to show fairly decent skill in the "spring barrier" period. The ECMWF,
or European Model, definitively shows a full-fledged El Nino event developing
later this fall and into winter. Note that temperature anomalies of +0.45C
or greater constitute El Nino, -0.45C or less correspond to La Nina, and
everything in between gets the ENSO-Neutral label.



Another interesting tidbit: all of the ten two-year La Ni?a events between
1900 and 2009 ended up either as a continued La Ni?a event for a third year
(four out of ten), or switched to El Ni?o (six out of ten), with none of them
ending up as ENSO-neutral.

So is a cool, wet winter in store for us this year? Heck, this last La Nina
episode already gave us one of the wettest October-March periods on record,
and the warmth was very much appreciated. Some would say "If that's La Nina,
I'll take another!" The trouble is you might get a 2010-11 La Nina instead of
the latest 2011-12 version.

But let's once again recognize our caveats: Not every ENSO episode acts the same,
Oklahoma is not always significantly impacted, and there are quite a few other
factors that can impact our weather. For instance, the lack of blocking high
pressure as indicated by a strongly positive North Atlantic Oscillation (NAO)
index helped give us our warm winter and March while other similar latitudes
on other continents shivered.

Stay tuned for other updates as we get farther into spring and out of the
"spring barrier" period. As usual, Mother Nature will have the final say, but
we can still sneak a peek at her plans from time to time.

Gary McManus
Associate State Climatologist
Oklahoma Climatological Survey
(405) 325-2253
gmcmanus@mesonet.org