El Nino: It's Effect On The Upcoming Winter

Forecasting ENSO Conditions This Winter

Baltimore, MD - MIKE MASCO


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As we round the corner into October, forecasters are eagerly watching the ENSO pattern and how it will play into the upcoming winter. A big piece of my winter forecast this year will focus on the state of ENSO (El Nino vs La Nina) in the equatorial pacific. This region which is broken down into several parts is the focus of how vigorous the southern jet stream will be and help determine how stormy the US will be this year.

During the El Niño phase, eastern Pacific temperatures near the equator are warmer than normal, while during the La Niña phase the same waters are colder than normal. These fluctuations in Pacific Ocean temperatures are accompanied with fluctuations in air pressure known as the Southern Oscillation. NASA.GOV

To make sense of this think about the winter of 2009/2010. That winter featured a very strong El'nino which amplified the southern jet stream delivering several snow events to the mid Atlantic. The winter of 2010/2011 was a very strong LA nina event which also brought severe storms to the mid Atlantic. Without considering blocking (which is critical to get storms to stay along the coast) you can expect a fairly active year, with El nino being the phase favored for the mid Atlantic to see snow!

SO where are we today?

The outlook for ENSO has been very complex. In the beginning of the Summer, our forecast models indicated a strong EL NINO to develop leading into fall/winter. So far, that has not been the case. We currently remain a whopping .1 on the ONI ( Oceanic Niño Index) which is located in the prime spot NINO 3.4 region. The forecast for this spot was a 1.1. We are 1° Celsius below where we should be, WHICH IS A BIG DEAL!

The forecast for EL NINO has been revised on many models:

The forecast shows the majority of the world models indicating a MAX of 1.0C with the possibility of ENSO staying at or slightly above neutral conditions.

If you took just the ONI numbers of .1 to .5 for the season you get analog years of 92/93 ( 24" of snow BWI) , 93/94 (18" of snow BWI), 03/04 (18" of snow BWI), 79/80 (15" of snow BWI).. ECT ECT. Non of which screams snow drought and most not saying well above average snowfall.

I am currently leaning towards a decent amount of blocking for the winter of 2012-2013 with a persistent negative NAO over the next several months. Should the ENSO state stay neutral without hitting moderate to strong levels (as shown in the models) we can expect COLD temperatures overall with normal to slightly above average snowfall, NOT my official winter forecast. BUT a forecast I would give if the conditions stayed this way.

Here is a look at various ENSO solutions vs the state of NAO and AO. Note that blocking or Negative NAO/AO will be KEY to a winter forecast showing COLD & SNOWY !

Here's a look at the current state of ENSO which is NOT pretty. Should a reversal happen and negative conditions prevail, the expectations are winters such as: 2001/2002  ( 2.3" of snow), * 1996/97 (15.3) , 1985/1986 (15" of snow) 1978/79 (15" of snow). These years are a mix of weak and strong blocking BUT indicate snow near or just below average snowfall.





IMAGE on the left shows a downward trend in sea surface temperatures from June/July (the uptick was responsible for the extreme temperatures over the USA). At the time the trade winds were near normal which prevented upwelling of the cold water in NINO region 1+2 however, a pickup in the winds resulted in new upwelling over NINO region 1+2 and 3 forcing the warm water to NINO region 4.







The good news is the trade winds look to weaken some more through September which could lead to a burst of warmer sea water in every region of the ENSO region.


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