Flash Weather: "El Niño Watch"

I know I gotta be careful talking winter weather in the middle of June, but in case you haven't heard, the probability of El Niño emerging and maintaining strength through the fall months has increased as of late. Earlier in the spring, the CPC (Climate Prediction Center) issued an 'El Niño Watch' (i.e. a 80% a weak to moderate El Niño solidifies before the end of 2014), with sea-surface temperature anomalies in the eastern Pacific signaling what could be our strongest El Niño event since 2009-10.

Now, some of us may remember how that winter panned out for middle Tennessee. In this case, I'll let the following videos do the talking...



WARNING: These recordings are highly amateur.

At any rate, I am quite stoked about the prospect of another weak to moderate El Niño winter. Why the cheery disposition, you might say? Well, after doing some middle Tennessee climate research, and sprinkling it with some Excel magic, I discovered a striking correlation between ENSO (El Niño-Southern Oscillation) type and middle Tennessee snowfall totals.

If we take the 20 winters since 1950 (when ENSO records begun) that featured 10+" of snow and compare this data to a projected SST anomaly chart, we find 20% occurred during La Niña winters, 35% occurred during neutral winters and 45% occurred during El Niño winters (if you don't understand the difference between El Niño and La Niña, please visit NOAA's ENSO FAQ page).

By now, you may be wondering why El Niño winters are so kind to the hopeless, snow-lovers of the midsouth. Well, for starters, a typical El Niño, regardless of its magnitude, is going to feature strong storm systems riding an active, extended subtropical jet stream track along the southern third of the US. For middle Tennessee, however, the primary wild card is the northern arctic oscillation (NAO). Since a standard El Niño involves a ridge over the northern plains helping to block off arctic air mass intrusions, a negative phased NAO can act as a saving grace to help merge colder air with storm systems riding along the subtropical jet stream. Under a -NAO regime, domes of high heights are displaced towards the Pacific coast and/or off the coast of Greenland, allowing arctic air to surge southward. As seen by the 2010-11 winter, the state of the NAO can overpower the ENSO to produce unexpected, forecast-busting surprises. Unfortunately, the exact phrase of the NAO cannot be determined months in advance; however, it's worth noting early long-range model guidance suggests a snowy east coast similar to 2009-10.

Granted, as we found out this past winter, anything can happen, especially in this part of the country where cold and moist air masses seem to repel each other; however, like any good forecaster, the idea this far out is to note patterns and make inferences based from those patterns. Thus, while I'm not going to dare make a snowfall prediction six months before the start of the next winter, it's still worth noting where the ENSO is going and what it could mean as far as next winter for middle Tennessee.

Moving forward, it will be fun to watch how the other atmospheric telecoms starts to line up with respect to the ENSO, but at least as of now, we have one significant piece of the puzzle shining hope into a cold, snowy pattern for middle Tennessee.

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