December 31: 2015 in Review, Looking Ahead to 2016


We’re wrapping up 2015 with close-to-normal temperatures, and that’s what we’ll start with in 2016 as well.  Clouds this morning will start to thin out by midday…we’ll still see more clouds than sun this afternoon, but I think we’ll see enough sunshine filtering through the clouds to push temperatures up to the mid 40s:
PAUL RPM 4KM Temperature

The clouds will fill back in tonight — despite that blanket of clouds, temperatures will drop to the mid 30s by the time the “note” drops in downtown Nashville at midnight:
It won’t be windy, but bundle up appropriately — that includes footwear!  Still, I guarantee you’ll see someone (or many someones) wearing very fashionable shoes that do absolutely nothing to keep their feet warm.

We’ll finally break free of the persistent cloud cover by Friday afternoon…hopefully.  Cloud forecasts are very dodgy this time of year, so it’s hard to express anything beyond a modest level of confidence in that forecast.  We should see clear skies throughout the weekend, which means cold nighttime temperatures…but it also means our afternoon highs in the upper 40s and low 50s will feel a little warmer if you’re standing directly in the sun.
7 Day PM
Another wave of chilly air heads our way early next week — even so, we’ll stay within shouting distance of what’s “normal” for early January.



Looking back on the year gone by…these are some of the statistics for Nashville:

To expand on those bullet points a bit…most of our snow/ice fell in a three week-stretch in late February and early March, a time frame that still emotionally traumatizes me.  Obviously there are parts of the Midstate that received substantially more snow, and there are parts of the Midstate that received substantially more ice.

We only had two tornadoes during our “peak” spring severe-weather season, an EF-0 tornado in Williamson county in early April, and another EF-0 in Decatur county in May.  But we saw eight tornadoes in Middle Tennessee in July, and four more just last week.  (I don’t have the southern Kentucky numbers available, as the Paducah and Louisville NWS offices haven’t updated their online tornado databases since 2012.)

We’re wrapping up the 2nd-warmest December on record in Nashville, and also the 2nd-warmest November-December combination.  The year as a whole ranks just outside the top 10 warmest since record-keeping began in Nashville in the mid 1870s — 2015 joins 1998, 2006, 2007, and 2012 in the top-15-warmest years on record.  (The last time a full year ranked in the top-15-coldest was 1979.)



We’re just going to look ahead to the next couple of months…even that stretches the limits of statistical analysis, but it’s still fun.  Unless you’ve been hibernating, you know that an unusually (even record-setting, by some measurements) El Nino event in the Pacific Ocean is affecting weather patterns around the globe.  For more on the specifics of El Nino and how it can affect the weather so far from the Pacific, read the post I published in early November regarding El Nino’s potential impact on the Midstate’s winter weather.  Within that post, I said this:

Let me be clear about [the long-range winter] outlooks: they DO NOT mean that we expect exactly normal temperatures and rain/snowfall this winter.  What they mean is that there’s no clear signal pointing toward a statistical likelihood of a warm/cold or wet/dry winter.  Long-range forecasts are just inside of the boundary between science and witchcraft to begin with, so all we can really say about the upcoming winter is:
1) It will be colder than fall and spring.
2) Some snow will fall, but ice is always a better bet in this part of the country.
3) People will complain.

Well, we’re one month through “meteorological winter” (Dec-Jan-Feb) and we haven’t seen any snow and ice, and our temperatures were barely colder than they were in autumn.  In fact, temperatures were so far above normal in December that it would take substantially below-average temperatures in both January AND February to drop our winter average down to near “normal.”  Possible?  Sure.  Likely?  Not really.

To get more specific, let’s do a month-by-month analysis of what January and February have generally looked like during past “strong” El Nino events.  Unfortunately, there are only five such events in the modern record-keeping era, so we’re dealing with a small sample size: the winters of 1957-58, 1965-66, 1972-73, 1982-83, and 1997-98.  Here’s how the January temperatures those years (averaged together) compared to normal conditions:
That pretty much conforms to what we expect in El Nino winters — warmer-than-average temperatures in the northern U.S., cooler along the Gulf Coast…with the Midstate stuck in between.  Those cooler conditions to our south correspond with higher-than-average precipitation amounts:
There’s a very weak signal toward drier-than-normal conditions in the Midstate…but again, we’re dealing with a very small sample size.

A quick look at February’s maps shows a northward shift of the cooler-than-normal conditions, with the Midstate now included in that area:
But there is no such northward shift to the wetter-than-normal region — the climate divisions around the Midstate show either normal or near-normal precipitation amounts:

El Nino is not the only large-scale weather pattern that affects weather conditions over a long time period…there are other “oscillations” that also impact the frequency of storm systems and the duration of warm spells and cold snaps.  But just based on a look at the pattern from the five strong El Nino events on record, you could make a preliminary forecast:
1) warmer than normal conditions to our north, with near-average precipitation
2) cooler than normal conditions to our south, with above-average precipitation
3) no strong signal toward a strong deviation from average temperatures and precipitation near the Midstate.

Lo and behold, that’s pretty much what the Climate Prediction Center is forecasting (EC means “equal chance”):

I’ll return to the point I made to start off this section: the outlooks DO NOT mean that we expect exactly normal temperatures and rain/snowfall in January and February.  What they mean is that there’s no clear signal pointing toward a statistical likelihood of a warm/cold or wet/dry weather in those two months overall.  It’s statistically unlikely that we’ll repeat the exceptionally above-average temperatures we had in December, but that doesn’t mean that Mother Nature will specifically “balance the scales” with below-average temperatures, either.

Weather forecast models only look a couple of weeks into the future — I can tell you that there aren’t any signs of significantly cold weather or wintry precipitation in that time frame.  Beyond that, the general outlook above is the best we can do.  It’s a fundamental property of physics: the arrow of time moves in ONE direction.  Anyone who tells you that they KNOW what’s going to happen is either lying or selling something (probably a Farmer’s Almanac).

About paulheggen33

Morning meteorologist for WNCN-TV in Raleigh.
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3 Responses to December 31: 2015 in Review, Looking Ahead to 2016

  1. almighty e says:

    I’m about to mount an expedition to Hy-Brasil to find the Horn Resounding. Anyone is welcome to join! Bring your cloak invisible!

    (Please someone get that reference…)

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