"Fall" and hurricane season end, so here's the winter outlook!

Meteorological Fall Comes to an End

As the calendar turns to December and minds collectively turn towards the end-of-year holiday season, meteorologists see a changing of the seasons. While the official start of winter is when the winter solstice occurs (December 21), "meteorological winter" for climate record-keeping purposes starts December 1 and runs through the end of February. That means the record books are closed on autumn. We'll have more detail in the November climate summary in a few days, but preliminary data indicates that the average temperature for fall this year was 65.1 degrees, which is above the long-term average of 64.4 degrees. Rainfall, however, was below normal, totaling 8.92" for September-November versus the average of 11.70". 

Winter 2021-2022 Outlook

So what does the crystal ball look like for winter, perhaps the most anticipated season of the year? Early prognostications are driven primarily by the state of El Nino-Southern Oscillation (ENSO), but there are many other factors that make it pretty unpredictable, especially in the south. What is likely is the current La Nina climate pattern - an oceanic pattern that features cooler than average waters in the central Pacific Ocean - will continue through the winter. In fact, it's a "double dip" La Nina after the pattern dominated last winter, receded this summer, but reappeared in the fall. The typical impacts from a La Nina pattern are shown below. The Mid-South tends to be in the battle zone between wetter conditions to our north and drier to our south, while temperatures tend to be above average.

Typical impacts over North America during a La Nina winter. (NOAA)

The official Winter Outlook from NOAA is very close to what we would expect from a La Nina pattern and is shown below. There is a 40-50% chance of temperatures averaging above normal and odds of wetter than average conditions dip as far south as west TN. 

The temperature outlook for December-February 2021 from NOAA.

The precipitation outlook for December-February 2021 from NOAA

Remember that these are predictions of average conditions over a three-month period. That means there can certainly be cold spells in an overall warm pattern, or rainy periods in a dry month. In fact, you will certainly remember the Arctic outbreak last February that occurred in a very similar overall pattern to this winter. Other factors and atmospheric patterns will dictate the day-to-day conditions.

Atlantic hurricane season also ends

The start of December also means that the Atlantic hurricane season has also come to an end. It also marks the first time that the pre-defined list of 21 storm names has been exhausted in consecutive years. The 2021 season featured exactly 21 named storms (the third most in a year), seven hurricanes (five of which classified as "rapidly intensifying" during their life cycle), four major hurricanes, and eight U.S. landfalls. It was also the sixth consecutive "above normal" season and seventh consecutive season in which a named storm formed before the official start of the season on June 1. (NOAA's outlook published in May called for 13-20 named storms, 6-10 hurricanes, and 3-5 major hurricanes.)

Erik Proseus

MWN Meteorologist

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So... is winter over??

You won't believe (or maybe you would) how many times I've been asked whether winter is actually over. The short answer? I think so.  Let's take a look...

First, if you think this was a "year without a winter," you are only partially right. It's been a while, and the recent heat has probably seered some brain cells, but December had some very cold periods. In fact, this blog spoke of at least three "Arctic blasts. Interspersed between some very warm days were multiple days with highs in the 30s and 40s. In fact there were low temperatures of 15° and 18° on consecutive days mid-month. Overall, December was about 1° above normal, mainly due to a few very warm days offsetting those cold ones.

Moving on, while January was very warm overall, we had 4 consecutive days with highs in the 20s and 30s and snow fell on Friday the 6th with most kids getting a snow day. There are many years when a snow day doesn't happen. Snowfall will end up below normal this year, but we only average about two small snow events a year. We got one. (And yes, I'm predicting we won't see another.)

Remember this snowfall on January 6? We didn't completely skip over winter this year!

After a top 10 warm January, February is likely on track to out-pace the warmth of January. As of the 20th, the average temperature for the month ranks third warmest on record...

Top 10 warmest February 1-20 periods on record, according to NOAA. 2017 ranks #3.

...and the forecast models indicate well above average temperatures to close out the month, with the exception of this weekend behind a Friday cold front.

The American-made GFS model ensemble system forecast temperature anomalies through the end of the month show plenty of warmth, with one "break" of near average temperatures this weekend behind a cold front that moves through Friday. (WeatherBell)

Looking towards March, we have a few products that can give us hints on what's to come. The first is NOAA's Climate Prediction Center outlook for days 8-14, which covers the first full week of March.

NOAA's day 8-14 temperature outlook, covering the first week of  March, expressed as percentage chance of above (below) normal. The Mid-South has a 60% chance of above normal temperatures. (NOAA/CPC)

No signs of any cold blasts there, with a 60% chance that temperatures will average above normal and a less than 10% chance they will be below normal. The week 3-4 outlook, which covers the period through the middle of the month shows a bit more promise, but even slightly below normal temperatures for that time of year would indicate highs near 60 (not winter, but not 80° either).

NOAA's week 3-4 temperature outlook, covering the period March 4-17, expressed as percentage chance of above (below) normal. The Mid-South has a 50% chance of below normal temperatures according to this graphic. (NOAA/CPC)

Finally, the NOAA temperature outlook for the entire month of March (issued last week), shows slightly enhanced odds of above normal temperatures for the month (first image below), while the March-May "spring" outlook indicates a decent chance of temperatures averaging above normal  (second image below).

NOAA's March temperature outlook, expressed as percentage chance of above (below) normal. The Mid-South has a 33-40% chance of above normal temperatures. (NOAA/CPC)

NOAA's March-April-May temperature outlook, expressed as percentage chance of above (below) normal. The Mid-South has a 40-50% chance of above normal temperatures (which according to their methodology means a 33% chance of near normal and a 17-27% chance of below normal temperatures). (NOAA/CPC)

Shifting from NOAA to the European model ensemble (basically the European model produced 50 times with slight variations and averaged), here is the latest temperature anomaly (departure from normal) map for the next 46 days (though April 6), also indicating above average temperatures east of the Rockies.

The European Ensemble model system predicts above average temperatures (overall) for the next 46 days. (WeatherBell)

And just for fun, the precipitation anomaly for the same period, showing the potential for a wet 6 weeks in the southeastern U.S.

The European Ensemble model system predicts a wet 6 weeks ahead for the southeastern U.S. (WeatherBell)

Does all this mean we won't see ANY more cold weather? Not necessarily. In fact, some areas will be back into the 30s again Sunday morning. However, it's POSSIBLE that the last freeze of the year has occurred in the city. The average date of the last freeze at the airport is March 19, which is still nearly a month away. I certainly can't rule out that still occurring. Our last 32° reading was February 16, While that is very early, if there isn't another freeze, it won't be the earliest last freeze on record, which was set 4 days earlier, on February 12, 1878!

The average last frost date is March 29, using 36° as a proxy for frost formation. There's still plenty of time for some 30s to affect the buds and blossoms that are arriving 2-3 weeks ahead of schedule, so if you have an itch to plant something, understand that frost, or maybe a freeze is still possible for some time yet.

The USA-National Phenology Network tracks the start of spring using models based on the Spring Leaf Index. Shown above is the spring anomaly through February 20, indicating that spring arrived in the Mid-South 2-3 weeks ahead of schedule.

So by all indications, spring has sprung and Punxsutawney Phil is #FakeNews! Just don't be surprised by a few chilly mornings mixed in with the occasional 80° day over the next month or so!

Erik Proseus
MWN Meteorologist

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El Nino ramps up - what it means to Mid-South weather

Climatologists and environmental scientists expected El Nino to appear over the winter of 2014-'15 and, though it never officially did, it appears it was only tardy, not absent. As we head into summer, NOAA has now indicated that a weak but strengthening El Nino is present and could become one of the strongest in quite some time later this year. In fact, NOAA is forecasting a higher than 80% chance that El Nino will continue through the remainder of the calendar year.

Sea surface temperature anomalies (departure from normal - orange to red above normal) increased over the past 3 months in the El Nino region from the west coast of South America into the central Pacific indicating a strengthening El Nino.

The various long-range computer models almost all support a strengthening El Nino this year with some indicating it could become very strong. 

El Nino's effects on winter weather are fairly well documented and understood (though local variations certainly exist and no two El Nino patterns are the same) but the effects in summer tend to be more muted and less predictable. There have also been many fewer instances of a strong summertime El Nino in recent decades, thus there are fewer cases to look back to and draw conclusions from.

So how will this summer's El Nino affect the Mid-South?

Dr. Jeff Masters, who writes on Weather Underground's Wunderblog, recently discussed the same topic and recounted the effects of two similar cases in particular, the summers of 1982 and 1997. Both of these summers were generally cool and wet across a large part of the continental U.S. Both of these summers were slightly below normal temperature-wise in the Mid-South as well.

El Nino also tends to bring wetter than normal conditions to the southern U.S. owing to a persistent subtropical jet stream. Masters indicates that "signals remain positive for widespread summer moisture." In fact, NOAA's June-August climate outlook shows the Mid-South on the eastern periphery of a large area of cool and wet conditions that they believe will dominate the central U.S. So, despite short-term trends that indicate a warmer-than-normal start to June, the summer average could end up a bit cooler (not to the exclusion of some periods of hot weather that we know are in store!).

The June-August temperature trends (left) as forecast by NOAA indicate a better than even chance of cooler than normal temperatures across the central U.S. with the western part of the Mid-South possibly cooler than normal. Precipitation-wise (right image), a large part of the Rockies, central, and southern U.S. could be wetter than normal, including the Mid-South.

It's also worth noting that there tends to be a marked decrease in Atlantic tropical activity during El Nino summers as well, owing to increased storm-destroying wind shear in the favored tropical formation regions. However, that could be partially offset by elevated sea surface temperatures (SSTs) in the Gulf of Mexico and Caribbean. So while the overall pattern could be quiet this year, it only takes one storm to feed on higher than normal SSTs near the U.S. to cause big problems for coastal residents. Tropical outlooks for 2015 that have been issued so far have indicated a below normal season. NOAA's Atlantic basin outlook, released  May 27, calls for a 70% chance of below normal activity due to El Nino. More specifically, NOAA predicts 6-11 named storms, 3-6 hurricanes, and up to 2 major hurricanes.

We'll see how the summer plays out - it will definitely be interesting to monitor!

Erik Proseus
MWN Meteorologist

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The Results Show: Reviewing our 2014-2015 Winter Outlook

Now that it is mid-March with highs in the mid 70s, we can probably safely safe winter 2014-'15 is over for the Mid-South. That doesn't mean we won't see temps drop below freezing for a couple of hours some morning or frost on the ground. In fact, on average the last freeze date is still about a week away (March 22 at Memphis International Airport, later in outlying areas), but we don't see it getting that cold this week!

Methodology behind this year's outlook

So, in the name of full transparency (and perhaps curiosity more than anything), I thought it would be educational to re-visit the winter outlook I prepared early last November. As I said then, "if I got paid for accurate long-range outlooks, my family would be hungry!" As a reminder, my outlook was based on a few key pieces of data:

• 10 analog years with weak El Nino conditions (1952, 1953, 1954, 1959, 1970, 1977, 1978, 1988, 2005, 2007)
• Recent research by NWS-Memphis on El Nino impacts in the Mid-South
• Research and 2014-'15 winter outlooks composed by WeatherBell, WeatherTrends360, and NOAA

Going into this winter, there was a better than 50/50 chance we'd see weak El Nino conditions before the season was over. As it turns out, NOAA declared just this month that El Nino had officially arrived. So while it didn't start until March, it actually takes a few months of above average Pacific sea surface temps to make it official. We were basically dealing with weak El Nino conditions in the Pacific for at least part of the winter.

The MWN Winter Outlook

Here's the outlook I made November 10, 2014 for the upcoming winter:

1. Temps slightly below to below average (possibly as cold as 2013-'14)
2. Precipitation near average
3. Snowfall near to above average (average is about 4")
4. Periods of large temperature swings and possible severe weather

For the sake of this discussion, since we had some of the earliest measurable snowfall on record last November and the biggest snow/ice events into the first week of March, I'm calling "MWN Winter" the period from Nov 10-Mar 10. I'll also look at the period meteorologists define as winter, which is Dec 1-Feb 28.

The Results... drum roll please

Let's look at each point in succession:

1. "Temps slightly below to below average" - CORRECT - The most recent 30-year average temperature for Nov 10-Mar 10 is 45.6°.  This year's average was 42.0°, which is more than 3.5° below normal, but not quite as cold as last year (41.3°), which will be remembered for a January that was colder than any since the mid 1980s. This year, February was #7 coldest on record. In 141 years of record-keeping, this period ranked #26 coldest, or in the top 20%. For meteorological winter, this year's average was 41.1°, which was 2.7° below the most recent 30-year average of 43.8°. 
2. "Precipitation near average" - INCORRECT - Total precipitation for the Nov 10-Mar 10 period was 13.22", which was 6.28" below the latest 30-year average. In fact, parts of the metro were classified as being in "severe drought" during this winter. For meteorological winter, precipitation totaled 8.25", or 5.63" below normal.
3. "Snowfall near to above average" - CORRECT - Snowfall (which includes sleet, but not freezing rain) averages 3.8" a year in Memphis based on the 30-year climatological record used by the NWS. For the entire winter (our Nov 10-Mar 10 window), total snowfall was 6.1". Since some of that was outside the traditional "meteorological winter" period, the total is higher for MWN winter than meteorological winter (2.3", or 1.1" below average). We firmly believe that the 3.1" in March in 0.2" in November (which was some of the earliest on record) should count though!
4. "Periods of large temperature swings and possible severe weather" - PARTIALLY CORRECT  - Starting with the second point, there were no severe convective storms this winter, which was what we were alluding to in this outlook. However the series of ice and snow storms that affected the Mid-South from mid-February to early March arguably had a wider impact on the entire metro than a round or two of severe thunderstorms would have. I believe these were "severe" for winter, but will only take half-credit for them! As to the point of large temperature swings, I think I nailed this one. Looking strictly at daily average temperatures (which averages the high and low for a day) between Nov 10-Mar 10, there were a total of 30 instances in which the daily average temperature varied by more than 10°F on consecutive days (many of them were much more than 10°). This is not a swing of 10° between one day's high (or low) and the next day's high (or low), it is the average daily temp moving by that much, which is harder to accomplish. All in all, despite the general cold weather pattern, we saw frequent large temperature swings over the course of the winter, from warm to cold, or from cold to colder!

In sum, 3 of the 4 points made in this year's winter outlook were correct, which surprised even me when I went back and re-visited the winter numbers. I can't guarantee that kind of accuracy on winter outlooks going forward, but this year I seemed to be on the right track!

What were your overall impressions of this past winter? Comment below or drop us a Facebook comment or tweet! We'd love to hear from you!

Erik Proseus
MWN Meteorologist

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MWN 2014-2015 Winter Outlook

Winter appears to be starting a bit early this year, as Arctic air is poised to ooze south of the Mason-Dixon by mid-late week. But is that a foreshadow of things to come or just an anomalous event in what would be a reversal of last year's cold winter?

This year's MWN Winter Outlook is presented below in video format and includes some background on processes such as ENSO that ultimately affect our seasonal climate, methodology behind the outlook, as well as our official forecast. I hope you'll take 25 minutes to watch the entire presentation, but if you just want the bottom line, jump ahead to about 21 minutes into the video or see below for the bullet points.

MWN Outlook Methodology:

• Based on 10 analog years with weak El Nino conditions (1952, 1953, 1954, 1959, 1970, 1977, 1978, 1988, 2005, 2007)
• Recent research by NWS-Memphis on El Nino impacts in the Mid-South
• Research and winter outlooks by WeatherBell, WeatherTrends360, and NOAA

MWN Winter Outlook:

• Temps slightly below to below average (possibly as cold as last year)
• Precipitation near average
• Snowfall near to above average (average is about 4")
• Periods of large temperature swings and possible severe weather

Of course, my typical caveats on long-range outlooks apply. I typically don't look beyond 7-10 days when forecasting and spend a great deal of effort focusing on the upcoming 36-48 hours. As a meteorologist and not climatologist, I have no formal training in long-range forecasting, but I do follow and learn from those that do. And if I got paid for accurate long-range outlooks, my family would be hungry!

The goal of producing these outlooks is as much to encourage preparation and education with regards to winter weather as it is for accuracy (though I would certainly rather be right than wrong!). Last winter was a cold and long one with some areas (especially the northern metro) experiencing multiple icing events and extended power outages. Plan ahead for how you will handle extended periods of cold weather and potential snow and ice.

Winter weather is extremely difficult to forecast, even sometimes on the day of the event (see March 2, 2014). Slight variations in temperatures (surface or lower levels of the atmosphere), available moisture, and previous or ongoing precipitation can all directly affect the type and amount of precipitation that occurs. These differences can also vary widely in a small geographic area. Once again, refer to last winter for obvious examples.

Have a safe winter and stay tuned to MWN for the latest information ahead of potential winter weather events!

Erik Proseus
MWN Meteorologist

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Cool weather expected to turn much colder next week

If you don't like cool weather, I recommend you stop reading now. OK maybe not, but this post is going to be all about below normal temperatures, so put on your gloves and earmuffs and continue on, intrepid readers!

What's average?

We'll start with where we're supposed to be, because sometimes that gets lost in the day-to-day forecasts. We get used to a certain pattern and don't realize that it's really supposed to be cooler/warmer than what we've experienced. The shock comes when it warms up/cools down to near normal and we instinctively think it's "abnormal." So, our average high on November 6 is 66 and average low is 47, resulting in a daily average of 57. Record highs are averaging the lower 80s right now and record lows are in the mid 20s.  Baseline established...

So what about this cold weather I am hearing about?

You may have already seen plenty of talk floating around on social media about typhoons resulting in Arctic outbreaks, polar vortices, and maybe even a "crap app" that had snow on its forecast for Memphis on November 15. I'm here to set the record straight.

It's all true. Kind of. (Yes, the app had it. No, it's not in my forecast!)

Former Super Typhoon Nuri in the northern Pacific is indeed making waves (massive ones in the Bering Strait, and even contributing to some in the upper atmosphere) that will result in an intrusion of cold air into the U.S., mainly east of the Rockies by next week. Before then, last night's cold front and another Saturday (which should pass through dry) will bring below average temperatures through Sunday, including upper 30s for morning lows.

By Tuesday, a much stronger push of cold air invades the central portion of the U.S., with a cold front forced southeast. We'll warm up nicely on Monday ahead of the front (upper 60s), then as the front passes through, rain chances go up Tuesday and temperatures will probably start to fall by late in the day. The airmass behind the front will have originated as Arctic air and, though modified, will likely bring our coolest weather so far this fall for the latter half of next week and into the mid-month weekend.

There is talk that this pattern of below normal temps could continue right through the end of the month... I'm not ready to go there yet, but we'll see.  Let's take a look at some graphics that will paint a picture of just how cold we're talking. (Click any image for a larger version. All graphics except the last courtesy WeatherBell Analytics.)  For our detailed MWN Forecast for the next 7 days, click here.

GEFS ensemble model forecast of departure from normal surface temps for the period Nov 7-12 (in Celsius). The Mid-South is depicted as 3-4C below normal, which would equate to about 50F vs our expected average of 55F.  Cool, but not too bad.

GEFS ensemble model forecast of departure from normal surface temps for the period Nov 12-17 (in Celsius). The Mid-South is depicted as about 7-8C below normal, which would equate to about 40F vs our expected average of 54F.  Now that's cold!

GEFS ensemble model forecast of departure from normal surface temps for  just one day, Nov 13 (in Celsius). The Mid-South is depicted as 9C below normal, which would equate to about 37F vs our expected average of 54F.  That's a daily average, meaning the low is colder than that and the high is warmer than that, but they average to 37. Whoa.

The GFS model surface forecast for next Thursday morning shows massive high pressure extending from central Canada to the Mid-South. The freezing line is the dark blue line that extends from the east coast through the Deep South into the Rockies. A HUGE portion of the U.S. would drop below freezing given this scenario with single digits (or lower) over the Northern Plains.

The GEFS ensemble model forecast highs and lows for the next 10 days shows the sharp dropoff in temps the middle of next week with a moderating trend starting the following week. These are NOT our forecast temps but provide an idea of the magnitude of cold air this model is forecasting. (BTW, our other long-range models agree fairly well.)

The official temperature outlook from NOAA for Nov. 12-16 indicates a 90% chance of below normal temperatures over a large portion of the Mississippi Valley and Upper Midwest. It's extremely rare to see 90% on these daily graphics, which speaks to the near certainty of this cold air outbreak, but not necessarily to its magnitude. Graphic courtesy NOAA.

So is this just a taste of things to come this winter or a one-shot deal? My 2014-'15 MWN Winter Outlook might provide some helpful information in that regard! I presented it to attendees of the NSA/Mid-South Winter Weather Workshop in Millington this morning and will be releasing a video blog containing the information to our MWN Insiders on Friday. The rest of you will get to view it a few days later, probably on Monday. If you want to see it early, we recommend you join our Insiders newsletter here!

Are you hoping for a cold and snowy winter or just hoping it goes by quickly and spring comes early?

Erik Proseus
MWN Meteorologist

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What do they say about broken clocks?

From the Farmer's Almanac, via the NY Post, I find this screen capture incredibly ironic:

The article above, dated April 14th and quoting the Farmer's Almanac (which I pulled up this morning on the NYC Post website), indicates an "oppressively hot and humid summer" for the New York area. In the margin are suggested articles relating to weather (that are obviously more recent). There we find  a headline stating "Summer 2014 is the coldest in a decade" (again, relating to New York). Wait a minute...

Say it ain't so!? The Farmer's Almanac -which boasts an 80% accuracy rating - was wrong (again)??

I pulled this year's stats for Central Park for June 1-August 25 (today). The average temperature has been 74.2, which is almost exactly the median over the nearly 140-year record at Central Park. In other words, it was an "average" summer by that metric. However, as quoted in the "coldest in a decade" article above, I also discovered that the highest temperature so far this summer in Central Park has been 91 degrees, which is the 3rd coolest high temperature ever recorded during a Central Park summer since records began (1876).

Graph showing the highest temperature recorded between June 1-August 31 each year at Central Park. In 2014, the highest temp of 91 is the 3rd coolest high temp ever recorded.

So why do I bring this up?

Because people are already asking what this winter will bring. Winter outlooks are starting to pop up, including the latest from the Farmer's Almanac, which predicts "colder-than-normal and wetter-than-usual weather for three-quarters of the country east of the Rocky Mountains,” according to the AP.  (By the way, the Farmer's Almanac says "chilly and wet" for the southeast U.S., while the OLD Farmer's Almanac predicts "much colder than normal, with below-normal precipitation." Which Almanac should I trust??  Are OLD farmers better weather-guessers than your average farmer?

There are hints, signs, and long-range models that will point you one direction or another. I can show you "evidence" of everything from cold to warm and wet and snowy to dry for our neck of the woods. I can tell you what it "should" do based on the El Nino that is "imminent," and then I will tell you El Nino isn't behaving like the PhD's that are way smarter than me thought it would. The truth is, I honestly have no idea what winter will be like.

If you like reading the Farmer's Almanac (either one of them), by all means go right ahead. But don't bring me their forecast and ask me to refute or defend it. It won't happen. "But it was right back when _______" you'll say! And I'll remind you of the old adage: even a broken clock is right twice a day.

Erik Proseus
MWN Meteorologist

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MWN 2012-2013 Winter Outlook for the Mid-South

Winter outlooks are always a tricky endeavor here in the Mid-South.  In fact, I'll be honest, I don't like doing them, but they seem to be popular among our readers so I put them together each year with some hesitation.

In the interest of full disclosure, I'm not a long-range forecaster.  I specialize in nowcasting.  So while I can hold my own in the 0-6 hour time frame (and am not too shabby when it comes to 5-7 day forecasts), 3 month outlooks are a challenge.  What I can do is cull information from multiple sources, put it in the blender, add a dash of experience and knowledge in Mid-South weather patterns, and present it in a coherent manner.

Note that while this discussion is heavy on the effects of large-scale patterns that help determine winter weather regimes across the U.S., and specifically the Mid-South, I do offer my thoughts on what to expect locally, this winter, at the end of the post. Skip ahead to "The Bottom Line" if you wish.

Last year's MWN outlook

At this time last year, I predicted near normal temperatures and precipitation, a couple of chances at winter precipitation, and also a few shots at severe weather late in the winter.  As it turned out, temperatures were in the top 10 for warmth, precipitation was very close to normal, and most of the snow that we received was early in the season (late November-early December, before it got excessively warm) with one brief snow event around Valentine's Day.  Severe weather struck on January 22 and the Memphis area just missed large-scale events on February 29 and March 2 (both exploded just to our east).  Except for the miss on temperatures, I pretty much had the winter pegged!

Status of ENSO / Recent Mid-South Winters

The driving factor in most winter outlooks for the U.S. is the status of El Nino-Southern Oscillation (ENSO), which is somewhat predictable out at least a few months.  ENSO refers to variations in the temperature of the surface of the tropical eastern Pacific Ocean and in air surface pressure in the tropical western Pacific.  These variations can bring somewhat predictable patterns to the weather in North America.  For instance, El Nino during the winter is associated with a more southerly track to the jet stream as it enters North America's western coast, resulting in stormy weather for California and much of the southern U.S.

The past few years have seen La Nina conditions the past two winters (2011-'12 and 2010-'11), El Nino in 2009-'10, and ENSO-neutral (or La Nada) in 2008-'09.  Here's how Mid-South weather has responded:

• 2008-'09 (La Nada) - snowy (3.8" at the airport, 8.9" at MWN in Bartlett), temps/precip slightly above normal
• 2009-'10 (El Nino) - 13th coldest winter on record, snowy (6.8"), precip slightly below normal
• 2010-'11 (La Nina) - 8th driest winter on record, but 9.7" of snow; temps just above normal
• 2011-'12 (La Nina) - 7th warmest winter on record, dry with little snow

Looking ahead to the winter of 2012-'13, one thing we know (or are fairly certain of) is that earlier predictions of an El Nino winter now appear to be fizzling and long-range models are nearly unanimous that an ENSO-neutral, or "La Nada" (neither El Nino nor La Nina), pattern will be present.  Looking back, the last ENSO-neutral pattern brought slightly above normal temperatures and precipitation and some snow of note (2008-09).

Typical effects of an ENSO-Neutral winter. Note the presence of a subtropical jet stream over the Mid-South.

The NOAA Winter Outlook

In fact, the "official" winter (December-February) outlook from the National Weather Service/NOAA for the Mid-South predicts a better chance of above normal precipitation (40%) than below normal (27%) (see second figure below).  From a temperature standpoint, equal chances of above and below normal temperatures are forecast, though above normal temperatures are likely across a large area just to the west of the Mid-South (first figure below).  NOTE: Not shown, higher chances of above normal temperatures are forecast heading into spring 2013, which could translate into late winter (Feb-Mar) as well.

Chances of above (A) and below (B) normal temperatures for Dec-Jan-Feb from NOAA/NWS.
Un-shaded areas have equal chances of above and below normal average temperatures.

Chances of above (A) and below (B) normal precipitation for Dec-Jan-Feb from NOAA/NWS.
Un-shaded areas have equal chances of above and below normal average precipitation.

Other factors, and their effects

Besides ENSO, there are several other factors that are much less predictable, especially beyond a week or two, that can have major influences on the weather pattern over North America.  To see the effects of one of the major players, look at the difference between the last two winters - both of which featured La Nina conditions.  2010-'11 had decent snowfall (9.7" officially), but was very dry when considering rainfall.  Last year was very warm with near normal precipitation and very little snow (all of it early in the winter).

The difference between these two winters was the strong influence of the NAO, or North Atlantic Oscillation.  The NAO changes based on the position and strength of the North Atlantic jet stream.  A positive NAO brings above normal pressure to the eastern U.S., which tends to result in above normal temperatures that can extend into the Mid-South. A negative NAO results in lower pressure along the Atlantic seaboard and below normal temperatures, as well as more general storminess, in the eastern U.S.

The winter of 2010-'11, which was a La Nina winter, resulted in several periods of cold and snowy conditions due to a persistent negative NAO.  The winter of 2011-'12 was influenced by NAO but was overcome in this region by one of the strongest La Ninas in recent memory, resulting in warm and dry conditions across the southern U.S. The negative NAO's effects were more pronounced along the eastern seaboard.  The NAO can vary several times over the course of a winter and is generally not predictable beyond a week or two in advance.  Thus it is a huge factor whose effects for a season cannot be accurately determined this far in advance.

Effects of the NAO in it's positive and negative phases (Image credit: Brad Panovich)

Another global factor is the Arctic Oscillation (AO), which produces similar results to the NAO - colder in the eastern U.S. when negative, warmer and drier when positive.  The AO is also unpredictable, though there are early signs that the AO could be in a more negative phase than positive at least early in the winter.  The AO was negative for much of the 2009-'10 (El Nino) and 2010-'11 (La Nina) winters, contributing to brutal winter storms over the eastern U.S. and near to above normal snowfall both winters in the Memphis area, despite an overall dry winter last year.

Effects of the AO in it's positive and negative phases (Image credit: Brad Panovich)

The bottom line

While we expect to see an absence of official El Nino or La Nina conditions, Pacific Ocean temperatures slightly favor El Nino warmth.  Couple this with the possibility of negative NAO and AO conditions over the North Atlantic and it's prudent to follow the NOAA experts in calling for a better chance of above normal precipitation than below normal here in the Mid-South.  These factors all indicate that, one way or the other, the region could be squarely in the path of a number of varying storm tracks.

However, temperatures (as everyone knows who has lived here for any length of time) are the biggest forecasting dilemma, even a day or two in advance of a winter low pressure system.  Frequently, the Mid-South sits right on the edge of temps that are cold enough (to the north) or too warm (to the south) to produce snow from passing winter weather systems (think "I-40 corridor").  I think that will continue to be the case this winter (which is not going out on a limb per se).

But, the chance of having more wet systems moving through the region gives us the potential for additional chances that cold air could be in place at just the right time to produce some snowfall.  I expect more snow than last year, but not necessarily enough to go down in the record books.

Lastly, given above normal precipitation and a more active storm track, as well as possible above normal temperatures, I also give the Mid-South a slightly elevated chance of experiencing severe weather, especially late in the winter.

MWN Winter Outlook for 2012-2013

Temperatures - near to slightly above average
Precipitation - above average
Snowfall - near to just below average (average is 3.6")
Severe weather - slightly elevated chances

We'll see how it plays out and you can call me a liar when the official stats come in next spring!  Just be sure to re-read the disclaimer at the beginning of this article before calling me out...  However it pans out, MemphisWeather.net WILL keep you updated on each system that affects the region throughout the winter, just as you have come to expect.

Erik Proseus, Meteorologist
Cirrus Weather Solutions/MemphisWeather.net

References: 
El Nino - http://en.wikipedia.org/wiki/El_Ni%C3%B1o%E2%80%93Southern_Oscillation
NOAA/CPC seasonal outlooks - http://www.cpc.ncep.noaa.gov/products/predictions/90day/
NCAR/UCAR - "Hola La Nada!" - https://www2.ucar.edu/atmosnews/opinion/8297/hola-la-nada
NOAA/CPC - Teleconnections - http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/teleconnections.shtml
2012-'13 Winter Outlook by Brad Panovich (image credit) - http://wxbrad.com/8th-annual-winter-forecast-2012-2013/

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NOAA releases winter outlook with lower-than-normal confidence, citing "elusive" El Niño

Earlier today, the National Oceanic and Atmospheric Administration (NOAA)'s Climate Prediction Center issued their 2012-2013 winter outlook.  Citing what forecasters term an "elusive" El Niño that has not made it's presence known as expected this fall, the forecast is "less certain than previous years."

"This is one of the most challenging outlooks we've produced in recent years because El Niño decided not to show up as expected," said Mike Halpert, deputy director of NOAA’s Climate Prediction Center. El Niño is the presence of warm ocean water in the equatorial Pacific that in turn influences the strength and position of the jetstream and storms over the Pacific Ocean and United States.  General climate conditions are fairly well understood during El Niño winters in the U.S.  When El Niño decides to play peek-a-boo is when the uncertainty rises, besides other complicating factors, such as the North Atlantic Oscillation (NAO).

According to the outlook, wintertime temperatures (defined as December-February) are expected to be above normal for much of the western U.S., which there is a greater chance of above normal temperatures than below normal temperatures extending east roughly to the Mississippi River Valley.  Below normal average temperatures are expected for the Florida peninsula.

Precipitation-wise, the Gulf Coast is expected to be wetter than normal while drier than normal conditions are more likely over the Upper Midwest and Pacific Northwest.

In the Mid-South, there are equal chances of above and below normal precipitation and slightly better chances of a warm winter than a cold one. However, after the 7th warmest winter on record in Memphis last year with one-third the average yearly snowfall, even closer to average conditions offer hopes for some cold spells and possibly winter precipitation.  Time will tell!

Graphics above courtesy NOAA/CPC.  For the full report from NOAA, click here.

What do you hope will happen this winter?  Are you a snow-lover or would you prefer another mild winter?

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Long-lead temperature forecasts indicate a hot Mid-South summer is likely

NOAA's Climate Prediction Center released their updated temperature probability outlooks today.  Below are the outlooks for July 2012 and the July-August-September period.  The tan colors indicate temperatures above normal are more likely than temperatures below normal. Light blue colors indicate temperatures below normal are more likely than temperatures above normal.

To decipher, consider first that in a "normal" regime, there is a 33% chance of above, near, or below normal temperatures. Inside the 33% outlook area (light tan) there is a better than 33% chance of above normal temperatures and a subsequent reduction in the chance that temperatures will be below normal (the chance of "normal" temps remains fixed at 33%). In the case of a 50% above normal area (dark orange), there is a 50% chance of above normal temps, a 33% chance of normal temps, and a 17% chance of below normal temps.

The primary drivers of these forecasts for above normal conditions are the return of ENSO neutral conditions (neither El Nino or La Nina) this summer, dry soil moisture conditions (which promotes heating), recent trends, and long-range climate models favoring above normal conditions. 

The Memphis metro is in the 33% area for July and 50% area for the July-September average.  In other words, if this long-range forecast verifies, we can expect a long hot summer!  

For more information and the remainder of the outlook maps, including precipitation outlooks and outlooks for further into the future, visit the CPC website.

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More tornadoes than normal this spring?

Image of funnel cloud north of Wolfchase area courtesy Dennis K. Russell

A couple of recent blog posts by Jesse Ferrell of Weather Underground and Paul Yeager of AOLNews and CloudyandCool.com have discussed the expected uptick in severe weather, specifically tornadoes, as we head into the heart of spring when cool, dry air collides with warm, moist air. Though the first three months of the year have been decidedly weak statistically (tell that to the folks in North Carolina and elsewhere where tornadoes have occurred in 2010), both expect that to change in April and May. The lower than average tornado count so far could be a factor of the El Nino pattern, which has brought cooler than normal conditions to typically tornado prone areas so far in 2010, among other things. Though the spring months are typically active for severe weather, both bloggers mention the likelihood of the waning El Nino pattern as a factor in the likelihood of increased severe weather and tornadoes as spring turns to early summer.

In fact, Accuweather has issued a "Tornado Season 2010" forecast, which Ferrell discussed in his blog, that indicates a heightened risk of the most severe of storms for the Mid-South region. The graphical portion of the forecast is shown below and was created by Accuweather meteorologists. It depicts the expected storm track and areas where a heightened risk is forecast, which includes the Ohio Valley, Midwest, Mid-South, and interior southeast states.

2010 Tornado Forecast - Accuweather

We'll certainly keep an eye out for severe weather possibilities at MemphisWeather.net and let you know when the threat is elevated via the website, this blog, Facebook, and Twitter.

By the way, if you haven't yet checked out Yeager's new book, Weather Whys: Facts, Myths, and Oddities, you should. As I stated in my full review:

[Weather Whys will] appeal to folks across the spectrum – from the seasoned weather professional, to the weather enthusiast, to one with even a passing interest in the weather. [Yeager's] folksy story-telling tone, a broad knowledge in an array of atmospheric topics, and the ability to explain complex processes in a way that an average middle school student could understand, have come together in Weather Whys to produce a text that is not only information and educational, but entertaining from cover to cover.

You can find a nice discount on the book on Amazon by clicking here.

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2009-2010 MWN Winter Outlook

With the winter season not too far down the road and an increased interest in long-range forecasts, I have put together some thoughts on what we may expect to see weather-wise here in the Mid-South.

Research
There is a plethora of data, long-range forecasts, and opinions available with regard to the upcoming winter season. I studied several that I find to be helpful, informative, or just plain interesting. Most of the information contained below comes from one of these sources. These include the NOAA/Climate Prediction Center (CPC) 90-day seasonal outlooks, the CPC's El Nino Diagnostic Discussions, NOAA's 2009-2010 Winter Outlook, Memphis International Airport climate records, recent blog posts from Cloudyand Cool.com, the Farmer's Almanac Winter Outlook, and the Old Farmer's Almanac Long-Range Outlook (did you know these are not the same thing?).

Overview

Current data confirms the presence of a weak El Nino event as sea-surface temperaures (SSTs)in the central and east-central equatorial Pacific Ocean regions are running approximately 0.5-1.0deg Celsius (1-2 deg F) above average (see map below). Based on trends and model forecasts, most climate scientists agree that the current El Nino will maintain itself or strengthen over the coming winter months, most likely becoming a moderate El Nino event this winter (SSTs 1.0-1.5 deg C above average).

An El Nino pattern in the winter results in a more southerly position of the Pacific jet stream, typically making landfall over California and continuing across the southern U.S. This results in an active weather pattern for the southern tier of states (wet and cool conditions) and warmer than average conditions across the northern U.S. (see map below).

For the Mid-South, El Nino effects are less pronounced than in other areas, particuarly to our south. However, typically the fall and early winter months see above average precipitation (so far so good!) with below normal precipitation during the core of the winter. Temperatures average near normal in the fall to perhaps slightly below normal during the winter.

Climate forecasts

CPC's seasonal outlooks and the recently-released NOAA Winter Outlook validate the "typical" El Nino winter (especially since they are based on those conditions occurring) - a warm/wet October-December period and a dry and slightly cooler than average January-March. The Farmer's Almanac predicts near normal temperatures and above normal precipitation. The Old Farmer's Almanac's crystal ball shows near normal precipitation and near to slightly below normal temps.

Recent Mid-South El Nino winters
Comparing to recent El Nino winters (December-March of 2003, 2005, and 2007), the Memphis area was slightly cooler (-0.9 deg) and wetter (+1.90") than average in 2003, while warmer and drier than average conditions occurred in 2005 and 2007 (2005, +3.0 deg and -3.76" and in 2007, +3.4 deg and -3.99") according to climate records for KMEM from MWN.

So...

...what do I think? First of all, I'm NOT a long-range forecaster or a expert in climate. Given that, and with all due respect to the farmers (and old farmers), the evidence is present that El Nino has begun this past summer and decades of measurements indicate that it will not wane over the winter. There is also plenty of data to support the "typical" conditions that occur during El Nino events across the United States. I expect to see the wet conditions of late trend towards generally drier conditions as we head into the winter. However, as the winter storms move along the jet stream to our south, a few will have the potential to bring soaking rains and perhaps even the possibility of severe weather to the area. Temperatures seem to be a little more tricky, but I'm hedging on slightly above normal temps overall.

Prospects for snow
Everyone always wants to know about snow prospects for the upcoming winter as well. Given the more southerly storm track, we should have some opportunities for a round or two of precipitation getting caught up in cold air near the surface and creating the potential for snow. The timing will have to be perfect (as is almost always required in this part of the country). Precipitation coming from the southwest overrunning a cold dome of air already in place behind a preceding frontal system would be the most likely setup.

Here's some interesting data for the past 11 winters for Memphis showing yearly snowfall amounts (at the airport) and the state of El Nino/La Nina for that winter (ENSO neutral means neither El Nino or La Nina conditions). It is interesting to note that the highest totals seemed to occur during La Nina years, not El Nino. However, there have also been only 3 years in the past 11 that we did not get at least a couple of inches. [NOTE: The 30-year (1970-2000) "climate average" for snowfall for Memphis is 5.7" - which we didn't actually hit once during the past decade.]

I'm guessing we'll get at least one "couple inch" snowfall again this year, though freezing rain/sleet seem to be fairly likely at some point, once again given the southerly storm track of typical El Nino years. I am NOT predicting "the big one" - many of you received that on February 28th this year and those don't occur all that often!

1999 - Trace - La Nina
2000 - 5.5" - La Nina
2001 - 0.1" - weak La Nina
2002 - 4.5" - ENSO neutral
2003 - 2.9" - El Nino
2004 - 2.2" - ENSO neutral
2005 - Trace - weak El Nino
2006 - 3.5" - weak La Nina
2007 - 2.2" - weak El Nino
2008 - 5.4" - La Nina
2009 - 4.1" - weak La Nina

So what do you think? Educated opinions, uneducated opinions, wet fingers in the air, arthritic knee forecasts, I'll take 'em all! (And yes, I know Nino has a tilde over the second 'n'.)

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