Early look at potential weather trends for the eclipse

The BACKGROUND

If you are a longtime follower of this site/blog and our content in general, you know I'm not real keen on looking beyond a week out in our forecast, especially when details unresolvable several days out could end up producing wild swings in the resulting weather. For instance: pinpoint temperatures that could mean the difference between rain, snow, or ice. Or temperatures, dewpoints, magnitude of the wind, and cloud cover that could mean the difference between severe storms and rain showers. All of these details can make a big difference in forecasts beyond 3-4 days, let alone a week.

However, trends in the overall meteorological pattern are a little different. While specific timing or forecast details may not be discernible, a colder/warmer or wetter/drier pattern CAN be discerned out to a week or more. So I may not be able to say WHEN on day 6 or 7 an upper level trough will drive a cold front through the Mid-South. But I could say if there is some overall model agreement on the pattern and can probably tell you that we'll see a cool-down, or a wetter than average pattern, a week or more out.

All that said, we have a MAJOR astronomical event occurring about 10 days from now that I know you are all aware of, and many of you (like me) are greatly anticipating! A total eclipse, like that which that will cross the state of Arkansas and block out 97% of the sun here in Memphis for a couple of minutes on April 8, will not occur again for another 21 years. And far be it from me to withhold information for such an event once we start to creep into the "forecast-able period" of said event.  

The DISCLAIMER

Information presented here, on March 28, is provided as a very early look at the possibilities, or trends, and includes NO guarantees. Do not change any plans you have based upon information presented. Do not tell me on April 9 how good/bad my "forecast" was on March 28 (believe me, I will be well aware!). Do not sue me. Do not TP my house. And do not call me or my family bad names. This is NOT a forecast - it is general "trend" information. It is presented vaguely on purpose, because anyone who will tell you on March 28 exactly what will happen at 2pm on April 8 is lying. I present the trends, because there is agreement amongst our various computer model sources on those trends - but certainly not the details. Moving on...

The OUTLOOK

To get to April 8, we start with the general trends leading up to it. 

The next several days will be influenced by building high pressure aloft and surface high pressure sliding to our east. That means dry weather and warming temperatures with increasing southerly breezes. That trend continues through the weekend. By early next week, models are in concurrence that low pressure will form in the Plains and move by to our north on Monday/Tuesday with an upper level trough advancing from the southwest U.S. This will lead to a generally wet and possibly stormy pattern to start next week. (Without diving into too many details, because we're 4-5 days out, the most likely severe weather threat appears to be to our west and north Monday and then to our southeast Tuesday.) 

Behind that system, high pressure builds back in for the latter half of next week and into the weekend. Then (are you sensing a pattern?), by the weekend of April 6-7, long-range models generally concur on upper level troughing (low pressure) forming  in the Plains again. With surface high pressure to our east, southerly flow sets up over the Mid-South by the 8th. This pattern typically results in building cloud cover and increasing rain chances. BOOOOO!!!!! 👎

Comparisons of the mid and surface level pattern on April 8 from the European and GFS (American) ensembles show fairly remarkable agreement on the overall pattern for an 11-day forecast. (WeatherBell)

Below, I have placed graphs from three of the major global model ensembles - the European, American (GFS), and Canadian. Ensembles basically are iterations of the model, run many times with slightly different parameters and schemes, to provide a range of potential outcomes. They are the BEST way to look at long-range trends. The models themselves can change multiple times a day. An ensemble effectively averages out all of those different possibilities. The averages, or oftentimes probabilities, of a particular scenario give us a much better idea of the range of possible outcomes than a single model does.

I've chosen to show precipitation in 6-hour increments, since if the model shows rain falling, that would also mean some amount of cloud cover - which ultimately is the forecast element we most care about for an eclipse! Each of the three model ensembles are shown below. Each ensemble is run four times a day, and those "runs" are stacked horizontally (oldest on top, most recent at the bottom) with time going out into the future from left to right and precipitation amounts shown in dark grey to green boxes for each 6-hour time increment. 

On each graph, I have boxed April 8 in red. There is one thing that stands out to me immediately when looking inside those red boxes (and either side of the box to see what might happen before and after the 8th). Each model ensemble, and each of the previous several times that ensemble has run (going back at least a few days), shows precipitation occurring on April 8 in Memphis. Essentially, what is shown is the culmination of hundreds of runs of the three models over the past 3-5 days. And each of those averages has rain falling in Memphis on April 8.

The RECAP

Now, before we break all the guidelines and disclaimers mentioned above and cancel all our plans, it is still many days before the eclipse happens. A "pattern" is NOT a "forecast!" There is not enough detail in this outlook to make any rash decisions. All we really need is partly cloudy skies for a few minutes on April 8 (preferably around 2pm) to see a pretty amazing astronomical spectacle. I'll continue to watch the trends, and as we get within a week, our daily forecast found on our website or app will reflect the latest information.

A final p.s.: For those that spent a bunch of money on a place to stay in Arkansas to see totality... I looked at this same data for Little Rock and there was almost no difference. They are in the same pattern we are according to the data. It is also too far out to define the details that could make a difference between here and there. Keep those reservations (I am!) and go chase the eclipse! If the sun doesn't shine, hopefully you still have had a nice day or two away from the daily grind.

Erik Proseus
MWN Meteorologist

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Regarding medium-range snowfall forecasts and this week's chances

From a weather perspective, most attention nationally is focused on potential impacts from a Nor'Easter early this weekend in the media capital of the world. But here in the Mid-South, we'll be dealing with the backside of the same low pressure system that becomes the Nor'Easter late Thursday night/Friday morning. As the low pulls away, cold air will dive south, potentially changing lingering rain into snow.

This post serves as a reminder of how best to consume "#snOMG forecasts" (snow-OMG, or models showing crazy, excessive, or improbable snow totals beyond a couple of days in advance). I'll also lump in any snowfall graphic that doesn't clearly describe the source and include some context on the confidence or probability of the depicted scenario occurring. In a nutshell, take any of those types of forecasts with a grain of salt! I'm not saying that the #snOMG scenario can't, or won't, happen, just as I'm not saying you won't win the lottery if you buy a ticket!

Looking past the early Wednesday event, which I have high confidence will be a cold rain in the metro, the next potential winter event is early Friday. I've seen several people sharing graphics from the "born-in-the-USA" GFS model this morning with little to no context. In fact I'll share this morning's hype-cast model run, with you too...

So those who would like you to believe (or maybe just want to believe themselves and also happen to have a public voice on Facebook or Twitter) that we will get accumulating snow will post something like the above, only without the caveats I added.

Let me add some responsible context to the above graphic - not because I hate snow (I actually love snow), but because it's the responsible thing to do. I don't shy away from discussing snow chances, I just do it in a responsible fashion.

1. The same GFS model has an "ensemble" system in which the model is run 21 additional times with very slightly different parameters as input in an attempt to address the uncertainty factor and provide a range of possible options. Of the 22 total members, only 7 have 2" of snow. This means that there is roughly a 32% chance that 2" or more of snow falls, according to the same model that everyone is sharing that says we'll get 3-5". Here is the snowfall forecast from all 22 GFS ensemble members:

All 22 members of the GFS ensemble forecast from this morning, showing the possible snowfall totals by Friday evening. Graphic courtesy of the awesome weather model site WeatherBell Analytics.

2. The morning run of the European (ECMWF) model that so many people like to hang their hat on for medium-range forecasting (especially when it is convenient to do so), indicates we could see a dusting to 1/2" of snow. (Graphic not shown due to sharing restrictions by the provider and European modeling center, so you'll have to trust me on this one.)

3. Like the GFS, the European model also has an ensemble, only its made up of 51 members rather than 21. A check of the precip totals from last night's European ensemble forecasts (this morning's run was not complete as of this writing) showed that only 9 of them forecast 1" or more of precipitation. So that means the Europeans, which are so darn good at medium-range forecasting, give us less than a 20% chance of 1" of snow.

4. I also looked at the Canadian, Japanese, UK, and Navy models - basically everything I could get my hands on - and none of them showed the amount of snow the GFS is showing. Finally, let's go to the official government source of forecasts for the U.S., the National Weather Service. Their 4-day winter weather outlook depicts just a 10% chance of receiving 0.25" of liquid equivalent (melted) snow/sleet. Since snow typically has about a 10:1 snow/rain ratio, that equates to about 2.5" of snow. Thus, a 10% chance of 2.5" of snow. Not out of the realm to see this much, but not likely by any means.

The NWS 4-day winter weather outlook shows a 10% chance of seeing roughly 2.5" of snow, based on .25" liquid equivalent. 

So, the best snowfall forecast beyond a couple of days is not a single model run from your favorite model, but simply...

For more on how to handle these long-range "hype-casts" and our goals at MWN with respect to these types of forecasts, see this write-up we posted a couple of weeks ago.

As always, we'll watch the models and evolving patterns and let you know what we expect when we have the confidence to say so, or if we have low confidence, we'll let you know that too! Please don't take the four-day forecast of 5" you saw on Facebook, disregard updates from your trusted sources between now and then, and wonder why "they got it wrong again" when you wake up to a dusting Friday morning!

More updates as we go through the week, including that low confidence Wednesday morning event. See our social media feeds or forecast in the MWN app.

Erik Proseus
MWN Meteorologist

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Commentary: On long-range "hype-casts" and YOUR responsibility

Winter has arrived and with it the appearance of long-range winter storm or snow maps that go viral on Facebook and Twitter. This post puts me "on the record" on these social media sensations, which I call "hype-casts."

The perceived need by many to try and reach the masses (whether with good intent or just as part of a game to try to go viral) has resulted in click-bait headlines (those intended only to get the reader to "click") and slick/catchy graphics, even if the part that catches the eye (or even the embedded content) is partially true, misleading, or just plain false.

A typical long-range hype-cast with vague wording and a broad-brushed impact zone, requesting an "immediate share." 

This applies in the weather realm as well. Sharing of weather graphics - whether created by professionals or novices or simply shared from computer model websites - has grown more common as access to weather model data becomes easier and social media has matured to the point that anything can go viral (and for some, that is the sole goal). Though there probably aren't a lot of "offenders" that spread misleading (to be kind) graphics and headlines, it doesn't take but a few to cause mass confusion, or in some cases, chaos. Professional meteorologists that are ethical end up spending as much time debunking, or at least attempting to explain, these misleading posts as they do creating their own forecasts!

Beware of internet trolls: There is currently NO WINTER STORM...NO SNOW or ICE in the forecast for our area. We will get cold (but dry).

— Brad Nitz (@BradNitzWSB) January 3, 2016

Millions in the path!

The graphics and/or headlines tend to be of two varieties - severe weather outbreaks or major winter storms. Neither of these are impermissible to share and inform the public of, per se. However, the offending posts are generally shared many days to weeks in advance of the so-called event, when the first long-range computer model "sniffs out" a major storm (or even a pattern that could support such a storm). Typically, the proposed outcome is not shared by other computer models and that same model has a completely different solution on its next run (these models produce a completely new set of forecast data 2-4 times each day, called a model run).

An excellent graphic from 2014 by NWS-Memphis on why "exact" long-range snowfall forecasts should be treated with skepticism. The further out from the time of the event (day 0 to the right) the wider the range of possibilities that exists. For a more detailed explanation, see the complete Facebook post that accompanies this graphic.

Dealing with the problem

There is increasing debate in the meteorological community about how to handle both the problem and the offenders. I will not wade into that topic too far at this point, other than to say that it isn't just "backyard meteorologists" or "kids" that are at fault for creating the mess. (Most of us meteorologists started as one of those kids that was eager to learn and practice our new love, we just didn't have the vault of available model data and social sharing platforms that are available today.) Some professionals are simply too eager to be the first on the scene, just in case it becomes breaking news a few days down the road.

There are ways to deal with each of these groups. Professional organizations are one means of doing so, by certifying meteorologists and issuing seals of approval for those who meet certain standards. However, I feel that most of the population would not look for, or even care, whether their source is certified. So the best way to deal with the situation for now is to educate you, the public.

What should I do?

So, what should the average Joe or Suzy Q. Public do when presented with a weather graphic or story with click-bait headline that they are uncertain of?

1. Beware the share! If you aren't sure whether it's valid, stop the bleeding and quit sharing. 
2. Know your trusted sources. Trusted sources are the qualified individuals that have told it to their audience straight before, admitted when they were wrong, and don't hype for hype's sake. 
3. Ask that source. They should take the time, either in direct response or through a general post on the topic, to address the issue. 
4. Be skeptical. If it's more than 5-7 days out and it's extreme weather for your area, trust me, it isn't "likely." It may be possible, plausible, or conditional, but it isn't a guarantee. If the graphic doesn't have a logo or source clearly labelled, paints a very general picture with wording that is "extreme," or has an explanation that seems far-fetched or just mixes in lots of big words and acronyms that don't make sense, skepticism is the best way to view it. 

Our goal at MWN

Our goal at MemphisWeather.net is to become, and remain, your trusted source for Memphis and Mid-South weather information. We do that with a stated mission of "protecting, informing, and educating" you, the consumers, on impactful weather scenarios. This includes letting you know when there is a decent chance of a particular event occurring, within a reasonable timeframe, but only when we have enough confidence in a plausible solution that it can be shared without hype. Typically this means the solution is proposed by multiple models and/or is fairly consistent over a series of model runs.

We also will clearly identify anything that is strictly model data as such, so that you know that there is inherent uncertainty in the final outcome. In essence, we strive to follow the guidelines in #2 above. We hope that you trust us to do as we state and will question us if we stray. At the very least, we'll be responsive, as long as you're not a troll. :-)

Erik Proseus
MWN Meteorologist

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MWN Lightning Round: On the end of winter, weather marketing, and tornado bans

Winter over? Not so fast...

I've seen and heard lots of complaints about the "return" to winter today in the wake of yesterday's cold front, especially with spring break in the rearview mirror and the latter half of March out the front window (and my #NoMoreWinter campaign notwithstanding). With cloudy skies and a breezy north wind, temperatures struggled into the upper 40s, or about 15 degrees below average, across the metro today.  High pressure moves to our east tonight, allowing wind to switch from the south. Temperatures will respond accordingly tomorrow with highs in the 60s. In fact, the 60s, and even 70s, will continue through the week.

However, if we look out a bit further, the Climate Prediction Center has issued a "high confidence" outlook of below normal temperatures for next week (shown below).  For the period of March 23-27, we have a 70% probability of below normal temperatures, meaning there is also almost no chance of above normal temperatures and about a 30% chance of near normal temperatures. Also, not shown, there is nearly a 60% chance of below normal temperatures for the period March 25-31. So, is winter over?  Probably.  But is the colder than normal weather over with this week's 70s in the forecast? Likely not.  And that leads us to the next vignette...

Don't shoot the messenger

I've been known to say "I'm in Sales, not Production" when darts start flying over less-than-ideal weather conditions. Another way of saying that was shared with me today by a fellow meteorologist and friend Kevin Selle, who posted the following in a Digital Meteorologist blog post today:

Thanks for the awesome graphic, and message, that describes our job so succinctly, Kevin!

Tornado Ban

Did you know that tornado watches and warnings used to disallowed?  It's true!  While I knew of this from other literature I had seen, I didn't know that today is the anniversary of the date when the tornado forecast ban was lifted.  From Weather Underground:

Did you know that a ban on the word "tornado" was lifted on this date in 1952 after nearly 66 years? The ban was started by the Army in 1886 (the Army handled forecasting at that time), when it was determined that the harm done by predicting a tornado would be greater than that done by the tornado itself (emphasis added). On this date in 1952, the new Severe Local Storm Warning Center issued its first "tornado watch".

Can you believe that?  The Army felt like predicting a tornado would cause more harm than the tornado itself!  What a long ways we have come in the past century!  (Another hat tip, this time to Olive Branch's own WeatherMayor Sam Rikard, for passing this info on.)

Follow us on social media via the channels below for more interesting factoids and a four-times-daily nowcast to help you plan your day and be prepared for whatever Mother Nature plans to throw at us!

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Peering into the crystal ball: Christmas Day 2013 weather outlook

Yesterday I posted on Facebook and Twitter that those who were interested in what the crystal ball said about Christmas Day weather in Memphis should tune in today.  I nearly jinxed myself - when I went to the computer this morning to update today's forecast, it wouldn't power up.  (Un)fortunately, I was able to resuscitate it this afternoon and now am obligated to bring you this update... unless a bolt of lightning from the blue strikes me down before I hit "Publish."

Ten-day forecasts are kind of like looking in the crystal ball, polishing it off, then looking again, shaking the Magic 8-Ball four or five times, then averaging it all together.  It's where the science of meteorology becomes the art of dancing around a forecast with just enough vague and non-committal wording to be able to say "I told you it would ____" no matter what happens! So here goes nothing...

First I point you to our updated "History of Christmas Day weather in Memphis" blog, which doesn't give you high hopes, other than that 3 of the past 4 years we've gotten VERY close to being snowy.  Then, I'll show you a video both entertaining and depressing at the same time, from Christmas Day 1963 - the only time this scene has played out in Memphis since records began:



Then, there's this:

So what about this year?  The long-range models (including the U.S.-based GFS, the European ECMWF, and Canadian GEM) just barely reach out to Christmas Day.  The last couple of runs of each of these don't provide much hope for scenes like that above.  Leading up to Christmas, a ridge of high pressure builds over the region this week, bringing warmer temperatures than we have seen in the past 10 days with highs reaching into the 60s by week's end.  Next weekend is where models begin to diverge, but all point to some sort of significant trough of low pressure and associated cold front pushing through between late Friday and early Sunday.  We expect a good deal of rain, likely some thunderstorms, and perhaps - if instability can be realized and dynamics are strong enough - a chance of severe storms.  Stay tuned.

Behind that trough early the following week (or basically around Christmas) is where we see multiple solutions from the models. The most recent GFS model run actually delays the weekend storm system (or perhaps I should say, gives us round 2 of a 1-2 punch) on Christmas Eve with very warm temps and storms, followed by a cold, dry Christmas Day. The rest of the models move the system out next weekend and settle high pressure in for the start of Christmas week with high temperatures averaging in the mid 40s to near 50 Christmas Eve, or roughly "near normal."  Most of these also point to a dry Christmas Day.

The Climate Prediction Center (part of the National Weather Service) has also been leaning towards next weekend's system moving out before Christmas with high pressure trailing.  Today's outlook for Christmas week gives us equal chances of above/below normal temperatures and a 50% chance of below normal precip with only a 17% chance of above normal precip.

The bottom line? I'll dance until the music stops to keep from making a call. :-) But typical December patterns and the timing of next weekend's system, as well as current forecast model data, point to a cool and dry Christmas Eve and Day.  Or just about what one would expect from any given Christmas in Memphis with an average high of 50 and average low of 33!  Those who know my propensity for playing down snow in Memphis until there is some degree of certainty won't be surprised by this outlook at all!  For those who prefer the glass-half-full approach,  I give you some classic Jim Carrey:



As any of our regular followers also know though, we promise to keep you updated as the number of shopping days diminishes and the magical day draws closer.

Erik Proseus
MWN Meteorologist

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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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