Winter Speculation 17/18 -December Thread

[Carvers Gap]

1 minute ago, AMZ8990 said:

Day Lilly's are starting to bloom in my neck of the woods.  The wheels of spring are trying to start turning it appears.  

Mine are up.  Pretty normal here for them to be up in my area at this time.  But with the daylight hours getting longer and accompanied by very temps, definitely will see plenty of activity.  Hopefully most activity will be the normal, early foliage.  That high latitude block could be a big problem if too much stuff buds out.

[Holston_River_Rambler]

Rain + warmth has = some of the largest crocus patches I've seen since I've been in Knoxville. Hyacinths not too far behind. Already a flowering tree about to pop in Old North Knox on a sunny hill top. I think if we get near 80 Wednesday with sun here, some of the early flowering trees will be well along. Nothing like last year though with Bradford Pears out in mid January. 

[jaxjagman]

I love reading Nashville's disco

 

National Weather Service Nashville TN
609 PM CST Sun Feb 18 2018

.UPDATE...
FOR 00Z AVIATION DISCUSSION.

&&

.DISCUSSION...

It`s an absolutely fantastic day in Middle TN.  The sun is out --
finally -- temperatures have climbed into the upper 50s and there
isn`t but a whisper of wind. Ok, yes. Most would like to see a
few more ticks north on the mercury. For those who want it warmer,
I`ve got a treat for you over the next couple of days. However,
let`s start with tonight.

Partly cloudy skies this afternoon are going to give way to an
overcast cloud deck this evening as a warm front lifts northward
through Middle TN.  Spotty showers are likely to accompany the warm
front passage, though I don`t think everyone will see rain.  Even if
you do, it isn`t going to be much. A tenth at the most. In
addition, overnight lows are likely to occur prior to midnight as
we should see temperatures climb after midnight.

Tonight`s frontal passage is going to set the stage for the next
several days: potential record highs (and lows) and yes, more
rain. I`ll address the record temperatures in the climate section
below, so let`s focus on the rain.

If you didn`t know, the ground is wet.  Really wet.  Even if you`ve
been living under a rock, you`d know this.  Several area rivers,
streams and many creeks are still swollen from rains last week and
yesterday.  These antecedent conditions are going to become very
important starting Wednesday afternoon, as our next batch of showers
begins to move into the mid-state.  Fortunately, we are going to
have a couple of days of very warm, dry and (very) windy days to
help dry things out, but QPF values being suggested in latest
medium and extended range forecasts have my attention. Between the
first weather system due in here Wednesday evening and another
progged for next weekend, the GFS and the Euro have 4 inch
contours encroaching into our NW counties and the Euro actually
has a 6 inch contour creeping into Stewart County. WPC has posted
a Moderate risk for areas west of here (AR and MO) for Day 3
(Tuesday into Tuesday night) and I wouldn`t be surprised to see
something like this for us by Wednesday and if not then, by next
weekend. RFC Flash Flood Guidance (FFG) values are already running
between 1.5 and 2.5 inches for both 3 and 6 hr guidance. This is
likely to improve a little come Wednesday night, however it will
still be running low.

Putting it all together, even if we don`t deal with any flash
flooding, area rivers and streams are likely going to have a
detrimental response to the rainfall this coming week.  Hear me
though -- I`m NOT talking about May 2010 flooding.  I`m saying, stay
weather aware throughout this week as there could be some minor to
moderate river flooding by week`s end and some other localized
flooding issues as early as Wednesday night.  I will update the
Hazardous Weather Outlook this afternoon to highlight these concerns
and likely issue a Hydrologic Outlook by Tuesday as we review what
the drier air can do to help us.

[Carvers Gap]

0z EPS and GEFS are now very close in their depictions of the 500 pattern over NA.  The long awaited pattern is now to roughly at d10(EPS is slower) w the SER breaking down before that even.  Nothing guaranteed, but nice to the potential moving forward in time and the transition now well within d10.  Edit....The Euro d8-10 also has the pattern change...not trusting it as it has been pretty awful at that range when depicting a pattern change.  As a matter of fact, it begins to build the eastern trough.  Seems slightly too fast.

[Carvers Gap]

12z EPS is a really good look.  The control is very aggressive and likely over doing it.  The mean is brings in BN heights a bit more quickly than previous runs.  Looking like d11.5 now.  The d10-15 850s are now seasonal to BN for the forum area w the trend towards colder each of those five days.  The control is very cold during that time.  GEFS, GEPS and now the EPS complete the 12z suite look w a cold and stormy pattern developing just after d10.

[Carvers Gap]

Tonight's Weeklies again confirm what we have been discussing.  There is a two week window from March 4th onward where temps are BN and precipitation is adequate....there will be less because systems are likely spaced further apart and are slower.   Big -NAO.  Nice to see the Weeklies retrograde the trough into the EC.  And honestly, the 12z run was faster and would likely have produced a colder Weeklies run.  Bout all I can add...pretty much all of the ideas have been placed out there for a couple of weeks(or more) beginning with the initial discussions of the SSW.  We have about ten days of nice weather, and then maybe we have something to track.  Some key pieces beginning to show for March now that have been missing during several of the past years during March.  

If anything the models are a bit quicker today w/ the potential switch to blocking.  The 18z GEFS is now up to March 2nd w the onset of cold.  Definite uptick in the 18z GEFS ensemble snow mean.

Below shows about what you need to know.  There is the -NAO.  That will be in correlation with the MJO being in winter phases, the SOI dropping, the QBO being negative, and the stratwarm doing its thing.   All in all, those teleconnectors and indices have been pretty solid this winter.  Last year, we had the MJO in the correct phase and no cold source.  This year, some is available.  You an see when the NAO goes negative which is now well within the seven day window.   It will take about one week for the pattern to adjust.

I probably won't add much until the details of the pattern(storms) come into focus a bit more.  I sound like a broken record at this point.  So, unless the pattern derails or there are details of note....time to sit back and wait, enjoy the warmth before the pattern change, and watch.

[Carvers Gap]

Here are the first five days of the 18z GEFS and the last five days of the 18z GEFS.  Pretty big changes in eastern North America.  We have been looking for model evidence.  There are trends for sure.  Now, time to see if they verify.  Things can always change, but this is where things stand this evening.   LR forecasting is full of busts and full of successes.  But the transition to the NAO is almost in short range forecasting now.  The subsequent cold is in the medium to LR.

[nrgjeff]

Some of those -NAO members are close to records for March. GFS actually does well with the stratosphere, despite all my bashing of its troposphere. We noticed back in 2010-2011 the GFS handles the stratosphere pretty well. SSW has been in progress and it looks to impact the 500 mb pattern with authority.

Some of the ECMWF ensemble members have low press far enough south the second half of the 11-15 day, but the GFS op wants to cut everything. We'll hope the GFS SSW forecast hands off to the Euro troposphere. 

[Icy Hot]

What does this mean in plain English? Sorry, I am not versed enough to comprehend.

[John1122]

The GFS gets the 500mb set up to a decent place but still shows cutters. Storms as a rule, shouldn't cut with the -NAO.  It's getting towards March 4-8th before the cold begins to arrive, lows stay above freezing before then on the GEFS.  In order for snow at this point we need some really dynamic ULL set up or a major Arctic invasion. Otherwise you'll see cold rain/mountain snow even with favorable tracks. Miller A/Slider season isn't over  in mid-March, but it's definitely on life support for most that aren't elevated. On the upside, when it does snow in March, it can be very large events even in non-elevated places, because storms have more energy and ULLs that can produce snow usually lay down very heavy snow in their paths. They are like the solar eclipse of snow events though. Narrow areas get hammered and the edges get little or nothing.

[Carvers Gap]

3 hours ago, Icy Hot said:

What does this mean in plain English? Sorry, I am not versed enough to comprehend.

No changes in my thinking at this point.  Great pattern on the horizon.  But I will try to answer the question...hope it helps.

We have a window for a coastal low(s) or inland runners during the first 2/3 of March.  Best dates look to be between March 4th and 18th.  I suspect that date might move up one or two days.  The -NAO in the modeled configuration is a very good driver and signal in the eastern valley for March snow and slightly BN temps. The NAO has the potential to go deeply negative.  The models have trended colder for that time frame during March.  As Bob Chill in the MA forum notes, -NAOs are not severe cold drivers as much as they are very good drivers for a decent storm tracks.  So really we wait...the details in operational models will be very out of focus at this time.  So, right now we can recognize a nice pattern at 500 and know that it correlates well to winter storms in the East, but that is about it.  There are no guarantees.  At this latitude and time of year, all usual caveats apply....Plenty of things can go wrong in the sub-tropics when it comes to snow at any time during the winter and even more so during March.   But pattern recognition is important.  The models actually look reasonably cold after the 4th, enough to make things very interesting.  I do think many big snows at this time of year happen at night...so that is one more restrictive rule that will need to be applied.  Very nice pattern being modeled.  The best thing about a -NAO is that is blocks storms and slows them down not allowing them to cut.  Once they slow down, cold air can be pulled into the system dynamically.  I think the 12z GFS did a better job depicting storms that don't cut.  Where jet streams phase is often confined to the MA or even south of that.  That is known as the point of confluence.  Many great  E TN snow storms have happened during a -NAO....not as much middle and west TN.  However, the -NAO pattern can strike out as well.  Right now, just no way to be sure.  My guess would be multiple coastal surface low pressures moving up the coast and attacking the AN heights over Greenland during that time frame.  I suspect most models are just now getting a handle on the weather pattern.  They are definitely depicting more cold and more BN heights over the east w each passing run.  But at this point....just using past experience.  There is a path to "no snow" as always.  But there is also a path to snow...which is not always present during March and has been lacking during our most recent March time frames.  

In a nutshell...the -NAO correlates to eastern snowstorms and some big ones at that, but sometimes those looks don't produce and sometimes they are very good.  No way to know right now.  Looks like we will soon enter a time of -NAO weather.  It could be very negative.  March climo (especially the first half) supports big snows. But at this point there are no systems to track as we are about ten days from the block really taking hold.  Many of the big storms will form at the beginning of the block(unlikely this go around) or right as the block goes most negative and begins to move slowly back to positive.

My area in NE TN does much better w a -NAO.  Kingsport often does not do well w northwest flow as we get a rain shadow from the Plateau.  Points east of I81 may differ in that opinion.  They have more elevation gain.  We do better w a fetch off the Atlantic.  Some years the Pacific can really help IMBY.  A decent Pacific set-up is a much bigger plus for the Plateau and points west.  In my lifetime, many of the big snows for Kingsport happened during a -NAO.  So, it is kind of like a big time hitter in baseball coming to the plate.  They don't hit a home run every time, but they are the most likely batter to hit one.  But they strike out as well....but just because they strikeout does not mean I won't watch when they come to the plate next time.  We are overdue for a big storm in the eastern valley.  Past performance does not guarantee future performance, but at some point we will see another big storm.  

[Carvers Gap]

Anyone have time to make one of these for the western, middle, and eastern sections of the forum area?  Also, what site are those folks using to make a map that would reconstruct the 500 pattern for biggest March snows in E TN compiled into one?

 

[tnweathernut]

With SO many false starts regarding the NAO over the past several years I have been playing the waiting game.  After several days of following the NAO forecasts, and a couple of weeks of SSW....... the coming -NAO looks legit.  It's on all global modeling ensembles and aside from the GFS trying to jump the gun with one false start, modeling has been INCREDIBLY consistent.  What does this mean though??

We appear (all that can be said at this moment) to be headed toward a period of late season winter.  That doesn't mean snow, but I'd expect and active storm track being forced under the blocking with below normal temperatures across a widespread area.  I think the mountains will eventually be hit with a good snow, but the jury will still be out for much of our subforum.  The Pacific is going to be a wildcard, but is showing indications it won't be as hostile as it appeared several days ago...

All this said, it's not often we are in the game with such a good look as we head into the last week or so of February.  Hopefully, in the coming 3-5 days a threat will emerge or at the very least we can begin to see how this block will set up and which areas are more likely for late season fun and games.

 

[Holston_River_Rambler]

2 hours ago, Carvers Gap said:

Anyone have time to make one of these for the western, middle, and eastern sections of the forum area?  Also, what site are those folks using to make a map that would reconstruct the 500 pattern for biggest March snows in E TN compiled into one?

[Holston_River_Rambler]

Sorry new computer and that quote got stuck and I couldn't add my text.

I think I found the site: https://www.esrl.noaa.gov/psd/cgi-bin/data/composites/plot20thc.v2.pl 

I don't know too many snowstorms to plug into it, so hoping y'all have enough! I could add March 93, Jan and Feb. 96, 2015?, but of course some of these would be just for my location at the time and I don't always remember the exact days.  

[Carvers Gap]

2 hours ago, Holston_River_Rambler said:

Sorry new computer and that quote got stuck and I couldn't add my text.

I think I found the site: https://www.esrl.noaa.gov/psd/cgi-bin/data/composites/plot20thc.v2.pl 

I don't know too many snowstorms to plug into it, so hoping y'all have enough! I could add March 93, Jan and Feb. 96, 2015?, but of course some of these would be just for my location at the time and I don't always remember the exact days.  

John could probably help here as well.  What we need are the major snowstorms on record that occurred during March.  Go back as far as we need.  It is not as easy as it looks to find these events.  We can then build a composite look.  We could also disaggregate that into ENSO years as well.  We could disaggregate by several other factors as well.  Biggest thing is that we need significant snowstorms for March say 6"+.  I just think it would be interesting to do. Eventually, we could do that for the other months.  Then, we know what pattern to look for for the forum area.  Now, that look might be a bit different for Memphis than say TRI.  Just grab storms for the forum area w amounts, years, specific dates, etc.  But while we bask in early summer temps, we could at least build something productive.  Thanks for the site!

Also, I don't want folks to think I will tie up this thread with all of that.  Maybe we could start here w a few posts...if it gets bigger, I can make a new thread for analogs.  Could be an interesting resource.  And I don't care who all works on this, even if we do duplicate work.  

[Holston_River_Rambler]

14 minutes ago, Carvers Gap said:

John could probably help here as well.  What we need are the major snowstorms on record that occurred during March.  Go back as far as we need.  It is not as easy as it looks to find these events.  We can then build a composite look.  We could also disaggregate that into ENSO years as well.  We could disaggregate by several other factors as well.  Biggest thing is that we need significant snowstorms for March say 6"+.  I just think it would be interesting to do. Eventually, we could do that for the other months.  Then, we know what pattern to look for for the forum area.  Now, that look might be a bit different for Memphis than say TRI.  Just grab storms for the forum area w amounts, years, specific dates, etc.  But while we bask in early summer temps, we could at least build something productive.  Thanks for the site!

Also, I don't want folks to think I will tie up this thread with all of that.  Maybe we could start here w a few posts...if it gets bigger, I can make a new thread for analogs.  Could be an interesting resource.  And I don't care who all works on this, even if we do duplicate work.  

Actually I think this is the proper site: https://www.esrl.noaa.gov/psd/cgi-bin/data/narr/plotday.pl/ for the above plots that have specific days put in them 

Still trying to figure out how to use it though..

EDIT: Figured out how to use it. Give me some dates and I will plug em in! 

 

[tnweathernut]

There shouldn’t be very many 6” snows in March across our forum area.  What are we talking, probably 3-5 at most? 

Question is, what resources do we use to find them?

[Carvers Gap]

Here is a middle TN link for wx events. We need one of these for west and eastern forum areas.  We could build three 500 analog maps for those areas and then consolidate all dates into one analog map.  

http://www.weather.gov/ohx/calendar

Updated:

Here is one for E TN...

https://www.weather.gov/media/mrx/calendars/tys_cal.pdf

 

[Holston_River_Rambler]

1 hour ago, tnweathernut said:

There shouldn’t be very many 6” snows in March across our forum area.  What are we talking, probably 3-5 at most? 

Question is, what resources do we use to find them?

Luckily you have a historian in the forum now who's spent a decade + learning how to research and teaching research.  Let's see what it's worth. In this case maybe not as much as I'd like. (I do have other responsibilities, but maybe this will be a nice break from other types of research) I'll take a stab over the next few days and poke around a bit. I'm guessing newspapers might be the best bet for some older ones, but I think those would have to be corroborated with nearby areas to guess at the extent of the event.   As Carver's said, John's resources might be extremely helpful in allowing me to get a beginning set of dates to look at newspapers in places like London, KY; Knoxville, TN; Tri-Cities (maybe all, but I'm betting sometimes Johnson City gets it when others don't); Nashville, TN; Memphis, TN; Chattanooga,TN; and Huntsville, AL. This seems like a wide net to catch anything in the middle I may have missed, but happy to include other places. 

Also: wonder how many of the Kocin-Uccellini  storms impacted us. I know that book is not primarily interested in the TN Valley, but might be worth a shot to look at to help eliminate or add some dates. Will check it out. 

Sounds kinda fun!  So much has been digitized that it may not be too daunting, but won't know until I start. 

 

[John1122]

I'll get on some of that later tonight. Obviously look at March 1960 to start. There were 3 or so 6+ inch events as well as prolonged NW flow. 

[John1122]

March of 1980 was bitter cold with 4-6 inches of snow in the area. Temps were down to -6 degrees on March 3rd. -10s in SE Kentucky and near 0 down to Knoxville. February 20th-27th was pretty warm with highs in the 70s a few days. Turned cold February 28th and a storm moved through March 1st.  Was rain to snow for areas south of 40, freezing rain and snow for the plateau and SE KY, if memory serves. Some of you guys may remember it. 

March 7th and 8th 1996 was very cold with 5 inches of snow here. 

[jaxjagman]

Here is Nashville averages 1971-2000

http://drought.unl.edu/archive/climographs/pdf/Nashville.pdf

Memphis

http://drought.unl.edu/archive/climographs/pdf/Memphis.pdf

 

You can try this site also, just click your state.But like it says: Important Note:  8/5/2011 - County names have been added, but there are some errors.  Use with caution.

http://ggweather.com/normals/monthly.htm

 

 

[Holston_River_Rambler]

8 hours ago, John1122 said:

March of 1980 was bitter cold with 4-6 inches of snow in the area. Temps were down to -6 degrees on March 3rd. -10s in SE Kentucky and near 0 down to Knoxville. February 20th-27th was pretty warm with highs in the 70s a few days. Turned cold February 28th and a storm moved through March 1st.  Was rain to snow for areas south of 40, freezing rain and snow for the plateau and SE KY, if memory serves. Some of you guys may remember it. 

March 7th and 8th 1996 was very cold with 5 inches of snow here. 

Something of interest already, without any research.  On WBIR this AM, looking at when KTYS's record highs for the remainder of this week were hit, ones we may break, two years stood out: 1996 and 1980.   

[jaxjagman]

Records lows in the west and highs in the east

 

http://coolwx.com/record/usamovie.day.php

[Carvers Gap]

That is one cold run of the 12z Euro operational from d8-10.  Matches the GEFS and EPS at 0z.  No idea if it holds...but nice to see an operational retrograde the cold into the EC.  

[WinterWonderland]

Hmmm.

[Carvers Gap]

The progression of the 18z GEFS is pretty awesome.  @WinterWonderland, it definitely evolves to that look.  Thanks for the share!

[Holston_River_Rambler]

After looking at some of the biggest March storms over the last century, it seems as though the upcoming pattern progression does have some similarities.  Retrograding and weakening -NAO and hopefully, eventually, some Pacific cooperation. For my evidence for this, see the images in the historic thread. The caveats here are I only plugged in successful dates for the TN Valley based on the KU book and John's data, so the generated pattern composites I posted there may not be the best for all in the forum and since I plugged in successful dates, maybe there were similar patterns that failed.  I will also say that the composite seemed to start the -NAO a little south of its current forecast. 

Wouldn't you know it, at about the same time those producing patterns progressed from big -NAOs to an actual storm (roughly two weeks) the 6z GFS pops something at the end of its run. I know its the 6z GFS in lala land, but the GFS has been pretty solid with a storm signal for a different storm for the upper MA for the past 5-7 days or so.  Now where that storm has been generated on each run has flipped and flopped like a big old fish, but overall it has trended south and the Euro is showing it way south now from where it originally popped at 384 hours on the GFS. If this is the trend for the new pattern when the storm now at hour 384 gets closer, say in 5-7 days, we will be excited. 

Or it could all be gone, since it is the 384 hour GFS.  

[nrgjeff]

If lows get going as far west as AccuWx depicts, we'd be in business, in contrast to a Carolina gin up. Appears from our Historical Events thread (thank you members) that the -NAO can get it done in March. The best non-model reason for hope is simply March moisture. What might take until SC to gin up in Jan/Feb could get going in Bama in March. That's not a forecast, but some hopeful climo.