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2016-2017 Great Tennessee Valley Winter Discussion


John1122

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Next Thursday, the GFS is showing a deep in the Gulf LP that comes from Southern Texas and goes towards Central Florida.  It was also way south with the early Jan storm as well as countless others over the years. The GGEM and Euro are kicking the storm out a little earlier, not giving it as much time to dig and it's further north. Still the 6-8 days from now timeframe features a storm on all the models. The UKMet is more similar to the GFS at 144.

The difference in this one and Early Jan is that the Early Jan storm was a late bloomer. It didn't get going in time to effect anyone but the far east areas. This storm gets going plenty early but is too far south on the GFS and too far North on the Euro/GGEM. If you split the difference in the tracks you'd get just about a perfect track. Climo wise. mid February is a prime time for major snowstorms in the region.

 

gfs_T850_us_31.png

 

GGEM is 18 hours faster/further north,

gem_T850_us_28.png

Euro is a day and a half faster, slightly south of the GGEM, way north of the GFS. A bit colder than the GGEM.

ecmwf_T850_us_7.png

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33 minutes ago, John1122 said:

Next Thursday, the GFS is showing a deep in the Gulf LP that comes from Southern Texas and goes towards Central Florida.  It was also way south with the early Jan storm as well as countless others over the years. The GGEM and Euro are kicking the storm out a little earlier, not giving it as much time to dig and it's further north. Still the 6-8 days from now timeframe features a storm on all the models. The UKMet is more similar to the GFS at 144.

The difference in this one and Early Jan is that the Early Jan storm was a late bloomer. It didn't get going in time to effect anyone but the far east areas. This storm gets going plenty early but is too far south on the GFS and too far North on the Euro/GGEM. If you split the difference in the tracks you'd get just about a perfect track. Climo wise. mid February is a prime time for major snowstorms in the region.

 

gfs_T850_us_31.png

 

GGEM is 18 hours faster/further north,

gem_T850_us_28.png

Euro is a day and a half faster, slightly south of the GGEM, way north of the GFS. A bit colder than the GGEM.

ecmwf_T850_us_7.png

Ok makes sense thank you 

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GFS moved north, the Canadian moved south. Track was perfect on the Canadian but it generates an extremely small precip shield. But that is a major model bias for many years as well, undermodeling precip shields on GOM systems.

No chance this low sitting right there is barely throwing precip 125 miles north and north east of it's center.

gfs_mslp_pcpn_frzn_us_25.png

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Euro is the better model here. See I'm not always a warm/miss monger, lol. Euro is simply better, and this time it has the more snow friendly forecast. GFS is lost as usual, no clue how to handle the two streams. Canadian is not a good tie breaker here. Use the Euro. It might change over the weekend, but it'll be better than the GFS.

If it happens, looks like I-40 north. Two streams are almost always a no-go south of I-40 due to boundary layer issues, poor dynamics, poor orographics and a host of other issues. I have to like maybe Nashville, perhaps Knoxville, and moreso TRI. Even up north/northeast, boundary layer concerns are noted. Euro has the better track but no true surface high north. One would look for surface ridging coming in in the wake of the northern stream trough, but not a GFS style scouring. What's new in the South? Thread the needle.

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The GFS may indeed be right, but the NW trend on it is legendary. We don't need it to run up the coast, just need it in the right spot. Sliders are often better for the entire region.  If it phases like the Euro is showing, big potential but for a smaller area. Either way it's a fine line between nothing/rain or snow. 

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GFS keeps creeping the precip shield further north.

gfs_mslp_pcpn_frzn_us_14.png

 

850s are sub freezing in most of Tennessee during this time frame and 6 hours later. May not quite get there, but I've seen the precip shield under modeled time after time with these.

Canadian gets precip to the Kentucky border. 850s are below 32 and surface temps are in the mid to upper 30s North of I-40. 

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Having that low in the Great Lakes is not a good thing(for our area) referring to the way it is currently modeled.   I like the weak  track of the southern feature...but that GL low is a big problem.  I have previously seen what appeared to be decent chances soured by even the weakest lows in the GL.  The mountains of E TN and the higher elevations of SW VA are still in the game for a quick shot.  I would not be surprised to see some minor mixing at lower elevations in NE TN and SW VA if the12z NAM is correct.   

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3 minutes ago, Carvers Gap said:

Having that low in the Great Lakes is not a good thing(for our area) referring to the way it is currently modeled.   I like the weak  track of the southern feature...but that GL low is a big problem.  I have previously seen what appeared to be decent chances soured by even the weakest lows in the GL.  The mountains of E TN and the higher elevations of SW VA are still in the game for a quick shot.  I would not be surprised to see some minor mixing at lower elevations in NE TN and SW VA if the12z NAM is correct.   

Would this be a scenario were we would want that GL low more to the west?  Maybe over the Dakotas or minnesota?  I only ask cause I'm trying to fully understand it.

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4 minutes ago, AMZ8990 said:

Would this be a scenario were we would want that GL low more to the west?  Maybe over the Dakotas or minnesota?  I only ask cause I'm trying to fully understand it.

Probably just want it gone.  LOL.  Need it earlier which means more eastward.  Looked like a good set-up at d7...but a non-phased slp over the top pretty much makes a mess of temps profiles and dynamics of the system to the south.  Been a tough winter, but I would not even list this as a miss.  Typical Feb system that lacks cold air.

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Thinking the same thing, Carver...didn't we have some severe weather in early March in 1993? This volatile weather can produce some wild swings.


The severe weather was in mid February of 93'. Oak Ridge and Lenoir City got F-3's and a F-2 came within a mile of my house in Powell.


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13 minutes ago, AMZ8990 said:

Would this be a scenario were we would want that GL low more to the west?  Maybe over the Dakotas or minnesota?  I only ask cause I'm trying to fully understand it.

I have, much like others in the forum, many things that are in the early stages of budding out. Likely, after this week with only two night, likely 12 hours or slightly more, below freezing, there will be lots of things blooming. I know my Saucer Magnolia is about two weeks out from blooming. I really hope we can avoid a situation like we were in March of 2007 where we had three consecutive nights with lows in the low to mid 20's 17th - 19th I believe. Was really the oddest thing because almost every tree was leafed out. Most did not appear damaged until a few days later when the leaves started shriveling. There were some trees that had not put back out again until mid to late April.

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12z CMC is the juiciest of the models so far today and also the coldest. It has 1-3 over NE TN and the mountains with .5 of QPF for most of the valley. Unfortunately the Great Lakes low will have to be there for us to pull the gulf low northwest. We have to have some sort of phase. I like how this has trended wetter this morning. I think the models have backed the northern stream up some allowing the southern stream to gain a little traction. I think that this will end up being a 2-4 inch storm for the mountains and SWVA and maybe 1-3 for the northeast valley. This is one of those "just in time" scenarios. The 850's will be fine but the surface temps will be a huge problem. Hopefully we can get the push of cold air and precip to arrive quicker overnight Tuesday.

12z CMC

463cda16697781ca3c32539d9af00d13.jpg

533a15721253b1b53c884569c9778f99.jpg

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2 hours ago, weathertree4u said:

I have, much like others in the forum, many things that are in the early stages of budding out. Likely, after this week with only two night, likely 12 hours or slightly more, below freezing, there will be lots of things blooming. I know my Saucer Magnolia is about two weeks out from blooming. I really hope we can avoid a situation like we were in March of 2007 where we had three consecutive nights with lows in the low to mid 20's 17th - 19th I believe. Was really the oddest thing because almost every tree was leafed out. Most did not appear damaged until a few days later when the leaves started shriveling. There were some trees that had not put back out again until mid to late April.

2007= Worst. Spring. Ever. 

Exactly 10 years ago.  Hoping that 2017 is NOT a repeat, but it's looking bad if we don't get some major cool spells in March.

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Models have been showing a robust shortwave towards the GC region, long range.Not sure i buy the Euro colder look in the 850's compared to the GFS.Winds coming from the S/SW should  warm that layer up than cooler.The MJO is going into the IO  unlike what the GEFS is showing towards the end of the month IMO

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10 minutes ago, jaxjagman said:

Models have been showing a robust shortwave towards the GC region, long range.Not sure i buy the Euro colder look in the 850's compared to the GFS.Winds coming from the S/SW should  warm that layer up than cooler.The MJO is going into the IO  unlike what the GEFS is showing towards the end of the month

Yep.  I have been operating on the idea that the MJO influence (of a given phase) is delayed by about a week.  Has worked pretty well for me this winter.  Plenty of evidence that another winter weather window around Feb 25th is there.  I really like seeing the active storm track to the northeast.  What is missing is cold and has been since Dec.. 80s all over the southeast today according to wxsouth.  Not unexpected, but still...it is Feb.

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30 minutes ago, Carvers Gap said:

Yep.  I have been operating on the idea that the MJO influence (of a given phase) is delayed by about a week.  Has worked pretty well for me this winter.  Plenty of evidence that another winter weather window around Feb 25th is there.  I really like seeing the active storm track to the northeast.  What is missing is cold and has been since Dec.. 80s all over the southeast today according to wxsouth.  Not unexpected, but still...it is Feb.

The euro is way to warm to me with the 850'S,NO snow pack towards the lakes region the 850's shouldn't have any problem to pump up the Valley.We could have a transient cold spell like you mention,but there is nothing going on in Asia before this mentioned time frame,not very excited for winter other than a hopefully clipper type system.Really think another severe threat first of the month might be looming ahead

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Here's how odd the weather is behaving. It was 70-80 across the region today. A powerful cold front moved through that will drop temps by 30+ degrees by tomorrow. It didn't even thunder. Normally that would be a recipe for a severe event.  But it was just a few passing rain showers and it didn't even thunder. 

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3 hours ago, John1122 said:

Here's how odd the weather is behaving. It was 70-80 across the region today. A powerful cold front moved through that will drop temps by 30+ degrees by tomorrow. It didn't even thunder. Normally that would be a recipe for a severe event.  But it was just a few passing rain showers and it didn't even thunder. 

What ingredients were missing exactly I wonder?

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11 hours ago, jaxjagman said:

The euro is way to warm to me with the 850'S,NO snow pack towards the lakes region the 850's shouldn't have any problem to pump up the Valley.We could have a transient cold spell like you mention,but there is nothing going on in Asia before this mentioned time frame,not very excited for winter other than a hopefully clipper type system.Really think another severe threat first of the month might be looming ahead

Twelve days out, details will be hard to come by.   For sure there are many negatives, especially eroding climo chances that are eroding daily.  However, the models have been honed-in on this time frame for weeks(25th or just after) as a window for some cold and storms.  Nobody is guaranteeing anything.  (The 0z EPS itself is chilly centered on this date.) Could easily cut, have no cold, etc...the usually problems for the SE exist.  Nothing is a slam dunk even during good patterns.  However, there is no denying the models have liked that time frame.  Whether it is reality...nobody knows that...Severe wx fits climo as it will be early spring.  

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