Winter 2013-14 Pattern Discussion II

[Batman]

Today is probably the most promising look we have had this winter for a combination of snow and cold in the MR and LR. I really think you have to realize that all the factors that folks like to harp on don't always materialize. And, when they do, they don't always produce.  January 2010 had a ton of cold with NAO, AO, and PNA nearly perfect. However MBY did not get snow with that January set up. Our big snow came in Feb. that year. It's kind of funny. People complain that the models aren't showing anything. Then, when it does show something, they say "it will probably be gone next run". Makes me laugh. You have to look at patterns. Compared to the last couple winters, this pattern is a big improvement. We have been wet and we have been cold. Remember .25 to .50 of precip. is not a big storm, but it is enough to make a very good winter storm in the SE if it falls as frozen precip. The models look promising to me, but what do I know? I take heart in the fact that some on here and other places that are more knowledgeable than I am are rather optimistic about the next few weeks. 

[Cold Rain]

OK, question time for me. Why do we desperately need a -NAO block go get a good snow? My guess is that it would allow a potential storm more time to develop before it gets out of the SE. It just seems as if we should still have opportunities with such a tall ridge in the west. All of the energy seems to want to head due east out of the Rockies instead of digging for the gulf. Would a -NAO help systems dig further out west too?

I'll admit a little frustration with us having a pattern that has been both very wet and very cold, but has yet to produce much winter weather.

When you don't have a true split flow, and you're relying on northern stream energy to create both cold air and precpitation, you have to get a tall enough PNA ridge and a strong enough shortwave to dig far enough to the south and west of you and sharpen up the trough enough to get it to assume a neutral/negative tilt in time to draw in moisture and create lift before it exits the area. That is not all that common of a scenario this far south. That's where a nicely placed -NAO can help. It can help in a couple of ways:

1) It can lock in the PV or a 50/50 in place to keep confluence up north. This allows high pressure to generate/remain in a favorable location, funneling cold into the area.

2) It can help slow the flow. You know how the trough is screaming across the east and it doesn't form a storm till it's way off the coast? The -NAO will act to slow that bad boy down. That allows the shortwave to dig more and spin up a storm closer to the coast. The storm would then move up the coast instead of rushing out to sea in a fast flow.

There are more subtleties that can come into play here, but that's the biggest thing.

You don't have to have a -NAO to get a snow event or even a bonafide snowstorm. A perfectly placed PNA ridge, a perfectly strong, digging shortwave having cold air to work with can do the trick...but it'll be a fast mover.

In a split flow, you can also get a southern stream system scooting across the southern tier in tandem with a northern stream system scooting across the northern tier. They can remain separate, and if the northern system moves out ahead of the southern one just enough, you can get a nice winter event, since the cold air would be laid down before the moist southern stream system moves in. Or there would be opportunities for phasing in this scenario too, which could create a bigger event.

I hope that helps some.

[oconeexman]

Not only that, but the Atlantic has some ridging in Greenland from hour 144 through the end of the run. If the day 10 euro is correct, winter would soon be rocking in the SE.

JB has been honking on this and doubting the winter cancelled folks for days...as well as Robert. Ive believed that the back half of Jan to early Feb will be our time in the SE thanks to the experts.

Somebody in here...hopefully most all of us will get some snow in the next 4 weeks.

[Batman]

When you don't have a true split flow, and you're relying on northern stream energy to create both cold air and precpitation, you have to get a tall enough PNA ridge and a strong enough shortwave to dig far enough to the south and west of you and sharpen up the trough enough to get it to assume a neutral/negative tilt in time to draw in moisture and create lift before it exits the area. That is not all that common of a scenario this far south. That's where a nicely placed -NAO can help. It can help in a couple of ways:

1) It can lock in the PV or a 50/50 in place to keep confluence up north. This allows high pressure to generate/remain in a favorable location, funneling cold into the area.

2) It can help slow the flow. You know how the trough is screaming across the east and it doesn't form a storm till it's way off the coast? The -NAO will act to slow that bad boy down. That allows the shortwave to dig more and spin up a storm closer to the coast. The storm would then move up the coast instead of rushing out to sea in a fast flow.

There are more subtleties that can come into play here, but that's the biggest thing.

You don't have to have a -NAO to get a snow event or even a bonafide snowstorm. A perfectly placed PNA ridge, a perfectly strong, digging shortwave having cold air to work with can do the trick...but it'll be a fast mover.

In a split flow, you can also get a southern stream system scooting across the southern tier in tandem with a northern stream system scooting across the northern tier. They can remain separate, and if the northern system moves out ahead of the southern one just enough, you can get a nice winter event, since the cold air would be laid down before the moist southern stream system moves in. Or there would be opportunities for phasing in this scenario too, which could create a bigger event.

I hope that helps some.

One of the best explanations I have ever heard on something folks try to figure out every winter. Great work CR!

[packfan98]

When you don't have a true split flow, and you're relying on northern stream energy to create both cold air and precpitation, you have to get a tall enough PNA ridge and a strong enough shortwave to dig far enough to the south and west of you and sharpen up the trough enough to get it to assume a neutral/negative tilt in time to draw in moisture and create lift before it exits the area. That is not all that common of a scenario this far south. That's where a nicely placed -NAO can help. It can help in a couple of ways:

1) It can lock in the PV or a 50/50 in place to keep confluence up north. This allows high pressure to generate/remain in a favorable location, funneling cold into the area.

2) It can help slow the flow. You know how the trough is screaming across the east and it doesn't form a storm till it's way off the coast? The -NAO will act to slow that bad boy down. That allows the shortwave to dig more and spin up a storm closer to the coast. The storm would then move up the coast instead of rushing out to sea in a fast flow.

There are more subtleties that can come into play here, but that's the biggest thing.

You don't have to have a -NAO to get a snow event or even a bonafide snowstorm. A perfectly placed PNA ridge, a perfectly strong, digging shortwave having cold air to work with can do the trick...but it'll be a fast mover.

In a split flow, you can also get a southern stream system scooting across the southern tier in tandem with a northern stream system scooting across the northern tier. They can remain separate, and if the northern system moves out ahead of the southern one just enough, you can get a nice winter event, since the cold air would be laid down before the moist southern stream system moves in. Or there would be opportunities for phasing in this scenario too, which could create a bigger event.

I hope that helps some.

Thank you very much CR.  I always like learning.  That's why I like to come to this site.  Unfortunately there hasn't been as much of a focus on learning the meteorology this year as there has been about model regurgitation, whining and complaining.  I am not a big fan of following the twitter generation one-liners to get my weather.  It's much more complicated than that.  Thank you to all who post the in-depth discussions and breakdowns for us who want to learn!

[NTriadwx]

When you don't have a true split flow, and you're relying on northern stream energy to create both cold air and precpitation, you have to get a tall enough PNA ridge and a strong enough shortwave to dig far enough to the south and west of you and sharpen up the trough enough to get it to assume a neutral/negative tilt in time to draw in moisture and create lift before it exits the area. That is not all that common of a scenario this far south. That's where a nicely placed -NAO can help. It can help in a couple of ways:

1) It can lock in the PV or a 50/50 in place to keep confluence up north. This allows high pressure to generate/remain in a favorable location, funneling cold into the area.

2) It can help slow the flow. You know how the trough is screaming across the east and it doesn't form a storm till it's way off the coast? The -NAO will act to slow that bad boy down. That allows the shortwave to dig more and spin up a storm closer to the coast. The storm would then move up the coast instead of rushing out to sea in a fast flow.

There are more subtleties that can come into play here, but that's the biggest thing.

You don't have to have a -NAO to get a snow event or even a bonafide snowstorm. A perfectly placed PNA ridge, a perfectly strong, digging shortwave having cold air to work with can do the trick...but it'll be a fast mover.

In a split flow, you can also get a southern stream system scooting across the southern tier in tandem with a northern stream system scooting across the northern tier. They can remain separate, and if the northern system moves out ahead of the southern one just enough, you can get a nice winter event, since the cold air would be laid down before the moist southern stream system moves in. Or there would be opportunities for phasing in this scenario too, which could create a bigger event.

I hope that helps some.

I have a question about the -NAO. How many times have we had a -NAO during some of the major, widespread winter events in the SE? The Jan. 88' storm comes to mind, along with some of the other major events. Thanks

[GaWx]

Today is probably the most promising look we have had this winter for a combination of snow and cold in the MR and LR. I really think you have to realize that all the factors that folks like to harp on don't always materialize. And, when they do, they don't always produce.  January 2010 had a ton of cold with NAO, AO, and PNA nearly perfect. However MBY did not get snow with that January set up. Our big snow came in Feb. that year. It's kind of funny. People complain that the models aren't showing anything. Then, when it does show something, they say "it will probably be gone next run". Makes me laugh. You have to look at patterns. Compared to the last couple winters, this pattern is a big improvement. We have been wet and we have been cold. Remember .25 to .50 of precip. is not a big storm, but it is enough to make a very good winter storm in the SE if it falls as frozen precip. The models look promising to me, but what do I know? I take heart in the fact that some on here and other places that are more knowledgeable than I am are rather optimistic about the next few weeks. 

 

 I agree with you. For what more can we ask? We appear to have a very cold pattern the next couple of weeks, even with cold intense enough to be called "stupid". We also already have two systems to track just this week alone. It may not be ideal (no persistent -NAO) but it sure is better than the average late January! We may end up with a top 10 to 15 cold Jan. going back to the late 1800's! Folks need to keep in mind that this is the SE, not the Mid-Atlantic or NE.

 

 I agree that 0.25 to 0.50" can make for a significant to major SE snowstorm if it is all snow and it sticks. Some of the major KATL snowstorms only had ~0.40-0.50" of liquid equivalent (4-5" of snow if no melting).

 

Edit: Fwiw, the 12Z Euro ensemble mean suggests an elevated chance for SE snow ~1/25, which would be between the 3rd and 4th cold airmasses. Looking at individual members, you can see some with enough digging to our west to allow for moist WSW 500 mb flow while 850's suggest it is still cold enough for many areas, especially those well inland.

[griteater]

From CPC Aftn update...

8-14 DAY OUTLOOK FOR JAN 21 - 27 2014   TODAY'S WEEK-2 500-HPA HEIGHT MANUAL BLEND SUGGESTS A MORE AMPLIFIED PATTERN  ACROSS THE CONUS THAN IN THE 6-10 DAY PERIOD; THIS IS A RARE OCCURRENCE,  CONSIDERING THE AMPLITUDE OF THE PATTERN IN THE 6-10 DAY PERIOD AND THE USUAL  INCREASE IN MODEL UNCERTAINTY AT LONGER LEADS TIMES. THIS SUGGESTS A  SUBSTANTIAL SUBSEASONAL CLIMATE EVENT IS FORECAST TO UNFOLD ACROSS THE CONUS,  WITH THE MEAN 500-HPA RIDGE FORECAST TO RETURN TO WHAT HAS BEEN ITS FAVORED  POSITION OVER THE PAST COUPLE OF MONTHS: THE FAR NORTHEASTERN PACIFIC. THE  DAILY PROGRESSION OF BOTH THE GFS AND ECMWF ENSEMBLE MEANS FROM DAYS 10 TO 15  IS IMPRESSIVE, WITH THE HIGH-AMPLITUDE RIDGE/TROUGH SYSTEM FORECAST TO SLOWLY  RETROGRADE.

[griteater]

I have a question about the -NAO. How many times have we had a -NAO during some of the major, widespread winter events in the SE? The Jan. 88' storm comes to mind, along with some of the other major events. Thanks

 

I would guess that 75% - 90% of the big events had some level of -NAO influence leading up to the storm.  2 of the biggies that did not are Jan '88 and Feb '73...both of those were during ninos

[Cold Rain]

One of the best explanations I have ever heard on something folks try to figure out every winter. Great work CR!

 

 

Thank you very much CR.  I always like learning.  That's why I like to come to this site.  Unfortunately there hasn't been as much of a focus on learning the meteorology this year as there has been about model regurgitation, whining and complaining.  I am not a big fan of following the twitter generation one-liners to get my weather.  It's much more complicated than that.  Thank you to all who post the in-depth discussions and breakdowns for us who want to learn!

 

Thanks guys.  And there are more cause and effect scenarios than what I posted, but those are some of the biggest elephants in the room.  And I agree...it's great to come on here every day and learn some new things.  Hopefully, we can cash in with some snow this winter.  I believe we will.

[Cold Rain]

I would guess that 75% - 90% of the big events had some level of -NAO influence leading up to the storm.  2 of the biggies that did not are Jan '88 and Feb '73...both of those were during ninos

 

Grit, do you know if the 1/25/2000 event or the Jan 2/3 2003 systems had a -NAO?  Those were two good ones for this area.

[GaWx]

Grit, do you know if the 1/25/2000 event or the Jan 2/3 2003 systems had a -NAO?  Those were two good ones for this area.

 

I'm not grit, but I have the answer:

 

1/25/2000: NAO was -0.529..so moderately negative

1/2-3/03: NAO was -0.050 to -0.115..so slightly negative but pretty much neutral

[Northern Foothills Snowman]

Grit, do you know if the 1/25/2000 event or the Jan 2/3 2003 systems had a -NAO?  Those were two good ones for this area.

What about January 1996 and March 1993 did those have -NAO ?

[griteater]

GA, I think Cold Rain meant 1/2/2002 instead of 2003.  One thing of note is that the most important period for the NAO to be negative is in the week / days leading up to the storm...moreso than the day of the storm (IMO).  

 

Back to those 2 dates, yes, the NAO was negative leading up to both Jan 25, 2000 (more east based) and Jan 2, 2002 (more west based).

[Cold Rain]

I'm not grit, but I have the answer:

 

1/25/2000: NAO was -0.529..so moderately negative

1/2-3/03: NAO was -0.050 to -0.115..so slightly negative but pretty much neutral

 

Thank you sir.  When I get a chance, I'm going to try to go back and look at those and see where the heigher heights were (east based/west based)...that can make a big difference.

[griteater]

What about January 1996 and March 1993 did those have -NAO ?

 

Negative leading into Jan '96 and neutral leading into Mar '93

[Cold Rain]

GA, I think Cold Rain meant 1/2/2002 instead of 2003.  One thing of note is that the most important period for the NAO to be negative is in the week / days leading up to the storm...moreso than the day of the storm (IMO).  

 

Back to those 2 dates, yes, the NAO was negative leading up to both Jan 25, 2000 (more east based) and Jan 2, 2002 (more west based).

 

I did...and you just answered my previous post!  Thank you!

[jharv]

From CPC Aftn update...

8-14 DAY OUTLOOK FOR JAN 21 - 27 2014   ....SUGGESTS A SUBSTANTIAL SUBSEASONAL CLIMATE EVENT IS FORECAST TO UNFOLD....

 

Anyone care to interpret that statement?  Looking through those analog dates I found this: http://en.wikipedia.org/wiki/North_American_blizzard_of_2009

 

Not particularly memorable for most of the southeast but I'm wondering if this is what they have in mind.

 

Edit: Disregard the storm comparison....wrong month in comparison to analog dates.

[griteater]

Anyone care to interpret that statement?  Looking through those analog dates I found this: http://en.wikipedia.org/wiki/North_American_blizzard_of_2009

 

Not particularly memorable for most of the southeast but I'm wondering if this is what they have in mind.

 

Edit: Disregard the storm comparison....wrong month in comparison to analog dates.

 

My guess is that they are expecting some areas in the east to experience well below normal temperatures, and some areas in the west to experience well above normal temperatures, in days 8-14

[BullCityWx]

I know that you typically get storms when the NAO is flipping. 

[Met1985]

Great discussion in here today guys. CR great explanation for sure.

[GaWx]

Euro weeklies (just released):

Week 2 (Jan. 20-26): precip. ~0.50"; temp.'s: 2-4 below normal NC/SC/most of GA & 4-6 below far SE GA into FL

Week 3 (Jan. 27-Feb. 2): precip. ~0.75-1"; temp.'s: 3-4 below normal NC/SC/GA & 1-3 below FL

Week 4 (Feb. 3-9): precip. ~0.75-1"; temp.'s: near normal

NAO: neutral weeks 2-3 and slightly positive week 4

AO: slightly negative week 2 and solidly negative weeks 3-4

EPO: strong negative week 2, moderate negative week 3, neutral week 4

PNA: strong positive week 2, weak positive week 3, neutral week 4

[Jon]

Euro weeklies (just released):

Week 2 (Jan. 20-26): precip. ~0.50"; temp.'s: 2-4 below normal NC/SC/most of GA & 4-6 below far SE GA into FL

Week 3 (Jan. 27-Feb. 2): precip. ~0.75-1"; temp.'s: 3-4 below normal NC/SC/GA & 1-3 below FL

Week 4 (Feb. 3-9): precip. ~0.75-1"; temp.'s: near normal

NAO: neutral weeks 2-3 and slightly positive week 4

AO: slightly negative week 2 and solidly negative weeks 3-4

EPO: strong negative week 2, moderate negative week 3, neutral week 4

PNA: strong positive week 2, weak positive week 3, neutral week 4

The weekly control also looks really active for the SE through Feb. Good to see!

[BullCityWx]

I'm pretty dadgumed impressed by the amount and longevity of the cold on the 12z euro ensemble mean.

[GaWx]

I'm pretty dadgumed impressed by the amount and longevity of the cold on the 12z euro ensemble mean.

Fwiw, several of the 12Z Euro ensemble members may be producing snow in parts of the SE 1/25, the same day that the 18Z GFS produces snow.

[metalicwx366]

Fwiw, several of the 12Z Euro ensemble members may be producing snow in parts of the SE 1/25, the same day that the 18Z GFS produces snow.

Do you know why this map only has the much below normal temperatures focused on SGA and NGA?

http://www.cpc.ncep.noaa.gov/products/predictions/threats/hazards_d3_7_contours.png

[NEGa]

Fwiw, several of the 12Z Euro ensemble members may be producing snow in parts of the SE 1/25, the same day that the 18Z GFS produces snow.

 

i'll take it lol. if i recall the 25th has had a number of snows over the years.  i think people got spoiled with two back to back knock out winters a couple of years ago. that kind of blocking and sustained cold is not common in the se. most of the ones over the years have been pop ups within a couple of days once we have cold air  or a reinforcing shot of cold hits with precip (other than the bowling ball effect).  it sucks but most of the time cold air chasing rain to changeover rarely happens.  we need the cold first as half of the ingredients.  once we get that its waiting for a little (or big haha) low to pop up or for some overrunning.  seems like we are also getting into the time of year where i recall several pretty good icing events

[Isopycnic]

Do you know why this map only has the much below normal temperatures focused on SGA and NGA?

http://www.cpc.ncep.noaa.gov/products/predictions/threats/hazards_d3_7_contours.png

Yes.

[Jon]

Yes.

lol

 

Do you know why this map only has the much below normal temperatures focused on SGA and NGA?

http://www.cpc.ncep.noaa.gov/products/predictions/threats/hazards_d3_7_contours.png

You didn't ask me, but it's because at 12z 1/16 there are -24.4 anomaly 2m temps on the Florida panhandle. That's definitely much below normal. By the looks of it they're hugging the Euro for their map.

[EmersonGA]

I was looking forward to the cold until the power bill came in today. $200 this past month when normal is close to $100. It is going to be a long winter.