Winter 2013-14 Pattern Discussion III

[WXinCanton]

I think you are jumping the gun just a little bit. This is going to be a powerful wedge..one that we don't normally see that is this strong. Given the setup here, I would expect there to be a really good chance of a meso high forming over the heart of the cad regions.  This is something that has caused many a busted forecast for those taking the models verbatim with the strongest wedges.  So right off the bat the warming the gfs is showing at the surface is virtually impossible from where I sit. So a lot of front end freezing rain and/or sleet here except in nc where 850s actually cool initially because the wedge actually extends up to that level. Although we saw signs of it with our last major storm, it's rare and another sign of the strength involved.

 

Then comes the upper low where the gfs has a near isothermal layer around freezing somewhere to the north of the low. That area is likely to be snow and heavy snow at that. As is the case a lot of times with upper lows though, areas further north might be warmer than areas further south. It all depends on the track of the upper low, where the heavy precip is, etc.

 

 Wedges are hard enough to forecast for as it is. Throw in the fact it's many days away and Throw in a strong upper low and you are talking about a pretty complicated scenario overall that is likely to change big time from run to run.  To pretend like it's going to be all rain, all snow, or anything but everything right now is really silly.

 

Have you ever seen a meso high modeled in CAD situation?  I can't seem to ever recall one

[packbacker]

I think you are jumping the gun just a little bit. This is going to be a powerful wedge..one that we don't normally see that is this strong. Given the setup here, I would expect there to be a really good chance of a meso high forming over the heart of the cad regions.  This is something that has caused many a busted forecast for those taking the models verbatim with the strongest wedges.  So right off the bat the warming the gfs is showing at the surface is virtually impossible from where I sit. So a lot of front end freezing rain and/or sleet here except in nc where 850s actually cool initially because the wedge actually extends up to that level. Although we saw signs of it with our last major storm, it's rare and another sign of the strength involved.

 

Then comes the upper low where the gfs has a near isothermal layer around freezing somewhere to the north of the low. That area is likely to be snow and heavy snow at that. As is the case a lot of times with upper lows though, areas further north might be warmer than areas further south. It all depends on the track of the upper low, where the heavy precip is, etc.

 

 Wedges are hard enough to forecast for as it is. Throw in the fact it's many days away and Throw in a strong upper low and you are talking about a pretty complicated scenario overall that is likely to change big time from run to run.  To pretend like it's going to be all rain, all snow, or anything but everything right now is really silly.

 

Your probably right, the last event the wedge was crazy strong.

[rduwx]

Cmc is way south w/ the 3/3 storm and looks interesting for a lot of NC.  Probably not right but interesting.

[deltadog03]

I fully agree with Chris. This wedge looks to be not only a descent amount stronger than last wedge, but in better spot and holding Longer. That airmass is just as cold as the last one. Super impressive cold. And the gfs is still struggling, IMO with that, as Chris said, the warming of temps. Not gonna happen. This run further shows me that the euro prolly has the right general idea here.

[packbacker]

Cmc is way south w/ the 3/3 storm and looks interesting for a lot of NC.  Probably not right but interesting.

 

Yeah, crazy run, has 1-2" of snow for NC for I-40 north (Rocky Mount, RDU to Triad), with almost 3" at the NC/VA border.  Plus it has some sleet.  Not buying unless Euro shows it.

[SD1]

The CMC model is 4DVAR like the Euro so it could be right.

[superjames1992]

The GFS is pretty far south with 3/3, too.  It's a long shot, but there's no doubt that every model has come significantly south today and any weenie north of the Mason Dixon Line is now on suicide watch.  I expect nothing, but I'm always open for suprises.  The frontal passage with its ridiculous temperature drop should be entertaining, if nothing else.

[SD1]

The extensive snow cover that is going to cover the ground to our North will definitely help with surface temperatures.

[superjames1992]

Another positive shift with the GFS, IMO.  Looks to start out as some snow for some of us.  It does go into torch mode later on, but baby steps...

 

LOL, looks like the GGEM gives N NC a fairly significant snowfall with the 3/3 storm.  I'll drink to that. 

 

If the GGEM was a hair colder on 3/6, it's absolute destruction.  I'll just say dynamics and trim mid-level temperatures by a degree or two Celsius and take my crushing.

[deltadog03]

Hell I think it took a gigantic step. Lol

[griteater]

GFS soundings for Charlotte...

 

hr 132 - snow

hr 138 - snow

hr 144 - sleet

hr 150 - frz rain

hr 156 - rain

[packbacker]

Another positive shift with the GFS, IMO.  Looks to start out as some snow for some of us.  It does go into torch mode later on, but baby steps...

 

LOL, looks like the GGEM gives N NC a fairly significant snowfall with the 3/3 storm.  I'll drink to that. 

 

Can we get the NAVGEM HP placement with the Euro SLP track, 

 

[rduwx]

CMC has the hp way to the north and not as strong so the cold air never gets in place.  Nice system out of the gulf but looks like rain w/ the exception of higher elevations of WNC.

[griteater]

I'm not positive the warm nose was necessarily overdone with the last event as much as we lost the snow growth zone (something a lot of us probably weren't looking for).  IIRC, MBY was getting pouring sleet with all layer of the atmospheres below freezing, but the dendritic growth zones weren't cold enough (they were below freezing, but not by enough to form snowflakes).

The mets have been over this. The warm nose wasn't underestimated, we lost moisture in the growth zone.

Temps during the portion of the storm we mention look safe. 850s are close to -1 and surface temps are at -2.

 

I actually think that there was a warm nose that moved into parts of central and western NC with the 2/12 storm.  Reanalysis maps confirm this.  Also, it is my understanding that you can't have sleet if you don't have moisture in the snow growth zone.  That is, sleet occurs when snowflakes melt, then refreeze before reaching the ground.  You have to have ice nuclei via moisture in the snow growth zone in order for the melted snowflake to refreeze into sleet.  If you have supercooled water droplets due to a lack of moisture in the snow growth zone, and thus no ice nuclei, you will get freezing rain or rain.  Someone correct if wrong.

 

See this post I entered in the Met 101 forum - http://www.americanwx.com/bb/index.php/topic/43038-saturation-with-respect-to-ice/

[packbacker]

CMC sucks overall, although the HP doesn't go east, it retreats north, which is way better than going east, but still mostly rain for everyone through 150.

[packbacker]

I actually think that there was a warm nose that moved into parts of central and western NC with the 2/12 storm.  Reanalysis maps confirm this.  Also, it is my understanding that you can't have sleet if you don't have moisture in the snow growth zone.  That is, sleet occurs when snow flakes melt, then refreeze before reaching the ground.  You have to have ice nuclei via moisture in the snow growth zone in order for the melted snowflake to refreeze into sleet.  If you have supercooled water droplets due to a lack of moisture in the snow growth zone, and thus no ice nuclei, you will get freezing rain or rain.  Someone correct if wrong.

 

See this post I entered in the Met 101 forum - http://www.americanwx.com/bb/index.php/topic/43038-saturation-with-respect-to-ice/

 

Well every model had us (RDU) with a warm nose so it wasn't shocking to see us flip to sleet/frzn.  The 2m temps verified colder than most models though.

[superjames1992]

CMC has the hp way to the north and not as strong so the cold air never gets in place.  Nice system out of the gulf but looks like rain w/ the exception of higher elevations of WNC.

 

Yeah, it's an irritating solution since it would be a crushjob with a few adjustments.  The surface low track is nice.  The good news is it's 6 days out.

 

Might be time for a new weenie rule that the Canadian slides HP out to the north too quickly or something.   

 

In all seriousness, we did see the HP gradually trend towards sticking around longer with the last storm, so maybe we can pull off that feat again.

 

I actually think that there was a warm nose that moved into parts of central and western NC with the 2/12 storm.  Reanalysis maps confirm this.  Also, it is my understanding that you can't have sleet if you don't have moisture in the snow growth zone.  That is, sleet occurs when snow flakes melt, then refreeze before reaching the ground.  You have to have ice nuclei via moisture in the snow growth zone in order for the melted snowflake to refreeze into sleet.  If you have supercooled water droplets due to a lack of moisture in the snow growth zone, and thus no ice nuclei, you will get freezing rain or rain.  Someone correct if wrong.

 

See this post I entered in the Met 101 forum - http://www.americanwx.com/bb/index.php/topic/43038-saturation-with-respect-to-ice/

 

Ah, well I stand corrected then.  Interesting.

[Northern Foothills Snowman]

The GFS is pretty far south with 3/3, too.  It's a long shot, but there's no doubt that every model has come significantly south today and any weenie north of the Mason Dixon Line is now on suicide watch.  I expect nothing, but I'm always open for suprises.  The frontal passage with its ridiculous temperature drop should be entertaining, if nothing else.

When is cold front supposted to go through NC ? I'm in NW NC foothills.

[packbacker]

CMC does get snow going in the mountains of NC after 150

[griteater]

UKMet not as strong this run with the wave and is more suppressed to the south, but still looks like it would be spreading some precip north...with temperatures, it has a strong damming high throughout.  Sfc high of 1040mb just NW of New York state at hr120, and 1035mb+ in western Massachusetts at hr144...at hr144, the 500mb trough axis for the storm runs through Alabama 

[GaWx]

 3/1 GFS is the best GFS run yet for N GA CAD areas for 3/6-7 and is, imo, a major ZR as modeled for ATL and AGS due to verbatim two meter temp.'s of 33-34 likely not quite being cold enough. (The 2nd best run was the 2/28 12Z run which had 1.25" of qpf with 2 meter temp.'s getting to ~35 at ATL-AHN.) Even verbatim, it is cold enough for major ZR or even IP (with 850's near +3 to +2 in AHN (31). MCN is only a little too warm verbatim for ZR (35) but it maybe would just reach near 32 in reality. With CAD like is on the 0Z run, 32 would get to ATL easily and would be very hard to dislodge. The wedging high is a very impressive 1041 and it moves out only very slowly. The 850's are near +3 to +4 at ATL, which is prime for major ZR. Wedge/prelow qpf is ~1", enough for major impact. Precip, starts earlier than the 12Z Euro, which started around 6 AM 3/6. The 0Z GFS starts near 9 PM 3/5.

 

  On the backside, the upper low produces generous qpf of close to 1"! It isn't as strong as that of the Euro and, therefore, 850's are ~+1 with no snow at ATL. With the main CAD retreating but no real warming source, this part is a tough call as to whether it be continued ZR at ATL, a switch to IP, or a switch to very cold rain. Verbatim, it warms a few degrees. Precip doesn't end til ~ 8 AM 3/7! So, ~35 hours of precip. and ~1.75-2"" of total qpf!! AHN is a little warmer with the upper low.

 

 SC: major IP (a few inches) at GSP with 28 and major ZR at CAE with 31.

 

 With it forecasted to get to 26-27 at HKY/CLT (mainly IP (several inches) though some SN HKY) and 28 at GSP, I think it would be colder in N GA than forecasted verbatim.

[superjames1992]

UKMet not as strong this run with the wave and is more suppressed to the south, but still looks like it would be spreading some precip north...with temperatures, it has a strong damming high throughout.  Sfc high of 1040mb just NW of New York state at hr120, and 1035mb+ in western Massachusetts at hr144...at hr144, the 500mb trough axis for the storm runs through Alabama 

 

You weren't kidding about it being more suppressed.  Quite interesting.  I do believe that is a bias of the UKMET, so it's good to see.

 

 

Nice CAD signature showing up there.  I think I'd take it, providing there was enough precip (which is not available past hr 72).

[GaWx]

UKMet not as strong this run with the wave and is more suppressed to the south, but still looks like it would be spreading some precip north...with temperatures, it has a strong damming high throughout.  Sfc high of 1040mb just NW of New York state at hr120, and 1035mb+ in western Massachusetts at hr144...at hr144, the 500mb trough axis for the storm runs through Alabama 

 

 As modeled, the 0Z UKMET's low going over C FL would probably still produce copious wintry precip. into N GA/upstate based on the SW 500 mb flow and the great CAD.

 

Example: today's 12Z GFS had the low similarly go over C FL and it still gave ATL-AHN 1.25" of qpf!

[deltadog03]

well the good doc/or maybe bad doc...has stepped up to plate and she is ready to fire away.

[dsaur]

 As modeled, the 0Z UKMET's low going over C FL would probably still produce copious wintry precip. into N GA/upstate based on

the SW 500 mb flow and the great CAD.

Well, this last ice storm is taking days to clean up from.  I just took a huge dead pine down today, and spent all day yesterday cutting trees off the back fence.  At least the coming storm will give me some pretty snow, maybe, to cover up all the new downed limbs and trees, lol...if the bulk is zr.  The UL  looks to favor me, and recent ones have done, but this time I need lower 850's from a much stronger high.  This last one just didn't get in quickly enough, or cold enough for much sleet...but at least the bulk of the precip missed being zr.  This one looks a good bit better, on a long range map, so maybe I'll finally get my sleet   That is impressive cad..and the last one wasn't bad.  T

[GaWx]

CMC has the hp way to the north and not as strong so the cold air never gets in place.  Nice system out of the gulf but looks like rain w/ the exception of higher elevations of WNC.

 

 Yes, the 0Z CMC may be too far north to provide cold enough CAD. However, that's not to say that highs that are SE Canada can't provide cold enough air/strong enough CAD:

 

 

Can SE get major ZR when parent high in SE Canada? YES per this

 

  I decided to look at old wx maps to see if I could find any major KATL ZR's for which the parent high was centered way up in SE Canada as opposed to the more typical NE US.

 

 Here are my results:

 

 Although not the preferred setup for the wedging parent high center, I was still able to find a respectable SIX out of 29 KATL major ZR storms since 1879 (21%) that were associated with a parent high that was initially in SE Canada and pretty much remained in Canada for the entire event:

 

1) 2/4-6/1905: 1045 mb high 150 miles NE of Lake Superior (in Ontario) that moved little.

 

2) 2/7-8/1905: 1042 mb high 150 miles NE of Lake Superior (in Ontario) that moved little.

 

**Note that the above two occurred only one day apart and therefore resulted in a severe situation at KATL.

 

3) 12/28-29/1935: 1030 mb high 100 miles NE of Lake Superior (in Ontario) that moved slowly eastward to 75 miles N. of Ottawa (in SW Quebec).

 

 ** This one above was a very severe one with 2.13" liquid at KATL!

 

4) 12/24/1945: 1043 mb high pretty far north near 51 N, 82 W (in E. Ontario).

 

5) 1/9-10/1968: 1045 mb high 250 miles NE of Toronto (in SE Ontario) that first moved NW ~300 miles (still in Ontario) and then moved further NW to SW of Hudson Bay (in NW Ontario) and then moved back SE to 250 miles NE of Lake Superior (still in Ontario). This high seemed to be blocked by a strong, nearly stationary closed low near the 50-50 position.

 

 ** This one above was one of the worst in NC/SC history as it produced 2-3" of ice and lasted up to one week in some of that area!! Worst power failure in Charlotte history (at least as of 1999).

 

6) 12/14-15/2005: 1040 mb high ~300 miles N. of Ottawa (in W. Quebec) that moved little.

 

CONCLUSION:

  Based on history, it does look as though a surface high centered in SE Canada is, indeed, capable of wedging all of the way down into GA and produce MAJOR ZR there (and of course in the Carolina's among other areas). It can happen as something similar has occurred at least six times since the late 1800's (mainly from Ontario as opposed to Quebec parent highs) with an average strength of 1041 mb. Furthermore, these six included some of the worst ZR storms at KATL as well as one of the worst and longest lasting ever for NC/SC (lasted from 1/9 though 1/15/1968 there due largely to a very slow moving 50-50 closed low).

[jburns]

Interesting. But there never has been one this late in the season. That doesn't mean there couldn't be, but it makes you stop and think.

[deltadog03]

Great work again Larry....Looks like its about the same as the 12z run through hr 96.  2m temps looks a little colder over the SE.

[superjames1992]

The 00z Euro argues for maybe some backside snow in N NC on the evening of 3/3.  It made a substantial shift south which is great for the DC area.

 

EDIT: Well, backside snow is iffy, but it's definitely either sleet or freezing rain as the surface is below freezing at hr 66 with another tenth or two to fall.  850s are crashing and would probably support a late changeover, but there might be a nasty warm layer in there at another level besides 850 mb that I can't see.

 

Of course, cold chasing the moisture always works out well, so I wouldn't get excited.

[deltadog03]

Run is a little slower through 6z thur, but colder a bit with 2m temps.  Looks like it may be a tick or 2 south vs 12z run.