December Forecast Discussion

[Wow]

It's amazing how much the -AO has decimated the Polar Vortex. This is honestly an amazing precursor IMO to a great pattern down the road. We just need some luck w/ the timing and pacific. December's AO number is going to be off the charts negative.

What's even more amazing is how that despite that sustained -AO, most of the US will end up above avg for December.

[nrhardin]

I dont post here too often, but I try to make them count. With that said, here are my thoughts on everything as it seems to be unfolding for the south:

Discouraging: The subtropical Pacific has really been hosing us so far this fall (it is still fall, after all). An anomalously persistent -PNA has also put a wrench in winter weather for essentially everyone east of the Mississippi. Models playing "catch-up" or adjusting to the Pacific, the result of which is a constant delay of cold air to the SE.

Encouraging: SOI plunging as WoW and others have mentioned. A solidly -AO aforementioned by Hky, which appears to really tank in the coming week and a half at least (net result a complete obliteration of the polar vortex). An apparent shift of the PNA to at least neutral, if not positive, values. CFS model output showing a cold look for much of the CONUS in Jan.

I believe the source of tension and nitpicking recently stems from the failure and uncertaintry of individual storms to pan out as modeled, even if we are attempting to diagnose them 7+ days out. If one pays attention, you will see mets harping on pattern recognition instead of minutia. This is all part of the "forecasting funnel" which starts with the longwave pattern and works down to smaller details.

With all of this being said, I for one am not "on board" with the post-Christmas storm resulting in too much excitement for the SE. Perhaps the arctic source high over Ontario will be stronger than modeled, which in my opinion will be the key for resulting in any sort of a sustained winter precip producer for CAD areas in this storm. What I do think we are seeing, and will continue to see, is a step down process of storm progression with time. Given the large scale signals I believe the beginning of the year provides a lot of hope for the SE. With each storm we will see a southward expansion of snow cover, which is another key to cold air and a more southern storm track. With the plunging SOI I believe we can expect to see a more active STJ with more disturbances in the flow. A neutral/positive PNA, -AO, and even progressive high latitude blocking...everything is looking up.

If I had two things to say for forecasting winter weather in the SE it would be this:

1. If you have to go out on a ledge to figure out a source of cold air (i.e. an anchored strong High over the lakes), it likely won't work out for lower terrain areas

2. Climatologically speaking, we are relegated to one or maybe two good events a season. Eventually we will cash in, but it may not be the blockbuster we all want.

Maybe some folks in the mtns and foothills of NC get some frozen precip around the 27, but if we can all stay patient for a little bit longer I think we will be satisfied with the results. In the meanwhile, enjoy the ride...

[GaWx]

Someone was asking me about climo for Dec. snow vs. Jan snow for KATL, but I can't find the post.

Anyway, Jan. is way snowier on average and the snowiest month longterm on avg. Even March has averaged more S/IP.

For Atlanta:

Dec.: only 29 of 122 (24%) with measurable S/IP; 16 of 122 with 1.0"+ (13%); 4 of 133 with major totals(3.5"+) (3%) with last one way back in 1917

Jan.: much higher 55 of 123 (45%) with measurable S/IP; 27 of 123 with 1.0"+ (22%); 15 of 136 with major totals (3.5"+) (11%) with last one in 2011

[buckeyefan1]

I dont post here too often, but I try to make them count. With that said, here are my thoughts on everything as it seems to be unfolding for the south:

Discouraging: The subtropical Pacific has really been hosing us so far this fall (it is still fall, after all). An anomalously persistent -PNA has also put a wrench in winter weather for essentially everyone east of the Mississippi. Models playing "catch-up" or adjusting to the Pacific, the result of which is a constant delay of cold air to the SE.

Encouraging: SOI plunging as WoW and others have mentioned. A solidly -AO aforementioned by Hky, which appears to really tank in the coming week and a half at least (net result a complete obliteration of the polar vortex). An apparent shift of the PNA to at least neutral, if not positive, values. CFS model output showing a cold look for much of the CONUS in Jan.

I believe the source of tension and nitpicking recently stems from the failure and uncertaintry of individual storms to pan out as modeled, even if we are attempting to diagnose them 7+ days out. If one pays attention, you will see mets harping on pattern recognition instead of minutia. This is all part of the "forecasting funnel" which starts with the longwave pattern and works down to smaller details.

With all of this being said, I for one am not "on board" with the post-Christmas storm resulting in too much excitement for the SE. Perhaps the arctic source high over Ontario will be stronger than modeled, which in my opinion will be the key for resulting in any sort of a sustained winter precip producer for CAD areas in this storm. What I do think we are seeing, and will continue to see, is a step down process of storm progression with time. Given the large scale signals I believe the beginning of the year provides a lot of hope for the SE. With each storm we will see a southward expansion of snow cover, which is another key to cold air and a more southern storm track. With the plunging SOI I believe we can expect to see a more active STJ with more disturbances in the flow. A neutral/positive PNA, -AO, and even progressive high latitude blocking...everything is looking up.

If I had two things to say for forecasting winter weather in the SE it would be this:

1. If you have to go out on a ledge to figure out a source of cold air (i.e. an anchored strong High over the lakes), it likely won't work out for lower terrain areas

2. Climatologically speaking, we are relegated to one or maybe two good events a season. Eventually we will cash in, but it may not be the blockbuster we all want.

Maybe some folks in the mtns and foothills of NC get some frozen precip around the 27, but if we can all stay patient for a little bit longer I think we will be satisfied with the results. In the meanwhile, enjoy the ride...

Well said

[rduwx]

I dont post here too often, but I try to make them count. With that said, here are my thoughts on everything as it seems to be unfolding for the south:

Discouraging: The subtropical Pacific has really been hosing us so far this fall (it is still fall, after all). An anomalously persistent -PNA has also put a wrench in winter weather for essentially everyone east of the Mississippi. Models playing "catch-up" or adjusting to the Pacific, the result of which is a constant delay of cold air to the SE.

Encouraging: SOI plunging as WoW and others have mentioned. A solidly -AO aforementioned by Hky, which appears to really tank in the coming week and a half at least (net result a complete obliteration of the polar vortex). An apparent shift of the PNA to at least neutral, if not positive, values. CFS model output showing a cold look for much of the CONUS in Jan.

I believe the source of tension and nitpicking recently stems from the failure and uncertaintry of individual storms to pan out as modeled, even if we are attempting to diagnose them 7+ days out. If one pays attention, you will see mets harping on pattern recognition instead of minutia. This is all part of the "forecasting funnel" which starts with the longwave pattern and works down to smaller details.

With all of this being said, I for one am not "on board" with the post-Christmas storm resulting in too much excitement for the SE. Perhaps the arctic source high over Ontario will be stronger than modeled, which in my opinion will be the key for resulting in any sort of a sustained winter precip producer for CAD areas in this storm. What I do think we are seeing, and will continue to see, is a step down process of storm progression with time. Given the large scale signals I believe the beginning of the year provides a lot of hope for the SE. With each storm we will see a southward expansion of snow cover, which is another key to cold air and a more southern storm track. With the plunging SOI I believe we can expect to see a more active STJ with more disturbances in the flow. A neutral/positive PNA, -AO, and even progressive high latitude blocking...everything is looking up.

If I had two things to say for forecasting winter weather in the SE it would be this:

1. If you have to go out on a ledge to figure out a source of cold air (i.e. an anchored strong High over the lakes), it likely won't work out for lower terrain areas

2. Climatologically speaking, we are relegated to one or maybe two good events a season. Eventually we will cash in, but it may not be the blockbuster we all want.

Maybe some folks in the mtns and foothills of NC get some frozen precip around the 27, but if we can all stay patient for a little bit longer I think we will be satisfied with the results. In the meanwhile, enjoy the ride...

Thanks for the input nrhardin...You have 6 posts and I think I rememeber them all. As you said, you make them count. Wish you would post more because your input would be much appreciated. Hopefully when that one or maybe two events come along, you'll post your thoughts. Thanks again!

[burgertime]

I dont post here too often, but I try to make them count. With that said, here are my thoughts on everything as it seems to be unfolding for the south:

Thanks for your input! As others have said please post more. If nothing else it looks like this storm next week is going to lay down a lot of snow cover in the heartland which as you say should be a good step in the right direction either way.

[NCSNOW]

Thanks nhardin

Out to 144 on GFS: Low sitting TX/Ark/LA. Has potential, well see

[calculus1]

1040 High in Canada, CAD signature up against the eastern slopes of the Apps at 150.

Same at 156 with some form of precip present. Surface low over Paducah, KY:

[DopplerWx]

Headed for chicago on the 00z...decent CAD signature at 162.

[burgertime]

Not as juicy this run as far as QPF and the CAD isn't as strong but it's still there.

[NCSNOW]

Actually pays Elvis a visit, gets to Paducah and hangs hard right. Getting ready to miller B off the tidewater area.

[DopplerWx]

Well the low transferred to off the va coast, but no cold air or qpf for sc or nc really.

[calculus1]

Surface temps appear to be too warm on this run for anything frozen in NC. Mid to upper 30s seems to be as cold as it gets from hours 136 onward. Of course, if the high were slightly farther east, models often overestimate temps during CAD situations...

It's an interesting situation, nonetheless, even if wintry precip appears doubtful at this time.

[calculus1]

Well the low transferred to off the va coast, but no cold air or qpf for sc or nc really.

I have to disagree. I think there's quite a bit of precip progged on this run for NC and SC. It just doesn't happen to be of the frozen variety.

72 hour precip map for hour 176:

[HKY_WX]

I like the 50/50 low position much better this run. The model is finally realizing this sfc low isn't going that far NW.,

[burgertime]

GFS in the LR continues to look great. If nothing else it seems for the most part to be holding on to fun and games around new year.

[Wow]

I dont post here too often, but I try to make them count. With that said, here are my thoughts on everything as it seems to be unfolding for the south:

Discouraging: The subtropical Pacific has really been hosing us so far this fall (it is still fall, after all). An anomalously persistent -PNA has also put a wrench in winter weather for essentially everyone east of the Mississippi. Models playing "catch-up" or adjusting to the Pacific, the result of which is a constant delay of cold air to the SE.

Encouraging: SOI plunging as WoW and others have mentioned. A solidly -AO aforementioned by Hky, which appears to really tank in the coming week and a half at least (net result a complete obliteration of the polar vortex). An apparent shift of the PNA to at least neutral, if not positive, values. CFS model output showing a cold look for much of the CONUS in Jan.

I believe the source of tension and nitpicking recently stems from the failure and uncertaintry of individual storms to pan out as modeled, even if we are attempting to diagnose them 7+ days out. If one pays attention, you will see mets harping on pattern recognition instead of minutia. This is all part of the "forecasting funnel" which starts with the longwave pattern and works down to smaller details.

With all of this being said, I for one am not "on board" with the post-Christmas storm resulting in too much excitement for the SE. Perhaps the arctic source high over Ontario will be stronger than modeled, which in my opinion will be the key for resulting in any sort of a sustained winter precip producer for CAD areas in this storm. What I do think we are seeing, and will continue to see, is a step down process of storm progression with time. Given the large scale signals I believe the beginning of the year provides a lot of hope for the SE. With each storm we will see a southward expansion of snow cover, which is another key to cold air and a more southern storm track. With the plunging SOI I believe we can expect to see a more active STJ with more disturbances in the flow. A neutral/positive PNA, -AO, and even progressive high latitude blocking...everything is looking up.

If I had two things to say for forecasting winter weather in the SE it would be this:

1. If you have to go out on a ledge to figure out a source of cold air (i.e. an anchored strong High over the lakes), it likely won't work out for lower terrain areas

2. Climatologically speaking, we are relegated to one or maybe two good events a season. Eventually we will cash in, but it may not be the blockbuster we all want.

Maybe some folks in the mtns and foothills of NC get some frozen precip around the 27, but if we can all stay patient for a little bit longer I think we will be satisfied with the results. In the meanwhile, enjoy the ride...

Good post, Nate. And good to see you're back in Raleigh.. I was back in town last week for my brother's grad from State. Good times.

[NCSNOW]

Turned out to be a nice noreaster and would give the big cities nice snow event and becomes our 50/50. Out to the following weekend more /better potential is on the horizon.

[HKY_WX]

edit that is new years storm

[GaWx]

KATL is obviously going to end up with a warm Dec. However, due to the extreme uncertainty of the models, how warm is very much in question. If KATL could get a major Arctic hit late this month like both Euro runs were showing on Tuesday, KATL would probably end up around 49 F for Dec. 2012, which would be a not so torchy 4 F above avg. However, if not, KATL would probably end up near 51 F or a torchy 6 above normal. Based on climo. for Jan.'s that follow warm Dec.'s, winter lovers should hope that a. we get that late Dec. Arctic airmass to get Dec. down to near 49 F; and b. January 2013 isn't warmer than +2. As you will see below, nonwarm Jan.'s that have followed Dec.'s that were within the 48-50 F range have actually had impressive S/IP on average. This hasn't been the case for Dec.'s in the 50-52 F range. Also, nonwarm Jan's have been a good bit more common when the preceding Dec. was in the 48-50 range as opposed to the 50-52 range:

KATL climo for Jan when Dec. is warm:

1. When Dec. averages 48.0-49.9 (13 Decembers): subsequent Jan's have done quite well overall

- For all 13 subsequent JAN's: impressive/above avg. 1.5" S/IP in Jan.; impressive 8 of 13 with measurable S/IP; very impressive 7 of 13 with 1.0"+; impressive 3 of 13 with major amounts (3.5"+) with two of these 3 being major IP's (Tony should like this stat); 2 of 13 had major ZR

- 9 of the 13 subsequent JAN's were +2 or colder

- When Jan. temperature anomaly +2 or colder (9 of the 13): very impressive/well above avg. 2.2" in Jan; a very impressive 8 of 9 with measurable S/IP; very impressive 7 of 9 with 1.0"+; an impressive 3 of 9 with major amounts (3.5"+) with two of these 3 being major IP's (smile, Tony); 1 of 13 with major ZR

- When Jan. temperature anomaly +2 or warmer (4 of the 13): none had measurable S/IP although one had a major ZR

2. When Dec. averages 50.0-52.0 (11 Decembers): subsequent Jan's not good overall

- For all 11 subsequent JAN's: unimpressive/below avg. 0.6" S/IP in Jan.; unimpressive 3 of 11 with measurable S/IP; unimpressive 2 of 13 with 1.0"+; only 1 of 13 with major amounts (3.5"+) and there were none with major IP (Tony shouldn't like this stat); 1 of 13 had major ZR

- Only 4 of the 11 subsequent JAN's were +2 or colder

- When Jan. temperature anomaly +2 or colder (4 of the 11): unimpressive/below avg. 0.4" in Jan; 2 of 4 with measurable S/IP; 1 of 4 with 1.0"+; 0 of 4 with major amounts (3.5"+); 1 of 4 with major ZR

- When Jan. temperature anomaly +2 or warmer (7 of the 11): only 1 of 7 had any sig. wintry precip. but it was a major snow (in 2002).

[packbacker]

0z GEFS has miller B with redevelopment off NC coast, would be very interesting for VA to the NE.

[bhamwx205]

Gfs ensemble mean is way south

[DopplerWx]

Gfs ensemble mean is way south

Yep.

[bjohnson102184]

http://raleighwx.americanwx.com/models/gfsensemble/00zgfsensemble850mbTSLPUS168.gif

http://raleighwx.americanwx.com/models/gfsensemble/00zgfsensemble850mbTSLPUS180.gif

[SN_Lover]

Gfs ensemble mean is way south

it appears the trend is now moving the low south and east? correct me if i am wrong.

[GaWx]

Based on the warm Dec./Jan. analysis I just posted, I'm rooting on the old Euro runs' late Dec. major Arctic outbreak scenario more than ever as my feeling about January wintry precip. potential and cold potential would be much better vs. if we don't get that Arctic outbreak. If we don't get it, climo tells me there is little reason to be optimistic about Jan 2013. If we get it, climo says it could easily be party time. So, I'm going to watch the about to be released 0Z Thu Euro very carefully.

Regardless, I'm not expecting any sig. wintry precip. this month at KATL.

[Jon]

0z Euro @ 120 looks to be headed to the lakes...lets see if it pops a secondary low/miller B solution

[Jon]

I guess no one else is here for the Euro PBP....I'll try...

@144 looks like develops secondary off coast of NC, little late though.

Next low digging over LA @ 150...plenty of cold this might be the ticket for the east coast.

Edit: @ 156 1008mb low over AL/MS border...looks like it will be up the spine of the apps or WNC

[griteater]

Not sure why, but I'm here Jon...lol. Looks like this is going to be good for Oklahoma City, fwiw

[Jon]

@168, cold chasing moisture pretty much...still 1008mb over GA/NC apps, 0c 850mb like all the way to southern tx/Mexico..

@174, 1004mb over SC/N GA

@180, low over WNC...not sure about pressure probably close to 1000mb...this is going to have snow on the back end for mtns

@186, 996mb over central VA, most likely big storm for WV/PA/NY/etc...

Plenty of cold air funneling behind this system, things can still change for NC to get in the mix after Christmas...the cold is there! -12 850mb temps into TN @ 192...0c line all the way to the gulf covering most SE states completely.