December 2023 Weather Discussion

[tpweather]

Like Les mentioned the map he showed is departure from normal. By next week at this time eastern Europe should have advanced to normal or above and even western Europe might get in on the action as well.

[tpweather]

Looks like the first day of December will have a rather dynamic system to follow. Have not had many in recent months. This most likely lead to some decent rains but the severe side most likely well south of here. How much rain is a big question because when you have severe weather in the gulf states this sometimes robs moisture supply further north. Still have plenty of time to watch this system

[tron777]

Les that would be great and then a little help from the pacific. The NAO has been negative for much of the year but the effects locally are felt from late fall to spring for the most part. I will roll the dice if the nao stays negative all of December.

It would also bode well for the rest of winter too. The NAO would be more negative then positive for Jan and Feb if the NAO averages out negatively for December.

[tron777]

Looks like the first day of December will have a rather dynamic system to follow. Have not had many in recent months. This most likely lead to some decent rains but the severe side most likely well south of here. How much rain is a big question because when you have severe weather in the gulf states this sometimes robs moisture supply further north. Still have plenty of time to watch this system

You can already see the effects of the -NAO. The last 4 runs of the OP GFS have shown a further south track of the low, a weaker low, and a faster arrival as well.

[tron777]

EPS Mean continues to show the PV getting weaker as December rolls on.

EPS Mean PV.png

All three global ensemble members continue to show a -NAO hooking up with a +PNA with a trough in the East. Below are the 500 MB average for Dec 6-11th from the GEPS, GEFS and EPS.

GEPS.png

GEFS.png

EPS.png

[tron777]

Good morning folks! We still look to begin December on a wet note this coming Friday. Sat will be in between systems, so just a chance of rain in the morning. Rain returns late Sunday into Monday with a more potent low / cold front. Rainfall amounts of an inch plus appear likely from this distance. Models diverge significantly after that with not only temps, but storm tracks as well. I don't think snow chances are very good until after the 7th if not the 10th depending on how things shake out. The -NAO looks good, and I do think we see an improving Pacific with time, but the details this far out cannot yet be determined. We should avg mild for the first week of December then after that is when I think we will begin to see some chances. I do think the snow signal is there in the long range but as I said the other day, the Mid Atlantic is favored due to the PNA ridge axis being a bit too far east for us. Obviously, that can change from this distance and these are just my early prelim thoughts on the subject. Ensemble Guidance from overnight fits this narrative very nicely.

[tpweather]

Good Morning Les and your post is great. Getting the nao and ao being negative is not everything in terms of snow and cold especially since the pacific is not playing ball but it usually keeps us from getting out of control in the warm department. Looks like the 1st half of December will ended up slightly milder than normal and hopefully wetter than normal. Looks like a system every 3-5 days with a warm up and then the front comes through and you may end up with a few flurries or a snow shower here or there but nothing that would cause any problems. This is the time of year the gfs heads into fantasy land around days 12-15 but again that model is known for that every winter season.

Second half of December and though I am still not expecting the polar vortex to help us much but the pacific hopefully will and we can at least draw down some Canadian air which is plenty cold and should get colder over the next few weeks. This can at least give us a better shot of winter conditions starting somewhere around the 20th though we know models tend to be a tad fast. My guess is just before the change a bigger storm will usher in the new pattern and that could be a nice rain to snow event. The good thing is the STJ looks to be very busy this winter so there will not be a lack of storms but where will the track set up this winter.

After last year I will take anything as we saw both the cold and warm signals and yes we had the blizzard just before Christmas but then the heat miser decided to take over until March and by then we just get the delay to spring. Give me a cold January and February then mild in March and I iwll be more than happy.

[tron777]

Good Morning Les and your post is great. Getting the nao and ao being negative is not everything in terms of snow and cold especially since the pacific is not playing ball but it usually keeps us from getting out of control in the warm department. Looks like the 1st half of December will ended up slightly milder than normal and hopefully wetter than normal. Looks like a system every 3-5 days with a warm up and then the front comes through and you may end up with a few flurries or a snow shower here or there but nothing that would cause any problems. This is the time of year the gfs heads into fantasy land around days 12-15 but again that model is known for that every winter season.

Second half of December and though I am still not expecting the polar vortex to help us much but the pacific hopefully will and we can at least draw down some Canadian air which is plenty cold and should get colder over the next few weeks. This can at least give us a better shot of winter conditions starting somewhere around the 20th though we know models tend to be a tad fast. My guess is just before the change a bigger storm will usher in the new pattern and that could be a nice rain to snow event. The good thing is the STJ looks to be very busy this winter so there will not be a lack of storms but where will the track set up this winter.

After last year I will take anything as we saw both the cold and warm signals and yes we had the blizzard just before Christmas but then the heat miser decided to take over until March and by then we just get the delay to spring. Give me a cold January and February then mild in March and I iwll be more than happy.

Thanks Tim! My expectation is to have a better chance of colder air and snow after the 10th. That could of course change from this distance. Concerning the rest of the winter, we are in 100% agreement on a good Jan and Feb then spring comes quickly in March.

[Bgoney]

Good Morning Les and your post is great. Getting the nao and ao being negative is not everything in terms of snow and cold especially since the pacific is not playing ball but it usually keeps us from getting out of control in the warm department. Looks like the 1st half of December will ended up slightly milder than normal and hopefully wetter than normal. Looks like a system every 3-5 days with a warm up and then the front comes through and you may end up with a few flurries or a snow shower here or there but nothing that would cause any problems. This is the time of year the gfs heads into fantasy land around days 12-15 but again that model is known for that every winter season.

Second half of December and though I am still not expecting the polar vortex to help us much but the pacific hopefully will and we can at least draw down some Canadian air which is plenty cold and should get colder over the next few weeks. This can at least give us a better shot of winter conditions starting somewhere around the 20th though we know models tend to be a tad fast. My guess is just before the change a bigger storm will usher in the new pattern and that could be a nice rain to snow event. The good thing is the STJ looks to be very busy this winter so there will not be a lack of storms but where will the track set up this winter.

After last year I will take anything as we saw both the cold and warm signals and yes we had the blizzard just before Christmas but then the heat miser decided to take over until March and by then we just get the delay to spring. Give me a cold January and February then mild in March and I iwll be more than happy.

Thanks Tim! My expectation is to have a better chance of colder air and snow after the 10th. That could of course change from this distance. Concerning the rest of the winter, we are in 100% agreement on a good Jan and Feb then spring comes quickly in March.

PAC has a long way to go for me, plenty of troughs /lows hitting the NW coast of North America the next 1-2 weeks for now , so agree first half of December to average near to above normal temp wise. I’d rather see a -EPO develop mid month, otherwise the cold for later December may have a tough time getting in the OV

[tron777]

12Z GFS looks good for the rainy period coming on Fri the 1st thru Mon the 4th. I think models are getting into better focus with those two systems. Then it's a wait and see game for whatever happens after that.

[tpweather]

I agree Bgoney that it take at least a few weeks. Only 3 storms at the moment in the pacific north but do we see more with the flow coming out of China or Korea. Sometimes you see the pacific so full of storms and the EPO takes forever to change. I agree a -EPO after mid-month would be nice to see and if stay positive then we may be stuck in the same pattern but just a tad colder.

[tron777]

I agree Bgoney that it take at least a few weeks. Only 3 storms at the moment in the pacific north but do we see more with the flow coming out of China or Korea. Sometimes you see the pacific so full of storms and the EPO takes forever to change. I agree a -EPO after mid-month would be nice to see and if stay positive then we may be stuck in the same pattern but just a tad colder.

Without the -NAO we would be torching like last December. So while it will be above avg for the first week or so of December, it should not be highly above. I still say after the 10th, the Pacific starts to get more favorable and if I am rushing it, I will of course change that call as we get closer.

[tpweather]

12Z GFS looks good for the rainy period coming on Fri the 1st thru Mon the 4th. I think models are getting into better focus with those two systems. Then it's a wait and see game for whatever happens after that.

Les we are getting more and more moisture out of the western GOM that is able to work further north. There will not be a lack of moisture for the STJ this winter but the storm path is more of the problem. I still believe this is the winter pattern for us locally that overriding events will be more common as warm air flows from the southwest into the Ohio Valley. This can cause all kinds of precip types. The STJ in many El Nino's work their way into southern California and then across the USA. The one this year may be further south into Mexico and head across towards the Carolina's Again nothing set in stone and really will need to wait for the PV to start getting weaker and where the cold air decides to go. All along I believe this is a great winter for the northeast USA and much of Europe as we remain on the western edge of the really harsh winter. Saying that I believe 2 bigger storms have a chance to invade the Ohio Valley and we know how hard that is to get just one in a winter. When I did my snowfall total I had about 2/3rds of the snow from 2 systems. If one of the storms remains liquid whether rain or ice could kill my forecast big time.

[tron777]

12Z GFS looks good for the rainy period coming on Fri the 1st thru Mon the 4th. I think models are getting into better focus with those two systems. Then it's a wait and see game for whatever happens after that.

Les we are getting more and more moisture out of the western GOM that is able to work further north. There will not be a lack of moisture for the STJ this winter but the storm path is more of the problem. I still believe this is the winter pattern for us locally that overriding events will be more common as warm air flows from the southwest into the Ohio Valley. This can cause all kinds of precip types. The STJ in many El Nino's work their way into southern California and then across the USA. The one this year may be further south into Mexico and head across towards the Carolina's Again nothing set in stone and really will need to wait for the PV to start getting weaker and where the cold air decides to go. All along I believe this is a great winter for the northeast USA and much of Europe as we remain on the western edge of the really harsh winter. Saying that I believe 2 bigger storms have a chance to invade the Ohio Valley and we know how hard that is to get just one in a winter. When I did my snowfall total I had about 2/3rds of the snow from 2 systems. If one of the storms remains liquid whether rain or ice could kill my forecast big time.

As always it boils down to the Pacific. If the +PNA ridge is centered more over the West Coast then that is great for us. Inland or over the Rockies then it's an East Coast storm track. I do like seeing the STJ more south coming in over Mexico and into Texas versus California. That should assist us with regards to having a better looking Pacific pattern down the road. I like seeing that trough NE of Hawaii which pumps up the +PNA ridge. As we've discussed over and over it's all about the Arctic domain also and especially the EPO as Bgoney just mentioned. If we can get the -NAO to teleconnect with the -EPO ridge then we should see a lot more interesting weather for snow lovers.

[tpweather]

Good Afternoon and heading for a few days of cold weather. Starting to see a few changes with the tellies and probably more in line with what I believe will happen during the first half of the month. AO still negative but closer to neutral and the NAO again negative but more of a jump to neutral. The mjo which again in phase 2 and was headed to phase 3 and then cod. Some models show phase 3 but hangs in the phase 4-6 though not strong. This to me makes more sense as I expect a milder first half of December. Again we are not talking a strong phase where we get a longer period of warm weather but one were by the 15th of December temps average a tad above normal overall. Next is rain chances and yes we should have several but Bgoney mentioned this recently and how the transport from the GOM has been hard and my guess is we are just not getting enough warm and cold to mix where you get a bigger and stronger storm. That may happen later this week but will be fun to see how far the heavier rain reaches. Could this be sort of a trend for the winter season where models show a more northward trend early on but back off as the system gets closer. Back to the pna and that looks to remain neutral and once again neither keeps us cold or warm.

So imo is the cold building in northern and central Canada. We started late this fall and even with the current cold period it shows that even with an okay shot of cold that no snow cover will temper the cold. Lets see a good 10-20 days of cold build up and then have the pna go positive and hopefully later the epo goes negative for January and February

[tron777]

The precip was meager with this last system because there was very little phasing between the two jet streams. If the current guidance is right, we will see much better phasing occur and the Gulf will be open for business as a result and thus, the heavier rain potential for Dec 1-4th.

[tpweather]

The precip was meager with this last system because there was very little phasing between the two jet streams. If the current guidance is right, we will see much better phasing occur and the Gulf will be open for business as a result and thus, the heavier rain potential for Dec 1-4th.

Les just hoping that is not a trend this winter. I will just watch this week to see if the heavier rain expected is further south each day. I agree about the GOM and that is not the problem but another one is severe weather and if that starts to increase in the south those storms can also rob us from getting moisture so far north.

[tron777]

The precip was meager with this last system because there was very little phasing between the two jet streams. If the current guidance is right, we will see much better phasing occur and the Gulf will be open for business as a result and thus, the heavier rain potential for Dec 1-4th.

Les just hoping that is not a trend this winter. I will just watch this week to see if the heavier rain expected is further south each day. I agree about the GOM and that is not the problem but another one is severe weather and if that starts to increase in the south those storms can also rob us from getting moisture so far north.

I hope it isn't a trend for the winter either lol I don't think that it will be as the Nino asserts more of its influence as time goes on.

[tron777]

Rain is still expected to begin Thurs night thru Fri night. We may squeak out a dry Sat with rain returning sometime Sunday into Monday Dec 4th.

[Bgoney]

Qpf amounts tbd by low track whether the OV sees a range of .25”-.75” or .50”-1.00” (Friday)

[Trevor]

06z GFS says “what storm?” for Sunday with only some showers as the system is suppressed to the south. GFS has been back and forth on this so take it as you wish.

[tpweather]

Good Morning and I do worry about severe weather in the south that could rob some moisture for the Thurs/Fri storm and then Sunday I believe we once again may miss out on some decent rains which will hit the southeast. Trend and maybe?

[tpweather]

One of the items that is always confusing to met's and forecasters is the mjo. The mjo is on several sites and depending which site can be completely different phase and also different forecast. I try to guess which is correct by the current weather and also possible upcoming weather. Usually I go with NOAA and believe that is not always the case in regards to weather.

The current phase is 2 going into 3 and then 4. A weaker phase as we get into phase 4. I bring this up because Chris Bailey out of Lexington in his forecast today talked about heading to phase 8 and 1. Maybe he is talking about later in the month but at the moment that is not the case imo. My guess is we stay on the weaker side but move steadily over the next 10-15 days and my guess will finally curve back into COD. Then where will it reappear is the question.

[tron777]

Tim CB is talking about going into phase 8 and 1 after mid month. You could see it on the Gefs extended mjo plot which is available on the CPCs website. I will check the other mjo modeling this evening.

[Trevor]

Tim you are absolutely correct re: moisture-robbing southern convection. Attached is the 00Z Euro and you can see how the south gets very heavy rainfall totals and lesser amounts up this way. I expect that to be the case.