griteater

Euro coming in is more broad with the storm trough, similar to the UKMet. Fairly light with precip amounts. A light wintry event roughly NW of CLT to RDU

It's a little more suppressive at 500mb, but it's throwing a new, strong vort max / short wave down into the Great Lakes which is disrupting the cold inflow from the sfc high up north (more Ohio Valley low influence)

In the old days, the GFS suite would typically be on the suppressed side with storms in the medium range, and the Euro would be more likely to throw out some amped up model runs. In recent years, the 2 have flipped with the Euro tending to be more suppressed and the GFS throwing out some amped runs. Don't know what will happen here in the end, but I'm just saying that the GFS is more likely to throw out amped and north model runs in the medium range compared to the Euro nowadays.

The trough over SE Canada out ahead of the storm to trend stronger and farther south, with the associated damming sfc high building in behind that trough to extend more cold air to the south

Lots to sort out as usual, but this does look like a viable light to moderate wintry threat with damming high to the north and slider type southern low

12z Euro

12z Euro looks a lot like the ICON this run at 500mb with west coast ridge spike dropping the northern stream down into the southern plains and linking up with the southern wave. Not a heavy event, but temps look like what we've seen with many of our wintry storms of late....i.e. wintry along and northwest of GSP to CLT to RDU

The models are going about the winter threat in different ways. CMC and FV3 are dropping in the northern stream whereas the Euro and GFS keep the streams more separated...but each camp at the surface has the gulf to SE coast low. The surface high and damming setup is better with the Euro/GFS camp IMO as the northern stream interaction on the CMC/FV3 brings in more Great Lakes/Ohio Valley Low influence

During an El Nino, we would expect to see more periods than not of below normal convection over the Maritime Continent (phases 7-8-1-2) from fall thru winter, but since late Sept, we've seen a lot of cycling of the MJO/tropical forcing - the lower stratosphere -QBO / low solar combo that hailstorm mentioned and the weakened strat PV are likely contributing to the enhanced MJO cycling that we've seen.

Well the tropical convection over the Maritime Continent and the Western Pacific has calmed down over the past week. If we don't see colder conditions develop during the 2nd half of January, it may be time to just throw the hands up as the tropical forcing should be more favorable then. Februarys are almost always cool in the east during El Nino, but: 1) we haven't come close to locking in typical El Nino-like ocean-atmosphere coupling, and related, 2) the tropical forcing (MJO) may not be in the colder phases during that timeframe (7-8-1-2). On the image below, you can see the GFS FCST taking the VP portion of the MJO thru phases 7-8-1 during Jan 4-17 (the green line).

LOL, in this wretched pattern, the Euro is setting up for glory at the end of its run. Cold high out front, suppressive flow in the east, bowling ball wave moving into SCAL, with kicker wave behind it in the EPAC.

hailstorm - do you know of the physical mechanism whereby enhanced solar wind (from rotating coronal holes) stalls the MJO?

The EPS looks straight wretched in the mid & extended range with the Alaska/Gulf of Alaska/West Coast trough trifecta. That's about as bad as it gets out west. In contrast, the GEFS develops a nice pattern in its extended range. The GEPS is somewhere in between the 2, but closer to the GEFS The MJO on the RMM plots has made steady progress the last 2 days and has finally reached the beginning of phase 6. The dynamical model RMM plots bring the MJO into phase 7 in the next 5 days, then have varying long term MJO solutions. Given the current MJO amplitude, we should expect the MJO to continue on thru phases 6-7-8-1 over time, with the specifics around the timing to be determined. The filtered VP portion of the MJO shows that the enhanced convection associated with the MJO has moved from the Maritime Continent out into the western Pacific over the past week (blues and purple). Loop of those images shown here: http://www.atmos.albany.edu/student/ventrice/real_time/maps/mjo/global_analyses.html The week 2 GFS forecast of MJO filtered VP shows the suppressed convection moving east and centered over the Maritime Continent, with the enhanced convection extending from the central & eastern Pacific to Africa. That's where we want to be from a tropical forcing standpoint to begin to see improving western ridging / eastern troughing solutions in the models. The official SSWarming wind reversal is occurring today. The extent to which it propagates down into the troposphere to affect our weather remains to be seen. It this one does propagate downward, it looks like it's going to take some time - at least a few weeks. I think there is good reason to remain optimistic about wintry weather returning in the 2nd half of Jan into Feb, but until we see good ensemble runs showing consistently, it's all speculation. I did find it kind of funny that the very last image of yesterday's Euro Weeklies for Feb 9-14 was the best image of the run, as if the model is just wanting to tease us

Well the ensembles look kind of 'meh' right now. Nothing terrible, but nothing spectacular either

Here's the GEFS for days 10-15. It's out there in range, but it looks really good out west at the end with the strongest anomalies over the Northern Hemisphere contained in the Aleutian Low / W Canada & Alaska ridge couplet. The Aleutian Low anomaly is displaced to the south and would seed storm waves at a lower latitude (into California/Baja), and the W Canada / AK ridge would deliver January-level cold east of the Rockies.

Starting to see some improving looks on the extended range ensembles. On the VP MJO phase chart, the MJO is currently in phase 5 and will move into phase 7 by early January. Phases 7-8-1-2 are El Nino-like and favor western ridging (+PNA/-EPO) so the ensemble improvements make sense. The last 5 12z runs of the Euro have shown an official SSWarming on Dec 30th, albeit the runs have become a little weaker with it, and it may get delayed or possibly even not make the SSW wind reversal. Regardless, the Strat PV will be severely weakened at a time when it should be at max strength. What effect this has is highly debatable as it's unclear of the effects the weakened SPV will have on the pattern, but a weakened SPV is certainly more preferred for eastern U.S. cold over a super strong one.

Here's this aftn's week 3-4 forecast from NOAA (for Jan 5-19). Their forecast discussion is good and touches on many things that have been part of the long range discussion in here over the past few weeks - http://www.cpc.ncep.noaa.gov/products/predictions/WK34/

Nino 3.4 / Modoki Index over the past 2 months (Daily AVHRR Data): 12/19: 0.54 / -0.08 12/10: 0.47 / 0.26 12/01: 0.96 / 0.82 11/20: 0.72 / 0.49 11/10: 0.50 / 0.50 11/01: 1.46 / 0.90

Enjoyed your thoughts Don, keep em coming. I agree with your thoughts regarding the MJO moving on into the colder phases by January - https://www.americanwx.com/bb/topic/50522-mid-to-long-term-discussion-2018/?do=findComment&comment=5072289 Anthony M made mention of the analog yesterday, but this winter seems to be following 2003-2004. The MJO timing is a very close comparison, and with the SOI and MJO behavior, this winter is kind of acting like a neutral year as +ENSO isn't locked in (2003-2004 was +ENSO Neutral). I'm curious as to why you think the ocean and atmosphere will begin to couple in January? I could envision a similar scenario as Feb 2004 with the MJO progression, but only time will tell. In addition to the tropical forcing comparison, there was a SSW on Jan 5, 2004 (which looks to be similar timing as this year). Here are charts from 2004: MJO / January 500mb and Sfc Temps / February 500mb and Sfc Temps

I think we'll see radar break out nicely across E TN / NE GA / NC / northern half of SC overnight into early morning and spreading east thru the day. For you and I, soundings are sketchy for snow, but the timing is good (night and early morning) and it may be just cold enough. I'd keep expectations low on amounts....seeing flakes fly and maybe some light accumulations

It's overnight into early morning for Western Carolinas

A visual of the upper low dropping down thru Nebraska and Kansas - https://www.tropicaltidbits.com/sat/satlooper.php?region=atlpac-wide&product=wv-mid

It’s a closed contour upper low that’s dropping down into the trough behind our departing storm. It’s currently located over S Dakota/Nebraska and will drop into E Oklahoma, then swing thru the SE states. Euro has precip breaking out with it in E TN / N GA a little before midnight then swinging east thru the Carolinas overnight and into the morning. Shouldn’t be anything major, but could be some nice embedded snow showers in there

Some of us have started adding some model performance thoughts on the storm here, FYI: https://www.americanwx.com/bb/topic/49398-southeast-winter-storm-threats-model-performance/?do=findComment&comment=5065039