griteater

Anthony Masiello tweets: "Stage 1 is complete (poleward, fast, less split jet stream with lots of Tropical Heat). Stage 2 has started (an increase in wave activity, loss of momentum and continued splitting of mean NH jet). Stage 3 is enhanced STJ/westerly AAM phase (think November)." "What is coming ahead is analogous to getting favorable intraseasonal oscillations at peak tropical season in early Sep. Predicting hurricanes in early Sep is kinda meh. Well, late Jan into early Feb will have favorable intraseasonal state for winter in E-C US/UK."

The best period on tonight's Euro Weeklies runs from Jan 24th to Feb 13th

Just don't have enough well-entrenched cold air to the south. We want to see both Tennessee and North Carolina full of cold air prior to the storm as opposed to cold air retreating in TN and hanging on via cold air damming in NC as the storm approaches. Cold air damming is great to have, just need it cold in TN prior to the storm as well for more snow.

Yeah GFS run was similar...it was a little warmer in the E Piedmont Canadian was colder at the sfc with freezing rain down into SC

Both NWS offices have become more apt to be bullish in the extended range over the years. Not sure why that is, but in the old days, they were typically conservative until it got close in.

The Greenville NWS "changes everybody to rain" wording is a bunch of bunk IMO, especially for the hardcore CAD areas in the foothills. Yeah, Raleigh NWS is going with more of a Miller A with mostly snow where temps allow and Greenville NWS is going with the Miller A/B Hybrid, mixed bag scenario. I favor the mixed bag scenario, but not "changing to rain in all areas".

New Euro Weeklies

Yeah GFS bumped south this run - puts more folks in NC in play for wintry precip this run compared to last

Happy hour GFS coming in - 500mb suggests this isn't going to be as far north as last run

Looking at the Euro Ensemble Trends thru today's 12z run, the western U.S. ridging and the amplitude of our storm wave over the Mississippi Valley have increased (at least on its backside)...but the storm wave is trending more positive tilt - so the amplitude/tilt trade off is kind of a wash. If you increased the amplitude, but kept the wave more neutral tilt, you'd have a farther north/warmer solution (but you can see that the angle of the height lines thru North Carolina really hasn't changed). The cold air damming signal is increasing as well, as to be expected. It kind of looks like a central/northern mtns, foothills, NW Piedmont (and north) wintry event at the moment IMO, but plenty of time for it to change.

From NOAA's Weekly MJO Update

I always find the whole self-limiting thing kind of funny. Like you said, if it's 28 degrees with NE winds and lots of steady precip, the only thing limiting is going to be the extent of the power grid. If it's 32 degrees, well that's a whole different story.

GFS is just more wound up with the storm wave closing it off over Missouri, so that throws the parent low up into Tennessee. Euro and Icon are more broad with the trough, with more of a weak Miller A sliding low

For the GFS and Euro, this fits well with their common biases nowadays IMO. It was opposite in the old days

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.