Carvers Gap

We really need a "wow" like button for this site. That is crazy. Are we talking the GOA or Aleutians when talking eastern Pac? I would think a more traditional placement would be likely. EPS was playing with that late in its run...either that or zonal with some northwest flow.

The 12z EPS has the period of Jan 3-10 BN for temps, and that is with a warm-up embedded. Both the GEPS and GEFS reflect a similar depiction. Precip during that timeframe looks at or above normal if smoothed. Could be a warm-up and rain deal, could be over-running, could be a slider....lots on the table. Looks like we have a cold shot around the 3rd, cold relaxes, and another (maybe more significant) shot arrives around the 7th. The EPS tries to lift the BN heights at 500 northward, but the cold(mslp maps reference) is so extensive it almost has to burn itself out.

The 12z EPS is a pretty much a complete reversal of the current pattern at almost all latitudes of NA, just flip the reds and blues at 500. Oh the irony if we switch to a +PNA pattern. Most of those flips are good...but not all.

12z EPS looks good. Not sure what is going on with the GFS operational...but all three ensembles show a nice period of cold weather for early January. Whew - the CFSv2 is really cold. Probably is not right for a number of reasons(little to quick with the MJO and it is always cold anyway), but crazy in terms of eastern cold. The ensembles look like a scaled back version both in intensity and duration.

I like your ENSO thread, especially during the off-season. I think you should keep it. Both threads(severe/ENSO) are kind of unique to our subforum. Your call, but just my two cents.

Euro looks more like the CMC though not to that extreme for the Jan 3 front. Looks like a wave rides the front w/ some winter potential north of I40.

12z CMC and GEFS look similar to previous runs, including the cold shot on the 3rd.

Most modeling has been very solid with the Jan 3rd cold front - Jan 1-2 have been warm(just not record warm). There is a cool front that comes through on some modeling around NYE or NYD. Looks to me like the GFS still had a good run and a pattern flip. Just giving it a closer look, looks like both the CMC and GFS get to a cold pattern with the same mechanics which is to use a piece of energy to rotate cold in behind it. The GFS is jumping on the second piece of the split trough. CMC deepened the eastern trough with the first piece. So, not sure that was an MJO issue as much as it was with model jumped on which piece of energy to slam the cold home. For now, my money is on the CMC.

The difference in the 12z CMC and GFS on the 3rd is stark - stark. The CMC is single digits shortly after and the GFS seems to be struggling with feedback over the eastern PAC. It could be right, but it doesn’t have support to this point. Again, its MJO looks nothing like the others. The CMC has been super consistent. We will se what the Euro does at 12z.

MJO for the gfs looked off this AM. May be right and it may not. We are going to see some runs today which are likely vastly different between model suites. I take some comfort in that the GFS continually busted on going into 8. LOL. So it’s jog back towards 6 is an outlier among models at this time. CMC at 12z looks good. Gfs will get there but later in the run.

18z CMC looks equally cold through Jan4th...and I am going to bed! LOL.

0z GFS commentary: -Cold from for Jan 3 is 10-15F below normal. -Temps go below freezing on the 3rd. Many places north I40 are not depicted to get back above freezing until the 5h. -Would appear the GFS is again feeding back with a split trough where the western portion gets cut-off. Could happen, but not sure -Temps over the East are BN to much BN through he 6th. -Impressive cold shot. Take a look at the mslp maps vs 500. You can see the cold underneath those ridges at 500 while looking at those surface maps. Crazy. -EPO ridge(albeit displace westerly a bit) goes into the Arctic. Bout it. Cold looking run from the 3rd onward to the 8th, brief interlude of warm, and appears another cold shot inbound after a cutter. -Possible feedback error with the slp that drifts off the coast of California after 340.

Thanks a ton!!!!

For those who enjoy reading Webber(I am included). Thanks to the MA forum for this share:

18z GEFS has turned sharply colder in the LR. Fairly unusual to see an ensemble which is -10F below normal at this range, especially in such a widespread fashion. Keep in mind those departures are during the coldest part of the year. Time will tell if these trends are indeed real. I would suspect that moderates during ensuing runs as extremes rarely verify. Seasonal will work along with( and this is important) an active STJ. That might be one of the coldest runs I have seen from the GEFS in regards to the entire continent nearly being BN for temps. @Holston_River_Rambler, can you GIF that just for posterity? Again, unlikely that verifies to that extreme, but would be interesting just to keep as a reference. Specifically, the daily temp anomalies for North America.....

This may just be a case of climatology taking over(January is our coldest month). We don't need as many things to be exactly right in order to get cold. We'll see. See all of those AN heights at 500 and so much cold at the surface is counterintuitive. So, wary I am.

@tnweathernut, looks like the first significant disruption of the AH begins around Dec 30/31 if modeling is indeed correct - between 120-130h. Looks like a couple of storms crash into it. Almost immediately after that, the area of hp loses its uniformity and lifts out over the next few days. And you are on the money about whether this is correct or not...just tough to know. I think this scenario very possible, but not ready to take the step and say it is likely. 18z GFS again with another flip of the pattern. Agree also it could be rushing, but other modeling seems to be there with it. What is crazy on this run is that NA gets so cold that the AN heights at 500 are still cold at the surface and the BN heights are even colder at the surface. What looks warm is just "less cold" air getting moved around. Not sure I have seen that on a map in a long time. At the end of the run, there is this big ridge in the central US....generally below normal at the surface with another shot of cold incoming.

Will just use this post(update as the run progresses) to cut down on tons of posts for the rest of the 18z run: -Hudson Bay high will drive this pattern for the rest of the way along with what would seem a very -AO. -By 288 the big red blob over the Pac is adios'd -The Hudson Bay high will force the storm track well south if real. This would be an Atlantic dominated pattern if real. Check that...AO dominated pattern and a HB high dominated pattern. -Europe has turned sharply colder by 288 which tele connects well to cold temps over the EC. -1068 high coming down out of Canada around 300. Super smiler to both the Euro and CMC which had monster highs coming down. -Fairly massive Arctic outbreak being modeled after 300. -This is 2020 February 2.0 light...yikes -Pretty epic run as at one point roughly 1/3 of the US (mid and upper Plains, Rockies) are below zero.

18z GFS does indeed begin to severely erode the AH immediately after 240. Going to be some crazy cold air coming into the Lower 48 this run it would seem.

18z GFS to a lean towards the 12z CMC with the cold front on Jan 3rd. Temps are 10-15 degrees below normal. Let's see what it does with the AH this run. Looks displaced already. Pac Ridge has connected to the NAO....stage would seem to be set or a fairly southward displacement for cold air on this run.

Past week or so we have seen an increased frequency of the AH(tired of typing Aleutian high) to lose some steam on LR modeling. Last night, JB mentioned the EPS may be hinting at the MJO firing. The IO has little convection. Need it to fire in order to push the MJO along. Right now the maps look very much like a phase 7 which is pushing near 8. Looks like we may potentially have a window for tracking between the 3-10 with the window between the 6-8th having the most promise. Crazy thing, nobody remembers those great Niña winters if you subtract 10-14 days of cold during those winters. Just need the pattern to relax which it may. Great discussion today by everyone!

I suspect we fight that Aleutian ridge all winter...There is a reason people out West absolutely love La Nina winters. Weak La Nina winters here(southern Apps) can be very cold at times(maybe even as a general rule), but not always. People on the EC don't like La Nina winters. West of the Apps it can work. We don't need super cool weather in early January to have a chance. Just need seasonal. Right now if forced...I would way the trough lifts out around the 10th. However, what happens after that is really open for debate. Does the Pac ridge reform or does another trough drop into the center part of NA? It has been my experience that La Nina cold comes in waves. Usually the dam releases, a ridge builds back in, and we are fortunate, we get a second shot later in Jan or early Feb. I was going to note that if you watch carefully, there is almost a large cyclonic flow over all of NA. The cold crosses the pole from Siberia which sees NA, is forced against the Rockies where it creates a huge cold air mass, warmth builds over the south, and the cold release SE once there is enough of it. So you get pulses of cold which head SE. A lot of those fronts wash out right as they hit E TN. The cold if it can get something to move it quickly, is often well below normal. You subtract those 2-3 weeks in 84-85, nobody talks about that winter. That cycling flow, if it stays in place, would keep pulses of cold in the pattern for as long as that "feature" is in place.

Really, because we cannot see past the 10th...can't be sure if this is a pattern change or just the PNA relaxing as a result of the Aleutian ridge weakening. The Aleutian ridge could restrengthen. We need the current block to reconfigure just enough to allow the buckle in the western jet to swing forward. That either is going to have to happen with a weakening of the ridge in the Pac OR (and this may seem counterintuitive and may even be an error in my thinking) a slight weakening of the NAO. I have been watching this very several days. When the NAO weakens just a bit, the trough kicks eastward. Only problem, it lifts right out with no block in place. So, we need the NAO to weaken just enough to allow the trough to slide underneath, but get get blocked and not allowed to scoot out. That may we an error in my part....but that NAO needs to soften up just a bit. But.... we still need it. AO may be the driver going forward.

The BIGGEST thing I thought was interesting....watch the Aleutian ridge on all three of those operationals. What do you all see?

Not Jax or Holston, they are the SOI gurus...but when you see the SOI move like that....all kinds of movement occurs regarding hemispheric flow. IMHO, usually means a sharp pattern change would be under way. Now, we may or may not like the end result of that pattern change, but that is usually a signal of things switching up.