Central/Western Summer Medium/Long Range Discussions

[brettjrob]

Zonal with small shortwaves is better than anything else we've had this season. Take what we can get at this point.

 

Exactly. I'm not sure there's anything worth getting legit excited over in the data right now. Probably lots of marginal, needle-in-haystack days coming up with a bias toward areas N of I-70. But still good news for chasecationers.

[Ian]

Exactly. I'm not sure there's anything worth getting legit excited over in the data right now. Probably lots of marginal, needle-in-haystack days coming up with a bias toward areas N of I-70. But still good news for chasecationers.

 

Ensembles look better than they have. Also more hints of attempts at EC ridging.  It's still too far out to get that into it but looks different than what we've seen thus far at least. That fast flow can have some good sleeper events.. not giant outbreaks prob but localized ones maybe.  Plus if the op Euro held on recent solutions that's a signal for more than just a zonal pattern.

[brettjrob]

Ensembles look better than they have. Also more hints of attempts at EC ridging.  It's still too far out to get that into it but looks different than what we've seen thus far at least. That fast flow can have some good sleeper events.. not giant outbreaks prob but localized ones maybe.  Plus if the op Euro held on recent solutions that's a signal for more than just a zonal pattern.

 

Are you guys referencing the ECMWF ens getting them on a pay site? I'm behind the times if they're available publicly.

[Ian]

Are you guys referencing the ECMWF ens getting them on a pay site? I'm behind the times if they're available publicly.

Yeah not sure if they are free anywhere. Maybe 500 maps tho if Raleigh doesn't have them prob not (haven't looked). They don't look like the op tho the mean gets oversmoothed at times.

[andyhb]

00z GFS appears to be on a good track with the second s/w (initial one helps to break down the Western ridge) coming ashore pre-truncation and what looks to be solid amplification of the ridge west of the Aleutians (perhaps a bit of a -PNA trying to form?) and a trough building over the Pacific NW and the Gulf of Alaska.

 

Either way, it looks nice.

 

The Ukie has the same breaking down of the Western ridge going towards the end of its run.

[brettjrob]

00z GFS appears to be on a good track with the second s/w (initial one helps to break down the Western ridge) coming ashore pre-truncation and what looks to be solid amplification of the ridge west of the Aleutians (perhaps a bit of a -PNA trying to form?) and a trough building over the Pacific NW and the Gulf of Alaska.

 

Either way, it looks nice.

 

The Ukie has the same breaking down of the Western ridge going towards the end of its run.

 

The 00z GFS looks fairly intriguing for next Fri-Sat now with excellent moisture return into the High Plains and lee cyclogenesis beefing up low-level shear. An absolute nightmare beyond that once the shortwave makes it east of the Plains, but we'll tackle 'em one at a time.

[andyhb]

The 00z GFS looks fairly intriguing for next Fri-Sat now with excellent moisture return into the High Plains and lee cyclogenesis beefing up low-level shear. An absolute nightmare beyond that once the shortwave makes it east of the Plains, but we'll tackle 'em one at a time.

 

00z GFS ensemble mean looks an awful lot like the 12z Euro mean (with the system late next week).

 

From the looks of it, it doesn't look nearly as bleak after that either like the operational. It keeps the Aleutians negative height anomaly through the full range as well, while the operational moves it north. There continues to be plenty of West Coast troughing from the looks of it.

[Thundersnow12]

Yes please

 

[andyhb]

00z Euro continues to look nice through 192 with the one towards the latter of next week.

[HM]

All of the 12z data is not in yet and I haven't really looked at everything closely today (busy morning) but I would say the potential for a small to moderate tornado outbreak (I don't actually have a definition here for what that means so I'll take suggestions, haha) is there next weekend/early that following week (5/18-5/22). This trough will be forced more east due to the blocking in the west NAO domain. I'm not entirely sure how the blocking is going to progress at the time of the potential and beyond. I also don't know how quickly the MJO returns to the Atlantic. Both of these things will affect the days after this potential window.

 

Things could really liven up in the northern Plains/Upper Midwest as we end the month and start June. Some of the analogs are suggestive of that as well as the long term pattern that is currently being portrayed. I'll have more in the coming days as usual.

[andyhb]

All of the 12z data is not in yet and I haven't really looked at everything closely today (busy morning) but I would say the potential for a small to moderate tornado outbreak (I don't actually have a definition here for what that means so I'll take suggestions, haha) is there next weekend/early that following week (5/18-5/22).

 

12z GFS continues to have the trough although it is more fragmented as it moves ashore which weakens the mid level jet streak associated with it.

 

Still has a decent LLJ response to the leeside of the Rockies though.

[Ian]

All of the 12z data is not in yet and I haven't really looked at everything closely today (busy morning) but I would say the potential for a small to moderate tornado outbreak (I don't actually have a definition here for what that means so I'll take suggestions, haha) is there next weekend/early that following week (5/18-5/22). This trough will be forced more east due to the blocking in the west NAO domain. I'm not entirely sure how the blocking is going to progress at the time of the potential and beyond. I also don't know how quickly the MJO returns to the Atlantic. Both of these things will affect the days after this potential window.

 

Things could really liven up in the northern Plains/Upper Midwest as we end the month and start June. Some of the analogs are suggestive of that as well as the long term pattern that is currently being portrayed. I'll have more in the coming days as usual.

 

I think it's loosely like 6+ tornadoes in a region from several storms tho there is no real definition. I think many mean more when they scream it on social media etc.

 

Just make it hold off. Would be sadness to see tornadoes while we're finishing packing. 

 

Last few sets of models not as good as some yesterday at brief look. Seesaw emotions continue.

[HM]

12z GFS continues to have the trough although it is more fragmented as it moves ashore which weakens the mid level jet streak associated with it.

 

Yes, there are still plenty of issues so I can't be reasonably certain about the threat. Another issue is that if the blocking retrogrades quickly into western Canada, it could force a split and send the southern piece even further south (kinda like what happened with this week's trough) and give room for the northern piece to go north. Even if that occurs, the boundary layer recovery will be much better anyway in comparison.

[HM]

I think it's loosely like 6+ tornadoes in a region from several storms tho there is no real definition. I think many mean more when they scream it on social media etc.

 

Just make it hold off. Would be sadness to see tornadoes while we're finishing packing. 

 

Last few sets of models not as good as some yesterday at brief look. Seesaw emotions continue.

 

I think something like a regional 6-12 tornado episode can be achieved with the players on the field right now. Way too soon to up the potential's certainty; but as you guys saw yesterday, there are possible solutions that could support something like that.

 

I think it was 2003 (yeah I know, not even close to this year) that had a blocking scenario like this but I have to check it out (I'm going by memory). Of course, that year, anything seemed to work. This year, everything seems to go wrong lol.

[nrgjeff]

Agree the day 8-12 period is looking better for the Upper Midwest. Exact days and location is still up in the air. However pattern recognition is encouraging. Won't repeat above analysis but just throw in some additional optimism. First system middle of next week probably not much, but it kind of sets the table. The associated CF never blasts south, leaving some moisture behind. Next system, the one of interest, comes in to finish pulling moisture up. I really like stalled fronts, then retreating north setups. Regardless of any hard definition of tornado outbreak, I'll call it a possible chasable event. How does that sound? Details are really murky after our "system of interest" but it looks more encouraging along the northern tier, barring a 06Z GFS verification which would be a total debacle. Upper Midwest also nice with less chaser convergence.

[HM]

2003 during the first half of the month saw the MJO round phase 3-4-5 quite strongly and dropped quite the trough into the West. It brought a respectable round of tornadoes, as you guys know. There was some Central Canadian Blocking at the end of April into early May just as this was happening.

 

But that year had a lot more cold air/trough action in the West than what's on the models now. Also, the blocking never retrograded into western Canada. Something to keep in mind.

[MidwestChaser]

 

[andyhb]

^ Lol, good stuff.

[HM]

The GFS/GGEM and their ensembles are clearly propagating the MJO quickly back to the Atlantic while the ECMWF suite all agrees on a death in phase 5. Currently, there is a kelvin wave blowing up the Walker Cell over Indonesia/western Pacific and it's possible this is messing up the GFS and GGEM. The ECMWF, and in particular the weeklies, seem to have a better handle on the MJO-KW.

 

The GGEM today, by the way, got even more convoluted and nutty in the extended range.

[MidwestChaser]

 

The GGEM today, by the way, got even more convoluted and nutty in the extended range.

 

Isn't that the usual SSDD for the GGEM?

[Dsnowx53]

I think it's loosely like 6+ tornadoes in a region from several storms tho there is no real definition. I think many mean more when they scream it on social media etc.

 

Just make it hold off. Would be sadness to see tornadoes while we're finishing packing. 

 

Last few sets of models not as good as some yesterday at brief look. Seesaw emotions continue.

 

 

Yeah, it's certainly looking like we might miss a decent outbreak on the 18th or just after, and then have to wait for the next disturbance. Frustrating. Though if it holds off for a couple of days, you might still have a chance. 

 

I would still think intuitively that with a big Central Canadian block retrograding westward, that would force disturbances southward and have a suppressed zonal flow, where the shortwaves diving underneath would hopefully yield enough height rises to tap into the Gulf. I don't really see a scenario of a ridge "bridging" with that block, especially with the active PAC Jet. 

 

Still annoying though to see some height rises out west following the May 18th disturbance and not knowing when exactly the next wave will come. And regardless of the block, it does look like the heights are going to retreat northward somewhat, so the northern tier looks more appealing at this juncture. 

[HM]

Isn't that the usual SSDD for the GGEM?

 

Oh yeah, I wouldn't worry about it. I wouldn't say "SSDD" in this case because it has noticeably trended toward a crazier solution over the course of the week.

[HM]

 

I would still think intuitively that with a big Central Canadian block retrograding westward, that would force disturbances southward and have a suppressed zonal flow, where the shortwaves diving underneath would hopefully yield enough height rises to tap into the Gulf. I don't really see a scenario of a ridge "bridging" with that block, especially with the active PAC Jet. 

 

Still annoying though to see some height rises out west following the May 18th disturbance and not knowing when exactly the next wave will come. And regardless of the block, it does look like the heights are going to retreat northward somewhat, so the northern tier looks more appealing at this juncture. 

 

I wouldn't worry, yet, about the period beyond the next weekend potential. The GFS, by that time, is shifting the forcing quickly into the "El Niño Phases" and this could be a little fast or wrong altogether. Let's wait and see if the ECMWF suggests this. Oh and I don't doubt a brief period of ridging behind this trough/tornado threat...but a total long-wave shift back to a PNA that lasts a couple of weeks is the issue I'm talking about.

[HM]

By the way, the pattern I like for Memorial Day Weekend and early June is something kind of like 1990 in a sense. Troughs in both corners of the CONUS and a ridge over the 4-corners/southern Plains. This should keep the threats coming in the northern-tier especially along with MCS activity riding the anticyclonic flow.  

[andyhb]

There definitely are differences in the PNA status between the Euro and the GFS, the GFS has kept the PNA positive for the entire run over previous few verbatims while the 00z Euro/Euro ensembles suggest a neutral/perhaps negative PNA pattern taking place (which would obviously be more favorable for Western troughing and a more active period).

 

I did some teleconnection analysis using ESRL data back to 1948 and found that 55/74 severe events that I pulled up had a negative PNA at the time of the event, which makes sense.

[HM]

Basically, the longer the MJO "loops" around in that phase 4-5 area, the more transient the follow-up ridge will be in 1-2 weeks. In 1990, the blocking also retrograded into western Canada and had a transient look over the CONUS until about the first week in June. That's when the southern-tier anticyclone really took over.  

 

But keep in mind, this year's MJO speed has been somewhat faster and this MJO is a tad weaker than 1990 (which also implies faster).

[Ian]

Yeah, it's certainly looking like we might miss a decent outbreak on the 18th or just after, and then have to wait for the next disturbance. Frustrating. Though if it holds off for a couple of days, you might still have a chance. 

 

I would still think intuitively that with a big Central Canadian block retrograding westward, that would force disturbances southward and have a suppressed zonal flow, where the shortwaves diving underneath would hopefully yield enough height rises to tap into the Gulf. I don't really see a scenario of a ridge "bridging" with that block, especially with the active PAC Jet. 

 

Still annoying though to see some height rises out west following the May 18th disturbance and not knowing when exactly the next wave will come. And regardless of the block, it does look like the heights are going to retreat northward somewhat, so the northern tier looks more appealing at this juncture. 

 

The LR on models is pretty useless so I'm not too worried about the "after" period yet (let's see if there is something to begin with).  But either way there's probably some sort of break behind any system. Hopefully just a few days. 

 

Was hoping to leisurely head out this yr.. we're always racing to a threat it seems. Might have to bump departure to Friday and drive nonstop..

[Dsnowx53]

I wouldn't worry, yet, about the period beyond the next weekend potential. The GFS, by that time, is shifting the forcing quickly into the "El Niño Phases" and this could be a little fast or wrong altogether. Let's wait and see if the ECMWF suggests this. Oh and I don't doubt a brief period of ridging behind this trough/tornado threat...but a total long-wave shift back to a PNA that lasts a couple of weeks is the issue I'm talking about.

 

 

Right, makes sense. The Euro as you said has the MJO wave being slower to progress and going into the COD in phase 5, whereas the GFS has the MJO progressing all the way to phase 7, which creates more PNA ridging out west. 

 

I'm not worried yet because as I said before, intuitively I would think a Central Canadian block retrograding westward should lead to a split flow/semi-zonal regime where waves can travel underneath that block and make for interesting threats for the central and northern tier. I don't really see a PNA ridge "bridging" with that block, as despite what the GFS is saying, I think the flow is too zonal/fast in the Pacific to allow for that much upstream ridging, especially given the "wall" in Western Canada. 

 

It's just harder to be objectively "emotionless" when it comes to analyzing the data for us chasecationers, since we've spent a decent amount of money on this trip and really, really want to see something happen, lol. 

[Dsnowx53]

The LR on models is pretty useless so I'm not too worried about the "after" period yet (let's see if there is something to begin with).  But either way there's probably some sort of break behind any system. Hopefully just a few days. 

 

Was hoping to leisurely head out this yr.. we're always racing to a threat it seems. Might have to bump departure to Friday and drive nonstop..

 

 

If the Euro's MJO forecasts are right, the break probably would only be for a few days. It's just hard to not take a look at the longer range when there really isn't much else to do and it involves a trip you're emotionally invested in

 

And yeah, just having a nice, relaxing drive where the landscape gradually changes was one of my favorite parts of the trip last year. Racing to a threat makes that a lot more stressful. 

[Dsnowx53]

Obviously there are many other factors at play, but this would explain why the OP GFS is loving a PNA ridge out west -- its MJO racing towards phase 7. This is the May/phase 7 composite.