Central/Western Summer Medium/Long Range Discussions

[brettjrob]

The ECMWF has really backed off its earlier solution of terrible moisture for Sunday. At this point, taking a consensus of the GFS and ECMWF, the environment along the dryline looks very impressive in many respects Sunday afternoon and evening. One big caveat is that the anvil-level flow is very weak with southward extent, probably enough to be a serious problem if you go more than a couple counties S of the OK/KS border. If the cold front can stay put in C KS through the evening hours, keeping the triple point closer to DDC or GBD, this could be a fairly significant day that crept up on us quickly. The other caveat, of course, is moisture and mixing, as the dryline looks to set up fairly far W keeping the zone of concern over parched territory.

[andyhb]

Well tomorrow is going to have to deliver the goods because that pattern afterwards is pretty atrocious for an extended period. Even though it's May, it's going to take awhile for the Gulf to recover from an eastern trough like that.

[Ground Scouring]

Thanks. What I'm more unsure of is trying to time quicker KW passages. That doesn't have a lot of skill and their effect is not as pronounce. However, timing a legitimate MJO or a CCKW (convectively-coupled Kelvin Wave) has more skill/effect. Soon, our MJO is going back into the IO. Toward the 20th or so, maybe 5/20-5/25, a CCKW will again cross the dateline/east Pac. It being late May means a slower jet, shorter waves etc. but this force should be enough to add some speed/downstream trough. We'll see...

 

Mike's Components Graphic:

The 00Z ECMWF actually does show a trough entering the PAC NW on/after Day 8 (May 19), which appears to match your time frame very well.

[Thunder Road]

I'm headed out for my own mini chasecation starting Sat, ending up at NWS FSD where I'll be spending the summer.

 

Not too enthused by that omega block on the 6z GFS...

[Ian]

I'm headed out for my own mini chasecation starting Sat, ending up at NWS FSD where I'll be spending the summer.

 

Not too enthused by that omega block on the 6z GFS...

It's had more runs than not lately without it that huge. The GFS at LR is pretty meh of course. 

 

The EC trough is a b**ch tho.

[Quincy]

Next road trip/chasecation for here starts on the 22nd. Cautiously optimistic that we can boot that trough out by then and start anew.

Even with today being a moderate risk, this first half of May should go into the books as yet another very meh period in terms of severe.

[HM]

The 00Z ECMWF actually does show a trough entering the PAC NW on/after Day 8 (May 19), which appears to match your time frame very well.

Thanks. Learning a few lessons here about El Nino forcing and internal/intraseasonal waves. Notice the slower progression out of the western hemisphere this last week, leading to an extended period of the favorable pattern (before the unfavorable pattern ahead) we've been in. But anyway, very complicated picture with a couple of CCKW, broadening the low-frequency signal across a large area. All at the same time, retrogression across N PAC in highly amplified pattern is leading to large run-to-run changes in MR.

I'm still liking 5/20-25 for the next potential outbreak. As others have mentioned already, issues with recovery and the cut-off over the East make the situation more uncertain.

[hm8]

I'm still liking 5/20-25 for the next potential outbreak. As others have mentioned already, issues with recovery and the cut-off over the East make the situation more uncertain.

I'm headed out west on the 25th, so hopefully you're just a bit off

Overall end of May/early June doesn't look awful.. . but we'll see

[Ian]

I'm increasingly cautiously optimistic about the beginning of our trip. We are leaving Friday, so we should finally get a slow ride out instead of the crazy all nighter to chase day.  Both the Euro and GFS suggest potential as soon as Sunday in the High Plains and 12z Euro drops a nice trough into the west late. Still some things to be resolved but better than it's looked at times.

[Thunder Road]

It's had more runs than not lately without it that huge. The GFS at LR is pretty meh of course. 

 

The EC trough is a b**ch tho.

 

Yeah 12z was a big step back in the right direction

 

 

I'm still liking 5/20-25 for the next potential outbreak. As others have mentioned already, issues with recovery and the cut-off over the East make the situation more uncertain.

 

Hey now.  Cut that out!  Getting me all excited...

 

 

I'm increasingly cautiously optimistic about the beginning of our trip. We are leaving Friday, so we should finally get a slow ride out instead of the crazy all nighter to chase day.  Both the Euro and GFS suggest potential as soon as Sunday in the High Plains and 12z Euro drops a nice trough into the west late. Still some things to be resolved but better than it's looked at times.

 

It's just so dry though.  We don't leave until Saturday morning (or Friday late afternoon if we think it's worth it for Sunday, which at the moment it doesn't look like it is). 

[Ian]

It's just so dry though.  We don't leave until Saturday morning (or Friday late afternoon if we think it's worth it for Sunday, which at the moment it doesn't look like it is). 

yeah it's pretty dry the ec trough going to make it a little tough to get moisture in fast. tho verbatim euro gets some near 60 dews up into SD/wy border area and does appear to convect in that area late day. i haven't seen a good storm since we left last yr so even lightning and pretty visuals might be worth it lol.

[Thunder Road]

Looks like next Monday has potential.  Capping/surface dryness will be a problem, but there might be some nice relatively high-based structure if we can overcome that.  The Canadian is actually a bit nicer than the GFS with low and mid level winds stronger.  Not sure how much I believe the Dew Points it's throwing out though.  50 F?  If so, yikes.  But it looks like a product of high grid spacing more than anything else.

[Ian]

0z Euro looked quite solid as does ens. I'm not turning on Sunday just yet.. models are actually pooling moisture a bit better now in the high plains and have continued to convect in the SD/NE/WY area. Soundings look pretty good. It's tenuous as moisture is enough but not sure why it's that high given drier surrounds.

[HM]

0z Euro looked quite solid as does ens. I'm not turning on Sunday just yet.. models are actually pooling moisture a bit better now in the high plains and have continued to convect in the SD/NE/WY area. Soundings look pretty good. It's tenuous as moisture is enough but not sure why it's that high given drier surrounds.

 

Yes, I'm growing more confident in a classic S-C Plains event in that window (you're all over the N Plains setups here). What the ensemble means won't show you is any jet acceleration yet. The average of the members will smooth that out. But what they are showing clearly is a trough over the 4 corners!

[HM]

Really interesting discussion, as always. Are you suggesting that IO forcing is more favourable for plains severe wx in nina springs while 180-100W forcing w/ +AAM is more favourable in nino springs? I believe that this is the paper you were referring too from roundy and thompson: http://journals.ametsoc.org/doi/abs/10.1175/MWR-D-12-00173.1

 

I'm not even suggesting that as much as I'm suggesting that the forcing will mean something different season to season (for its unique set of conditions/parameters). But yes, ENSO clearly regulates intraseasonal oscillations and how those anticyclones/jet accelerations will behave in the mid latitudes. So your question here might be a good first hypothesis.

[HM]

The MJO, on the RMMS, is rushing into phase 3 but the two KWs are making the projections of the low frequency wave tricky still. Should everything MJO, AAM and AO-wise occur has expected, this would be a multiday outbreak likely moving through the MS Valley / MW too.

[Ian]

Sunday signal continues. GFS still convects in SW SD which the models have been doing in that region quite a bit now, pretty ideal upslope flow as depected with good shear on the front edge of the PAC NW trough.  Of course if the dews are like 5-10 too high on the models it could be a bit meh but 55 works for sure in that region.

 

[andyhb]

Yes, I'm growing more confident in a classic S-C Plains event in that window (you're all over the N Plains setups here). What the ensemble means won't show you is any jet acceleration yet. The average of the members will smooth that out. But what they are showing clearly is a trough over the 4 corners!

 

I'm interested to see how fast the ridging in the Gulf moves out in the wake of the eastern trough this coming week. A look at the 12z Euro (even GFS as well) would suggest quite a bit of potential with this type of broad upper trough developing assuming moisture return ends up cooperating.

[HM]

I'm interested to see how fast the ridging in the Gulf moves out in the wake of the eastern trough this coming week. A look at the 12z Euro (even GFS as well) would suggest quite a bit of potential with this type of broad upper trough developing assuming moisture return ends up cooperating.

This could, all-around, be a good scenario. A broad trough over Rockies may allow more storm coverage, over more days, to be in better chase territory (for a change).

Another thing to point out is: there appears to be yet another cool season-like N PAC jet extension day 6-10. This is getting more and more noticeable on the NWP. Perhaps they see the CCKW moving the anticyclone eastward in the MR now. How that alters the waves will be interesting in the days ahead too.

[andyhb]

I mean I'm a bit suspicious of the moisture given the trouble we have had with getting moisture to the dryline this year.

[Ian]

Eh, it's almost late May. Moisture is easier to come by from here out. The EC trough sucks though it looks less problematic as we close and that's probably not shocking since some models had it close at 500 over DC and then sit there for like 12 years which almost never happens (knock on wood). Not to mention plenty of big Plains events had troughing somewhere near the EC or on the NE coast etc. 

 

Many years have turned on a dime.. not that this one will.. though I think we've already seen things trend back toward a more 'normal' progression over recent weeks.  Granted, not a huge ton of prime territory days.  

[Ian]

Sure it is.

 

Not.

Thanks for your useful contribution. 

[HM]

I mean I'm a bit suspicious of the moisture given the trouble we have had with getting moisture to the dryline this year.

There's nothing I can say to that except, "yep." Getting the pressure/wind right is the first step and recovery starts this weekend. Other than that...got to get lucky.

[andyhb]

There's nothing I can say to that except, "yep." Getting the pressure/wind right is the first step and recovery starts this weekend. Other than that...got to get lucky.

 

What I think we would need is a setup where the dryline mixes east in addition to having good forcing (i.e. a surface low further east than it was yesterday). Of course, this would likely bring the metros like OKC and Wichita into greater threat.

[HM]

Check out the CPC analogs:

http://www.cpc.ncep.noaa.gov/products/predictions/610day/610analog.off.gif

http://www.cpc.ncep.noaa.gov/products/predictions/814day/814analog.off.gif

It's the 1986 date that interests me the most. It was right around then that the MJO behavior did the thing I was watching for this year. It led to a pretty active period a few days later:

http://www.srh.noaa.gov/oun/?n=tornadodata-ok-1986

[brettjrob]

Eh, it's almost late May. Moisture is easier to come by from here out. The EC trough sucks though it looks less problematic as we close and that's probably not shocking since some models had it close at 500 over DC and then sit there for like 12 years which almost never happens (knock on wood). Not to mention plenty of big Plains events had troughing somewhere near the EC or on the NE coast etc. 

 

Many years have turned on a dime.. not that this one will.. though I think we've already seen things trend back toward a more 'normal' progression over recent weeks.  Granted, not a huge ton of prime territory days.

 

Your statement about moisture in late May is generally accurate, but I fear this year could prove to be the rare exception. I've never seen dew points verify so much lower than forecast over such a wide area this late in the season as yesterday. The short-term, vegetation-effecting drought conditions are worse this year than any of the past three. It's been bone dry over most of the Plains ever since October. The western areas have been in awful shape since 2011, but driving through the Flint Hills this weekend, even they were brown and looked like they should in October.

 

Hopefully the late growing season, due to a brutally cold winter and early spring, has been a significant part of the problem thus far, and that will finally reverse over the next week or two. Throwing any substantial eastern troughing into this cocktail just gives me a sinking feeling, though. We need everything to go right that possibly can (i.e., short of the drought disappearing overnight). Otherwise, I see moisture being a big factor on virtually every setup. There can still be plenty of pretty storms and some tornadoes, of course, and you guys will have the flexibility to find whatever needles-in-the-haystack there might be while you're out.

[Ian]

Your statement about moisture in late May is generally accurate, but I fear this year could prove to be the rare exception. I've never seen dew points verify so much lower than forecast over such a wide area this late in the season as yesterday. The short-term, vegetation-effecting drought conditions are worse this year than any of the past three. It's been bone dry over most of the Plains ever since October. The western areas have been in awful shape since 2011, but driving through the Flint Hills this weekend, even they were brown and looked like they should in October.

 

Hopefully the late growing season, due to a brutally cold winter and early spring, has been a significant part of the problem thus far, and that will finally reverse over the next week or two. Throwing any substantial eastern troughing into this cocktail just gives me a sinking feeling, though. We need everything to go right that possibly can (i.e., short of the drought disappearing overnight). Otherwise, I see moisture being a big factor on virtually every setup. There can still be plenty of pretty storms and some tornadoes, of course, and you guys will have the flexibility to find whatever needles-in-the-haystack there might be while you're out.

Admittedly I haven't paid much attention to how moisture is verifying.. I know it's been less than advertised in general but not sure exactly how to quantify it.  Definitely a concern for a chasecationer or someone out there all the time.  I'm not out to kid myself into thinking we're about to run into another bounty or something (though who really knows). 

 

I'm big on persistence when it comes to LR forecasting and most of those variables are rather negative. It is a bad mixture this year of a slow growing season plus drought.  There seem to be signs maybe June will be the month on the CFS etc, but putting much faith in that given the drought it difficult.  No matter for me either way except tracking at home I suppose.  And if anything it does appear to be leaning toward a season that favors central plains or north? 

 

My whole take on the EC trough portion of the nearer term long range is that it's showing to be less and less of a game ending problem as we close.. which is not that surprising. You can get a really blocked up patter in May of course but getting some huge closed low to stall out over the lakes or mid-atlantic for almost a week is a different animal than something chilling off the EC or New England. Plus there will be sfc/mid lvl highs between it and the plains trying to push moisture north... and if for some reason the trough in the west does actually meander and take its time coming out as shown on the Euro and increasingly the ensembles you open up a decent window to get the juices flowing. 

 

You used to live out here but we've had about the worst 1-2 yr run of storms locally that you can imagine. Pretty sure I haven't seen anything of real interest since a day or two after I got back last yr and it was a non-severe warned rotating cell that had some unique features and not much else.   So.... I'd probably take a KS supercell with 55 degree dews and a base 12 miles up at this point lol. Plus the other options of getting skunked or close to skunked are far less desirable.. and many in the chaser community have been eager to proclaim this year dead based on d10 maps a few times which hasn't come to pass yet.

 

It does help I'm not necessarily looking for an outbreak and we're able to travel 3-500 miles a day for 2%ers. As long as there's something to do...

[andyhb]

Your statement about moisture in late May is generally accurate, but I fear this year could prove to be the rare exception. I've never seen dew points verify so much lower than forecast over such a wide area this late in the season as yesterday.

 

Most models were in agreement 24 hrs out that there would be mixing into the upper 50s/low 60s along the dryline south of NE. It's not like a significant event was really expected there.

[Minnesota Meso]

I find this disco about lack of vegetation depressing dews very interesting.  Up here it's been mostly wet, and I understand the farmers are behind getting their crops in. I wonder how much of the crops have gotten in south of us, say northern MO, KS, NE and IA.  It seems like cold air over southern Canada is taking it's time retreating to the north and may depress their severe season. 

 

So I have a question for those that know better than me.  Could those of us living in the Upper Mississippi Valley be looking at a stronger than usual severe season from the end of May through June and possibly July?

[brettjrob]

Most models were in agreement 24 hrs out that there would be mixing into the upper 50s/low 60s along the dryline south of NE. It's not like a significant event was really expected there.

 

I don't really agree with this. Dew points late afternoon yesterday over W OK ahead of the dryline looked to be 52-56 F, on average. The NAM and GFS had advertised mid-upper 60s from 36 hours out, perhaps declining to 60-63 F by Saturday evening's runs. Even the ECMWF was 5-7 F too moist in the short range.

 

Looking farther E and NE, the situation wasn't much better. All models were in agreement on solid mid-upper 60s dew points throughout the E half of KS through the afternoon, but they mixed out to the upper 50s to low 60s.