Central/Western Medium-Long Range Discussion

[nrgjeff]

Sunday and Monday looks like plenty of CAPE. What about turning with height? What makes the composite parameter soar? Is it CAPE without good turning? Is it turning on a warm front with cloudy stable stratoform rain? Obviously the former is much more likely than the latter this case (CAPE chart previous page); however, the latter happens often early season. For legit severe we need both juxtaposed. 

Is turning with height forecast? Let's take a look at the Central Plains both Sunday and Monday on the ECMWF.

At 250 mb winds are seasonable (modest but not dead) from the WSW. At 500 mb a short-wave passes Sunday but winds weaken Monday. Both days 500 mb is WNW. Despite AN heights, 700 mb is not too hot. 700 mb wind is also from the WNW. Sunday and Monday 850 mb is straight south (good) but modest. Surface and 925 mb are from the southeast.

So, we have great turning with height from surface to 700 mb. Winds are not too strong however. Pretty sure not tornado outbreak. Actually this is what late season chasers seek. Keep it subtle. Avoid crowds. Maybe find an isolated gem. Veer back is forecast from 500 mb to 250 mb; however, that high up is not a deal killer. It's especially OK late-season vs early. 

I've already taken my chase trip and found what we sought last week. I think the weather pattern looks good for those out there late-season and/or still looking for their tornado; but, it is not good enough to justify another trip after seeing a two-cycle tornado event last week. Who knows? Maybe a CO/WY gem could happen in upslope flow.

Best to check all constant pressure level forecast charts in the extended. Forecast soundings are worthless past 36 hours, esp if convection contaminates. Constant pressure level forecasts are OK a few days out to discern forecast turning with height (or not).

At the very least, check both CAPE and Helicity forecasts separately for juxtaposition. The latter forecasts turning with height, but even it can mislead if speed overwhelms no turning. Composite parameters are not that useful. So, drilling down (or up) the constant pressure charts is best.

[Quincy]

The overall pattern looks unseasonably quiet across the Plains through at least the next 5-7 days. This is reflected well by the CFS severe weather guidance dashboard, which has blue boxes in the coming days, something that is very unusual for early to mid-June.

The Northern Plains area into the Upper Midwest may see some severe thunderstorm activity this weekend, as a trough ejects eastward. What happens with that trough next week is the glaring issue. Medium-range guidance and ensembles are fairly consistent with broad troughing across the Missouri Valley/Midwest/Great Lakes vicinity through much of next week. In uncharacteristic form for mid-June, instability appears limited through at least the middle of next week and possibly the end of the week as well. Northwest flow events tend to become more common into July and sometimes even mid to late June, but with modest instability, at best, that does not bode well for severe thunderstorm prospects via NW flow next week.

As we approach next weekend, there have been signs that the pattern shuffles and there could be a return to at least near average severe thunderstorm activity for the third week of June. European ensemble data and the weeklies, to a lesser degree, show a more zonal flow-type pattern across the northern tier of states by next weekend or early in week 3. (roughly the June 15-18 window) The potential may exist for one or perhaps a few shortwaves to impinge on the northern High Plains/Northern Plains vicinity with an uptick in severe potential there. This is also highlighted by the CFS dashboard, although it does not take much in the way of wind shear to throw blanket regions of elevated SCP values in June when there is seasonably-typical instability in place. (The CFS dashboard is based on supercell composite parameter / SCP values, either over a broad area or elevated in any area)

On the other hand, the latest Euro weekly data seems to imply that any pattern shift is short-lived and that more Upper Midwest/Great Lakes troughing could set up by the middle or end of June week 3.

As we go deeper into June, the Great Lakes/Midwest vicinity could experience northwest flow severe threats, but that type of pattern needs instability in place. The trends suggest that moisture is going to be scoured south and east (quite a feat for June), even when there is appreciable upper level flow in the northern states. Who knows, maybe that could result in an unusual late season threat across the Mid-South, but that's speculation on an already conditional scenario.

Any way you slice it, the prospects for severe thunderstorm activity in the Plains in the near future are very slim. Sure, you can get some High Plains magic here or there, but that's to be expected, even in the quietest months of June. I'd be cautiously optimistic about prospects for June week 3. On the bright side, that period (June 16-22) has featured some significant events over the past decade. Almost each year seems to have at least one noteworthy event in that window, but we'll see.

[andyhb]

Early June has been very quiet for most of the 2010s, the exception being 2010 itself.

I definitely think the latter part of next week will have a chance beyond the amplification of the ULL near the Great Lakes. There is a strong signal in the GEFS for at least some activity in that period (and there has been for awhile), and note that the GEFS SCP chiclets on Gensini's website are anomaly based, rather than using raw count, so it gives a better idea of elevated activity relative to climo. Signal on the EPS is rather nebulous, but I wouldn't expect a really large signal in the heights at this point since it looks to be more centered around subtle disturbances in the flow.

[nrgjeff]

ECMWF still points to a little more activity starting on Friday, and through the end of the model run. ECMWF Para/Beta (2nd deterministic) looks even a little better. The latter keeps westerly flow instead of that northerly junk end of EC Op. Both have modest LLJ response most days starting Friday.

Moisture quality is slow to return, but by Friday is enough for central/high Plains. Moisture gradually improves each day, esp on the EC Para. Given what happened Saturday, Colorado and Goodland, chasers may be able to seek meso-scale events again. Good luck to those June-ing!

[Bob's Burgers]

New ECM (12z run of the Para) forecasts environments next week that would corroborate with the impressive GEFS SCP chiclet charts -- possible hyperactive end to June? 

[nrgjeff]

I put my chips on 3-4 chase days next week. However I don't see any big outbreaks. It is typical June chasing, but could be quality chasing.

First half of the week starts with the Upper Midwest. Tuesday the ECWMF shows a true system in chasable terrain of the Northern Plains. Wednesday goes into the MN/WI forest, but maybe something can get going down in Iowa. 

End of next week moderate flow is forecast to remain in the Plains (almost unseasonable NE/northern KS). LLJ is forecast to respond. Might get a couple days out of that if cap is not thermonuclear. Placement is uncertain attm.

So I propose we have two pairs of possible chase days. Take out one for terrain and/or bust. Nets 3 chase days?

[Windspeed]

Did not see a recent banter thread so thought I would just post here. This new video by Pecos Hank discussing super computer mesocyclone and tornado genesis with Dr. Leigh Orf is an absolute must watch:

[nrgjeff]

Monday Sept. 23: SPC did a great job interpreting the GFS in the Day 4-8 outlook. ECMWF in contrast lights the warm front Saturday and Monday. Who do I believe? Not the GFS! However the Euro is days 6-8; so, caution there too. I'm watching though!

Understand I'm roasting under the SER and need something for which to look forward, lol.

[raindancewx]

I went with a fairly snowy cold season for parts of the Plains, West and Northeast this year. Not many areas of the US came in with less than 75% of average snow. For New Mexico, the "average" snowline seems to be 7,000-8,000 feet - areas above that level will be snowier than average.

The ocean temperature pattern globally in early October is pretty close to opposite of what the 2016-17 winter ended up, essentially a Modoki El Nino instead of a Modoki La Nina. If it was truly opposite to 2016-17, maybe it'd be severely cold in the Southeast, but I have the cold somewhat to the Northwest of the South. I do think with Atlanta and areas west of it currently 10F above normal in October after a hot September that a lot of nights in the South will be pretty cold as the warm air is replaced by cold/dry air. Longer term, the subsurface heat is draining in Nino 4 to some extent, and the wave of ocean heat is moving East, so you'll see less of a Modoki look as Nino 4 cools and Nino 1.2 warms. The PDO also looks like it is going to go negative for at least a little while which is not great for cold in the Southeast.

[jojo762]

Nobody has posted in here in quite awhile, so guess i'll try and kick start some 2020 severe season discussion.

Looks like a fairly boring pattern will exist until at least early next week, Operational models and Ensembles have been persistent on showing a western trough ejecting into the plains at some point early next week, so that will be something to pay attention to. As of right now moisture return is seasonably impressive on most models -- but timing is an issue in model land--   this will change to some degree given that it is about a week-plus out.

Beyond that, it look's like we'll have another few-day period of quiescent weather... Followed by what *could be* an interesting period in mid-April.

Stay tuned. 

[Chinook]

I believe we should start a new general severe weather thread, since it's a new decade. 

[jojo762]

Looks like the "early next week" trough (cut-off low) got pushed back by about four to five days, even so it is more likely than not that either the trough de-amplifies significantly INVOF the four corners, OR dives south into Mexico, so as far as a central/southern plains threat is considered, this is toast; Dixie Alley is a different matter however. Compounding this, a cold-front crashes across the central and southern plains on Wednesday evening and into Thursday, muting any potential threat regardless of the mid/upper level pattern.

So that is a swing and a miss for some early April action.

To make matters worse, the pattern becomes... really boring on the global models into at least mid-April. Should be noted, however, that substantial differences exist with respect to the mid/upper level pattern between the 12Z Euro and GFS by day 8+. GFS shows a ridge off the coast of California while the Euro shows a substantial trough approaching the southwestern CONUS.

[WhiteoutWX]

10 hours ago, jojo762 said:

Looks like the "early next week" trough (cut-off low) got pushed back by about four to five days, even so it is more likely than not that either the trough de-amplifies significantly INVOF the four corners, OR dives south into Mexico, so as far as a central/southern plains threat is considered, this is toast; Dixie Alley is a different matter however. Compounding this, a cold-front crashes across the central and southern plains on Wednesday evening and into Thursday, muting the any potential threat regardless of the mid/upper level pattern.

So that is a swing and a miss for some early April action.

To make matters worse, the pattern becomes... really boring on the global models into at least mid-April. Should be noted, however, that substantial differences exist with respect to the mid/upper level pattern between the 12Z Euro and GFS by day 8+. GFS shows a ridge off the coast of California while the Euro shows a substantial trough approaching the southwestern CONUS.

Yeah seems pretty clear the pattern will be unsupportive of much severe in the plains for at least the next 10 days. After that, like you said, models begin to diverge on whether we can get some western US troughing or continue with more of the same. 

[jojo762]

40 minutes ago, WhiteoutWX said:

Yeah seems pretty clear the pattern will be unsupportive of much severe in the plains for at least the next 10 days. After that, like you said, models begin to diverge on whether we can get some western US troughing or continue with more of the same. 

I am pretty optimistic about late-April though. Not like that is anything surprising, but still... CFS loves late April/early May, severe wx dashboard is lighting up like a Christmas tree for that time frame. 

[WhiteoutWX]

19 minutes ago, jojo762 said:

I am pretty optimistic about late-April though. Not like that is anything surprising, but still... CFS loves late April/early May, severe wx dashboard is lighting up like a Christmas tree for that time frame. 

I'm still not entirely sure how much weight to give the CFS dashboard...but I know last year we  went the whole season without it looking anywhere close to as active as some of the recent runs have for later in the month, so I guess that's encouraging.

[Sydney Claridge]

With the COVID-19 pandemic and all, getting a major tornado outbreak (or just one major tornado striking a populated area) would be horrific, especially once you consider the need for hospital beds for both the injured and COVID-19 patients.  It would be much more manageable if the tornadoes stuck to rural areas, but that is never a guarantee; just look at what happened back in 2011.  Something like the 2011 Joplin tornado (which destroyed a hospital), if it occurred today, would be a lot worse given the current pandemic.

A quiet pattern is a much needed reprieve right now, and hopefully we don't have to worry too much about severe thunderstorms and tornadoes until COVID-19 quiets down somewhat.  But you never know, especially considering that we are now in the most active time of year for severe thunderstorms and tornadoes (April/May/June).

[It's Always Sunny]

Once that ULL passes through in about 4 days or so the ensembles remain mostly favorable through the end of the month for unsettled weather here, including severe potential. May not be in your backyard stuff but even on the 12th that area just east of the panhandle and over SW OK could be in a marginal or slight risk potentially and of course that can all shift so not a high confidence forecast by any means but there is certainly potential imo. Then from there on out we still got ridging over the west and troughing over central part of CONUS. That along with climo (it still being early in the month) I remain optimistic which I feel like is the general consensus here beyond day 10.

[CheeselandSkies]

19 hours ago, BrandonC_TX said:

With the COVID-19 pandemic and all, getting a major tornado outbreak (or just one major tornado striking a populated area) would be horrific, especially once you consider the need for hospital beds for both the injured and COVID-19 patients.  It would be much more manageable if the tornadoes stuck to rural areas, but that is never a guarantee; just look at what happened back in 2011.  Something like the 2011 Joplin tornado (which destroyed a hospital), if it occurred today, would be a lot worse given the current pandemic.

A quiet pattern is a much needed reprieve right now, and hopefully we don't have to worry too much about severe thunderstorms and tornadoes until COVID-19 quiets down somewhat.  But you never know, especially considering that we are now in the most active time of year for severe thunderstorms and tornadoes (April/May/June).

Yes. The pandemic has significantly tempered my enthusiasm for violent weather for the time being.

[raindancewx]

Actually think May will be pretty active, even for the time of year.

[cheese007]

Got a big D4/D5 risk out this morning from SPC. Something to watch...

[Chinook]

Models are generally showing a deeper warm sector developing near a low pressure/warm front on Easter Sunday, 12z.  I wouldn't be surprised to see some sort of outlook for central/east Texas on Saturday. As for Sunday, I would expect possibly an enhanced outlook for Louisiana, Mississippi, and Alabama.

[MUWX]

On 4/6/2020 at 11:34 AM, jojo762 said:

I am pretty optimistic about late-April though. Not like that is anything surprising, but still... CFS loves late April/early May, severe wx dashboard is lighting up like a Christmas tree for that time frame. 

Starting to see more talk of this on twitter. Late next week could be interesting. 

[DanLarsen34]

3 hours ago, MUWX said:

Starting to see more talk of this on twitter. Late next week could be interesting. 

Seems to be a growing consensus in the models that we are about to embark on another active period in the weeks ahead. I've seen the same talk, and the CFS is lighting up for sure.

[It's Always Sunny]

Next week or so looks favorable for severe but end of the month/early May in question with EPO trending positive per GEFS. EPS following similar suit.

[It's Always Sunny]

Op GFS remains active for remainder of the month so remains to be seen if it changes course.

[WhiteoutWX]

Looks like another incredibly slow start to the season here in Oklahoma, after very slow starts in 2018 and 2019 as well. We've had 5 tornadoes so far this year, with 3 back in January and 2 in March. Extended range guidance suggests it not at all out of the realm of possibility we get to May without any additional tornadoes. 

For comparison, 2019 had 2 tornadoes in April until a big day on 04/30/2019, while 2018 made it all the way to May without a single tornado on the year. 2019 ended up being a record year for number of tornadoes while 2018 was fairly slow, so there's not much you can say at this point on whether the pattern will flip to a more active than normal May. 

While the severe enthusiast in me is disappointed at another slow start, it's good mother nature could cooperate at least for our EM's across the state who are already overloaded with COVID-19 related tasks. 

[jojo762]

If you like LOTS of chaseable plains days, the long-range 12z GFS was your type of run... Not much else can be said besides that it shows a large, lumbering trough with day after day of southwest flow in the extended fairy-tale range atop a very moist PBL.

[SluggerWx]

7 hours ago, jojo762 said:

If you like LOTS of chaseable plains days, the long-range 12z GFS was your type of run... Not much else can be said besides that it shows a large, lumbering trough with day after day of southwest flow in the extended fairy-tale range atop a very moist PBL.

That's pretty crazy... starting on 4/27 there are like 5-6 days in a row. Of course it's la la land range, like you said, but maybe it indicates at least a potential upward trend in plains activity towards the end of April.

[WhiteoutWX]

20 hours ago, jojo762 said:

If you like LOTS of chaseable plains days, the long-range 12z GFS was your type of run... Not much else can be said besides that it shows a large, lumbering trough with day after day of southwest flow in the extended fairy-tale range atop a very moist PBL.

The GFS is a dirty liar. 

[Sydney Claridge]

Would definitely be interesting to see the severe storm potential start to move further north.  So far, the Gulf Coast states look to remain prone to severe thunderstorms and tornadoes for the next couple of weeks.  Given what happened in Mississippi on Easter (and with said areas still recovering), it would be nice to get the severe storm potential away from that area.  But they have another significant risk for tornadoes tomorrow (also including Louisiana once again, so still relevant to this subforum), and the 22nd and 23rd are also looking like potential severe weather days in that same area once again.

With all that warm water in the Gulf, it would not surprise me that whenever the severe storm potential marches north, that things could get intense with plentiful low-level moisture.  As for the traditional Tornado Alley, this is a Dixie Alley pattern, but parts of Texas may get in on the action (I don't want to necessarily rule out the I-35 corridor or the Southern Plains of TX/OK completely, especially if the storm systems come in northwest of where they are modeled, but everything looks like it will be east of there).  I'm just a little surprised that it has remained quite cold in the Midwest and Great Lakes regions, but they will probably get their turn for severe storms once this warm, humid air can move further north than Dixie.