Central/Western Medium-Long Range Discussion

[jojo762]

53 minutes ago, Quincy said:

On the bright side, recent heavy precipitation events have wiped out almost all drought areas across the central United States:

Man... Crazy to see the region THIS drought-free. I remember 4-5 years ago when it seemed like the entire plains was covered in extreme drought.

[Quincy]

I've taken a bit of a deeper dive into the medium-long range period and based on trends, model guidance and climatology (analogs), it seems probable that the next 2-3 weeks will feature below average tornado activity. Additionally, we may continue to see typically active areas in early/mid-May (North Texas, central/eastern Oklahoma, eastern Kansas; Missouri) remain very quiet.

Global guidance is consistent in showing an omega blocking-type pattern through at least the start of next week. This will mean that favorable upper level flow will remain largely split away from the Plains, with a seasonably strong northwest jet from the Midwest/Great Lakes into the Southeast and similarly strong upper level flow across the western United States (transitioning more toward the Desert Southwest by the end of the weekend). Aside from sporadic severe (mainly damaging winds) across the West and East Coast, this looks like about as benign of a pattern as one could draw up for the first 5-10 days of May.

Going forward, there is some potential for severe threats to materialize across the southern/central High Plains during the first half of next week, as a cutoff low ejects east from the Four Corners region. Kinematic and thermodynamic fields don't look particularly impressive, especially not for mid-May, although it's likely that tornado activity ticks up a bit next week.

My main focus is on the period beyond that. Does this month get out of this seemingly extended early May dearth of tornado activity? Probably not, at least not in any big way.

I took a look at two main model projections, the CPC day 8-14 analogs and the new Euro weeklies, which were released within the past few hours. The signal from both camps is more or less the same. The CPC analogs are centered on May 15th and I took the top 5 analogs and ran out tornado counts from days 1-10 in those periods for a comparison.

The analog days 1-10 period averaged 55 tornadoes, which is well below the average of 79 for May 15-24. Also, the focus for tornado activity is centered across Kansas/Nebraska/Iowa, which fits the weeklies progs very well. The pattern is projected to feature some troughing over the Great Basin, with a tendency for shortwaves to transverse the central Plains to upper Mississippi Valley. (The period starts with a "death ridge" across the Plains, before the pattern becomes less ugly with time) That would tend to favor severe in the central Plains, which means the May tornado season could effectively "skip over" the Oklahoma/southeastern Kansas/Missouri area. There are at least some instances of tornadoes across the southern High Plains into Oklahoma in these analog periods, but the likelihood of a deep trough bringing substantial tornado threats to the southern Plains through weeks 2 and 3 of May seems fairly low.

Overall, the analogs and medium-long range guidance both support below average tornado activity across the Central United States over the next 2-3 weeks, with at least some potential for near/somewhat above average activity in the central Plains/middle Missouri Valley. (Don't count out the southern High Plains early next week) It will be mid/late May, so you can't rule out a bigger event that could throw a wrench in this thinking verifying, but the odds seem lower than 50/50 on such a scenario, which is also climatologically abnormal.

It was going to be difficult to bring this year's tornado count back to seasonable levels after such a busy early season, but a below (if not well below) average May could manage to achieve that.

[WhiteoutWX]

Thanks for putting that together, Quincy. It really is amazing how few tornados there have been in the southern Plains this year. And like you said, it would be hard to draw up a much worse pattern for the first 10-15 days of May. There is always the end of May when good things can happen with less than stellar troughs but I have to admit my optimism has really trailed off the past few weeks. 

[jojo762]

I get the feeling we might be able to get some Panhandle magic this coming week. The more SSW orientation of the mid-level flow makes it a little less certain to me though. Not looking like we'll see any "big" days at this point... but severe storms with large hail and damaging winds are still likely on a couple/few days next week across the plains. 

[Jim Martin]

3 hours ago, jojo762 said:

I get the feeling we might be able to get some Panhandle magic this coming week. The more SSW orientation of the mid-level flow makes it a little less certain to me though. Not looking like we'll see any "big" days at this point... but severe storms with large hail and damaging winds are still likely on a couple/few days next week across the plains. 

For Wednesday of next week.

[brettjrob]

The crappy closed low next Tue-Wed reminds me in a really vague sense of 15 May 2013. Mind you, there wasn't a massive east coast trough then. But it is evidence of how these barotropic-ish closed lows whose shear profiles leave something to be desired can still get the job done in May.

[mfgmfg]

On 5/4/2017 at 9:47 AM, Quincy said:

On the bright side, recent heavy precipitation events have wiped out almost all drought areas across the central United States:

I was actually looking at this earlier today and thought I hadn't seen a map this good in years. Turns out this is the highest clear % map in the archives and hasn't looked this good since June 2010 or Jan 2001.

 

Below table is CONUS percentages (Total US is similar)

 

[Chinook]

Looking back 18 years in the past, to a deadly, historic storm of May 3, 1999. Loop of this radar is at US Tornadoes twitter feed.

 

[brettjrob]

Although we've seen most of the Plains drought-free by late spring the last two years, what's most striking on those DM maps is that the most significant drought nationwide is in the Southeast. I can't recall seeing that since 2007.

[jojo762]

**Takes peek at long-range in 00z GFS** Oh my god... It's over 10-days out, so it's frivolous to get into much detail, as the details are obviously nebulous, but needless to say I would NOT be upset if that happened. FWIW, op-GFS has been consistent in showing significant troughing across the plains sometime in the May 17-22 time frame, GEFS/EPS are also consistent in showing mean western troughing leading up to this time-frame, with many GEFS members -- to varying degrees -- showing a significant trough. 

[Quincy]

29 minutes ago, jojo762 said:

**Takes peek at long-range in 00z GFS** Oh my god... It's over 10-days out, so it's frivolous to get into much detail, as the details are obviously nebulous, but needless to say I would NOT be upset if that happened. But, FWIW, op-GFS has been consistent in showing significant troughing across the plains sometime in the May 17-22 time frame, GEFS/EPS are also consistent in showing mean western troughing leading up to this time-frame, with many GEFS members -- to varying degrees -- showing a significant trough. 

A pattern flip is certainly plausible. I wouldn't be surprised if late May is rather active. With that said, seasonable activity in comparison to the current state of affairs would seem like a big difference. It's hard to screw up late May unless you get a bizarro cutoff low over the Ohio Valley, or massive ridge over the Rockies. 

[bjc0303]

EPS mean shows a pretty prolonged period of western troughing 

[nrgjeff]

Back half of of May is looking good for chasers who can forecast. Might be a couple big days, and maybe a big crap-out; otherwise, looks like a nice set-up picker's market. Closed lows (like this week) can and do produce like Wray Colorado. Week of the 15th, late that week near the Rozel anniversary, looks like a gorgeous open trough. Still fighting remnants of East trough, but the Plains can recover quickly in mid-May. Ensembles and weeklies hint at another trough week of May 22, again maybe later in the week. The later in May the better. Yes, it is hard to screw up late May barring a total debacle pattern.

[Misstertwister]

38 minutes ago, nrgjeff said:

Back half of of May is looking good for chasers who can forecast. Might be a couple big days, and maybe a big crap-out; otherwise, looks like a nice set-up picker's market. Closed lows (like this week) can and do produce like Wray Colorado. Week of the 15th, late that week near the Rozel anniversary, looks like a gorgeous open trough. Still fighting remnants of East trough, but the Plains can recover quickly in mid-May. Ensembles and weeklies hint at another trough week of May 22, again maybe later in the week. The later in May the better. Yes, it is hard to screw up late May barring a total debacle pattern.

What do you look at for troughing long term? Wind fields? GFS, CFS,?  This one thing I'm getting new at and haven't really understood what to look for.

 

im getting better at looking at short term for different variables i.e., EHI, dewpoint, wind speeds form 850 to 500, cape, CIN but I never really dive in to long term like a lot of y'all fo

[nrgjeff]

You are on the right track. Keep it simple weeks 3-4. Actually keep it simple week 2 also. GFS/Euro go out through week 2 but you've seen us make fun of the 11-15 day. Looks for a nice trough and the right pattern, not details. Weeks 3-4 are available on the CFS and Euro weeklies. That's an even quicker glance for the right pattern.

First the GFS/Euro: I like a Rockies trough at 500/200 mb with SW/WSW flow over the Plains. SSW or S flow is not as favorable. If you are curious check 850 mb for a LLJ response S/SE there. It'll be there with a good trough, so maybe only check if a marginal trough. I prefer the downstream ridge over the Southeast, not the Upper Midwest, for several reasons including upper level winds and low level moisture. Just checking for wind direction with height and surface temps/dews.

Weeks 3-4 are even simpler and quicker using the CFS/Euro weeklies. Most of the 500 mb presentations are height anomalies. While similar to the 500 mb heights chart, some cautions. What might look like a deep Southwest low could be a closed low, not ideal but can work. On the plus side, what looks like a meh northern Rockies trough could be favorable for subtle waves ejecting. The latter will start to look better on the GFS/Euro if the forecast holds.

Finally I only use indices within a few days. Indices really just summarize the fundamentals. Turning with height and instability should yield good indices. Indices that incorporate directional shear should show local maximums along boundaries. Mismatches require looking back at the fundamentals. Another outflow better than the warm front? Any ongoing rain? Could be anything, but one has to figure the mismatch and adjust. If all lines up, a chase target is born.

12 hours ago, Misstertwister said:

What do you look at for troughing long term? Wind fields? GFS, CFS,?  This one thing I'm getting new at and haven't really understood what to look for.

im getting better at looking at short term for different variables i.e., EHI, dewpoint, wind speeds form 850 to 500, cape, CIN but I never really dive in to long term like a lot of y'all fo

 

[bjc0303]

Gotta say that ensemble mean forecasts for next week look pretty impressive, with promising events possible Tues, Weds, and Friday it looks.

[jojo762]

3 hours ago, bjc0303 said:

Gotta say that ensemble mean forecasts for next week look pretty impressive, with promising events possible Tues, Weds, and Friday it looks.

Also, 12Z op-Euro shows what would appear to be a fairly substantial threat next Tuesday evening across KS/OK, GFS does as well but there is still some disagreement in timing of the S/W and location the better threat area.

[bjc0303]

While details get washed out in the mean, I really can't complain about this sequence throughout the week. impressive.

 

 

 

Considering various deterministic and ensemble solutions... Tues, Weds, and Fri look interesting to me. Weds is conditional on timing, where Tuesday looks more certain. Friday looks solid on the large scale. we'll see how things pan out but I really like the prospects of next week.

[1900hurricane]

I went ahead and pulled the trigger in setting aside most of next week for chasing. I've never dedicated this big of a time block to chasing in the past, so I'm really excited to finally be able to do something like this. The persistent western troughing progged across all guidance helped solidify it in my mind.

[jojo762]

1 minute ago, 1900hurricane said:

I went ahead and pulled the trigger in setting aside most of next week for chasing. I've never dedicated this big of a time block to chasing in the past, so I'm really excited to finally be able to do something like this. The persistent western troughing progged across all guidance helped solidify it in my mind.

I have Monday-Friday off next week as well, still have some finals on Tuesday and Thursday but those are all in the morning. Looking like an active period, with several impressive days (at least it appears there will be). Surprised by the lack of talk about it.

[1900hurricane]

The failure mode I'm worried about most right now for next week is 2015 style MCSs prematurely clearing out the warm sector actually. It might be a little early to be overly concerned about it, but guidance is throwing some persistent and robust splitting upper level jets over the southern plains, which is driving the QPF fields way up.

[Jim Martin]

 From the Storm Prediction Center...

...Day 6/Tue - Southern/Central Plains...

   Guidance has become more consistent in ejecting a stronger shortwave
   impulse across the southern Rockies and into the Plains on Tuesday.
   Rich boundary layer moisture will have had enough time to surge
   northward ahead of this feature while a lee low deepens over the
   northern/central Plains. Confidence in an organized severe threat
   developing in the vicinity of a dryline across parts of central KS
   into western/central OK and perhaps the eastern TX Panhandle into
   north TX has increased enough to introduce 15% probabilities. The
   severe threat may extend further north into the mid-MO Valley ahead
   of the eastward progressing surface cyclone, but confidence in
   quality moisture that far north is low at this time. 

[cstrunk]

18 hours ago, bjc0303 said:

Gotta say that ensemble mean forecasts for next week look pretty impressive, with promising events possible Tues, Weds, and Friday it looks.

10 hours ago, 1900hurricane said:

I went ahead and pulled the trigger in setting aside most of next week for chasing. I've never dedicated this big of a time block to chasing in the past, so I'm really excited to finally be able to do something like this. The persistent western troughing progged across all guidance helped solidify it in my mind.

10 hours ago, jojo762 said:

I have Monday-Friday off next week as well, still have some finals on Tuesday and Thursday but those are all in the morning. Looking like an active period, with several impressive days (at least it appears there will be). Surprised by the lack of talk about it.

 

I also am free for the first half of next week, and if Tuesday/Wednesday are looking good I might make a two-day chase out of it, depending how things are looking closer to the event, which would be my first multi-day chase. 

 

[jojo762]

Both the 00z Euro and 12Z GFS operational runs are in fairly good agreement on a fairly substantial threat developing along and east of the dryline across Western/Central KS and Western OK on Tuesday afternoon and evening with an impressive 35-50kt LLJ by 00Z and a 50-60kt mid-level jet penetrating the strongly unstable warm sector by 00Z... Both models, as you can imagine, show an impressive parameters space along with isolated, discrete convection by 21-00Z. Main difference between the two would appear to be the Euro showing VBV above 500mb, and the GFS showing no VBV. Don't have too much time to delve into any other details, perhaps someone else could add something more... Capping appears to possibly be an issue...

[bjc0303]

Disagree on capping. If anything, 1) morning convection and 2) high LCL heights may be an issue, but given we are five days out, it is hard to put much stock into analyzing anything more than the large scale pattern. 

12z ECMWF edit: early precip looks to be less of an issue Tues this run. Again - kind of pointless analyzing details like this, but the ECMWF lights up a large portion of the OK/TX/KS dry line with QPF 18-06z Tues. Does so again Thursday... Will have to watch.

[jojo762]

Somebody should go ahead and make a thread for this coming week 5/15-20/21 as it looks like we will have several days with severe possibilities with perhaps a big/interesting day or two mixed in. Tuesday continues to look like a highly volatile day, moisture is perhaps a little less than I would want (still mid/upr 60s DPs per GFS along the DL, a little less on previous euro runs though), but moderate/strong instability juxtaposed to a somewhat favorably timed strong mid-level jet streak coinciding with a strong LLJ of 35-50kts by 00z, could be quite a day. 

[MattPetrulli]

36 minutes ago, jojo762 said:

Somebody should go ahead and make a thread for this coming week 5/15-20/21 as it looks like we will have several days with severe possibilities with perhaps a big/interesting day or two mixed in. Tuesday continues to look like a highly volatile day, moisture is perhaps a little less than I would want (still mid/upr 60s DPs per GFS along the DL, a little less on previous euro runs though), but moderate/strong instability juxtaposed to a somewhat favorably timed strong mid-level jet streak coinciding with a strong LLJ of 35-50kts by 00z, could be quite a day. 

Already have

[Quincy]

The overall CONUS pattern looks favorable for really the balance of May. That may not be saying a lot (as the period is active in most years), but general troughing in the West should allow fairly steady shortwave ejections into the Plains over the final 10-15 days of May. It's really a solid looking pattern for at least near average severe activity as we near the climatological peak of the season. The potential exists for a couple of bigger days, as one would expect with such a pattern, if things line up just right  

There has been volatility in the ensembles regarding the final days of May into early June, where the Euro weeklies suggest there may be a bit of a lull. I'm not too concerned about anything beyond week 2, as things could change substantially.

Nonetheless, a relatively active pattern not only next week, but probably the week following should be on tap. 

[bjc0303]

Looking more and more like tornado activity will pick back up again late this week into the weekend.

 

Models now converging on what I would call a typical late may tornado setup with rich gulf moisture, strong-extreme instability, and a well developed evening LLJ. More fine-scale details cannot be resolved right now, such as strength of the EML/base temps, boundary placement, etc.. but looking increasingly conducive for tornadic supercells. Unlike recent setups  this one may have more densely populated areas in the mix. 

 

Not worth going over much more at this point. GFS forecasts have quite the hot EML, but no real consistency. While some parts may get shut out due to capping, someone is going to see CI. Even now the GFS convects, and I imagine smaller scale perturbations provide glancing influence to erode capping. 

 

Saturday may be an outflow boundary day.

[jojo762]

OUN highlighting how models are starting to converge on at least modest, but potentially somewhat strong, W/SW flow atop moist/unstable environment for multi-day severe threat.