State of the Chase Season 2021

Jessica B.

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Mar 1, 2021
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I did look at the CIPS analogs for day 8, and it did show this. 1614778712784.png
I don't know if this should be taken as face value, but it only has the probabilities of wind and hail separately, which does tell me that it may not even be a tornado threat, but rather primarily a damaging wind threat.

1614778855949.png

Above is the wind probability, and the image below is the hail probability.
1614778908005.png
 
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adlyons

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Just a question for my own continuing education - isn‘t the position of the jet independent of drought conditions? I understand the unfavorable impact of drought conditions, but didn’t think it could actually affect the synoptic jet configuration?
With how interconnected everything is its tough to say things like jet position are truly independent from this or that. Drought likely plays some role in the position of the mid-level jet given that synoptically it's driven by anomalous large-scale descent or lack of ascent. There's also the chicken vs egg argument where an anomalous condition can result in feedback to modify the larger pattern. Ie, warmer and drier conditions can result in greater sensible heat flux increasing mid-level heights prolonging a drought.

My wording is a tad confusing, I was going more for showing the link to early-onset ridging from early decaying La Ninas and how that in combination with western US drought can cut into storm chances. Early decay La Ninas can result in a rapid northward retreat of the jet across the CONUS. Couple that with a stronger EML from elevated temps and drought across the Rockies you have a scenario where you have weaker than average forcing for ascent working against warmer than average mid-level temps.
 

Jeff Duda

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Just a question for my own continuing education - isn‘t the position of the jet independent of drought conditions? I understand the unfavorable impact of drought conditions, but didn’t think it could actually affect the synoptic jet configuration?
Oh, it absolutely can. Keep in mind that tropospheric jets usually delineate a large-scale horizontal temperature gradient (integrated vertically over the remainder of the troposphere). A drought can help cause a heat dome to form which would amplify heights over the top of the dome. This could either cause the hemispheric temperature gradient to shift north, or just weaken it altogether. Thus the jet could either shift north or weaken.

Then again, a weakened jet has a tendency to get all squiggly/dippy/dodgey/ducky/divey/...and...dodgey...and thus could potentially result in more shortwaves and overall...more events.

(Bonus points to anyone who gets the reference)
 
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Mark Stephens

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Feb 2, 2021
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Oh, it absolutely can. Keep in mind that tropospheric jets usually delineate a large-scale horizontal temperature gradient (integrated over the remainder of the troposphere). A drought can help cause a heat dome to form which would amplify heights over the top of the dome. This could either cause the hemispheric temperature gradient to shift north, or just weaken it altogether. Thus the jet could either shift north or weaken.

Then again, a weakened jet has a tendency to get all squiggly/dippy/dodgey/ducky/divey/...and...dodgey...and thus could potentially result in more shortwaves and overall...more events.

(Bonus points to anyone who gets the reference)
Dodgeball? If you can dodge a Tennis ball sized hail stone you can dodge a ball.
 

adlyons

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Oh, it absolutely can. Keep in mind that tropospheric jets usually delineate a large-scale horizontal temperature gradient (integrated vertically over the remainder of the troposphere). A drought can help cause a heat dome to form which would amplify heights over the top of the dome. This could either cause the hemispheric temperature gradient to shift north, or just weaken it altogether. Thus the jet could either shift north or weaken.

Then again, a weakened jet has a tendency to get all squiggly/dippy/dodgey/ducky/divey/...and...dodgey...and thus could potentially result in more shortwaves and overall...more events.

(Bonus points to anyone who gets the reference)
Jeff makes a really good point using a thermal wind argument here that I didnt consider. But there is a fair amount of evidence that droughts and even anomalously wet periods can influence the large-scale synoptic regime. James, I hope that answered your question a bit!
 
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Randy Jennings

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@Warren Faidley The 3/3/21 CFS dashboard doesn't look any better than the 3/2/21 one you posted and tweeted about. I was kind of kidding when I replied to your tweet about that if 2021 was anything like 2020 then the 3/3 run would be the one to verify, but if this trend continues the first half of spring could be really slow.
 

adlyons

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@Warren Faidley The 3/3/21 CFS dashboard doesn't look any better than the 3/2/21 one you posted and tweeted about. I was kind of kidding when I replied to your tweet about that if 2021 was anything like 2020 then the 3/3 run would be the one to verify, but if this trend continues the first half of spring could be really slow.
Reminder about the dashboard, they switched from calculating Supercell Composite at 500 J/kg of MUCAPE to 1000 J/kg on March 2 as a rough proxy for the change from cold to warm-season thermodynamics. That's the drop off that we are seeing. Its still progging the same environments, but the grid point counts are lower due to the higher CAPE constraint. Another reminder about the dashboard, beyond day 10 its essentially useless compared to climatology. View it with caution.
 

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Randy Jennings

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May 18, 2013
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Thanks @adlyons I had forgotten about that. I always treat the dashboard with a grain of salt. I mainly use it to see if I might have missed something in my analysis and need to go back and take a second look.
 
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Feb 19, 2021
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I am no longer connected to AccuWeather. With that stipulated, I don't like anyone's >30day outlooks. No consistent skill has been demonstrated.

But, if you are going to criticize AW, what about the NWS making specific daily forecasts of severe weather? https://www.spc.noaa.gov/exper/CFS_Dashboard/n Shouldn't you also criticize them?





Off-topic, but I see AccuWeather's seasonal forecasts as akin to throwing shit against the wall and seeing what sticks.

I don't think there's any reliable way to predict activity level of the spring tornado season beyond aggregate statistics, but we're heading into spring with massive drought in the southwest (although, parts of NW TX, W OK, and W KS have escaped the bad stuff), so that can't be great. Could be looking at strong caps.

Worst part is the synoptic pattern, though. That's what hosed 2018 and 2020. I don't see how that can be predicted at this length.
 
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Jeff Duda

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I am no longer connected to AccuWeather. With that stipulated, I don't like anyone's >30day outlooks. No consistent skill has been demonstrated.

But, if you are going to criticize AW, what about the NWS making specific daily forecasts of severe weather? https://www.spc.noaa.gov/exper/CFS_Dashboard/n Shouldn't you also criticize them?
Somewhere along in this forum is me discussing how useless the CFS chiclet charts displayed on SPC are for predicting severe weather.

Also, that chiclet chart isn't predicting tornado counts...it's reporting the number of grid points at which SCP > 1 from the GEFS...that's it. It makes no promise that these numbers translate to above or below normal tornadoes (there is no "normal" even indicated on the charts). AccuWeather, on the other hand, tries to declare (1) tornado counts (2) above or below normal, two very specific quantities that are not featured on the CFS chiclet chart.
 

Jeff House

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Back onto the drought situation, also note the dry line may want to mix east faster and farther than progged some days. By late spring the drought and jet stream can get more correlated; and, there may be some causation (both directions).

Regardless of the chiclets, if one can infer southwest flow over the Plains in the weekly charts, then it's all good. Trough West/Rockies SER east. Early season Dixie push all that east, Plains to Mississippi Valley trough and more suppressed SER mainly right on the SE Coast. It's nice when QPF makes sense too. Chiclets can cross-check late season when the above analysis is more diffuse. Early season, just look at the weekly charts.

In all cases, remember accuracy degrades past Day 10. Keep to broad themes weeks 2-3. No comment weeks 4-6.

Finally, for mid-March I still see opportunity after the first one or two systems. I'm thinking after the time change March 14. First couple systems either lack moisture, go north, or go positive tilt. After the time change (convenient) could be better set-ups.
 
Feb 19, 2021
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Hi Jeff,

I'm aware of what the chiclets forecast. However, if you click on the chiclet, you see a map of locations of severe thunderstorms, including possibly tornadoes, out to 45 days into the future.

If you apply the same logic to both, AW's forecasts of the severe weather/tornado season as a whole, is a far less egregious stretch of forecasting ability than trying to draw isolines around local severe wx maxes out to 45 days.

Note: I do not show any forecasts beyond 30 days on my blog nor do I share them on Twitter. I don't believe any of these demonstrate consistent skill.

Best wishes,
Mike

Somewhere along in this forum is me discussing how useless the CFS chiclet charts displayed on SPC are for predicting severe weather.

Also, that chiclet chart isn't predicting tornado counts...it's reporting the number of grid points at which SCP > 1 from the GEFS...that's it. It makes no promise that these numbers translate to above or below normal tornadoes (there is no "normal" even indicated on the charts). AccuWeather, on the other hand, tries to declare (1) tornado counts (2) above or below normal, two very specific quantities that are not featured on the CFS chiclet chart.
 
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Feb 19, 2021
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While I certainly would prefer if the ECMWF depicted faster open-wave systems, these two vigorous, negative-tilted lows combined with a digging, negatively-tilted trough at Day 15, doesn't look like a bad start to me. Combine those with 140+knot winds over the central U.S. and I think we'll see some action. The circulations with the first two systems has sufficient meridional flow over the west Gulf to bring the moisture the moisture north.
 

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Oct 10, 2004
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La Nina really can go either way, especially as it tends to promote drought over the southwest and thus strong EMLs. Perhaps the technical discussion is better left to the "state of the season" thread, but lately the signs sure have been pointing more in the direction of another "dud" Nina season.
 
Oct 10, 2004
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Well, the Southern Plains have three days of potential coming up late this week into the coming weekend per SPC. Details such as timing, location and magnitude of greatest threat; storm mode, and overall chase quality all TBD. It's early, so my expectations wouldn't be too high, but at the very least could be a good shake-the-rust-off chase for those based in/near the risk area, especially since it's a weekend. Besides, recent years have shown that the old "wait for May" mantra doesn't always work anymore, so if a chaser has the finances/schedule flexibility to do so, he/she should be prepared to jump on early/out-of-season opportunities should they present themselves.

*Note I haven't personally looked at any models for this potential event yet, since it's out of my range and the last several years have indicated to me that it's pointless for anything beyond entertainment to look at models more than 4, maybe even 3 days in advance when you're trying to nail down details on things such as tornado potential; winter storm precip types and amounts; or TC track/intensity. Being a hobbyist rather than a professional, I have that luxury.
 
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Above all else, I'd like to lock in current progs for a deep and slow-moving cutoff by late week. Some of these QPFs would be a godsend for southern Plains chasing over the next couple months, provided any favorable setups materialize. There's currently strong agreement over much of OK and S KS for totals that could really mitigate short-term drought through at least April, with extension back onto the adjacent High Plains less certain. I'm waiting for the rug to get pulled out over the course of the week because this would be very un-Nina-like. But since this entire cold season has been that way (and watch us get robbed of the active mid-spring jet that Nina is more often associated with), maybe we catch a break here?

models-2021030800-f240.qpf_acc.us_c.gif
 

Jeff House

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Split flow will be great for snow lovers in the Upper Midwest this weekend, put some cold air in place. While far from ideal Southern Plains, we'll see how stout the southern stream behaves.

Split flow is definitely an issue early season. It's less of an impact late season, unless untimely. Once the moisture is in place (perhaps east due to drought) and southwest flow establishes in May, good things can happen. At least systems have been coming through. I would not let a couple March debacles discourage; however, one would want to see April behave better.

Then May does May however it wants, and sometimes mesoscale makes or breaks. Oh yeah @Mike Smith the daily chiclets charts are about as valuable as most NCAA brackets by late March, lol!
 
Apr 10, 2008
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This weekend's system has definitely helped improve the drought situation across the southern and central high plains. Better to have a drought in the cool season than in late spring. While chasing in the Texas panhandle this past Friday and Saturday I noticed that the area didn't have the appearance of being in a severe drought. Vegetation was just starting to green up.

There has been a lot of talk about tornado activity being focused east of the plains this year, however that has yet to be the case. Perhaps we continue to see more activity over the preferred regions of the traditional alley moving forward deeper into spring.