2018 severe wx/chase season discussion

[Jeff House]

Hi @Richard Mark Stephens, I second what @Royce Sheibal says previous page. Kind of depends on your risk (of failure) tolerance. Gosh, I sound like a mutual fund adviser!

I believe 3-5 chasable set-ups will take place next week, probably not in a row. Could be in pairs or 3 and 1. Yeah targets might be pretty spread out even from one day to the next.

What is considered success? If one decent tornado, I think you can do it. If looking for two good tornado days, assuming a .333 batting average, it could be tough. Who knows, just one multi-cyclical meso-scale accident can make a year.

You know what's most frustrating? Not having a total solar eclipse to fall back on in August!

 

[Quincy Vagell]

In times like these, I like to watch the patterns day by day without getting to ahead of myself. "Day before the day" is a good motto, as some of the days in the past that were not hyped up, ended up performing. Predictability with respect to mesoscale details is very difficult in a pattern like this. Yes, Friday looks to have some "enhanced" potential, but for now, I'm focused on the complexities of the next two days. The synoptic pattern does not look great by any stretch of the imagination, but severe weather should occur both days and I'd think there will be some photogenic storms, somewhere...

Tomorrow (Wednesday) features modestly rising heights and lackluster deep layer wind fields, however, the recent trends suggest that the southern High Plains has some chase potential. Combine marginally favorable upper level winds with the possibility for leftover outflow boundaries and the West Texas vicinity looks like the area to go for. As recently as this afternoon, my initial plan was to target the central High Plains tomorrow, but I'll explain why that's becoming less and less likely, aside from the fact that any robust convection, period, appears highly conditional there.

Thursday should feature increasing mid and upper level flow as Plains ridging eases a bit, in response to the slow approach of a shortwave trough. The interesting thing with Thursday is that there should be a very broad threat area, expanding from the southern Plains, all the way up to North Dakota. Going back to an earlier thought, I really like the looks of North Dakota (possibly northern South Dakota) on Thursday, but with Wednesday's target trending south, the Dakotas play for the day after tomorrow seems unrealistic, at least for me and most people on chasecations. If you're up north and can't chase Wednesday, don't overlook Thursday, locally.

This is yet another example of not getting too far ahead of the forecast. With that said, the threat area should become more focused and clear for Friday as the large scale pattern is more indicative of what you'd like to see for severe weather in the Plains in May.

Remain cautiously optimistic. We may have some ridging over the Plains, but we don't have a death grip from the ridge just yet. Expect almost daily chase"able" targets through at least Friday and days beyond that don't look like shutouts either.

 

[Andy Wehrle]

Am I seeing things or did 06Z GFS just significantly up the ante for Saturday over NE KS/SE NE?

Still on the fence about Friday due to distance (would basically have to leave immediately after work Thursday afternoon and stay overnight somewhere en route) and now moisture concerns.

 

[JamesCaruso]

I really don’t see the appeal of the northwestern portion of SPC’s outlooked area for Friday. I don’t like the northeasterly surface winds in northeastern CO, and even the mid levels appear to back somewhat. The Denver AFD also mentions easterly 500/700 flow. I am more interested in southwestern KS, maybe east of DDC, where surface winds are backed, the LLJ looks good, and there should be sufficient moisture. Outflow boundaries from Thursday night may help or hurt this particular area, but will definitely complicate the forecast. Looking at flying to ICT on Friday morning; it’s somewhat risky to make it in time, but a Thursday afternoon flight from Philadelphia is a little challenging at this point.

Saturday I think is potentially a triple point play in northwestern OK, but I’m not thrilled with messing around with the cold front.

Sunday I am thinking southeastern TX panhandle. Decent moisture makes it into the region. Flow is weak (25 knots) but magic can happen there. The AMA AFD says Sunday is its forecast area’s “next ‘interesting’ day” for severe weather.

Monday I am less comfortable with, flow remains quite weak, would hope for some Colorado magic but moisture will be limited, even for that region where we can do more with less.

Looks like a potential midweek play up in the Dakotas but I am not looking too far out in detail at this point.

Still wrestling with whether to make the trip only because of my daughters’ being in a play on Sunday but they always knew I would likely be out chasing and I think if anything it goes downhill after these next few days so might as well get out there, worried this could be it unless the next week beginning with Memorial Day Weekend turns around.

 

[Paul Knightley]

Ensemble output through next week throws up a few chances early-mid week, with hints of a southern stream closed low/trough moving in from the SW, but trends have taken this a little west - even so, some upslope fun could be had for parts of the west central Plains.

Later in the week there are indications of a trough moving into the PAC NW...but then considerable differences in its evolution thereafter. ECMWF ensembles have trended towards bringing it further inland 25/26th May onwards - but with the blocked pattern of late, confidence is below average for output in the medium range.

 

[Jeff House]

Paul covers my mid-long range thoughts well, so I will switch to short-term.

Maybe not worth starting a Target Area thread for just one Saturday thought, but I want to note caution for the CF/DL intersection. Normally a second target behind, east of the surface low, but Saturday ECMWF has terribly low dewpoints near the CF/DL. One might be forced to settle for east of the surface low, and hoping no MCS wash-out. Saturday is four days out; so, much can change either direction. GFS votes Bennington 4 (kind of).

After 12Z data I may opine on Thursday and Friday, perhaps in Target Area if threads are already going.

Finally, @Tony Laubach I am glad nobody was hurt in your May 14th chase. Other driver on cell phone? Cannot really reply in Target Area, so I do so here. Everybody, I think Tony sets a great example of focusing on the positive. Chase vehicle was totaled, other driver's fault. However Tony celebrates a successful tornado intercept and living in Kansas. Yeah, I miss that last part.

 

[Andy Wehrle]

Agreed, great intercept for Tony of a surprise photogenic tornado. Bad way to end the day but glad no one was hurt!

 

[Quincy Vagell]

Am I seeing things or did 06Z GFS just significantly up the ante for Saturday over NE KS/SE NE?

Still on the fence about Friday due to distance (would basically have to leave immediately after work Thursday afternoon and stay overnight somewhere en route) and now moisture concerns.

The GFS and Euro diverge quite a bit.

In general, I'm not particularly fond of sweeping cold fronts. The Euro and NAM (take the latter with a grain of salt at this range) show increasingly unidirectional flow in the mid and upper levels by Saturday afternoon.

While the GFS does look more favorable with much better 850mb winds (S to SE), it is slower/farther west than the Euro. The GFS has the 850mb low over northwestern KS at 00z Sun, while the Euro is up near Omaha.

My guess is that the setup needs to slow down, or it needs a more pronounced dryline over eastern KS to help with shear. I can recall a couple of eastern KS dryline threats this season that both more or less fumbled. It can be done, but the needle would need to be threaded just right.

I may also be slightly biased since I can't chase on Saturday, but objectively, it's far from a slam dunk, so I do agree with SPC's "predictability too low" for day 4.

 

[chrisbray]

84 Hour nam (taken with grain of salt) in agreement with 6z GFS in regards to potential in IA/MO/IL warm sector Saturday.

 

[Jeff House]

12Z NAM seems to vote ECMWF over GFS. Unfortunately it may be right. 12Z soundings have upstream air over OK/TX scoured our harshly at 925/850 mb. Tenn Valley low did a number on the moisture. NAM struggles to get Td65 into the Kansas target zone Friday. I prefer Td68+ so a caution flag. Sounding forecasts have that moisture recovering JIT, but then mixing out again at lowest levels. Radar simulation Friday looks like trash because the model is trying to gust out the storms on insufficient dewpoints. No inflow signatures on 850/925 mb or lowest 30mb or 80 meters. All of those show gust out signatures. Could be model cancer at hour 60 but it is very discouraging.

Well @Quincy Vagell you are (likely) not missing anything Saturday. Thursday I see the Denver Cyclone play. Friday could be Raton Mesa magic but very subject to overnight and morning convection. When the pattern is awful, I look for physical geography help. Even nicer with outflow juxtaposition. Good luck to all!

 

[Dan Robinson]

That's the problem with these "ripples in the flow" setups without a robust warm sector. They have very little tolerance for things going wrong and no spatial coverage for the targets to shift before things are hopelessly out of alignment. Friday's setup seems to be hanging on a thread with no room for anything at the surface or aloft to shift even 50 miles in any direction. Saturday's NAM has the better overlap of decent flow and moisture, but surface flow is weak (and in Iowa of course).

 

[Tony Laubach]

Finally, @Tony Laubach I am glad nobody was hurt in your May 14th chase. Other driver on cell phone? Cannot really reply in Target Area, so I do so here. Everybody, I think Tony sets a great example of focusing on the positive. Chase vehicle was totaled, other driver's fault. However Tony celebrates a successful tornado intercept and living in Kansas. Yeah, I miss that last part.

Thank you... no, per the driver, she was a little freaked out about the tornado warning and was trying to get home from work. I don't think she was on a cell phone. Unfortunately I didn't get that great a look at her prior to impact

 

[Quincy Vagell]

The 12z Euro shows a prolonged period with relatively unfavorable (marginally favorable at best) upper level flow from days 4-10, pretty much all of next week. Winds struggle to reach 30kts at 500mb, even for the balance of this week. That coupled with the CFS "looking blue" next week is a sign that any widespread or significant severe weather will be fairly unlikely, barring a significant synoptic change in the model progs.

As always, localized severe events remain possible, as well as mesoscale "accidents," but aside from that, the outlook is not encouraging.

 

[JamesCaruso]

Now I’m really depressed. This morning I made the decision I was a “go” for Friday morning and earlier today booked a flight to Wichita. I wasn’t expecting much and was just in the “when it’s May, you chase,” for better or for worse mindset. But now you guys have me second-guessing that decision, with the above posts sounding bleaker than ever. In a normal year I wouldn’t care, but now I am missing my daughters’ play on Sunday. The last thing I want to do is end up missing that for absolutely no reason, jerking around out there under a blue sky, unable to even claim to actually be chasing, and who knows, maybe even coming home a few days later if nothing is on the horizon. What a ridiculous scenario that would be...

I can always cancel the flight, I was just using mileage anyway, I guess at this point I will make another go/no-go decision at this time tomorrow night.

 

[Brandon Centeno]

Regarding near term..

Moisture is not terribly promising for any of the upcoming three days. NAM is, predictably, pulling back substantially on its outlier 84 hour forecast everyone freaked out about.

A big reason I am having second thoughts on my upcoming Friday chase is the current state of the gulf. Moisture across the coastal plains of Texas, LA, etc are not tropical at all. In fact it’s modified continental air rather than any sort of maritime airmass. The LCH sfc Td and mean mixing ratio are both at or below the 25th % for moving average.... not exactly what you want to see this time of year 48 hours before an event.

Moisture should improve by Saturday, but not nearly to the degree the NAM is showing. Yes there will be storms, but whether they are supercellular and/or tornadic is a much different story.