2018 severe wx/chase season discussion

[Brandon Centeno]

Summary of late-evening ensemble guidance suggests that mid-late May could very well pick up the slack of the entire season. Very encouraging signs across the board of ensemble guidance...

In particular, this evolution has me quite giddy, as depicted by the European EPS:

Euro weeklies suggested a transition to an extended period of -PNA conditions, which seem to be manifesting here with the breakdown/retrogression of the pac NW ridging towards the end of the forecast period. Time will tell, but I'm feeling better about prospects beginning next week.

 

[Jeff House]

Brandon beat me to it! Starting around 22Z yesterday with those Euro ECMWF weeklies, NWP / Ensembles have looked simply gorgeous through this morning. CFS weeklies sniff out even more action weeks 2-3. Weekly charts are trusted more, but Dashboard is lit up too.

Other than good late May climo, here is why we can start to believe it, or at least be cautiously optimistic. That awful cut-off low in the Eastern Pacific is finally lifting out. It had created almost a Rex block. The shift helps early next week. West Pac jet is really cranking up. Most NWP has some of that making it to the US West Coast in the 11-15 day.

Hopefully the reshuffle in the Pacific will get the Central Pac convection to calm down. A new Kelvin wave out of the IO would also help West US troughing. MJO forecast to favorable phases was delayed, but better late than never.

 

[Andy Wehrle]

Now let's just hope that GFS TC Warren alluded to doesn't form.

 

[chrisbray]

Fantasy land is lit up!

 

[Brett Nickeson]

My kingdom for an open wave negatively tilted trough. It seems these somewhat closed lows as positively tilted as they are just create elongated surface lows, veered surface winds, and bring in cold air sooner than they should. See Friday and Saturday's setup. Hopefully these change a bit and we get nice southwest flow for a few days at a time towards late May. At least the moisture seems to be there!

 

[Ethan Schisler]

I've been eyeballing around May 15-17 (later next week) in the Central Plains. We seem to establish some southwest flow (albeit pretty weak), or one could even argue somewhat zonal. Anyway we have the moisture in place as others have mentioned and climatology this time of year favors higher instability setups....so in my eyes, the odds in this scenario are favored for at least a couple chase days, not sure how significant they could be, but I'm sure there will be some chasing to be had. I don't wanna miss out again like I did in May 2016....granted that was mainly due to timing issues with my work/school...however this year I have most of the next few weeks off before I start back up on something different, so I'll be watching. May 16th has been good to me in the past, so that's another reason why I'm probably keeping an eye on it!

 

[Andy Wehrle]

This morning's 00z GFS run develops plenty of moisture and instability over the Plains for my vacation window, but seems reluctant to spread anything beyond meh H5 flow over the warm sector. We know that subtle shortwaves can get the job done, but I'd rather not have to count on that. Of course, at this time range I'd be more worried if everything looked perfect. Then it still has that random tropical cyclone rolling up from the Carribean toward the end of the run.

CFS run from the same time on the other hand looks awesome with multiple periods of 40-50 KT SW flow from hours 312 to 408. Of course it has been bouncing around like a pinball.

 

[Brandon Centeno]

You shouldn’t rely on deterministic guidance outside of 200 hours.. just stick with ensembles.

 

[JamesCaruso]

At this point I am still not spending any time looking at the long range, due to the flip flopping and model disagreement noted by Andy just above. In past years I would drive myself nuts with this so I am trying to avoid that. I am also keeping my overall expectations in check, given last year’s completely uneventful trip that I aborted after just a few days. When I do get out there, I am going to be pretty rusty as it will essentially be two full years since any serious chasing. Even 2016 was only one week for me, right after Dodge City (which I was at) and Chapman (which I missed due to being at the more southern target near Wichita), it was going to be dead for a week so I came home early; was going to return to the Plains but the season remained inactive for the next few weeks. So I’ve basically chased for one week since the 2015 season [emoji19]

My two-week trip can *start* anytime between May 14 and May 21. I am already of the mind that there won’t be much reason to head out before the 16th at the earliest (that would be my travel day, first day available to chase being the 17th), mostly just from the sense I am getting from reading this thread. I prefer not leaving before then anyway. I need to be around for Mother’s Day and then I have a big work deadline on the 15th, which I could manage from the road if I had to but I would rather just get it done here at home. Also, since I only have two weeks off from work, I would much rather start the trip on a weekend, which creates a 16-day trip bookended by the weekends (and it’s easy enough to squeak in the first Friday as an extra day); in contrast, if I leave mid-week then I have to return mid-week and the trip is not quite as long. But if it looks good before the weekend of the 19th, I will certainly head out. If by some chance it looks good earlier next week, I am prepared to miss it, get through my work deadline, and take my chances on the latter portion of the month. As a chase vacationer, you know you’re always going to miss stuff.

Although as noted above I am trying not to expect too much, FWIW I do have a hunch this season can turn out to be like 2013, with all the action condensed into only two weeks but chaseable weather nearly every day with some significant (and unfortunately tragic) events. Hopefully it will be like that again (minus the tragedies) and will allow me to redeem myself, because 2013 turned out to be a 14 consecutive day experiment in how many ways I could manage to NOT be in the right place at the right time, culminating with getting stuck in the mud and ending a chase on May 30 and deciding to fly home as scheduled on May 31 rather than changing plans and staying for El Reno - which was probably for the best, given my bad luck the previous two weeks.

 

[Jeremy Bower]

I live in Lincoln, Nebraska and I have a full time job (that's what I get for being a responsible adult) so my chase opportunities are limited to either something local or weekends and thus far I'm batting .0000 on those so far in 2018. I was glancing at the SPC WCM page to look at the U.S. Annual Trends of LSR Tornadoes to gather insight on this season thus far. For amusement purposes only, let's compare 2018 to previous years:

As of May 9th, 2018 has 317 tornado reports.
2015 - 316
2014 - 306
2013 - 244
2012 - 659
2010 - 327
2005 to 2015 avg. - 566

From a climatology standpoint, I'm not too worried just yet. I've had a lot of success in late May/early June and I'm cautiously optimistic that things will change as we head into the 3 to 4 weeks of prime chase season. The ensembles have at least given me some hope and the dreaded cutoff low in the Eastern Pacific is finally lifting out. My chasecation this year is June 10 to June 15, similar to 2016. My choices that year was either that week or the week of Dodge City/Chapman and boy do I choose wrong. My luck in picking a good week to chase since 2012 has been met with some type of ridge pattern (exception was 2013) or prominent NW flow so don't expect to chase during that time period I mentioned above.

Recent ensemble guidance is saying chase season isn't over yet and business could very well pick up as we head towards mid to late May.

 

[Dan Robinson]

FWIW on spring tropical systems - they have happened before, and while they are a big concern, the last time we had one was early June of 2005. That had been a relatively slow May (late May was nearly dead) and everyone thought the TC in the Gulf was the end of the season. This was followed by the stellar June 9 - 12 system. Climo heavily favors no TCs in May, so it is reassuring that so far one is only showing up in the fantasy ranges of the GFS.

Here's the old forecast thread for June 12, 2005 lamenting the tropical system:
https://stormtrack.org/community/threads/06-12-05-fcst-plains.4416/

June 9th and 12th summary pages:
https://stormtrack.org/weather-library/storm-chasing-event-archive/2005-events/

 

[Brandon Centeno]

I don’t think there is concern that tropical system = end of season. I think people are only worried about impacts to the return flow cycle. But I agree, very very unlikely this materializes.

 

[Jeff House]

The GFS forecasts 9 out-of-every 1 tropical cyclone. Quote paraphrased from Mike Smith, still a gem! Keep in mind even if it did happen, it's not the same debacle as an East trough. Likely it won't happen though.

Rather than a GFS storm in the 11-15 day, my main focus is on the ECMWF 6-10 day with a little trough caught in the Tennessee Valley. That delays the main chasing show. Early next week could feature a couple meso-scale accidents, but I do not consider it a day(s) before the day deal because midweek the flow falls apart.

Late next week (May 18) could get more interesting. While this may feel like a delay, weekly charts, the MJO, and Pacific jet signals had always kind of hinted after May 16. Previous troughs were always progged a little flaky. In contrast, weeklies and ensembles have hinted at an active May 18-21 period for a while now.

 

[Brett Nickeson]

I know virtually nothing about long-range weather forecasting or large scale patterns, but is that Hudson Bay low going to ever go away? It seems that large scale feature is really limiting the amount of western US troughing that can eject onto the plains, as a small ridge seems to be pinched near the middle of the country and can't really move, causing western troughs to stall out west and eventually weaken.

 

[Greg McLaughlin]

I have a $20 bet with a friend on this phantom TC the GFS is trolling. He thinks because it has shown it for 6 consecutive runs that it will happen. I believe it will not happen. I am looking forward to my payday. I have noticed the GFS continues to delay the onset of the TC and last night's run is weaker.