2018 severe wx/chase season discussion

[samuel stone]

Im not really an expert on hemispheric pattern recognition in the long range. A lot of cautious optimism amongst us chasers i think for for early to mid next week. I've seen the GFS runs and certainly like what i see so far, gives me some hope after long dull times. but i do think it is smart to temper those hopes at this range.

Also the CFS has been much less bullish on that trough through that time frame so im not sure what to beleive.

 

[Greg McLaughlin]

The good thing about May is you don't need a powerhouse trough to get a decent setup to chase. 30-40kt bulk shear can go a long way with May instability. If you end up with a dryline bulge or ofb, magical things can happen. The big caveat will be capping, especially with the ongoing drought over the southern high plains. As the saying goes, "it's May...you chase."

 

[Warren Faidley]

The latest CFS is clearly showing a more active pattern. It will be interesting to see if the trend continues.

 

[Royce Sheibal]

May 2nd, Ladies and Gents. Will be the Day.

Ignore all of the indexes, and ignore May 1st. 12Z GFS just spit out a wonderful solution for May 1st and 2nd that looks totally TERRIBLE and underwhelming. But that's just what I wanted to see. May 1st the upper level support is too far south and west, but we still may get some isolated storms along a dryline in W TX or SW KS. But the real show is on the 2nd. The trough starts to kick out, the low is WAY up north along the NE/SD border, and there is ample moisture in place that has been there for a solid 24-48 hours. Moisture influx is not an issue, the issue becomes CRAPVECTION, which is why all the CAPE and index readings look terrible.

My point is this. If GFS is pushing out tons of crapvection for 2 days, you know we'll at least have good moisture in place + evapotranspiration, we'll have outflows, and there will be clearing and CAPE somewhere. GFS to shows that we've got cap breakage all along the entire dryline and action on the triple point all afternoon. It's even liking the area all the way down to E TX on a secondary vort max kick. So many possibilities that will get narrowed down over the next week.

We're 7.5 days out, so timing is always an issue and the trough could wash out..., but I think our probability is looking really good. The trough is going to happen, the question is when. If the GFS trends toward the EURO, speed everything up 1 day and May 1st becomes the big day, but looking at the ensembles and GFS, the 2nd would be my bet. I could be off by 24 hours, but the big setup is out there somewhere. Now for the waiting game.

Also I work that day and can't chase, so clearly that will be the big day.

 

[Jeff House]

Agree the Plains could get 1-3 days next week. Be open to the day before the day. Royce explains above.

We have a trough slowly moving through the Rockies, key to action a couple days. Quasi-stationary front should be in the central Plains. 7 days out upper winds could change, but right now the ECMWF progs nice turning. Euro has upstairs nearly westerly. LLJ is forecast to back/respond at 00z a couple days.

Travelers should be open to as early as Monday, but models verbatim favor midweek.

 

[Paul Sherman]

Nice to see the GFS nailed this down from about T260 (A very good longer range model I have found) What it is showing after the 4th does not look so nice though so hopeful it can start to pick up some troughing signals. The formula I use and what most of you use I would suspect is GFS 6-14 Days, ECM for 4-10 and obviously NAM and HRRR for the closer in Mesoscale.

 

[Jeff House]

Yes this current week trough worked out well from the models/NWP. Since that is now Target Area material, I will shift to Mid-May here.

My NWP tools include the GFS, Euro Ensembles to Day 15, and weekly charts (Euro and CFS). I also look at MJO forecasts, AAM, and occasionally WPO/EPO if I'm desperate for the next Pacific Jet (2017 lol). If the CFS Dashboard does not match its own weeklies, I favor the weeklies pattern recognition over the Dashboard. ERTAF is loosely based on weeklies, but they also use non-model methods and add useful discussion.

Week of May 14 could be the next opportunity. MJO is forecast into good phases and -AAM is supposed to persist. Euro and Canadian Ensembles both introduce new Pacific jet energy by May 13-14, chipping away at the then forecast West ridge. GFS Ensembles may be late to the change (I hope GFS is wrong). Both weekly products show the same chipping away. Few clusters have a good West trough. Warmth returning to the Mid-Atlantic is also a plus, if correct.

Hopefully NWP will perform well again. Signals and NWP both hint at the next chance the week of May 14.

 

[Andy Wehrle]

I went ahead and took off from Friday the 18th through Friday the 25th (which gives me through Sunday the 27th before I have to go back to work Monday morning). I saw what Jeff was seeing but I think the western ridge will take a couple days to break down, and the last three runs of the CFS have shown some kind of trough rolling through the following week with a multi-day play.

 

[chrisbray]

Looks like Jeff beat me to it. CFS Dashboard, GFS/GEFS, and Euro all pointing at a long dead period starting Friday with Alaska/B.C ridging holding on for a while. I'll be hoping for signs it breaks down by mid-May, as I would hate to waste ~10 days in May with absolutely nothing. I'm not well versed in the oscillations etc. so I will take Jeff's word for that.

 

[John Homenuk]

Yes this current week trough worked out well from the models/NWP. Since that is now Target Area material, I will shift to Mid-May here.

My NWP tools include the GFS, Euro Ensembles to Day 15, and weekly charts (Euro and CFS). I also look at MJO forecasts, AAM, and occasionally WPO/EPO if I'm desperate for the next Pacific Jet (2017 lol). If the CFS Dashboard does not match its own weeklies, I favor the weeklies pattern recognition over the Dashboard. ERTAF is loosely based on weeklies, but they also use non-model methods and add useful discussion.

Week of May 14 could be the next opportunity. MJO is forecast into good phases and -AAM is supposed to persist. Euro and Canadian Ensembles both introduce new Pacific jet energy by May 13-14, chipping away at the then forecast West ridge. GFS Ensembles may be late to the change (I hope GFS is wrong). Both weekly products show the same chipping away. Few clusters have a good West trough. Warmth returning to the Mid-Atlantic is also a plus, if correct.

Hopefully NWP will perform well again. Signals and NWP both hint at the next chance the week of May 14.

Great post. I agree and I think we're starting to see increased signals for another period of activity during the week of 5/14 - perhaps even beginning that weekend? Global and hemispheric pattern support exists in full during this time frame as well.

A second period looks very likely to develop as well near the 5/25 time frame and perhaps continuing for a few days as we move toward 6/1. The ebbs and flows of the pattern are becoming apparent.

 

[Oliver G.]

I hope for storms mid May... Im in the usa for chasing 14 days at 10.May... Is there a good chance? what do you think? i have read eventually more active severe Weather during the week on 5/14 right?

 

[Joerg Kudella]

Currently, all models show northwesterly flow and ridging over the Plains for the extended forecast period. We will fly into Denver Wednesday 9th and I hope we´ll see a positive trend towards a better flow regime by then. Looks pretty shut down for now.

 

[Jeff House]

Weeks of May 14 and May 21 both offer chances at/above climo. Week of May 7, um just watch NBA/NHL Playoffs, lol. Seriously, mid-late May chase vacationers should be in good shape.

@Oliver1986 you should be golden. Welcome to the USA! CFS had a strange run overnight, but verbatim you'd still have chances early and late in your two weeks. I believe it'll be better than that last run. Sounds like a bold forecast, but my faith is also in climo.

MJO is forecast to go into favorable phases. -AAM persists, which helps leverage the MJO phase. ECMWF weeklies have improved since my last post, great news! GFS Ensembles are starting to trend toward the more favorable ECMWF Ensembles. They put a new trough into the West US week of May 14. ECMWF weeklies hint at another after May 21. Chase vacationers want slow moving West troughs, ejecting short-waves each day.

Bottom line: Week of May 14 confidence continues to increase. Week of May 21 is certainly on the table. Climo remains excellent week of May 28 and into early June.

 

[Andy Wehrle]

Time to start blasting "Humans Being" at least once a day to get psyched. Yesterday helped, even though I couldn't be there. Just observing legit supercells doing their thing on radar and watching the reports/images roll in is a pleasure. Looking forward to seeing how today plays out, too. Might even get a local chase in today and/or tomorrow.

 

[John Homenuk]

As mentioned by a few others there are increasing signals for something of significant around mid month. The EPS last night shows a pattern progression that is quite similar to the one we have discussed. After a quiet period here the next several days (after the current ongoing event) there is another uptick in activity as the Pacific waveguide readjusts around mid-month. A broad signal exists on the ECMWF EPS MSLP normalized anomalies.

Thereafter, there are conflicting signals toward the end of the month, but I suspect we will continue on this ebb and flow type pattern. After the mid month event, a quiet period appears plausible, with another re-charge and reemerging potential towards the end of the month near Memorial Day. The EPS show this quite well also.

Pictured below are the mid month MSLP normalized anomaly and late month favorable pattern adjustment.