After having a descent chase trip last year capturing the May 21, 2011 Ada, OK tornado, another near the Okeene, OK, and some well structured storms it's time to start looking ahead to the 2012 season. This year was already off to an early start given the active April but that is not completely unheard of, unfortunately May seems to be off to a slow start and looks pretty marginal for the extent of the long range. 

Overall the long range models as of late have really been struggling to come up with a coherent solution and continuously flop back and forth between runs, particularly the GFS. My suspicion is that a few years now of abnormal trends and a mild winter are starting to take effect on most of the long range models having them confused and sending out mixed signals. But I'm going to try and make sense of them here as out window for a chase season is rapidly closing.

Right off the bat it's difficult for me to want to put any trust in the GFS at the moment due to its large inconsistent trends, on top of that its GEFS ensemble members have trended away from the operational run more often than not over the past few weeks. None the less it’s something that needs to be taken into account.

For this season we were hoping for a May 17 potential but is looks as though this will be pushed back to possibly the 18. The 3 panels below show the GFS (top), ECWMF opp run (middle), and the ECMWF ensemble(bottom). Note that the ECWMF panels are not all the same time stamps as the GFS but its the closest hr I could get from the ECMWF page. All three do show strong trough over the Canadian prairies but are slightly out of phase and the ECMWF opp run is not agreeing with anyone of them. The only real potential is the very weak subtitle trough the GFS shows along the KS/NE border where the ECMWF opp run and control run to hint at. Its marginal but it's something which, as the trough rounds the Rockies, may provide some upslope events which only need marginal conditions to make stuff happen (I'm reaching a bit but it's true)

Look at the ensemble members here, although noisy to tend to hint at some subtle troughing along the region. The top panel shows the upper GEFS upper thickness and the middle panel shows sfc isobars. What looks to be promising here is that the ensembles also hint toward some sfc cyclogenesis along the lee side of the Rockies. The real underlying question then becomes will there be sufficient moisture return to even allow for anything to produce. Well if I do put any faith into the GFS here, this would tell me yes. The bottom panel pulled for the Nexlab page shows sufficient moisture return to provide some sort of upslope or even extreme W OK/TX event.

Next potential day is looking like May 19 as once again looks to be possibly another weak shortwave rounds the Rockies to give another upslope or extreme W OK/TX event. Examining the GFS and ECMWF once again (the control run as the opp run ends at 240 hrs) shows some agreement with the ECMWF looking a little more appealing. Both models look to have the broad trough over the west with the GFS axis east of the ECMWF axis. Secondly the ECWMF shows a much stronger trough beginning to dig its teeth in as well which could prove to be a good setup in the later days. Looking at ensembles there is a little bit of similarity with the 228 hrs panel shown above although a little noisier still showing a spread amongst members with some showing weak troughing and the sfc ensembles having some members showing some sort of sfc cyclogenesis. Unfortunately I cannot find a streamline/Td chart, but the 850 mb GFS chart and the ECWMF 850 mb chart would indicate a sufficient flow from the Gulf that should provide at the minimum the lower threshold of moisture for some sort of convective activity.

By hrs 264 the ECMWF pushes that trough through as shown in the above panels but the GFS/GEFS ensembles begin to trend away from it thus I have a little less confidence in that trough really being able to produce anything noteworthy. Its positive would also render a WSW flow through the 700 mb level thus bringing with it some capping issues. Mind you if the GFS does improve this scenario looks like a possible northern Mid-West opportunity for MO/IA/MN.

Lastly we head out into dream land...although I believe we may already be there by now with all this modelology...to the 360 hrs panels. It gets pretty interesting as the ECWMF really gives us something to chew on here with a trough finally settling in near the 4 Corners region. Again some issues I can see is one being the tilt is not quite ideal would like to see it more negative but at this point it’s something on the horizon given it doesn't flip flop around again another 50 times, which will likely be the case. Secondly the GFS opp run shows a meagre weak little impulse rounding the base of the mean upper flow. I'm not overly discouraged by this though because examining the GEFS ensembles we see that a lot of the members are on board with the ECWMF solution with some sort of broad troughing over the western portion of the U.S. Mind you the members are really noisy as to where the main trough axis will sit but again it’s something and the sfc ensembles do again show some cyclogenesis present. Oh and the GFS, I'm not entirely buying that hurricane like feature you have over FL either although some ensemble members do hint at it...I'm kind of wishing that one away. But again this is 360 hrs out and will change and flop around some more.

To wrap this up, after the analysis here it looks like there could be some hidden gems out in the plains during the latter parts of May. This will make the daily forecasts tough and more stressful since we have limited time on the plains we have to make sure we pick good targets to give us the best chance to see something. I'm still encouraged though the models do not show a complete shut down and the pattern still looks relatively progressive. I would like to point out I would also usually looks at the GLB models as well but it's 12Z run is not complete and thus chose to leave it out. What I can say though is over the past few weeks the ECWMF and GLB have been on par with each other thus I’m putting some faith in to. Just going to have to really make sure our short range and point forecasts are on par this season. Thus with all this being said looks like out hypothetical departure could be Sunday May 13 or Monday May 14 depending on how the models progress the first setup discussed above or if it even will still exist at all. If nothing materialises, then next departure data would have to be May 16 to capture the May 19 possibility.