After two days of driving finally made it out to our destination here in west Kansas...well sort of...Was hoping to stay in Dodge City, KS but all the hotels in the area were booked solid so we had to drive about 45 minutes west to Garden City. This actually worked out for the better because now were a little closer to our area of interest for tomorrow and actually pretty much in it.

Things for tomorrow look very marginal and is really dependant on how much Gulf moisture can start to return overnight tonight and in through tomorrow. But aloft conditions are slightly more favourable but with a little luck may be able to produce something to look at. Starting aloft here we have the NAM 250 mb flow and 500 mb vorticity for 00Z May 17. Right away two things catch my eye, one being the 250 mb Jet has its let exit (cyclonic portion/divergent region) in line with where the 50 mb vorticity maximum sits. The second is the timing of which the trough rounds the Rockies in the mid-afternoon thus causing the column to spin up during prime heating. Furthermore the jet interactions from above may render a little more cyclonic energy and amplify the vorticity a little more. Below that is also the GFS 500 mb vorticity, I'm putting it here to show that the  timing of the main trough is pretty well handled thus some confidence can be put into the upper air Fx.

Next we move down a bit to 850 mb where there is a decent axis of strong flow from the south, this should help reach any convection (if any happens) to at least push severe limits anyway. What’s not ideal is that I would like to see them a little more backed given the moisture situation (see below), since it would help to advect a little more mid level moisture up from the Gulf.

At the sfc shows some more promise with the convergence setting up in the SW corner of KS along the CO border and into the OK panhandle as shown in both the sfc wind/T panel and the sfc Td and streamline panel. What is very disappointing is the moisture return and  we came out here at this time well aware of this risk but sadly with the time we have left we had to pull the trigger. With such weak parameters going to need a little luck but not all is lost since there still some positives to pull from this scenario.

Here we have CAPE and a sounding for the general target region. Looking at CAPE, things look ok from energetics point of view but the sounding looks horrible with no moisture except aloft. Thus with the slightly stronger dynamics pushing in looks like the possibility of some elevated storms is what the potential is for today as the dymical lift may be able to tap into the moisture aloft. The 4km WRF seems to think so as well.

So the pattern appears to look pretty bleak and best way to describe it would be subtle. Synoptically there appears to be no real evidence of a descent stretch of active weather across the plains until near the end of May which I will get into momentarily. But it appears as the bulk of the flow remains in the northern portion of the plains and up into Canada the wobble and weaker troughs near the base of the flow could prove to be the hidden gems I mentioned in the previous post. Here we see the GFS, NAM, ECMWF respectively all indicating the first potential active day for May 16. The NAM/ECMWF are slightly slower with the trough and the Canadian GLB model barely even shows it anymore. The GFS a little on the fast side, let’s hope that the NAM/ECMWF are more right since the slower solution may allow for more moisture return and little more instability. Another extra bit of comfort here are the GEFS ensemble solutions which show rather good convergence on the trough actually being there with a slight spread in the timing.

What does have me concerned is; I believe Dave Lewison termed it perfectly, saying that this initial trough is more of a "sacrificial trough" to help moisture return into the plains. Here are the 00Z GFS and 12Z NAM sfc Td and streamlines. I had to pull the 00Z GFS as the 12Z run did not fully load onto the Nexlab page. So I also included the GFS sfc chart to get a feel of the low level flow for the same time frame. The NAM looks pretty scary and shows hardly any moisture return at all with the GFS showing some promise and even breaking out some QPF along the CO/NE border. Thus leading me to conclude that possibly the slower solution of the ECMWF/NAM may start to render little more moisture return as the situation continues to unfold, or Dave's theory is bang on. None the less with the time we have out there looks like we may chance it and hope from some upslope magic.

May 17 also holds some merit as the GFS and the GEFS ensembles have the trough lingering into the south central NE and north central KS area as seen on the 500 mb charts showing the GFS, GEFS ensembles and ECMWF. As the trough does render a weakly cyclonic sfc flow this day here may be a little better allowing some better moisture return. The ECMWF also shows a subtle hint that the trough will linger as well as the GLB. However the GLB keeps the trough down in southwest KS near the OK panhandle which is a little out of sync with the other models thus I’m going to reject it here.

With the how weak the upper pattern is here I am really just hoping for some sort of mesoscale accident. There does seem to be enough dynamical energy to render the sfc slightly more cyclonic as seen here in the GFS and ECMWF sfc pressure charts. I've also included the GFS 850mb chart as the ECMWF chart shows 850 winds. They both to appear to agree on a axis of stronger 850 flow through the central plains but the ECWMF orientation of the axis is not ideal and may prove to be more harmful than good. What also has me concerned is these weak lingering upper lows can cause low cloud to linger killing any instability that may be able to build up.

The days to really look over here are May 18/19 as things looks to get going a little more in terms of the overall synoptic pattern. What is odd though examining the 500 mb charts below where the GFS opp. run shows barely any real trough over the southern plains and the GEFS spaghetti plot, and ECMWF seem to agree more on having a slightly deeper trough. With the weaker impulse that will have passed in the previous two days the moisture return should be sufficient here to provide something noteworthy. Another positive aspect to take from this particular setup is the general tilt of the trough axis. It’s not overly negative, but is showing more of a negative tilt rather than a positive one which should help with any capping issues, if any do present themselves.

The disconnect between the upper flow with the GFS and the general sfc pattern is interesting. Here the top panel is the 850 mb flow from the GFS and the bottom from the ECMWF. With how subtle the GFS opp. run is with the upper trough you would think the sfc/low levels would not render such a strong cyclonic feature and low level flow, but the ECWMF seems to backup this solution as well. Thus is makes it a little more difficult to conclude whether or not the ECWMF or GFS pattern is more correct. Looking at what the GFS lower level say the ECMWF may be the better solution but there cannot be any real distinct conclusion. 

May 19 is where things start to diverge some with the ECMWF continuing with a more aggressive 500 mb trough and the GFS showing a more zonal flow. The GEFS ensembles actually show a midpoint solution, I find, giving a subtle trough with a little more amplitude than the GFS but not as aggressive as the ECMWF upper air charts show.

But again with descent flow at 850 mb there appears that there could be some extreme western plains action along the dryline. The other option if it pans out more like the GFS, could possibly be in for some more upslope events in S CO or even some baroclinic instability along what could be a stationary front or pseudo stationary warm front.

After this run of active weather the flow appears to jump north again with some weak ridging taking over. There appear to be some noise along the base of the upper flow which could give a few chase days of marginal convection but tough to pin point anything at the moment. There real kicker comes near the end of the 12Z GFS run with what is shown below. The first panel shows the GFS 500 mb vorticy and the second is the 250 mb flow. This is promising to see because 1. What was to be a DEATH RIDGE appears to have had its axis gradually shifted ESE. The GFS begins to break it down completely giving a deep trough and a more synoptically driven setup that may prove to be descent. Even better is finally we get the polar jet dipping south into the southern U.S. If this can pan out, with the return of some much needed Jet dynamics this can prove to be very active last few chase days. Were not in the clear yet but the trend seems promising.

Granted this isn’t all glory yet, as the ECWMF is not as aggressive with this trough and not all members of the GEFS ensemble are on board with this solution showing a pretty large spread, but at the same time not indicating a death ridge. The NAEFS also is not too bad, again no as aggressive with the trough but trending away from the ridge that has been forecasted the past few runs.

So to wrap this up, not much has changed from the previous post; a departure on Tuesday May 15 is a go. Now depending on how the models play out the May 16 potential, we may put in a few extra hours of driving on the 15 to put us into striking distance if need be for May 16 so that we can drive right to a target area if needed. If not we will be in position to play on the May 17-20 opportunities in the central plains. This season looks to be tough forecasting and will have to find those hidden gems that are out there which should be little easier to do once the high resolution and mesoscale models can come into play, but for now going to have to really study the subtle hints and play on those.

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.

After being extremely patient, the target of Ada in southeast Oklahoma paid off huge. We were able to see a beautiful stovepipe toranado which managed to plant itselt right in the middle of the road and not obstructed by any trees. Waitting for the dry line to fire off storms paid off, since the dynamics were in place via a left side of a 500 mb jet increasing divergence and cyclonic vorticity production in the vicintiy of the dry line. Uncapped environment of about 4000 J/kg of CAPE made for 55 000 foot tops and some impressive structure.

Todaye with a left exit region 100 kt 250 mb jet entering into north central texas and southwesterm Oklahoma upper level divergence should be in place for for good storm developement. At 500 mb the flow is a little slack but should still have a maxima to the south which will do much of the same as yesturday. Advancing dry line throughout the day combined with around 6000 J/Kg of CAPE will make for cloud tops into the 60 000 foot range and extremely large hail. Shear and helicities are on the lower end and an eliviated mixed layer may put an slight damper on things but nothing major. We will be in the Ardmore or Waurika Oklahoma region.

Yesterdays chase could not have gone any better. We picked Pratt Kansas as our target, on a day where parameters were so marginal the forecast had to be perfect and we nailed it. With the vorticity maximum ejected around the base of the trough, right entrance of the 250mb jet and the left exit of the 500 mb jet sitting over the target, this allowed for a weak surface cyclone to develop. For a brief period the winds in the vicinity of Pratt were backed out of the southeast and in behind the dry line around dodge city the winds were veered out of the northwest making for an area of strong convergence just to the east of Pratt. Multiple discrete storms fired off this area with weak rotating updrafts. No tornadoes were able to form due to the absence of sufficient shear, but there was enough to get some hail, rotation, and some incredible structure. The last storm of the day took on all characteristics of a supercell and was barely moving almost due east. We were able to get on it as the sun began to set which made for some of the best structure and lighting.