A weak trough sat along the west coast with a deep(er) upper level low out in the Gulf of Alaska. A weak 500mb ridge was situated across the center of the plains. The day prior, as the trough approached, southerly flow began again on the plains and pushed a stationary boundary which was stretched across Kansas further north into Nebraska and points northward. Colorado spent the day mostly in downslope, mixing out a lot of moisture in the air. Early in the morning, a weak shortwave came through and fired some elevated storms in northeast Colorado which persisted and moved NE across the Sand Hills.
That morning, dewpoints in Colorado were between the upper 20s and low 50s (in the far NE corner of the state). 60ºF dewpoints existed across the border in Nebraska and Kansas.
Looking at the models, it appeared that the moisture would increase throughout the day and while lee cyclogenesis was not expected, troughing was certainly present. Though there appeared to be just enough moisture convergence at the surface along the eastern border of the state, I did see a bit of upper level support moving through at 0Z on the 500mb vertical velocity charts. Though the cap looked strong (on both the NAM and GFS) in Kansas and Nebraska, there was enough CAPE west of that for me to be happy with our chances. At least, I figured, we could score a nice isolated supercell like the week prior in the Nebraska Panhandle. Plus, the hodos looked great if we could get something to fire. I called Eric back and told him if he didn't mind a ward, I'd be in for going.
SPC's Convective Outlook for September 14th
I made my preparations and drove out to his place in Elizabeth and we were on our way east. Our preliminary target was Wray/Idalia, CO, so we hit CO 86 and then continued on I-70. Along for the ride was Eric's basset hound Fred, who is pretty awesome, by the way.
As we headed east, I saw one thing that worried me and one thing that looked promising. The worry came from the dewpoints in eastern Colorado and northwest Kansas beginning to mix down. However, even in the dry environment over the Palmer Divide, showers were forming. Considering that there was little if any mixed layer CAPE showing up on mesoanalysis, I figured we had a bit of upper level support moving through. I figured at least we'd have some storms then... but I wished we weren't sitting in 90/48 air. McCook, Nebraska still had a dewpoint in the 60s, so I thought maybe going further north might behoove us. We ended up heading to Wray, which was our target anyway, by the time a line of high-based thundershowers was within a county or so. Even though reflectivities were low, there was a decent amount of lightning showing up, which I figured was a good sign. We drove a bit east of Wray and then south on dirt and just kind of watched the sky for a while, making sure to pick the burrs out of poor Fred's paws. Poor fella'.
We sat a few miles south of Eckley for a good while, watching the thundershowers approach from the west. They were rather disorganized (or at least the radar presentation was) and there was an awful lot of anvil cloud which soon cast a shadow over us. I didn't like the fact that there was shadow now dampening the heating on air that had already mixed out a lot of moisture. We were struggling to keep a 50ºF Td at our location, though it was much more moist and cool to our northeast. The strongest cell in the line was on the southern end, in the driest air, no less.
High-based storms approaching.
Portrait of Eric & Fred.At 2243Z, Mesoscale Discussion #1828 was issued, including our location and points northeastward. It basically discussed the "jetlet" moving through the area and the propensity for storms to continue, especially in Nebraska late. It even mentioned the T word. That was a bit of a boost of confidence, so we now had to decide whether to go north or to stay south with our line. I liked the environment to our northeast but the cloudcover worried me. Plus, it was hard to ignore the line moving at us, especially the southern cell which was beginning to strengthen to my surprise (even in the 35-45ºF Td air). It really was too hard to ignore, so I made the recommendation to head south and we did just that, on a nice, broad dirt road known as County Road U.
From what we could see, everything looked messy to the southwest. We couldn't see the base of the southern storm, but the precipitation looked scattered and diffuse. Looking at the radar presentation, this was a bit confusing. I mean, it *looked* supercellular on radar. Surely it was just a trick.
Finally, just a few miles north of US 36, we found ourselves looking at a beautiful high-based supercell. The radar wasn't lying to us! It had a big, flat meso on it and no visible wall cloud. On the southern flank of the meso, a lot of dust was getting kicked up, though we were still in info. A tornado watch, #660 was issued, but to our disappointment, it was far to the north. We were still happy, though. I think both of us were a little pessimistic about the day and here we were staring down the barrel of a beautiful Colorado supercell.
View to the north.
Wider shot of the big, flat meso and the golden light pouring through from behind.At this point, we noticed that some strong convection was forming to our southeast, probably near Sharon Springs-Cheyenne Wells. It wasn't showing up on radar yet, but looked very strong.
We readjusted south and east as the storm approached. The outflow on the rear-flank was quite strong and was kicking up a lot of dust, but a narrow inflow notch existed wherein scud continued to rise to the base.
Brief wall cloud that formed at the base before precipitation wrapped, seeming to cut it off for a while.
Tumbleweeds getting lofted along the rear-flank gust front, wall cloud dissipating. 
Surface obs at 0043Z showing moisture on the increase again with strong southeasterly winds ahead of the storm.Around this time, Severe Thunderstorm Watch #661 was issued for our area. We briefly were outrun by the outflow and subsequent dust storm before hitting pavement on US 36 and getting back ahead of it. Fat drops were occasionally falling out of the anvil and the cloud-to-ground lightning, even far away from the main cores was very impressive. By now, the cell to our southeast had strengthened and was showing returns on radar. It was moving due north ahead of our storm, which was heading due east, its storm motion, perhaps influenced by the low-level jet kicking in. As we got to US 385, intent on staying ahead of it, we stopped for another photo op. The structure, though I've perhaps seen similar, was nothing short of amazing. There was the flat meso which stretched southward, a tiny wall cloud and what looked like two horns stretching up, coreward. It looked like a bull.
"The Bull"At this point, the storm lost its wall cloud and seemed to become outflow dominant. Several more small cells appeared in its path as well as the larger storm which had just crossed I-70 and was screaming northward. The cloud-to-ground lightning was incredible and seemed to be everywhere around us, though we were only seeing a few fat drops from time to time.
Lately, I fell as if I have lost some of my fear of lightning, which I know is not good! However, as we sat on higher ground near a radio tower close to the KS/CO border on US36, my fear of lightning returned! No part of me wanted out of that protection of that rolling Faraday Cage.
I figured our storm was going to be rolling into turned over air from the cells in front of it and also into the highly capped air in Kansas, so I didn't give it much faith. At this point, our mission turned toward lightning. We desired to stay out in front of the storm, so we headed to Saint Francis and found some higher ground northwest of town for some lightning shots. Though our original storm was warned for high winds (not surprising considering the outflow we saw), we set up for lightning.
Since everything was getting messy up north and the original storm was still heading east, in fact, now diving a bit to the south, we decided we better head south. Even in the wake of the northward moving storm, which was just about upon us in Saint Francis, the warned storm maintained strength. We decided to punch south on KS 27 through the northward moving cell to get out ahead of our original cell.
As we punched the core of the northward moving cell, it appeared to exhibit a bit of rotation on radar. In fact, so did our original cell. I couldn't wait to see what things looked like when we made it through, though it was dark. We encountered only small hail and heavy rain as we passed through, and I could see a nice meso to my west, belonging to the northward moving cell. It was then that I looked southwest and saw that the original cell had a nice lowering on it. I struggled to get my video camera out to try and record it and unfortunately, the first video I took did not have the correct settings, so it turned out very dark. I was able to pull this screen capture, though which corresponds to about 0159Z:
I'm not sure that I am able to eloquently communicate how I was feeling when we gained visibility and saw one mesocyclone to our west and another HUGE mesocyclone with a distinct lowering to our southwest. My eyes got as big as dinner plates and luckily, I changed my settings and was able to get some decent night-time video. We stopped south of the county line in Sherman County and got out. I couldn't decide what to take pictures of!
Lowering on the storm to the southwest. The wall cloud looked to lower and almost contact the ground before the rain from the forward flank obscurred it (and probably added to the lowering as scud was being drawn up from it). 
Wall cloud begins to develop on the northern storm. 
Another shot of the northern cell with a nice cloud-to-ground strike.
Back to the southwestern storm, rain has wrapped completely around the lowering.At this time, a tornado warning was issued for the storm as NWS employees had spotted a cone tornado, which we didn't ever see, though it looked close several times. Facebook friends can watch a video taken from 0200Z to 0210Z here: VIDEO. In the video, you can see the incredible structure of the southwestern storm and the shadow of the meso of the northern storm. I thought that was amazing! I do have another *dark* video from 0158Z to 0159Z which shows a lowering VERY close to the ground (as seen in the screen cap above). Here is what the radar looked like at about this time. Our position, again, is in pink.
We knew we were going to have trouble keeping ahead of it unless we made haste, especially since it was really right moving into the low-level flow. We blasted south to Goodland and negotiated some brief road construction before getting on I-70 and getting ahead of the storm. I tried to keep tabs on it through the rear-view, but didn't have a good bead on any lowerings as it was night and hard to maintain a good watch. We stopped in Brewster for another look and had made decent progress on keeping ahead of it. The notch was less apparent at this time and it almost looked linear; shelfy. However, we did see a brief wall cloud form in a little kink and then quickly fall apart. We reported it since we had a moment, but resolved to keep ahead of the storm. Here are a few pictures from Brewster:
The inflow was really screaming into the storm and I was surprised that it hadn't become completely elevated. I guess the low level flow was warm enough to keep from decoupling.
The storm was really making a hard right turn at this point, so we dropped south out of Brewster and began to stair step our way south and east ahead of the storm. I can say that it had some of the most incredible structure I have ever seen and as it evolved, became this huge mothership mesocyclone, if you will. It just seemed to fill our windows and vision at all times as we kept pace.
We stopped for pictures again 7 miles east of Brownville and had time to set up tripods. In retrospect, I wish that I had put the video camera out, but I was able to get some decent stills. We watched a lowering for a while and for a minute or two, it appeared (convincingly) as a nice cone tornado. As it lifted, there was a distinct staccato lightning bolt right in its vicinity. This was the only time in this stage of the storm that I witnessed lightning like this. There were a few normal cloud-to-ground strikes and and insane intracloud lightning, but this was a very brief and extremely bright strobe. There was also some fairly strong rotation on radar here. We did call it in while it was down but stopped short of calling it a definitive tornado. (In retrospect, it's convincing to me)
Tornado lifted a minute or so later. 
Staccato bolt. 
Reflectivity at the time, our position in pink.
Base velocity at the time, our position in black.We continued on to the east side of Monument, KS where we set up shop once again. I noticed that a light of some sort seemed to hover off to the east of, but very close to the meso. It wasn't until we stopped that I convinced myself that it was an airplane. In fact, we saw two such planes seeming to fly very close to the meso. It's hard to say what they were doing, perhaps looking for a way around. I believe Eric has a picture of one of them.
Anyway, the scene at Monument was monume-... amazing... incredible. Eric chose a good place to stop with the town in the foreground... it really set the meso off. The lightning was incredible as well and the thunder never stopped. We sat there in the 25kt inflow for a twenty minutes or so enjoying this incredible storm. Even Fred seemed to be enjoying it. To top things off, a very bright moon lit up the southern edge of the meso, setting it off even more. It is definitely worth checking out Eric's wide angled shots of the meso at the link to his report below. He got some incredible imagery.
Monument, about to get devoured.
The extent of this incredible mesocyclone.I'm still not sure why, but at this point we just decided to pack it up and head home. Dare I say we were satisfied? It was getting late... but really, I think we were just very happy with what we had seen. Part of me wonders why we didn't just keep going as the storm carried a tornado warning for an additional two hours, if I'm not mistaken. Whatever the reason, we briefly endured some rain near Monument but then went to Oakley and got on I-70 for our trip home. To say that we were high on this incredible storm would be an understatement.
We arrived back at Eric's place between 7-8Z and I was back home before 9Z. My head was buzzing as I briefly looked through my photos before heading to bed. The lightning stair-stepping on the outside of the meso about made me cry. Seriously, that is probably one of the best captures I've ever made.
Finally, I'd like to give a shout-out to the HRRR. On a day that I had low confidence the HRRR seemed to see something like this coming. Like I stated in a previous post, I don't rely on the precipiation models for an exact geographical presentation of where to chase, I like to look at the predicted storm type (via reflectivity) and distribution. The model generated an isolated "supercell" and right-moved it into NW Kansas. Not too bad, eh?
STATS
Mileage: 654
(Year-To-Date): 16915
Largest Hail: 0.5"+
Winds Of Consequence: 50kt+ (estimated)
Tornadoes: 1+ [4NE Brownville (or 10SSE Brewster) and one or two close calls northwest of Goodland.]
Other reports on the date:
Eric Treece (VIDEO)
Goodland NWS Recap
Official storm reports for September 14th.
Detail map:
Finally, I know this sounds selfish, but one of the most satisfying aspects of this storm was that for the most part, no one else was on this storm. There was a young fella' Nebraska that wasn't too far off, but it was our storm. With the proliferation of storm chasing over the past few years, it is not often that you get to experience a nice storm like this without tripping over someone else. I think we saw only one local out spotting as well.
Between this incredible supercell and that beautiful LP in the Nebraska Panhandle the week before, September 2010 will be a month to remember. Thanks again to Eric for letting me come along.
Dann.
