"cold core" event in southeast CO/far southwest KS?
I plan to depart DDC at 1330 UTC (8:30am) for Highway 50 corridor of southeastCO somewhere between La Junta and Lamar. -23 to -25C at 500mb (wow!)with lower-mid 40s dewpoints and temperatures rising into the mid toperhaps upper 50s along/south of east-west boundary which is expectedto become more defined (supporting corridor of ~ 800 to 1000 J/kgCAPE). I think an arc of low-topped supercells may develop from west toeast along or near Highway 50 corridor as early as 17z as far west asPueblo. This could be an interesting event for southeast CO andadjacent far southwest KS.
Below is a visible satellite image as of 1930z. I am NOT a fan of all the mid level cloud that has developed over my target area in the zone of maximum surface vorticity at the nose of the west-northwest surge in dewpoints toward south-central KS. I’m not sure what to make of this. The nose of surface heating is displaced south of the moist axis by a fair distance, which is something I’m also not a fan of. I remember at this time of the day both on 10 November 2008 and 26 October 2006, there was NOT a large area of mid level cloud that spontaneously developed across my target with the best heating displaced south. I expected a surge in warm air northward toward Kingman-Wichita, but it is not happening. 19z obs show 70 at Alva, 71 at Medicine Lodge, and 73 at Wichita. The best warm surge is south of ICT across far north-central OK…thus am now thinking that the western limit of tornadic storms may be I-35 south of Wichita, perhaps. If I was in Kingman right now (like I probably would be at this time), I would seriously be considering heading southeast toward I-35 corridor down into Sumner County. This isn’t an easy virtual chase, and is not as "obvious" to me all of a sudden as I thought it may be like 10 November 2008 and 26 October 2006. No two "cold core" events are the same, that’s for sure, which is why it is a dangerous game to use comparisons to historical events like I do, LOL! History never repeats itself, but it does like to follow a rhythmic beat, which is why I think conceptual models and events of the past are helpful in forecasting. If this event busts, it isn’t the first time and certainly won’t be the last! That being said, it is still 20z at the time of this writing, so a lot can happen between now and 00z. In fact, I’m interested in the cyclonically rotating echoes on the DDC and ICT radars south of Pratt. There’s a 45 dewpoint in Pratt at 20z, so who knows. There could be a fluke brief tornado in Kiowa or Pratt counties since it’s so cold at 500mb.
Here is a 15z Surface plot with some subjective analysis of the temperature and dewpoint fields. Subjective surface vertical vorticity max is encircled. The short-term RUC and NAM suggest the surface vorticity max will strengthen and perhaps drift north through 21z…thus would expect moist advection to continue northwestward into the Wichita-Kingman area. If I was off work today, I would be driving toward Kingman right now (although I probably would have left at 11am!). Visible satellite, not shown, does reveal a very promising pristine sky in this area, so direct insolation will only aid in increasing low level lapse rates (decreasing static stability) to help spin-up the surface cyclone even more across south-central Kansas.
Early this morning, it appears the setup for possible tornadoes in south-central KS still looks pretty good. In fact, I think it looks really good! I just took a look at the 09z RUC 12-hour forecast for 21z, and I am pleased to see that it matches the NAM forecast pretty good in most of the fields supporting "cold-core" surface-based severe convection. The only difference is positioning of the fields. The 00z NAM forecast was a bit farther south from previous runs, however the 09z RUC is very similar to the previous NAM runs (farther north along Highway 54 corridor). Below are a few of the 09z RUC figures I put together to illustrate:
Figure 1. 12-hour forecast of surface wind and dewpoint from the 09z run of the RUC model. The region I am most interested is encircled dotted-black. I observed tornadoes both on 26 October 2006 and 10 November 2008 in this same area, conceptually speaking in terms of the surface wind and dewpoint fields. The western nose of the dewpoint/Theta-E field at the point of maximum surface vertical vorticity is the "place to be", in my opinion, for observing (a) tornado(es) given the tremendous source of vorticity and baroclinicity a storm has to work with. There will be a southeastward extension of this rich vertical vorticity along the occluded front, so as additional storms form southeast by late afternoon/early evening, there may be several storms producing tornadoes along the surface occluded front. I feel quite confident the occluded front will be very productive! 500mb Temperatures are also shown in this figure. Note how far east the -20C isotherm extends!
Figure 2. The 12-hour RUC is generating convection in the exact area I expected it to, which leads confidence in the forecast for (a) severe storm(s) with tornado prospects. This is even farther west than I was thinking yesterday, should this be a perfect prog. Model forecast CAPE is higher than I typically see for the true "cold-core" events, with the RUC suggesting near 1000 J/kg CAPE nosing as far west as Stafford County, KS!. Usually model CAPE doesn’t capture the true surface-based instability for these events very well. This could be a signal that today could be a very productive "cold-core" day.
Figure 3. The 00z run of the 4km WRF-NMM is interesting. Hourly graphics of the simulated radar reflectivity show intense convection developing as far west as Coldwater-Medicine Lodge, KS at 22z… Wow! They may have to watch this closely at work (NWSFO Dodge City, KS) for our eastern counties from in the 21-22z time frame. I am scheduled to go into work at 21z!
So, the 64-thousand dollar question. Where would Mike target if he wasn’t at work this afternoon/evening?
Pratt, KS by Noon and watching the sky/visible satellite/observations/short-fuse composite very closely, with eyes set east (or east-northeast or east-southeast??) of Pratt for the 21-22z time frame!
I am intrigued by the setup for localized tornado event in south-central Kansas tomorrow. It is shaping up to be an event with similarities to 26 October 2006. I think (a) tornado(es) may occur farther west than the current Day 2 SPC (the 1st, 06z, issuance) outlook slight risk in a small corridor where upper 40s to lower 50s dewpoints will sneak west along the Highway 54 corridor from Wichita to Kingman. Surface vorticity will be maximized in this area due to the presence of a significant middle tropospheric potential vorticity (PV) anomaly. I like to look at 400mb for wind speed fields and related PV anomalies. It is just downstream of a 400mb PV anomaly where surface cyclogenesis (in the wind field) is maximized (dZeta/dt at the surface for you meteorologists out there!). I think if surface based storms form in this zone, it will take advantage of a tremendous source of vorticity in the low levels — both vertical vorticity and horizontal streamwise vorticity. Given the substantial ageostrophic motions present in the low levels in response to a small scale jet streak like this, there will be an enhancement in ambient vertical wind shear as well as the atmosphere tries to restore itself back to geostrophic balance. Okay, that’s some heavy meteorology, but that’s what is going on in these small space/time scales. Timing is critical. Like 10 November 2008 and 26 October 2006, the event occurred in a very short time window…usually centered around 21-22z. If the current NAM model holds, then the best area at the 21-22z time frame will be along the Highway 50 corridor somewhere in a Cheney Lake-Kingman-Wichita area. Below is a conceptual model I put together for an informal presentation back in January at a local AMS High Plains chapter meeting regarding these special events. What is very interesting about my conceptual model is that the area I drew this conceptual model — south central Kansas — is exactly where I think things may unfold tomorrow (very near the yellow area on the graphic!).
Below is the 33-hour forecast from the NAM valid 21z April 9th. The graphic is of 400mb wind speed and surface wind barbs. I annotated where the 400mb PV anomaly would be based on the wind speed field…as well as where the greatest vertical vorticity would end up being as well. This all seems to point to the Wichita area or points just west at 21z:
Tomorrow is a chase day if I can get off work early. I am scheduled an "easy to get off" supernumerary day shift, and since I’m not working a forecasting shift + the fact that severe should avoid the Dodge City forecast area, I can probably take a half day off, leave at noon, and head east toward Wichita. I do plan to "join the masses" and play the conventional obvious target from Wichita, KS to the Oklahoma border. This does appear to be the best play — along the dryline and ahead of the cold front which will be moving rapidly southeast through central KS by late afternoon/early evening. Surface winds should back to about 170 or 180 degrees by late afternoon, increasing surface convergence along dryline. I like to play the thermal noses along and immediately west of the dryline…and this also appears to be setting up along the KS-OK border by late afternoon somewhere between Medicine Lodge and Harper, KS. My target is somewhere between Kingman and Harper at this point (see black circle in image below). I will have Underthemeso.com in "chase mode" by early afternoon if I do indeed get off work early. That final decision will be made in the morning while at work. At this point I’m about 80% sure I’ll get off and be able to chase.
I am really intrigued by the meteorological setup across the far southwest Kansas/western OK Panhandle/extreme northeast NM corridor for later this afternoon. An intense, yet compact (important!) mid level potential vorticity (PV) anomaly will eject northeast out of New Mexico by midday and become centered across the area mentioned in the first sentence. This setup has some similarities to the 26 October 2006 setup, although probably not as intense. Nevertheless, there is the possibility for interesting low-topped, intense convection near the nose of the mid level vort max/PV anomaly where low level convergence/frontogenesis will be extremely favored. A narrow corridor of 45 to 50°F dewpoint air at the surface may extend northwest as far as Guymon, OK or even points west of there, sneaking into an area with ~ -21°C temps at 500mb. Since this isn’t all that far from Dodge, I will try to chase this setup and see what I can come up with. Just the thought of possibly seeing a brief "cold core" setup tornado in November is enough for me to get out the door, however small that probability may be. I look at the short-term RUC forecast and have visions of 26 October 2006 running in my mind. This would be a low CAPE event, with forecast CAPE on the order of 300 to 500 J/kg in a narrow corridor, but that is enough convective instability given the degree of focused, intense ascent from this small system at the nose of the mid-level PV anomaly. Below is a 9-hour RUC forecast:
I will be chasing today, Thursday, July 17th. It is my two days off between midnight and day shifts which start Saturday. Obviously, with it being summer, the wind shear setup is less than ideal for long-lived supercell thunderstorms, but the thing today has going for it is a lot of moisture. As I type, much of western Kansas is soaking in 65-67 degree dewpoints, with a 66 dewpoint at Imperial, NE. Coincidentally enough, Imperial, NE is my target. All the models generate quite a bit of convective precipitation, so I am giving today about a 60-75% chance of observing and photographing a severe thunderstorm of some sort in the target area of Southwest Nebraska and adjacent far Northeast Colorado. Since I am fresh off midnight shifts, my sleeping pattern is F*d up. My day has essentially begun at 1:30am. I plan to do some moonlit landscape photography at the Monument Rocks north of Scott City before heading north toward the chase target. I’ll probably get there late morning which will allow me to grab a midday power-nap of sorts before storms start developing.
I will be out chasing today, Saturday 31st, to June 2nd on my 3-day weekend. Today’s target is tough to decide on, but I am making the decision to play upslope across the NM-CO border area north and northwest of Clayton, NM — my favorite storm photography area. Deep layer shear will be excellent for rotating storms, but the question will be how far west quality moisture can get. Upper 40s to lower 50s dewpoints linger just east of the elevated Raton Mesa terrain with north winds… however winds are expected to veer to the east by late afternoon, allowing this moisture to spread toward a developing storm. The other target is northern Oklahoma, but am thinking it might be more difficult to get a storm in this area now as convergence will probably weaken by late afternoon in favor of the enhanced easterly upslope winds farther west. I will probably stay in Clayton or Lamar tonight then be around eastern Colorado Sunday for what looks like a quality upslope chase day. Monday also looks pretty good around the same general area of eastern Colorado and adjacent far western KS.
Likely targeting western KS
Today is my day off, so I plan to chase. I have really been waffling between two areas of interest: The more consensus TX Panhandle choice or western KS. I think I am going to target western KS. The reason I like the looks of DDC-GLD CWA border region of western KS is 1) a band of increased 250-300mb flow in this area around 70-80kts (despite the more anemic ~500mb winds of 30-40 knots or so)… and 2) the roughly 0-2km lower tropospheric convergence looks pretty darn good late this afternoon/early evening across western/northwestern KS — a lot better than what I’m seeing progged across the TX Panhandle. The NAM has shown a very persistent "convective QPF bomb" signal at the nose of the 850mb speed max that sets up from, say, Tribune northeastward to Wakeeney…then continuing northeast to Stockton-Osborne by the 03-06z time frame. Dewpoints in the 60-62F territory may be realized up in this target as convergence increases later on. And lastly 3) it’s the "secondary" target as all the "hordes" will be in West TX. Will continue to monitor. I can sit here until Noon in-case TX PH starts calling my name again.. but as it stands now, I think I’ll be heading NW or WNW from DDC instead of SW.
