High Plains Drifter

Sitting in Childress at this time about to take off for Lubbock area where I’lllikely spend much of the afternoon. RUC and NAM suggest near 2000 J/kgto develop in the northward advecting moist axis through West TX. Del Rio morning sounding shows pretty good moisture which is already advectingnorthwest just off the surface. Midland sounding had highest mixing ratiojust above ground level with near 50F. I think by 00 UTC, there shouldbe widespread upper 50s to near 60 dewpoints from Midland to Lamesa toSnyder…perhaps as far north as Lubbock. I think the best play is right atthe nose of the good low level juice… so my initial target isLamesa-Post-Snyder area for initial 22-00 UTC development…thentowards Jayton-Rotan-Aspermont area later in the evening.
 

I will be driving to Childress, TX after work this afternoon to set up for a Saturday chase in West Texas.  Low level moisture will return back north tomorrow across West Texas with dewpoints reaching upper 50s to near 60 as far north as northwest Texas.  Another shortwave disturbance will dive southeast out of the Rockies tomorrow putting West Texas in substantial forcing for ascent and subsequent deep, moist convective development.  Surface-based CAPE values may reach 2000 J/kg by late afternoon.  At this point, I’ve got my eye on an area between Lubbock and Childress, but may travel as far south as I-20 to Abilene.  The key tomorrow is to a) be close the advancing low level moisture and b) remain well south of the charging cold front.  I think both should be accomplished with relative ease.

Last Night was another night I won’t forget.  ~70 local residents, many of which from Greensburg, showed up at the Project Greensburg storm chaser fundraising event in Pratt, KS.  I was invited by Greg Stumpf and Mick Ptak, the event organizers, to give a 15-20 minute presentation on Greensburg in between the showing of chapters from the "Storms of 2007" DVD.  A $3100 check was presented to Greensburg Greentown from profits of the previous year’s DVD.  70-80 copies of the 2007 DVD were sold at the event last night at Pratt Community College, all the profits of which will also be donated to Greensburg Greentown.  A few other showings are planned, including the Central Plains Severe Weather Symposium in Lincoln, NE at the end of March.

Believe it or not, today is a chase day!  I have the day off, and today is a good day to get the storm chasing feet wet again.  A strong storm will eject out of New Mexico later on today and it looks like the best focus for possible supercell storms will be west central or southwest Oklahoma.  The tentative target right now is the Mangum-Altus area.  Storms may develop fairly early, which for early in the season, may not be a bad thing given early sunset.  I plan to depart around 8:30am or so.  I will put the website into "chase mode" probably by early afternoon or so. 

Target Benkleman, NE.  I am typing this afternoon from my target area in Benkleman, NE.  I failed to post a brief forecast, so I’ll do that now.  I decided to chase today after it appeared that decent severe threat may extend farther south than anticipated yesterday.  I had originally thought I would chase farther north after staying the night somewhere after yesterday’s chase, however since yesterday’s chase was rather close to home, I decided to semi-blow off today and just head back to Dodge after the chase.  I left Dodge City this morning around 10:30 or so and arrived here in Benkleman around 3pm.  There is a dryline extending north-south through this area and all the models suggest fairly vigorous convective development late this afternoon and this evening.  So I await here in Benkleman under mostly cloudy skies with a large band of cirrostratus clouds over this area.  Surface temperatures, however, have now warmed into the upper 80s here, so the clouds are of very little impact on heating.  We’ll see what happens, there’s a very nice, strong system centered over the Great Salt Lake region this afternoon, and strong lift will continue to spread east interacting with the warm/moist sector (where I am at!) anytime now. 

Target: Eastern/Northeastern CO to far western Kansas.   There is a fairly strong subtropical jet streak moving towards the High Plains today.  This morning, there were lower to even mid 60s dewpoints advecting northward from western Oklahoma and the eastern Texas Panhandle.  A dryline will set up this afternoon along the KS-CO border area northward to western Nebraska.  By this evening, widely scattered storms are expected to break out along this dryline.  The question is where to target for the best location on the dryline.  I think I will head up towards the Goodland area and perhaps re-evaluate from there, leaving around noon or so perhaps.  Both the RUC and NAM are breaking out convective precip along the dryline farther south on the edge of the good upper flow, so I will have to watch out for that possibility as well.  I will probably chase Saturday, too, farther north in Nebraska… thus I may stay the night in Colby or McCook or something… it will be a seat-of-the-pants operation, as it usually is with storm chasing

Target area NW KS.  Well, today is a chase day.  A warm front will be moving north through western Kansas this afternoon with fairly good dewpoints in the mid 60s present.  Low level and deep layer wind shear will support supercells today, especially the farther north you go into northwest Kansas.  The plan is to "ride the front" north until convection initiates, probably around the I-70 corridor, or at least that’s the idea.  I’ll be leaving around 11:30am or so, taking a leisurely drive up towards Oakley/Colby, grab lunch, catch a shut-eye (I just came off midnight shifts), and re-evaluate the situation.  I’ll put the front page into "chase mode" by early afternoon.
 

Another marginal setup.  I’ve been dying to get out and chase at least something during my 4-day scheduled off weekend.  The pattern has been really poor for chasing.  Today, there is a possibility at photogenic High Plains storms anywhere from central Nebraska to northeast Colorado.  Yesterday, I made the decision to go for this marginal setup, for a number of reasons… mainly because since I will not be taking a chase vacation this year, the number of days I will be able to chase this season will be limited… so I will be chasing more marginal setups.  It appeared yesterday there would be a decent possibility at a supercell for today somewhere in the Nebraska Panhandle, like around Scottsbluff.  Today, this focus at the surface has shifted farther to the south around the Cheyenne Ridge area, mainly between I-80 and I-76.  The problem with a farther south surface setup is the shear profile looks less supportive of supercells.  Mid level winds will be at or less than 10 knots… not good for supercells.  Upper level winds will also be pretty weak…but at least they will be around 30-40 knots…such that with a nearly stationary moving storm, there should be some precip evacuation.  The other problem for today will be warm surface temperatures for the marginal moisture.  Highs today should hit the upper 80s over much of far northeast CO into central Nebraska.  This means more outflow-dominant storms.  The hope is that convection can be vigorous enough with enough storm relative inflow such that a picturesque high-based shelf cloud can form or something photogenic.  I am in Ogallala this morning, as I stayed the night here.  The Northeast CO play would be a very interesting one.  The shear profiles almost support left-moving favored supercells, should supercell processes even exist.  Surface inflow will be primarily out of the northeast in this area.  The secondary target extends from roughly where I am now in Ogallala northeast into Central Nebraska through the southern Sand Hills.  A quasi-stationary front with higher CAPE may promote a severe thunderstorm or two in this region as well.  The upper level winds will be a little stronger… approaching 50 knots near the tropopause, but mid level winds will still be anemic.  I am torn between the two targets, and I will likely hang around Ogallala until early afternoon when it will hopefully become more clear which marginal target looks best.  Here’s this morning’s NAM12 3-hr convective precip forecast from 7pm to 10pm CDT this evening:

Northeast Colorado or the OK-TX Panhandles? 

I’ve got a difficult chase forecast ahead of me this morning. Fortunately, either target is about 3-4 hours drive, so I’ve got about 5 hours to make up my mind. Roger Edwards 6z SPC disc was a good one, as always, highlighting my thinking at least from a storm chasing perspective. Yesterday, I was not really thinking much about a TX-OK PH dryline scenario… but now, I’m trying to find a reason NOT to chase south today. Morning obs suggest mid 50s dewpoints in place. It looks like a fairly classic "Day before the big day" dryline setup with convergence increasing towards 00z. There should be no problem reaching peak heating potential today, and the NAM shows highs in the lower 80s along and west of the dryline over W TX PH. Farther north over NE CO/NW KS… there will be more of a low level baroclinic zone with that retreating boundary so there will probably be a frontogenetic enhancement to upward vertical motion and subsequent initiation.

One thing I usually look at in the NAM model are 700mb RH/Omega clues from the NAM, especially with potential dryline initation… I think you get a good idea how much dryline upward motion from boundary layer convergence, etc you are getting for potential initiation. Another clue is 700-775mb temps. Usually the NAM will show a tongue of lower (roughly 1 to 1.5C) temps in this layer due to enhanced dryline lifting. Even though the 12km NAM convective parameterization schemes don’t show QPF along the dryline, the signals are shown that it’s trying hard to force convection from roughly Elkhart KS down to perhaps as far south as Plainview, TX. I went and checked the 00z explicit 4km NAM (http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/cent4km/v2/) and it indeed shows one isolated storm forming along the dryline over the western OK Panhandle.

24hr forecast of 1-hr convective precipitation from the 4km NAM model valid 7pm CDT 4/20.  This is suggesting isolated severe thunderstorm development along the dryline.

The 19th and 20th are my two days off that I could chase.  This evening (19th), I chased a very marginal setup close to home north of Dodge City.  A weakening Pacific cold front moved southeast towards western Kansas by afternoon, however ahead of this front, the lower atmosphere was just marginally unstable with CAPE values less than 1000 J/kg.  The deep layer shear was pretty good, but the lack of deep atmospheric upward motion prevented good storms to develop.  At sunset near Wakeeney, a weak storm did form, however by the time it developed it was already getting too dark.  

Friday the 20th chase forecast.  The setup for tomorrow looks better with more instability  present.  Another strong Pacific storm system will be moving into the desert southwest region allowing southwest flow to develop over the high plains of Colorado and West Texas.  The NAM model suggests increasing dryline convergence by afternoon from northeastern Colorado south-southeastward into the western TX Panhandle.  The NAM develops convection along this dryline near the KS-CO border by early evening (see the graphic below).  Anyway, I plan to target the region shaded in yellow in the graphic.  If a storm does indeed develop in this area around 7pm CDT, then supercells would be likely given the shear/instability combination.