High Plains Drifter

West to east flow aloft and southerly flow in the low levels… directional shear is very good for storm organization/supercells as far south as southeast Colorado… with mode more than likely on HP side of things. Mid level flow is better farther north into northeastern Colorado and adjacent southwest Nebraska/northwest Kansas. I think there is going to be adequate moisture across all of eastern Colorado into far southwest Nebraska for decent storms. Given the not-so-hot 700mb temps, 8-10C and adequate insolation farther north, I think storms will form… with perhaps the Palmer Divide initiating stuff. Other storms may also form in a weak convergent area farther northeast from Wray/Yuma to Imperial, NE. I think there will be a larger area of possible severe storms than what the SPC guidance suggests. That being said, I will target farther south closer to home where better low level convergence and moisture signal is in the model fields… initiation of storms far eastern Las Animas County or western Baca County. I think I’ll head to Lamar and re-evaluate from there… as I don’t want to totally rule out chasing a Palmer Divide initiated storm… which would probably roll east along I-70 corridor during the 23z to 02z time frame. I’m about 75%/25% in favor of farther south (Baca County) target vs. Palmer Divide (Limon, Genoa, Arriba, etc. along I-70) at this point

Day 1 of 3 of weekend mini chase trip

I am in Ogallala, NE this morning.  My target all along was southeast Wyoming into the Nebraska Panhandle, and this still appears to be on track.  There are lower 50s dewpoints awaiting upstream of the Laramie Range, and the best low level flow by early this evening will be funneled up into the southeast Wyoming/Nebraska Panhandle area.  1500 J/kg CAPE is expected by early this evening.  I will head in the general direction of Torrington, WY by mid-afternoon and re-evaluate from there.

Day 2 (May 22):  Still looks good for southern South Dakota area into far northern Nebraska.  Not sure where I will stay tonight, as it depends on which portion of the Nebraska Panhandle I’ll end up in.

Day 3 (May 23):  I will be making my way back south closer to Dodge City since I have to work Monday morning.  There could be a potential play for supercell storms in Northwest Kansas as a weak front slips south into this area with still good upper level southwest flow and pretty high CAPE.

June 5 will be the first of a 3-day weekend chase with my friend Robin Lorenson.  I met up with her this evening in Salina and we will depart at around 8:00am heading west on I-70 to Burlington then likely north toward our mid-late afternoon target of Sidney to Sterling.  It looks like a fantastic setup for supercell thunderstorms with at least mid 50s dewpoints advecting west-northwestward toward the Cheyenne Ridge.  Elevated heating and orographic lift with east-southeast winds will be more than sufficient to aid in thunderstorm development.  CAPE will likely exceed 2000 J/kg downstream of the high-terrain development, and the plan is to intercept storms as they develop/coalesce into supercell structures sometime around or after 21-22z… at least that’s the plan!  There could be quality chasing/photography well into the evening so a late night may be in order.  We will likely settle for the night somewhere along I-76 or I-80.  Saturday, June 6 chase area will likely setup in the same general area, perhaps a shade farther east or northeast along I-80 corridor.  Sunday could be yet another good day in broad southwest flow aloft around western Nebraska or northeast Colorado.  The surface front farther southeast could be another potential play, which would be much closer to central Kansas where we would have to end up at the end of Sunday’s chase.

That’s right.  Eastern New Mexico.  Why?  I had a good day yesterday, so this will be a more relaxed chase… with a target a bit closer to home then, say, Junction, Texas.  I have 3 options:  1)  Play the front with upper 60s dewpoints ahead of it in questionable chase territory in the Junction-Menard-Llano-Kerrville polygon… probably messy structure given all the moisture… the farther southeast one gets, the less photogenic storms tend to be.  I’m a High Plains storm photographer… so going clear down to almost San Antonio to chase storms isn’t exactly my cup of tea.  2).  Play storms coming in New Mexico at the nose of the 250mb jet in the narrow return flow region where some upper 40s dewpoints will sneak back up into eastern New Mexico yeilding perhaps up to 1000 J/kg CAPE… but, the high-res models have been showing convective signals approaching the TX-NM line northwest of LBB for several runs… and there will be a lot of upper forcing in this area.  3)  Go home.  I’m not ready for 3 yet, so I’m playing #2.  I’m going to target Ft. Sumner to Portales.  Totally unconventional chase play, and I’ll be the only fool out there, but if I keep my expectations low, then it won’t be that big of a bust.  We’ll see what happens.

Friday and Saturday May 1-2 are my days off and after thinking about it for a couple days, I will be chasing.  A fairly aggressive cold front was really worrying me regarding the quality of chaseable supercell thunderstorms, thus resulting in the last-moment decision to go for a 2-day chase.  Friday May 1st looks to be perhaps a spectacular supercell day somewhere along the Red River valley, perhaps along the Highway 287 corridor.  A target centered around Vernon-Seymour, TX has my eye at this point.  There will probably be a dryline/front intersection near here, which is the place to play Friday — right at the nose of the 90+ degree heat intersecting upper 60s to near 70 dewpoints.  Below is a forecast sounding from this evening’s 00z run of the NAM model valid 24 hours from now (when a storm should be in progress) for a location near Seymour, TX.  The hodograph looks very favorable for supercells to go along with the more than adequate CAPE of 3300-4000 J/kg.  This hodograph structure would support slow moving deviant supercell of 10 to 15 knots!  I’ll take that any day of the week   This hodograph is not too dissimilar from the hodograph/wind profile of the Garden City/Plymell, KS Supercell just last night (April 29th) which yeilded the incredible "spaceship" supercell and even a few tornadoes.

Saturday, May 2.  This is a little more problematic, but has the potential to be a very nice surprise somewhere across Southwest TX or adjacent southern New Mexico.  I am in favor of playing the area right at the nose of the 300mb jet streak poised to nose right into the Midland, TX area by Saturday evening.  The question is how far west moisture can make it.  The NAM has been very aggressive with the cold wedge nosing down into West Texas, however my gut feeling is that the NAM is probably a bit overdone, and has backed off on this in the latest run… more in line with the GFS and ECMWF.  The ECMWF had me quite excited about Saturday’s prospects when I was looking at it at work earlier today.  The forcing will be very good across the Jal, NM to Midland, TX area by early evening Saturday.  Even if mid 50s dewpoints can sneak back northwest up to Midland-Seminole, TX then that would be enough given the degree of ascent to help get storms going.  The shear profile looks excellent with the west-east oriented jet streak.  The "nose of the upper jet" pattern in the upper levels reminds me of my May 9, 2006 chase in the TX Panhandle, where models struggled in the westward advection of moisture by early evening toward the nose of the upper level jet. 

48-hr GFS forecast valid 00z 5/3 (7pm CDT May 2nd).  300mb Jet streak (in blue) nosing into southern portions of West Texas.

I will be chasing this Friday, as it will be my only opportunity to chase this upcoming pattern due to work.  It isn’t the best setup in the world, but I do envision at least some photogenic storms given the pristine skies out there.  A cold front is pushing south through central Nebraska this morning, but should slow down due to surface heating both sides of the front.  Storms should form in a quasi-linear fashion along the northeast-southwest oriented front.  There is a very small possibility of non-supercell type tornadoes if storm updrafts form in a southwestward propogating manner along the front in a "zipper" type fashion.  The cold front must stall out, though, for this to pan out.  It is not out of the question, though.  Will try to play the western edge of the 55-57F dewpoints where 1700-2200 J/kg CAPE may be realized.  Target:  Belleville KS-Hebron NE by 21z (4pm CDT)