Chase Log: May 21st, 2005
Click on any of the SPC products below (Convective Outlooks, Watches, or MCDs) to see the SPC's "Severe Thunderstorm Events" page pertaining to this event.
Total Distance: 760 miles
Target Area: Concordia, KS, to Beatrice, NE
Chase Area: BUST
Maximum SPC Risk category: Slight
Watches:
Tornado Watch 311
Mesoscale Discussions (MCDs): 951, 952, 954, 955, 956, and 957
Big Bustola. An on-the-fence decision was needed by mid-morning, as the target area of northern KS / southeastern NE would require a drive. Morning surface obs showed dewpoints only in the 50s across the area. Despite this, the 12z NAM was still indicating low-70 dewpoints making it into eastern Nebraska, though my suspicion was that low-mid 60 Tds were more likely given that the 70s were well into central/southern Texas. Weak but sufficient mid-upper level flow would yield deep-layer shear of 35-45kts across eastern Nebraska and northern Kansas, along with NAM-forecast 0-3km SRH in the 300-500 range.
I looked at the 18z Omaha sounding (and the incredible cap), and quickly realized that we didn't want to get too far into Nebraska, given that mixing was likely to be much stronger in the non-cirrus covered areas of Kansas. We noted rapid growth of TCU line from Concordia, KS, to Hebron, NE, and northward from there. We made it to Hebron and waited for a storm to take hold. In time, by late afternoon, the TCU to the south were looking much healthier than those to the north, so we slid back south into KS. The TCU were very rock-solid much of the time, especially in KS -- quite impressive updrafts. However, it was also apparent that the storms were very high-based and struggling to persist.
We made it south to Salina and made a data-stop. AT this time, we noted decaying storms in northern Kansas (certainly confirmed what we were seeing), as well as a few cells west of Salina that looked much healthier (60-65 dbz). SPC Mesoanalysis showed parameters that were largely conducive to signficant supercells (Supercell Composite Parameter of 40 at one time, EHIs very high, 2000-4000 CAPE and 250-400 0-3km SRH, etc), though the favored area was certainly east of I-135 (east of a Salina to ICT line). We meandered south and west to see if we could get a good view of the bases, and indeed we did, though they didn't look too impressive. By a little after 8:20, it appeared that the storms weren't going to be able to tap the upper-60 - 70 Tds to the east (and the nicely juxtaposed very strong low-level shear), so we called it quits as the storms appeared to rain themselves out to the west of McPherson. Very nice sunset and lots of mammatus, however.
Eating at the local Applebees, I get a call from Aaron Kennedy notifying us of an awesome supercell to our west. Hmm. I must not have looked west very well as we drove into McPherson and into the Applebee's parking lot, or else I certainly would have seen a nice supercell I'm sure. I did see a decent updraft, but figured that storm would meet the same fate as the others that were located west of I-135. Indeed, the storm did, but not before a brief bout of intense supercell living.
Again, this event holds true of the rest of 2005. Low 70 tds would have meant less CINH (release of latent heat lower in the troposphere), a weaker cap, and much better prospects of initiation. Actually, we did have initiation in KS, but the storms just couldn't persist in the relatively dry air (50's - low 60 Tds). Things would have been very good had they been able to move into the deeper moisture and strongly-shear environment to the east. Alas, that was not to be the case.
For the record, we have had a few days this year with the relatively rare juxtaposition of strong shear in the warm sector -- 3-21, 4-25, 5-11, and 5-21 namely. But aagain, the lack of real Gulf moisture on each of those days largely precluded the development of tornadic supercells (or at least certainly to the magnitude possible if we had had more "typical" moisture profiles available). I could keep complaining about this year, but it's clearly evident that it's sucked, and largely courtesy of unclimatologically poor moisture availability. Not too often do you see 250-400 0-3km SRH aligned with 2000-4000 CAPE.
05-21-2005 Chase Pictures
Click on any photo to see a larger version
