May 31, 2016

Team Duck Forecast:

"Day 1 Morning Synopsis: Even moreso than yesterday, an extremely complex scenario is evolving this morning with composite outflow boundaries and numerous convectively addled airmasses. The morning hand analysis is below, and suggests 65 dew points extend from near the Big Bend region northeastward through SE OK. North of this airmass, a composite OFB and a reinforcing of the cold front extends through south central OK, delineated by fairly sharp gradients in both dew point and temperature for a (nearly) June front. Farther west there is a relatively sharp dryline cutoff from west TX to central NM. Model moisture is not far of the observation mark at this point, though along the developing OFB in west TX near the Big Bend 70s are being driven back more than the model forecasts. Some moisture forcing is expected by the frontal system during the day, perhaps leading to slight moistening, particularly over the southern and Caprock/Red River regions. Moisture depth and quality suggests that mid-high 60s are likely in either target region. GFS since its recent upgrade has shown a tendency towards resolving a greater degree of convection, and for this reason its parameter space needs to be closely monitored for outflow regions, as can be seen west of LBB at 00Z. In light of this, a hedged double target seems to be a safer bet for today for maximizing tornado potential, with upslope potential along the Caprock complementing a reasonable severe storm environment and non-zero tornado chance, or for storms coming from the high terrain in Eastern NM/ dryline along the west TX border region - consistent with the SPC 2% risk region along the western panhandle extending to near the Caprock. Dews in this region will recharge reasonably well, and given the elevation, this reduces the need for higher values to some degree. Elsewhere, the southern region near Big Bend seems to have similar problems to previous days, being high/mid-level overcast from convective debris, and a morning MCS will likely spoil any potential in this region. Shear is relatively weak throughout the warm sector but still sufficient for SCs thanks to the SE to W turning, though this improves to the west and south associated with the sub-tropical jet. SBCAPE is progged to around 1500-2500 over the target regions.

CAMs depict a messy afternoon evolution, with convection firing along the dryline, numerous OFBs, the front in OK, with boundaries and therefore helicity likely to be flying left and right. Nonetheless, HRRR while depicting a wholesale convective initiation over the warm sector, shows supercells developing in NM and tracking eastward into the TX Panhandle, while NAM is less likely to initiate the warm sector and instead develops storms along boundaries and the dryline. In light of this evolution, an initial target for the west LBB region seems appropriate with appropriate watching of the days evolution to further refine the forecast."

Day 2 doing National Geographic tornado research operations, all three teams were finally assembled.

Dramatic supercell structure south of Lamesa:

I was testing a new "box" camera enclosure on top of the van during this chase, meant to replace the dome. It wound up being a complete failure, and I had to take it down and revert to a less than ideal dome setup.

Team Duck's Summary:

"We awoke to partially cloudy skies and a relatively cool north wind, and cold tea that was later remedied by exceptional and most importantly hot coffee at Starbucks with Skip and Jenn. An MCS was underway in the west TX region, so despite the favourable parameter space in that area, afternoon convection would likely be compromised somewhat.

Our Initial target was for along the outflow boundary extending just north of Hobbs NM to Sweetwater TX. SPC suggested a 2% tornado risk over our target area, surprisingly completely independent of the hail and wind slight risk area. Satellite profiles revealed a pronounced boundary fostering convective development westwards to the high terrain in NM. CAPE fields from RUC extended to 2000-3000 j/kg east of the NM border. Together with dew points into the mid 60s and a rather steep gradient on a west to east basis, we anticipated that the boundary would provide a source of both initiation and near surface helicity if a storm could track along it, potentially compensating for relatively anaemic wind shear profiles, particularly at the mid levels.

We headed east around 3:30pm CDT to better position along the boundary. Cells were developing over the higher terrain in NM, with the boundary extending from near Roswell toward Abiline. A new cell developed just northwest of Wellman TX, and after taking a while to mature somewhat, it began to resemble a right moving storm. The cell produced a significant dust and precipitation foot just north of Wellman, and continued to move southeastward. We continued to drive east from Wellman in pursuit of the storm, witnessing a moderately nice structure and interesting rain curtains, however the storm encountered cool wet inflow from it's southeastern friend, impinging its ability to remain viable in the environment, after which the storm promptly gusted out. Around that point, Anton and Tracie joined the chase.

We proceeded to head south on 87 toward a new cell near Lamesa TX, which appeared to have formed on the surging outflow boundary and was already looking quite impressive visually and on radar, and was tracking southeast to the west of highway 87 toward Big Spring. The storm developed a strong couplet but was wrapped by heavy precipitation. Sun filtering through the storm illuminated it quite nicely, as the storm continued to ingest dust, with a substantial but slightly cooled inflow. Despite this, the storm maintained a surprisingly low base structure, at times ground scraping, particularly during the strongest mesocyclonic occlusion. The storm may have been briefly weakly tornadic during this phase, but we were unable to confirm this due to low contrast. Our positions were maintained to the southeast of the storm throughout the chase, which facilitated a high contrast viewing angle, and maximised our ability to view structure.

We continued to track the storm until just southwest of Ackerly, where it appeared to lose structure and ingest cooler air. The relative strength of the forward flank downdraft appeared to impinge on the storm’s ability to rotate, thus while the outflow boundary along which the storm travelled promoted the near-surface helicity, the midlevel mesocyclone was comparatively weak. Lighting from the storm was visually impressive with tall bolts out of the striated structure. However, in light of its impending demise, we decided to abandon the storm, repositioning north in hopes of observing the easterly advancing squall line backlit by the sinking sun.

Along the road north to Lubbock, we encountered some local minor flooding over highway 87. Unfortunately the squall line to our west was struggling to develop across outflow from storms to its east, looking quite shabby. Hence, we called the chase as the sun was setting and headed for dinner.

Our radio system was quite effective at short range throughout the active pursuit, particularly for route planning, road hazard warnings, dinner plans and mosquito congregations, though effective range seemed to only be a couple of miles. During that case, group texting was a more effective and clearer way of communication. "