Two rounds of severe convection developed over the Texas Panhandle during the afternoon and then evening of 07 May 2020. Storms developed amid increasing forcing associated The Amarillo NWS forecast office (AMA) utilized GOES-East imagery to track development.
GOES-East water vapor imagery highlighted a well-defined upper low digging southeast into the central US plains, with periodic and much more subtle perturbations in the W/NW flow to it’s south (Fig 1). Large scale forcing associated with these features aided convective development along surface/low-level boundaries.
The first round of severe storms developed over the southeastern portion of the Texas Panhandle along a dryline during the afternoon. Leading up to convective initiation, the AMA forecasters monitored the 1-min Day Cloud Phase Distinction RGB imagery for signs of imminent convective initiation (Fig 2). By 2055 UTC, it was apparent from the imagery that convective initiation was most most likely in the near-term over the southeast portion of the panhandle along the AMA/LUB county warning area (CWA) border. The cumulus cloud field was well established and maturing, cloud color was transitioning from cyan to green (glaciation), and orphan anvils were generated (failed initiation attempts). Shortly thereafter, deep convection initiated successfully just south of the CWA border in LUB’s area.
Forecasters from AMA noted the value of 1-min VIS/IR sandwich combo imagery as the convective scenario evolved (Fig 3). Of note early on was a new, stronger updraft developing ahead of the original updraft, quickly producing an above anvil cirrus plume. By 2216 UTC, a new updraft developed ahead of the main storm per cooling of cloud tops and increased cloud texture. This area of convection developed within the AMA CWA and forced the issuance of a severe thunderstorm warning. A storm split was apparent in the imagery a little later, by 2230 UTC, with continued cooling of cloud tops on the northeast cell (left split) and development of an OT. The right split accelerated to the southeast and maintained a large OT and prolific AACP. Forecasters noted the early signs of new updraft development and storm split were apparent in the 1-min satellite imagery just prior to radar.
An uninterrupted loop overlays MRMS MESH on the sandwich imagery, revealing the long hail swath associated with the main cell and right split, and apparent hail development from the forward convection in the southeast corner of AMA CWA, and eventually with the left split (Fig 4).
Later on that evening, additional convection developed across SW KS and the OK/TX Panhandles along a cold front within increasing large scale forcing for ascent ahead of the aforementioned shortwave. AMA forecasters noted the value of the 10.3 um IR window channel at night for analyzing this second round of convection (Fig 5). The imagery was utilized to identify the main updrafts of the stronger cores aloft given the appearance of overshooting tops, and to infer which updrafts were more likely to sustain themselves given cloud top IR temperature trends.
An animation of grayscale IRW and GOES-derived CAPE for the full-duration of the event shows a corridor of increasing instability ahead of the dryline during the afternoon, along/within which the initial round of convection developed and evolved. Instability remained high to the north ahead of the pressing cold front, with the second round of convection developing along the northwest CAPE gradient (cold front) as analyzed in the satellite product.
This blog post from CIMSS highlights the value of NUCAPS products from this event.
Bill Line (NESDIS and CIRA) and Kaitlin Rutt (NWS AMA)