A severe thunderstorm developed quickly in the Pueblo, CO area during the early evening of 10 August 2019. GOES-16 imagery and lightning data provided clues to a rapidly intensifying thunderstorm with the potential to be strong to severe. While the environment was not all that supportive of large hail, steep low-level lapse rates and anomalously high Total Precipitable Water (TPW) values (~130% of normal) indicated the potential for strong downdraft wind gusts and heavy rainfall. Indeed, there were reports of heavy rain with this storm, as well as a 76 mph wind gust recorded at KPUB Pueblo ASOS (Fig 1). One-minute satellite imagery was available to forecasters during this event.

Analyzing 1-min visible and IR imagery from GOES-East over a 99-min period, we see several areas of cu initiate in the moist environment just west of Pueblo before organizing into into a single strong updraft (Fig 2 and 3). The updraft quickly reaches the tropopause and spreads out radially. An overshooting top is first apparent around 0000Z, while an above anvil cirrus plume starts to become noticeable after 0015Z.

The sandwich RGB combines the VIS and IR into a single image (Fig 4) into a single high-resolution qualitative product.

Looking at semi-transparent GLM Flash Extent Density (5-min accumulation updating every 1-min) gridded product overlaid on the VIS, we diagnose a rapid increase in total lightning between 2335Z and 2344Z (7 fl/5-min to 31 fl/5-min), or a lightning jump (Fig 5). This jump is an indicator of a strengthening updraft and often a precursor to hazardous weather at the surface. Cloud tops cooled from -45C to -64C during the same 9-min period. Lightning activity remained relatively stable through around 0000Z, while cloud tops continued to cool. Between 2345Z and 0000Z (after the lightning jump and during the continued cloud top cooling), very heavy rainfall (at least ~0.5 inches in 15 min) and gusty winds (estimated around 50 mph) were reported with this storm, in addition to improved presentation in radar imagery.

A second lightning jump occurred between 0002Z and 00009Z when FED increased from 23 fl/5-min to 56 fl/5-min). Cloud top temperatures bottomed out at around -76C at this time as well. During this lightning jump, very strong winds associated with the storm were measured at the surface, including the first severe wind gust of 59 mph at 0008 UTC, the first significant severe gust of 75 mph at 00010 UTC, and maxing out at 76 mph at 0016 UTC. The storm advanced into primarily rural areas thereafter, with lightning activity slowly dropping off, and cloud tops warming. See graph of IR and GLM trends for this storm in Figure 6, made using the AWIPS Tracking Meteogram Tool.

Bill Line, NWS