GOES-16 1-min satellite imagery was available over the southern High Plains for monitoring of severe convection on 30 May 2018. One storm in particular displayed rapid intensification, as displayed in Figure 1 below. Using a 1-min updating sandwich image combo, rapid cooling and overshooting top development is easily diagnosed with the southernmost storm. The overlaid tracking meteogram trend graph is another way to show the rapid cooling/strengthening that occurred. The storm top cooled roughly 13C in 20 minutes! Severe wind damage and 2″ diameter hail were reported with this storm about 10 minutes after it was at its coolest.
Figure 1: 30 May 2018 GOES-16 1-min VIS/IR Sandwich combo. Overlay: Tracking Meteogram graph of minimum 10.3 um brightness temperature during period of animation. Severe reports are also overlaid. The northernmost wind report is associated with a different storm, while the southern wind and hail reports are associated with the storm of interest. Full res
Bill Line, NWS
Severe thunderstorms developed across the high plains during the afternoon on 28 May 2018, Memorial Day. In this post we focus on convection over the southern High Plains. In addition to storms developing off of the high terrain of Colorado and advancing east to the adjacent plains, convection also fired along a dryline over KS/OK/TX/NM. Using the 10.3 – 12.3 split window difference from GOES-16, forecasters could locate and track (in 5-min intervals) the precise position of the moisture gradient as early as the morning hours, prior to even the first cu development. This difference has been discussed in previous posts. With this straightforward linear grayscale color map, darker grays represent relatively drier air at the low levels, while lighter grays indicate increased low-level moisture. The key with the split window difference is to identify the gradients in the field. As an overlay on the difference is the 10.3 um IR window channel with warm brightness temperatures transparent, so only the cold cloud tops are highlighted. In this event, the aforementioned dryline is clearly evident in the difference imagery, along which convection develops. A relatively dry slot is diagnosed pushing north into southeast Colorado, west and north of which the airmass is moist again. Severe thunderstorms developed off the high terrain and into this moist region as well.
Figure 1: 28 May 2018 GOES-16 5-min Split Window Difference (Gray scale) with 10.3 um IR overlay (color scale; warm temperatures made transparent). Full res
Bill Line, NWS
An abundance of strong thunderstorms developed across portions of the US High Plains on 18 May 2018, producing severe criteria hail, winds, and a few tornados. 1-min satellite imagery from GOES-16 was available over the region for this event per a request by the Storm Prediction Center. Notable during this event was the abundance of satellite cloud top signatures apparent with the storms during the early evening. The VIS+IR Sandwich image combo highlights these features quite well. This image combo is created using the 0.64 um VIS as an underlay, and 10.3 um IR as an overlay. The 0.5 km VIS captures the detail in the imagery, while the IR captures the quantitative brightness temperature information. The IR overlay is fully transparent below a certain threshold to allow for detailed analysis of cumulus clouds pre-CI using the VIS alone. The coldest brightness temperatures, which are associated with the cloud tops, are made semi-transparent (40%). Cloud top features apparent in this animation are overshooting tops (cooler temperature, increased texture, shadow), above anvil cirrus plumes (warm anomoly downstream of overshooting top, relatively smooth), and gravity waves (ripples) emanating from the updrafts. The rapid anvil expansion with these storms is also indicative of strong updrafts. The persistence of these features indicates long-lived strong updrafts.
Figure 1: 18 May 2018 GOES-16 1-min VIS+IR Sandwich image combo. Full res
Bill Line, NWS
A Supercell thunderstorm brought accumulating hail to east-central Colorado on 14 May, just east of I-25 and north of Castle Rock. The hail on the ground was observed by GOES-16 products. The 0.5 km, 0.64 um VIS revealed the hail swath quite well as the storm advanced east (Fig 1). The Day Cloud Phase Distinction RGB, which utilizes the 0.64 um channel (green) in addition to the 1.6 um NIR channel (blue) and 10.3 um IRW channel (red), made the hail swath even more apparent (Fig 2). The ice is highly reflective in the VIS and lowly reflective in the 1.6 um channel, like the thunderstorm clouds. However, unlike the clouds, the hail swath is warm because it is being sensed at the surface. The result is a hail swath (dark green) that contrasts nicely with the surrounding clouds (yellows, reds).
Figure 1: 14 May 2018 GOES-16 5-min 0.64 um VIS. Hail swath is apparent north of Castle Rock. Full res
Bill Line, NWS