Landspout tornados and severe thunderstorms impacted southeast Colorado and southwest Kansas during the afternoon of 21 May 2020 (spc reports). GOES-East satellite imagery was used by NWS PUB forecasters to analyze the cumulus cloud field leading up to convective initiation, and gauge convective evolution as storms matured.

Analyzing 1-min visible imagery during the two hours between 1859 and 2059 UTC, the cu field across southeast Colorado from just north of Holly to Campo became increasingly agitated, with the greatest clumping and vertical growth occurring between Lamar and Holly (Fig 1). These cumulus cloud trends were signs of imminent convective initiation. Additionally, forecasters diagnosed significant low-level cyclonic vorticty given the evolution and character of the broad cu field in the imagery across southeast Colorado into southwest Kansas. Finally, the movement of cu clouds to the west with towering cu tops and orphan anvils drifting to the east highlighted the presence of substantial low-mid-level shear.

The insight gleaned from satellite imagery along with additional knowledge about the environment gave forecasters confidence that a landspout tornado threat existed with any storm that might develop in the area, in addition to the large hail threat. The trends in satellite imagery also helped forecasters to message this risk to core partners and the public. Two tweets were sent during this period, highlighting the threat for strong to severe thunderstorms (Fig 2), and landspout tornados (Fig 3).

We'll give this visible satellite view a 9/10. Also… it shows low level cyclonic rotation in the congested cumulus fields. A few strong to severe storms are possible over the southeastern plains over the next few hours. #COwx #Colorado pic.twitter.com/sp2q7DwhX3

— NWS Pueblo (@NWSPueblo) May 21, 2020

There is a landspout risk over the southeastern plains over the next few hours. These are very hard to see with radar, so if you see any spin-ups, report it to us! We'll monitor using the #pubspotter hashtag. #COwx #Colorado

— NWS Pueblo (@NWSPueblo) May 21, 2020

Visible imagery during the following two hours (2059 – 2258 UTC) showed continued upscale growth of cumulus clouds across the region, including convective initiation and eventual development of strong-severe thunderstorms (Fig 4). Multiple instances of landspout tornados were confirmed during this period near the CO/KS border in association with the growing cumulus clouds.

In addition to the landspout threat, forecasters were motioning the development of severe thunderstorms. As convection continued to grow upscale and mature from Springfield to north of Holly/Lamar, forecasters paid close attention to IR-Window imagery (Fig 5). The IR imagery showed where the most rapid convective initiation was occurring, and was used to help forecasters determine which cell(s) would become most dominant. The most impressive and persistent cold cloud top temperatures and overshooting top developed within the broader region of convection with a storm between Lamar and Holly. This storm also quickly produced an above anvil cirrus plume, indicating a particularly strong updraft and severe potential. Severe thunderstorm and tornado warnings were issued with this region of development, which produced confirmed tornados and baseball sized hail.

Combining the VIS and IR into a sandwich image combo reveals the development of a dominant cell quite well with this case through the blending of texture and brightness temperature information (Fig 6). Details of the overshooting top and above anvil cirrus plume become obvious.

Viewing an animation covering the full duration of this event, the evolution of the cu field in the context of RAP analyzed sfc vorticty and 0-3 km MLCAPE (good fields for assessing landspout potential) is observed (Fig 7). The large values of sfc vorticty from the model generally agree with what is implied from the satellite imagery. Values of 0-3 km MLCAPE increased over and east of Campo during the afternoon. The region of overlap between the two fields near the CO/KS border is where landspout tornados were observed.

Bill Line (NESDIS and CIRA) and Klint Skelly (NWS PUB)

Very dry and breezy conditions developed across southeast Colorado during the afternoon of 20 May 2020 ahead of a broad western US upper trough and behind a surface dryline. With deep vertical mixing occurring behind the dryline, RH values fell to around 10 %, and winds gusted 30-40 knots. A wildland grass fire initiated north of Kim, CO during the early afternoon.

A GOES-East 1-min meso sector was available over a region including the wildfire during the day in support of convective warning operations (Fig 1). A watchful eye would notice the flickering of a faint hot spot below thin cirrus clouds by around 1945 UTC. With 5x more images , a forecaster can be more confident in wildfire detection earlier when using 1-min imagery over 5-min imagery. A simple gray-scale color table applied to ABI single-band 3.9 um imagery has proven to be a very reliable method for detecting wildfire starts, especially when 1-min imagery is available.

Later, as the fire continued to grow, an impressive smoke plume developed. The 1-min visible imagery shows the rapid growth of the plume, and even development of pyrocumulus adjacent to a colder cloud shield. IRW brightness temperatures associated with the pyrocu reached -20C shortly after 0100 UTC.

A long animation of the wildfire combines visible, SWIR and IRW imagery along with RAP surface analysis RH and wind gust fields for the duration of the event. The animation shows the fire initiating as wind gust speeds increase over 30 knots and RH values drop below 15%. The fire continues to burn hot well after sunset, before decreasing in intensity as wind speeds died down and RH values rose.

A 4-panel image of the wildfire and smoke plume during the early evening provides a variety of unique RGB displays for tracking the hot spot and associated smoke plume in unison. At this time, the hot spot was quite expansive, and pyrocumulus developing within the smoke plume.

S-NPP and NOAA-20 VIIRS imagery also captured the wildfire during it’s early stages, and during the evening. The same gray scale color table is used for each VIIRS/ABI image pair.

The 375 m I-4 band (3.74 um) imagery captured the wildfire earlier than was possible in the 2-km ABI imagery, and pinpointed it to a smaller region (a single dark pixel at 1915 UTC; Fig 5). At 2000 UTC, the fire had spread to a few pixels, but was still quite faint in the ABI imagery. However, as was shown, the animations of 1-min ABI imagery (not possible with VIIRS) allowed for confident detection of a hot spot by this point. By 2051 UTC, the wildfire hot spot was obvious in both VIIRS and ABI, but with VIIRS narrowing down the location to a much smaller area.

During the evening, both instruments continue to detect heat associated with the wildfire/burned area, with VIIRS pinpointing the burn region more precisely (Fig 6).

Bill Line (NESDIS and CIRA) and Mike Umscheid (NWS DDC)

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)

Strong winds on the western portion of a deep surface low in association with an exiting shortwave trough resulted in lofted/blowing dust from the IA/NE/MO/KS Missouri River Valley (MRV) southeast across central Missouri. This is a favorable region for winds to go unimpeded, and the lofted dust is likely due in part to sedimentation/silt left behind from the big spring flooding of 2019. Further, it is still early in the planting season, so fields are susceptible to having dirt erosion. Local media shared photos of blowing dust across I-29, which runs along the eastern side of the MRV (Fig 1).

Blowing dust may be an issue on some highways this afternoon! Gusts to 55mph kicking up dirt from fields and creating limited visibility. This is from I-29 near mile marker 24 in Iowa. @NWSOmaha @WOWT6News pic.twitter.com/g0UMYY4qmQ

— David Koeller (@dkoellerwx) May 5, 2020

The Omaha NWS office noted the blowing dust on social media in the nighttime microphysics RGB (Fig 2). This RGB is effective in detecting lofted dust due primarily to the inclusion of the 12.3-10.3 um split window difference (SWD), which has been shown to be an effective ABI channel combination for dust detection (see previous blog post).

See the light pink streak just right of center? That's some blowing dust causing issues along I-29 where Iowa, Nebraska and Kansas meet.

Darker pink represents actual clouds. #IAwx #NEwx #MOwx pic.twitter.com/4d6XWB2TQJ

— NWS Omaha (@NWSOmaha) May 5, 2020

Given the conditions, the NWS in Omaha issued a Special Weather Statement for “reduced visibility due to blowing dust” along I-29, and the NWS in Pleasant Hill mentioned, “reductions in visibility as a result of the blowing dust” in their Wind Advisory.

The SWD-IR combo procedure perhaps provides the best depiction from ABI of the blowing dust across the region for the duration of the event (Fig 3). The blowing dust appears as very dark gray to black (very low positive or negative difference values), while most clouds will appear as colors with the inclusion of cold brightness temperatures from the IR window channel. Small cumulus clouds will be lighter gray) The lofted dust is diagnosed to initiate near northwest Missouri in the presence of a tight surface pressure gradient and 40+ knot wind gusts. The lofted dust is carried southeast over I-29 and into central Missouri as it wraps around the southwest and southern portion of the surface low. The animation, lasting 10 hours, depicts the long duration of this event.

The blowing dust can also be diagnosed in the 500 m 0.64 um VIS channel. The color table used is modified to highlight lofted material (Fig 4). The blowing dust becomes most apparent near sunset, when forward scattering of dust particles toward the satellite is heightened.

Finally, a modified Dust RGB provides a great depiction of the blowing dust, while capturing cloud details as well (Fig 5). In this example, the dust appears as deep magenta, low/cumulus clouds dark blue, stratus or mid-level clouds as red, and cirrus clouds as black. The RGB recipe is shown in Fig 6.

SNPP and NOAA-20 consecutive overpasses provided higher resolution (750 m vs 2 km for GOES) VIIRS M-band SWD imagery near the beginning of the event, allowing for slightly more details (spatially) to be gleaned from the lofted dust. (Fig 7).

Bill Line (NESDIS and CIRA) and Andrew Ansorge (NWS DMX)