Supercells were expected to initiate along a dryline in west-central Oklahoma during Saturday evening on April 23rd. The Storm Prediction Center had issued a slight risk of severe storms in their 1630 Z (1:30 PM CDT) outlook, with the risk tornadoes (5%), damaging hail (15%), and damaging wind (15%). Thunderstorms initiated around 2200 Z (5:00 PM CDT) as shown from the Day Cloud Phase Distinction RGB animation below. As the sun began to set near the end of the animation, decreasing contributions from the green (Channel 2, visible) and blue (Channel 5, near-IR) bands created a shift to more red colors in the imagery (Channel 13, clean-IR).
As convection matured into supercells after sundown, satellite imagery became confined to the infrared bands (Channels 7-16), with Clean-IR imagery most often used. Additionally, rapidly updating (1 minute) lightning data from the GLM Flash Extent Density product can provide information about thunderstorm trends between NEXRAD full-volume scans (4-5 minute updates). At night, the GOES-16 GLM detection efficiency often exceeds 90% across the south-central United States.
Intensification of two supercells and tightening of their low level mesocyclones, southwest of Oklahoma City and southwest of Stillwater, as indicated by radar prompted the NWS Norman office to issue tornado warnings for both storms. The Tornado Warning for the Stillwater supercell was issued at 2359 Z (6:59 PM CDT), and the Tornado Warning for the Oklahoma City supercell was issued at 0003 Z (7:03 PM CDT).
The animation above is from 2330 Z to 0030 Z (5 minute intervals), and shows how both storms intensified from the perspective of the GLM FED and ABI Clean-IR products. Deep overshooting tops were observed from the ABI along with notable increases in GLM flash rates. In this scenario satellite information may have provided a ‘heads-up’ on which storms to monitor, along with additional confirmation of trends observed from NEXRAD.
One-minute data was observed from the GOES-East Mesoscale Domain for both products (below). In this scenario NWS Norman also had access to the Terminal Doppler Weather Radar at the Oklahoma City Airport (TOKC), providing 1-minute radar reflectivity and doppler velocity data within the vicinity of the airport. For the supercell near Oklahoma City, this may make a forecaster less reliant on one-minute satellite data when making warning decisions. However, for the storm southwest of Stillwater no TDWR data was available. The rapid increase in lightning flash rates identified by the GLM FED product for this storm can provide additional verification for an NWS forecaster that the updraft was intensifying, and tightening of the low level mesocyclone prior to tornadogenesis may be imminent.
During the early morning hours of April 22nd, fog began to form across southern Ohio, West Virginia, and Pennsylvania. In anticipation of the fog, the NWS Weather Forecast Office in Wilmington OH issued a Dense Fog Advisory for a portion of their forecast area.
Latest guidance increases confidence in development of areas of dense fog late tonight. Based on this, have hoisted Dense Fog Advisory south of Interstate 71.
Confirmation of the dense fog can be observed via satellite from the Nighttime Microphysics RGB starting around 0500 Z (1:00 AM EDT), with greater contributions from the Green Band (10.3 um – 3.9 um band difference) and minor contributions from the Blue Band (10.3 um band). The stationary, more faint, and highly localized appearance of the fog stands in contrast to the low level clouds in southwest Pennsylvania and central West Virginia, which often have a similar color due to similarities in their composition. Additionally the movement of cirrus and stratocumulus clouds into the area, from precipitation over Indiana, did obscure the extent of the fog in western Ohio by 1000 Z (6:00 AM EDT). This is one limitation of the product, as skies have to be fairly clear in order to properly identify fog.
Based on surface observations and imagery from the Nighttime Microphysics RGB, it was apparent by 0830 Z (4:30 AM EDT) that the dense fog was expanding north of Interstate 71. This confirms NWS Wilmington expanding the Dense Fog Advisory north into the Cincinnati and Dayton metro areas, prior to the increase of traffic during the morning rush. In this case the combination of surface observations and the Nighttime Microphysics RGB can provide confirmation of developing fog and its spread overnight for the Dense Fog Advisory. Using satellite RGBs in tandem with other observations can help maximize situational awareness, especially when satellite data cannot be relied on exclusively as shown in this example.
The fog is becoming dense in many locations across northern KY, southern Ohio, and southeast Indiana. Have expanded the dense fog advisory north to about I-70.
During the late evening hours on April 12th, 2022, convection initiated along a retreating dryline and advancing cold front in southern Nebraska and central Kansas. Initiation across the line can be observed from the Clean-IR band (Ch 13) from GOES-16 and the NEXRAD mosaic below. The near-uniform initiation of these thunderstorms along the dryline provided a unique example of how GOES imagery can be combined with radar data to monitor rapid thunderstorm development and dissipation.
Additionally, the initiation and subsequent outflow boundary along the leading edge of the front produced an undular bore, which traveled across central Oklahoma from 0600 Z to 1000 Z and initiated convection just after 1030 Z. Tracking the bore/front in this scenario could have been done by the Clean-IR band or radar (as seen below). However, the Nighttime Microphysics RGB can provide additional information not observed from a single ABI band or from radar.
Strong contributions from the Green band (Ch 13 – Ch 7) and moderate contributions from the Red band (Ch 15 – Ch 13) in the RGB recipe make the green-yellow clouds formed along the bore stand out from the magenta surface. Early signs of initiation along from the front can also be observed from strong contributions by both the Red and Green band, with low contributions from the Blue band (Ch 13), and the development of stratus clouds in central and eastern Oklahoma indicate an environment with greater low level moisture. In this scenario, the Nighttime Microphysics can provide an early ‘heads up’ that CI may be coming soon as the front moves into a more favorable environment for severe weather in southeast Oklahoma, southwest Arkansas, and northeast Texas. This coincides with the SPC Mesoscale Discussion issued just after 1200 Z.
An active weather pattern involving a persistent mid-level jet over US high plains resulting in several days of widespread hazardous blowing dust. As has been captured previously on this blog, NWS offices leverage satellite imagery to detect and track blowing dust, specifically for diagnosing the spatial extent of blowing dust, which is important for the issuance of advisories and warnings, and for including blowing dust in forecast grids. Further, satellite imagery is used to communicate the threat to the public via social media, as well as to partners in decision support service briefings. NWS Area Forecast Discussions provide some insight into how blowing dust appearance in satellite imagery influences forecaster thinking and decision making. This blog post captures some of these applications from 06-07 April 2022.
GOES-East water vapor imagery from 6-7 April capture a very broad upper low meandering over the upper mid-west (Fig 1). It’s western periphery over the high plains resulted in considerable northwesterly upper flow across the region, along with the embedded periodic and subtle shortwaves.
Gusty winds developed early in the day on the 6th, resulting in morning blowing dust and associated considerations by impacted NWS offices:
From NWS Cheyenne, WY at 1609 UTC: Only minor forecast change is related to blowing dust. Latest satellite observations has indicated a few isolated patches of blowing dust in the southern Nebraska Panhandle near Sidney. Nearby locations across central NE and eastern CO have reported areas of blowing dust. Updated the forecast to include patchy blowing dust through the afternoon which could locally reduce visibility at times.
From NWS Goodland, KS at 1600 UTC: Widespread dust developing across the area now. A couple distinct larger areas are showing themselves on satellite… For the moment, issued a blowing dust advisory for the locations of the bigger plumes. However, it’s quite possible that warnings will be needed soon as we’re starting to get a few reports of near zero visibility. And then 1624 UTC: Went ahead with blowing dust warning across SW Nebraska and a large portion of NW Kansas. Started getting several reports of zero visibility and decided an upgrade to a warning was necessary. Expanded the advisory to include Graham and Norton counties as dust being observed both at Norton AWOS (7 miles) and satellite.
From Dodge City, KS at 1650 UTC: Up to 50-60 mph likely for much of the CWA during peak heating of the afternoon with temperatures in the upper 50s to near 60 degrees. Blowing dust during this time will be an issue as already seen on satellite for western counties in the driest ground conditions.
From NWS Pueblo, CO at 1655 UTC: Blowing Dust Satellite products are showing blowing dust occurring over the far eastern plains, so a blowing dust advisory has been issued until late afternoon for the far eastern counties.
From NWS Boulder, CO at 1710 UTC: The second change was to add in additional blowing dust into the far northeastern corner of the state. Webcams and surface observations have indicated some areas of reduced visibility due to blowing dust. CIRA’s DEBRA dust product also shows blowing dust has increased quite a bit over the past couple of hours. Have joined our neighbors to the east with a Blowing Dust Advisory for Sedgwick and Phillips counties where dust could impact travel.
As for DSS and social media, NWS Goodland analyzed GOES-East DEBRA Dust imagery in a morning web briefing posted to social media. NWS Dodge City highlighted problem areas in GOES-East Dust RGB imagery in early day social media posts.
NWS offices were confirmed to have used the CIRA DEBRA Dust product (available on CIRA Slider and in some NWS office AWIPS), as well as the AWIPS Dust RGB, shown in Figures 2 and 3, respectively.
One can also easily diagnose the blowing dust in the simple Split Window Difference with grayscale colormap, as regions of relative dark gray to black (Fig 4). The Split Window Difference is a key ingredient to satellite-based blowing dust detection products.
Geocolor imagery with blowing dust highlighted by the SWD is shown in Fig 5, which also overlays wildfires via the Fire/Hot Spot product. Finally, an experimental Blowing Dust RGB highlights lofted dust as dull to bright yellow (Fig 6).
On the 7th, with the same pattern in place, blowing dust developed across much of the same area, again early in the day. One-minute satellite imagery was available to forecasters to help analyze early development of blowing dust
From NWS Goodland, KS at 1513 UTC: Satellite is already indicating dust plumes developing across portions of the area. The first area is between Sterling, CO, Akron, CO, and Wray, CO with 4 mile visibility already being reported in Yuma, CO. The other area of dust is south of Burlington, CO extending southeast towards Tribune, KS. Decided it was necessary to extend the blowing dust advisory across the rest of the forecast area as a result of the dust plumes viewable on satellite as well as observations. Will be monitoring for and looking for reports of near zero visibility and that will determine if Blowing Dust Warnings are needed once again. And at 1724 UTC: Received a couple reports of near zero visibility, and along with the impressive dust plume observed on satellite imagery, was pushed over the edge to issue the blowing dust warning for eastern Colorado (Yuma, Kit Carson, and Cheyenne Counties) and extreme northwestern Kansas (Cheyenne, Sherman, Wallace, and Greeley counties). This is currently the most impressive signal we’ve seen so far.
From NWS Boulder, CO at 1520 UTC: Blowing dust will be an additional hazard through the afternoon, and current satellite imagery depicts a few dust plumes beginning to surface over Washington County. May consider Blowing Dust Advisories down the line depending on how widespread/persistent the blowing dust looks to be.
A blowing dust advisory was eventually issued for Washington County.
From NWS Hastings, NE at 1544 UTC: The Blowing Dust Advisory has been extended to include more of the forecast area today. This is due in part to expected potential strong winds and suggestions of dust showing up on satellite imagery.
From NWS Pueblo, CO at 1726 UTC: Updated to issue a Dust Advisory for the far Eastern Plains through this afternoon. Satellite imagery indicates widespread blowing dust moving into the far Eastern Plains.
On social media, NWS offices communicated the blowing dust threat with satellite imagery, including these posts from Goodland, Hastings, Pueblo, and Boulder. Various NWS personnel have commented that DEBRA Dust is a preferred product for public-sharing (blowing dust information) given it’s easy-to-understand nature.
DEBRA Dust imagery for the full day again captured the lofted dust quite well (Fig 7).
Focusing on 1-min imagery over E CO and W KS during the morning, we can analyze the period of blowing dust initiation in detail. The grayscale Split Window Difference can sometimes be difficult to interpret on such fine scales (Fig 8).
Geocolor (and other reflectance imagery) from GOES-East will not highlight lofted dust and other aerosols too well from GOES-East in the morning due to lack of forward scattering (Fig 9). Enhancing the imagery with Split Window Difference helps (Fig 10).
During this time of day from GOES-East, and especially when clouds are present, IR-based products might be best for blowing dust detection, such as with the experimental blowing dust RGB (Fig 11) or traditional Dust RGB.
Viewing the 10-min GOES-West Geocolor, we see how forward scattering helps produce the dust signal in reflectance-based imagery.