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.
A potent jet streak overhead resulted in strong/gusty winds across the high plains on 5 April 2022. The wind combined with dry conditions, resulted in a broad area of elevated to critical fire weather conditions. Further, a shortwave trough rounding the base of a broader upper low to the north sent a cold front south through the high plains, resulting in dramatic wind shifts along it’s path. NWS Dodge City, KS summarized the situation well leveraging GOES water vapor imagery (Fig 1): “Water vapor imagery shows a strong upper level jet moving into the Pacific Northwest and northern Rockies overnight with an upper low starting to close off along the border of Montana and Canada. This low will move out across the Dakotas into Minnesota today into tonight. A cold front will move south across western Kansas today…”
A large wildfire developed in the Oklahoma Panhandle early in the day within gusty westerly winds, but abruptly spread south with the passage of a cold front. An AWIPS procedure captured all aspects of this situation, and is shown in Figure 2. Using the Geocolor as the base layer, we overlay the 10.3 um channel with 10% transparency and a white/cold to black/warm grayscale colormap centered on the brightness temperature range of the pre and post frontal clear sky, and 3.9 um shortwave IR brightness temperature >45 C to capture hot spots. The first part of the animation captures the wildfire hot spot and smoke plume as the cold front approaches. Once the cold front and associated wind shift push through the fire, the hot spot quickly begins to move south, along with the low-level portion of the smoke plume. The shallow nature of the cold airmass is apparent in the smoke plume behavior, with only the low-level portion nearest the fire falling within northerly flow, while further aloft, the plume continues to drift east within the westerly flow.
The location of the wildfire fell within three consecutive VIIRS passes around the time of the frontal passage, allowing for a detailed (spatially) view of the fire and wind shift. The VIIRS Natural Fire Color RGB with a similarly semi-transparent VIIRS LWIR channel overlay is shown in Fig 3.
While surface obs provide the ideal source of quantitative information regarding wind shifts, satellite imagery (especially 1-min as in Fig 2) can be leveraged to analyze frontal movement and associated wind shift with more spatial and temporal detail. In cases of wind shifts at a wildfire, such real-time information is extremely important in the protection of life and property, both for the local public and for emergency personnel working the fire (see example from one year ago here).
For this event, NWS Amarillo, TX (AMA) leveraged GOES Imagery and products in order to illustrate the dramatic fire growth associated with the frontal passage on social media (see post below). NWS/AMA also utilized satellite imagery for their Decision Support Services (DSS) phone briefings supporting the Beaver County fire and other fires in the area. Specifically, the GOES 1-min satellite imagery allowed forecasters to track the front in detail and communicate to emergency personnel the precise timing of the impending change in wind direction at each fire. The Beaver County EM confirmed that they moved personnel based on the NWS briefings of the frontal passage timing, which they got directly from watching the 3.9 um satellite imagery. In particular, forecasters noted their use of the 1-min 3.9 um band (which captured the frontal position and hot spots well) with the Fire/Hot Spot derived product (Fire Temperature) as an overlay (See Figure 4 for grayscale version and wide view of area).
Thunderstorms and their associated severe winds have a long history of impacting aircraft. Many tragic incidents demonstrate how avoiding the turbulent updrafts and downdrafts within thunderstorms is paramount to protect the aircraft and ensure the safety of the passengers and crew. Convective activity can significantly alter flight paths for both commercial and general aviation. Airlines incur costs in the tens of millions of dollars each year in extra fuel, diversions, and labor costs to manage thunderstorm-related impacts and delays. This case study uses GOES-R series satellite imagery to examine severe weather and its relationship with the resultant flight paths of nearby aircraft.
In mid-May 2019, a strong upper-level trough was present over the western United States, advecting positive potential vorticity over the Central High Plains and the upper Great Plains (Fig. 1). Upper-level support for ascent was combined with low-level support in the form of a developing leeside surface cyclone advancing northeastward across northeast Colorado and into northwest Kansas and southwest Nebraska. A mesoscale dry line front developed along the downslope terrain of eastern Colorado and western Kansas, providing strong localized support for convective initiation coupled with thermodynamic atmospheric parameters supportive of further convective development. This eventually resulted in thunderstorms and severe weather in the form of tornadoes, large hail, and damaging winds.
The National Centers for Environmental Prediction (NCEP) Central Operations stewards a meteorological observational archived database called the Meteorological Assimilation Data Ingest System, or MADIS. MADIS incorporates data from a wide variety of sources, including international, federal, state, and local agencies, universities, volunteer networks, and the private sector. Part of this private sector data included within MADIS is the location, time, heading, and altitude for registered aircraft within US airspace reporting via the Aircraft Communications Addressing and Reporting System (ACARS). Aircraft data from MADIS is encrypted such that flights specifics (i.e., tail number, aircraft operator, etc.) are not seen by the user, but the archived locations and headings of registered aircraft are available. While this dataset takes considerable care to develop into a GIS-friendly product, it can be a powerful tool to demonstrate the impacts weather has on aviation.
For this severe weather event, convective initiation was a core component of the forecast. Thunderstorms were expected to mature quickly as insipient updrafts were able to break through a relatively strong capping temperature inversion. The Geostationary Lightning Mapper (GLM) supplies valuable satellite confirmation of convective initiation by quickly highlighting the initial flashes and their spatial extent with gridded imagery. The GLM lightning observations pair well with GOES-16 ABI imagery, including the Day Cloud Phase Distinction RGB, which can highlight the development of ice and charge separation within clouds. Please note, the Day Microphysics RGB, which has notably different ingredients and recipe from the more familiar NWS AWIPS Day Cloud Phase Distinction RGB, but shares a similar purpose, is shown in this blog post. In this RGB and relevant to our discussion in this case, convective initiation can be diagnosed as cumulus clouds grow and transition from shades of tan/pale yellow to deeper red/orange.
From NWS Goodland at 1919 UTC: “GOES-16 Day-Cloud Phase Distinction imagery indicating a few failed attempts at thunderstorm initiation along dry line and with mesoscale data supporting ML inhibition between 50 in the south to 150 j/kg in the north. Will likely take another hour of insolation to further weaken capping, which will coincide with approaching pv anomaly from the west. Expect strong storms to fire between 2 and 3 pm MDT. Relatively high LCL’s and weak 0-1km shear support initial threats being very large hail greater than 2 inch and diameter. Tornado threat is somewhat low, but should increase as storms move east and north towards triple point near NE border and as LLJ increases around 6 PM.”
Overlaying the ACARS flight data with the GOES-16 Day Microphysics RGB during the early afternoon hours before initiation along the dry line near the Colorado/Kansas border shows a busy corridor of aviation traffic arriving at and departing from Denver International Airport (DEN) as well as many other busy regional airports in the area (Fig. 2). It is also apparent how planes are instructed to fly along arranged routes from point to point, and how those routes can be adjusted on the fly by weather. A considerable amount of traffic traveling across the domain appears to have taken off from and is destined for airports which are not displayed here. [The destinations and origins of the aircraft are not specified in this dataset available to the public.]
The failed attempts at convective initiation in the early afternoon as noted by NWS Goodland can be seen on the RGB imagery, and it finally gave way to thunderstorm activity around 2020 UTC. Just before the first lightning strikes are observed by the GLM, a distinct, robust turret confirming the presence of a building updraft can be seen in the RGB imagery just southwest of the GLD airport (Fig. 2). At the same time, more widespread red pixels, associated with an increasing amount of ice present at the top of the cloud, are shown in the RGB imagery just before lightning was first observed with this particular storm by the GLM.
After convection began in earnest along the dry line, it is clear that the rapidly developing weather conditions were having a significant impact on aviation by affecting the flight paths of hundreds of aircraft in this area. However, when looking at Channel-13 Longwave Infrared ABI imagery alone (Fig. 3), it is difficult to ascertain distinct trends in the flight paths of aircraft when compared to brightness temperatures at the top of the cloud. The gridded products from the GLM provide insights into the spatial extent of lightning with satellite-based lightning observations with 1-minute updates over much of the full disk of both GOES-East and GOES-West. The spatial extent of lightning can be investigated with the Flash Extent Density GLM gridded imagery through supercell development as in Figure 4.
The GLM provides unique observations of the spatial extent of lightning, and in this context demonstrates how aircraft are diverting around ongoing lightning flashes within thunderstorms as they are occurring. The convective cores of the thunderstorms can generally be identified by the more numerous flashes occurring within or near the updraft. Greater flash counts manifest as warmer colors in Flash Extent Density imagery, and vice versa. Due to the relatively low flash rates in this event, the standard color scale for Flash Extent Density may not always highlight convective cores.
Another GLM product which may provide additional value in identifying the location of rapidly evolving convective updrafts is Minimum Flash Area, which reports the area in square kilometers of the smallest lightning flash observed by the GLM within each pixel in the specified time window. In addition to being more numerous, flashes which are more associated with strengthening or mature updrafts are typically smaller in spatial extent. This occurs because of the large amount of charge separation taking place over a spatially small area within the vertically oriented updraft. Thus, Minimum Flash Area highlights these updrafts, with warmer colors indicating smaller minimum flash sizes, and vice versa. Minimum Flash Area alone can provide a significant amount of context for immediate impacts on not only aviation but also severe weather warnings and reports (Fig. 5).
Aircraft take a circuitous route on this day to avoid thunderstorm activity, if possible. Flash Extent Density alone may not necessarily give the full perspective on which lightning strikes pilots and air traffic control may be actively avoiding. Minimum Flash Area imagery provides additional context on which flashes are more likely associated with core convective updrafts and which are more likely associated with the anvil/stratiform regions by classifying flashes by the size of their spatial extent. In this imagery and in other cases, airplanes tend to more acutely avoid the more numerous, smaller flashes within the turbulent updrafts, and less so avoid the less frequent, larger, anvil/stratiform region flashes.
Incorporating the GLM gridded products of lightning observations into aviation forecasting operations can be a vital tool for meteorologists when spotting convective initiation and turbulent updrafts by classifying lightning flashes by their spatial extent. This additional information about convective activity can more precisely guide aviators through natural hazards such as thunderstorms, snow squalls, and other atmospheric phenomena.
One key advantage of the Nighttime Microphysics RGB is its ability to depict low-level cloud layers at night. These are marked by elevated red and green contributions within the RGB recipe, however a case from 6 April 2022 shows that not all low-level clouds look the same. Overnight a cold front was advancing southeastward through the central United States. Behind the cold front (Oklahoma, Kansas, Missouri, and Arkansas) we see that the stratus clouds are colored green-yellow, however, the stratus clouds ahead of the cold front (Texas, Louisiana, Mississippi, and Alabama) are light blue. The question is why?
While stratus clouds often have strong contributions from the red and green bands (indicating thick, water clouds), the relative bluecontribution from the Channel 13 Clean-IR Brightness Temperature (10.3 um) can highlight the relative temperature differences of stratus clouds. See the abbreviated RGB recipe for the Nighttime Microphysics RGB below.
To see this effect for yourself, you can compare the Nighttime Microphysics RGB to the Clean-IR Brightness Temperature imagery using the slider tool below. Note the position of the cold front (via the surface observations), where the colors of the stratus clouds change in the Nighttime Microphysics RGB, and the higher/lower Clean-IR Brightness Temperatures ahead/behind the cold front.