Thunderstorm outflow winds resulted in lofted blowing dust across west-central Nevada during the early evening hours of 25 June 2020. GOES-West Meso-1 was available over the region per a request from SPC for “SPC Elevated Fire Weather Risk in the Southwest and Marginal Severe Risk in WY”. NWS Reno, NV issued a Dust Storm Warning (polygon) at 0129 UTC for the blowing dust plume (Fig 1). They were able to confirm the blowing dust using satellite imagery, radar imagery, sfc obs, and local webcams/video. From an early evening AFD update: “Wind gusts 40-50 mph were widespread behind this outflow with satellite, observations and video showing blowing dust accompanying the outflow.”
The region of blowing dust can be diagnosed accelerating west away from the area of thunderstorms after 0030 UTC through sunset in GOES-West 1-min visible imagery (Fig 2). The Dust Storm Warning Polygon is included in the animation. Although the 0.5 km VIS provides a detailed view of the plume which is characterized by moderate reflectance values and laminar appearance, the signature is not obvious when viewing a broader area, and does not catch the eye.
The plume of blowing dust is similarly apparent in daytime geocolor/true color imagery (Fig 3).
Now viewing GOES-West 1-min SWD imagery, typically reliable for 24/7 lofted dust tracking, the region of blowing dust extending from the thunderstorm complex is even less apparent (Fig 4). The signature is very dark gray using this color table. The stripes/noise apparent in the imagery are associated with the G17 cooling issues.
If we combine multiple IR channels/differences into a single RGB, we have a method that allows the blowing dust to pop while also maintaining cloud classification (Fig 5). Dust appears as a bright cream or white, compared to the background bright blue bare ground, red/orange for cold/thick clouds, dark blue or black for cold thin clouds, and magenta for warm/low clouds. This RGB combines the SWD, IRWD, and IRW channel, and will capture dust day and night. The noise associated with G17 cooling issues are exaggerated in channel combinations. However, important signatures are still able to be diagnosed.
Taking a quick look at 5-min CONUS GOES-East VIS, the dust signature is not readily apparent (Fig 6). Given the viewing angle, much of the blowing dust is hidden by the thunderstorms to the east along with new cumulus cloud development. Forecasters within the western 1/3 of the US must always keep in mind the two GOES satellites available and how viewing angle may affect the appearance/detectability of a given feature in a given situation.
Bill Line, CIRA and NESDIS