A strong upper low digging into the southwest US forced the development of strong southwesterly winds and very dry conditions at the surface out of Mexico into New Mexico and western Texas. Winds gusted over 60 knots across the region, and dew point temperatures fell to below zero degrees F. The gusty southwesterly winds lofted a significant amount of dust out of northern Chihuahua, Mexico which quickly advanced to the northeast into New Mexico and Texas. Additionally, dust was observed emanating from White Sands in southeast New Mexico. The blowing dust resulted in a widespread drop in visibilities to below 1 mile, including reduction to below 1/4 mile at times. Given the conditions, Blowing Dust Advisories and Blowing Dust Warnings were issued by the National Weather Service.
A VIS-SWD Sandwich combo captures the evolution of the dense and wide dust plume quite well during the daytime (Fig 1). The procedure uses a VIS underlay, and semitransparent yellow 10.3 – 12.3 um Split Window Difference overlay for values less than zero. This procedure can easily be created in AWIPS (or delivered upon request) using already available data. Surface observations are included in the animation, showing the exceptional wind gusts, bone dry dew points, and reduced visibilities.
A similar animation uses products derived outside of AWIPS to capture the dust evolution. The CIRA Geocolor product provides a colored image of the scene, while the semi-transparent DEBRA-Dust overlay captures the dust as yellow through a dedicated dust detection algorithm (Fig 2). Both products are available on CIRA Slider, as well as via delivery of additional data to AWIPS.
The Dust continued to advance north and east during the overnight hours, wrapping around the eastern side of the upper low. An animation similar to Fig 1, but transitioning to IR at night, continues to capture the dust plume through the evening hours as yellow (Fig 3). By the next morning at the end of the animation, a faint dust signature is still apparent over the low clouds in Kansas.
The DEBRA-Dust product similarly continues to capture the blowing dust signature through the evening and into the next day (Fig 4).
RGBs utilizing the SWD are valuable tools for tracking lofted dust day/night, in addition to cloud classification and other applications. Additionally, weak dust signals can be captured in carefully crafted RGBs that are missed in products that include strict thresholds. An experimental Dust-Fire RGB highlights dust (day/night) as a relatively bright cyan to bright green (thick dust plume), as well as wildfire hot spots as bright red, high/opaque clouds as darker green, cirrus as dark blue or black, and low clouds as gray (Fig 5).
VIIRS I-band imagery during the early afternoon provided a very high resolution (375 m) view of the dust plume. The higher resolution imagery provides more insight into the blowing dust, allowing forecasters to more easily and more precisely identify the onset of blowing dust, dust plume edges, relatively dense portions of a dust plume, and location of dust origination. Compared in Figure 6 are the 375 m Day Land Cloud RGB from VIIRS (left), and 1 km GOES-East ABI Day Land Cloud RGB (right; at nadir, so lower resolution at this location so far from nadir).
Bill Line, NESDIS and CIRA