A shortwave trough digging southeast across the eastern Rockies and into the high plains sent a cold front south across the region during the overnight hours early on 14 Jan. Evolution of the shortwave and associated cold front can be analyzed in GOES Water vapor imagery from the 13th through the 14th (Fig 1). An overlay of RAP 250 mb wind speed shows the development of a 150+ knot (red contour) jet in relation to the water vapor features. The jet becomes increasingly amplified as it digs south on the backside of the broader trough and as the western US ridge builds. Fast moving high clouds are observed in the location of the jet core, along with a temperature gradient (cold to warm poleward) across the jet. Finally, plentiful gravity waves are apparent, many in association with the high terrain, throughout the animation, representing areas of potential aircraft turbulence.

Winds behind the front increased during the morning of the 14th, resulting in areas of blowing dust. Viewing GOES-East visible and geocolor imagery alone, however, the lofted dust is difficult to discern (Fig 2 and 3).

Bringing in IR based products, split window difference in Fig 4 and Dust-Fire RGB in Fig 5, the lofted dust becomes more apparent across southeast CO and southwest Kansas into the OK/TX panhandles and eastern NM. Note, for the SWD product, the VIS-Square-Root color table was applied with a range of -1 to 12. This allows the lofted dust signature on the low end of the range to pop (dark gray to black), while ensuring high clouds on the upper end of the scale do not become washed out (light gray to white).

The GOES-East DEBRA-Dust product, shown here as a semi-transparent overlay on Geocolor, also captures portions, but not all, of the blowing dust in the area (Fig 6).

Finally, the (10-min) GOES-East Aerosol Detection – Dust derived product, available during the daytime, did a decent job at capturing much of the dust during this period, primarily with medium to low confidence (Fig 6a).

Turning our attention to GOES-West imagery, the lofted dust is significantly more apparent in the reflectance imagery/products; VIS in Fig 7 and Geocolor in Fig 8. The improved detection during the early daytime period by GOES-West vs GOES-East here is due to increased forward scattering given the position of the sensor (component west of location) relative to the sun (component east of location). Of note, the GOES-West CONUS sector does not extend east to this location. GOES-West full disk imagery (shown here) captures the event at 10-min resolution, but full resolution full disk imagery is not available to forecasters in NWS AWIPS. Therefore, forecasters would need to view the GOES-West products via other means (for example, CIRA Slider) in order to analyze the best high resolution view of the lofted dust during the morning. After midday, forecasters should transition to viewing GOES-East reflectance imagery for the ideal view of the lofted dust.

As pointed out by Tim Schmit (STAR/ASPB), the lofted dust was detectable in the 1.37 um “cirrus” band. Recall, this band is sensitive to absorption by moisture in the atmosphere, so to detect a near-surface/surface feature requires a dry atmosphere. Analyzing the imagery, the early day blowing dust discussed above was not apparent (Fig 9). However, a pocket of blowing dust becomes obvious by late morning traveling south across the middle of the domain. Comparing with surface observations, this area of blowing dust apparent in the 1.37 um imagery matches well with a minimum in surface dew point temperature (down to -2F!). The early day blowing dust occurred with dew points around 20F, confirming enough moisture was present in the atmosphere here to limit detection into the low-levels in the 1.37 um band.

The southward progression of the dry air pocket is also diagnosed in GOES-East TPW imagery (Fig 10).

Bill Line, NESDIS and CIRA