A sequence of 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) Dust RGB and Mid-level Water Vapor (6.9 µm) images (above) showed the development of dense plumes of blowing dust (whose source regions were primarily in southeast Colorado and the Oklahoma/Texas Panhandles) on 15 December 2021. These dust plumes were being lofted by strong winds along and behind a cold front — which was associated with a rapidly-intensifying midlatitude cyclone. This storm then caused a broad swath of severe weather (SPC Storm Reports) as it moved rapidly northeastward toward the Great Lakes. 

GOES-16 Mid-level Water Vapor images with and without contours of hourly RAP model PV1.5 pressure (below) identified a Potential Vorticity (PV) anomaly which tracked northeastward across the region, indicating that the “dynamic tropopause” descended to the 700-750 hPa pressure level — which helped to transfer the momentum of strong winds aloft toward the surface. The general appearance of the water vapor imagery was similar to that seen in other cases when a “sting jet” helped to transport momentum aloft to the surface where high winds were observed (a sting jet is often found near the hook-shaped “scorpion tail” portion of the water vapor signature). The downward transport of dry mid/upper tropospheric air was supported by a rapid decrease in surface dewpoint temperature, seen at at a number of sites where the dewpoint dropped to below 0ºF (for example, from west to east across Kansas at Johnson KS | Ulysses KS | Pratt KS). Note that the brightest shades of pink/magenta on the GOES-16 Dust RGB images were located behind the primary eastward-moving cold front, where stronger winds associated with the sting jet had descended to the surface.

A toggle between NOAA-20 NUCAPS-derived Tropopause Height, Total Column Ozone and Total Column Ozone Anomaly from the NASA SPoRT site (below) supported the presence of a PV anomaly over northwestern Kansas around that time, characterized by a low tropopause with anomalously-high total column ozone (2000 UTC GOES-16 Water Vapor image + PV1.5 pressure).

GOES-16 True Color RGB images created using Geo2Grid (above) highlighted the tan-colored blowing dust plumes (along with a couple of brighter-white wildfire smoke plumes) as they progessed northeastward across Kansas and Nebraska. A larger-scale view of GOES-16 Dust RGB images (below) showed that during the subsequent nighttime hours into the next morning, the brighter pink/magenta signature of blowing dust that became entrained into the circulation of the midlatitude cyclone could be followed as it eventually moved over parts of Minnesota, Wisconsin, Upper Michigan and Lake Superior — and eventually over far southern Ontario, Canada.  

It looks like some of the dust from Colorado and Kansas made it all the way to the Northland! The liquid from our rain guage was very cloudy this morning! #mnwx #wiwx #cowx #kswx https://t.co/2NxRvEkaV8 pic.twitter.com/1BuYc0Wn4O

— NWS Duluth (@NWSduluth) December 16, 2021

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NOAA-20 overflew the central United States twice in the afternoon of 15 December 2021 (NOAA-20 orbits that day shown here, from this website) as a potent weather system moved through. SPC‘s Convective Outlook showed a Moderate Risk of severe weather (link); There was widespread wind damage on this day (link). How could NUCAPS soundings (available in AWIPS as demonstrated here) on that day assist in understanding the state of the atmosphere? The toggle above shows where NUCAPS profiles were available. Blue boxes highlight profiles that are shown below. Note right away that the NOAA-20 orbits on the 15th allowed for multiple samplings of the atmosphere at the northern edge of the Moderate Risk. The soundings along the western edge of the ca. 1800 UTC NOAA-20 NUCAPS pass, below, show steep mid-level lapse rates, and MUCAPE values (as diagnosed by NSharp in AWIPS) increasing to the south.

GOES-16 data can also be used to diagnose instability, and the Level 2 Product (Derived Stability Index) Lifted Index at 1751 UTC is shown below. The Level 2 product also shows stability decreasing to the south in Iowa. Keep in mind that southerly surface winds at this time (as shown in this visible image with surface observations in a toggle with the Dust RGB and NUCAPS Sounding Availability) were very strong with this dynamic system: advection could be very large.

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Select vertical profiles from the subsequent NUCAPS swath shortly before 2000 UTC are shown below.

Several profiles in the animation above deserve special mention. The first two comparisons, below, compare profiles from the two overpasses.

The sounding in southern Minnesota samples a region very close to a sounding location from 90 minutes earlier. The toggle below of sequential profiles shows a change in stability as diagnosed by NUCAPS. The mid-level lapse rate has steepened, and mid-level moisture has increased. Observations from sequential passes do not happen every day, but forecasters (north of about 41 N) can (and should!) take advantage of them, time permitting, when they do happen.

A similar comparison over southern Iowa is shown below, showing the ca. 1815 UTC profile first (the one with the highest diagnosed MUCAPE) toggled with two later adjacent profiles. Note how the mid-level lapse rates have destabilized in the later profiles

NUCAPS soundings that are in the moist air ahead of developing convection and within dry, dusty air behind the convective line at around 1953 UTC in Kansas are shown below. As with other soundings in the moist air, mid-level lapse rates show weak stability. The sounding closest to the developing convection shows abundant moisture in the lower troposphere. Soundings in the dusty air are very very dry : diagnosed total precipitable water is less than 0.3″. Visible imagery in the background image below shows the dusty air over western Kansas, it’s far more apparent in this toggle of visible imagery and the dust RGB at 1931 UTC!

NUCAPS profiles over Kansas in front of the developing convection, below, show very steep lapse rates in the mid-troposphere! (Among the largest values this blogger has seen!) This suggests explosive development is possible if convection develops.

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Gridded values of NUCAPS temperature and moisture (and of values derived from those fields) are available at this website. In addition, those values will shortly be available in RealEarth. Gridded 850-500 mb Lapse Rates derived from the two sequential NOAA-20 NUCAPS profiles are shown below. Much of the central/southern Plains has very low mid-tropospheric stability.

NUCAPS profiles give timely and independent estimates of atmospheric temperature and moisture in the mid-afternoon over the central United States; thus they are frequently useful for estimating convective potential.

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A GOES-17 airmass RGB, above, shows a strong feature in the Gulf of Alaska. It’s common to associate the orange and purple regions within that polar feature (that is accompanied by cloud features consistent with very cold air aloft) with enhanced ozone. What products are available online to gauge the amount of ozone?

The OMPS instrument on board NOAA-20 (and on Suomi-NPP) senses in the ultraviolet (from 250-310 nm) to compute ozone concentration. (For more information on OMPS, refer to this document) The figure below, taken from this Finnish website, shows ozone concentration for the 24 hours ending at 0110 UTC on 13 December. A distinct maximum is apparent over the Gulf of Alaska. Note the northern terminus of the observations that are related to the time of year: there is little Sun north of 60 N. The data for this were downloaded from the Direct Broadcast site at GINA at the University of Alaska-Fairbanks. OMPS data are also available (from Suomi-NPP) at NASA Worldview.

To determine the time of the data in the image below, consult the NOAA-20 orbital paths here. This image (from that site) shows a NOAA-20 ascending overpass between 2235 and 2245 UTC over the Gulf of Alaska.

NOAA-20 also carries the Cross-track Infrared Sounder (CrIS) and Advanced Technology Microwave Sounder (ATMS) instruments that are used to create NUCAPS vertical profiles; one of the trace gases retrieved in this way is ozone. The distribution of ozone (with values in regions where it was dark) from NUCAPS is shown below (from this website maintained by SPoRT), and it corresponds roughly with the OMPS estimates shown above.

Conclusion: The assumption that upper-tropospheric ozone values are large in regions where the airmass RGB is tinted red or purple is a good assumption, especially if other structures in the RGB — such as cumulus cloud development in the cold air — reinforce the idea that an intrusion of stratospheric air is occurring. The strong storm that this lowered tropopause is supporting is accompanied by a moist feed of air moving into central California, as shown below by MIMIC total precipitable water fields.

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Gridded NUCAPS fields are being tested within RealEarth, as shown below. They should be generally available soon.

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LightningCast probabilities are part of the ProbSevere portfolio, and they are available in RealEarth (link). This machine-learning product relates Band 13 and Band 15 observations to the probability of lightning occurrence (in daytime, Band 2 and Band 5 are also used). When your blogger was awakened by thunder (at 0826 UTC), as cold rain fell on the roof, he naturally thought: “I wonder what LightningCast is doing?” The animation above shows probabilities increasing as lightning developed over southern Wisconsin. Initial lead time for lightning from the probabilities is not big — but probabilities do expand and encompass the region that is experiencing lightning. The time of the lightning did match the closest approach of the surface low, as shown in this 0900 UTC surface analysis.

That lightning was produced in near-freezing surface temperatures reflects the vigor of this extratropical system that spawned a deadly tornado outbreak over the mid-Mississippi River Valley and lower Ohio River Valley (SPC Storm Reports).

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