The mp4 animation above, downloaded from the CSPP Geosphere site, shows true-color imagery in the 90 minutes surrounding an EF-3 tornado in Virginia Beach, VA shortly before 2200 UTC on 30 April 2023 (CIMSS Satellite Blog post; SPC Storm reports; ProbSevere imagery for the storm is here). Note the overshooting tops moving from southeastern Virginia northeastward to the extreme southern Delmarva peninsula, likely associated with the strongest thunderstorms. This blog post considers how the addition of Polar Hyperspectral Sounding (PHS) data into a numerical model affected the model simulation of this tornadic event (model output is available here). This PHS modeling system is being demonstrated at the Hazardous Weather Testbed late in May, and in early June (PHS model output was also available at last year’s HWT!)

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The two-panel image above shows 5- and 6-h MUCAPS distributions from a WRF simulation (with 3-km resolution) initialized with conventional data, and the image below shows 5- and 6-h forecast MUCAPS from a HRRR simulation (with 4-km resolution) that includes as part of its assimilation cycle temperature and moisture fields that include information from Polar Hyperspectral Soundings (in this case, from the morning overpasses from IASI on Metop-B and Metop-C). Compare the fields above and below. The HRRR simulation that includes the influence of Polar Hyperspectral Sounding data leads to a MUCAPE field that extends more seamlessly north towards the Delmarva peninsula.

The PHS simulation from 1700 UTC, below, shows good consistency with the 1600 UTC run shown above. In particular, both show the most unstable CAPE lingering over extreme southeastern Virginia at 2100 UTC and offshore at 2200 UTC.

HRRR data was also used to compute Significant Tornado Parameter (STP), and the animation below shows parameter forecasts (from the model initialized at 1700 UTC) for 1900, 2000, 2100 and 2200 UTC.

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From coastal California to the Sierra Nevadas to the Rocky Mountains, precipitation totals this past winter reached historically high levels, especially when it comes to snowfall and mountain snowpack. The health of western watersheds in terms of mountain snow is readily apparent in VIIRS True and False Color imagery.  

Significant drought relief occurred over the winter months as well, as seen in these graphics from the U.S. Drought Monitor comparing April 2023 to November 2022. Atmospheric Rivers played a huge part in the turn-around. California is nearly drought free!

And according to the USDA, many snowpack levels were still at or above 200% as of May 1^st. For states like Utah, where 95% of municipal water comes from melting snow, this is great news.

It seemed somewhat intuitive that Lake Powell and Lake Mead, two of the largest reservoirs out west, would benefit from the wet winter.  Now a recent report from the Bureau of Reclamation confirms this scenario. Record snowpack in Utah, Colorado and Wyoming are expected to boost lake levels with inflow (melting snow) projected to be 177% of average during the April-July runoff period. Graphs included in the report (below) show rebounding lake levels benefiting from the historically high snowpack through 2024. But they also show that lake levels will likely remain below historical averages.

Meanwhile in the short term the National Weather Service has issued numerous Flood Watches, Advisories and Warnings from the Canada-U.S. border to southern Utah due to rapidly melting snow. The water is freezing cold rushing in high, fast flows. Along with avoiding flooded areas, the NWS is advising people to stay away from river banks where erosion could result in sudden surprise submersion and nearly instant hypothermia.

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Did satellite soundings provide information during the surface wind event on 1 May 2023 that lead to the closure of Interstate 55 (click here for a Google Traffic map from 6 PM on 1 May 2023!) south of Springfield IL (see this CIMSS Satellite blog post)? On 1 May, the location in question was observed twice by NOAA-20, shortly before 1800 UTC (above) and ca. 1930 UTC (below). The low-level lapse rates from the NUCAPS soundings show the very strong lapse rates that accompany blowing dust.

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Gridded NUCAPS fields of low-level lapse rates are very revealing at 1933 UTC. Lapse rates from 925-850 and from 950-900 mb, shown below, suggest the steepest low-level lapse rates in the region just south of Springfield where the blowing dust occurred.

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GOES-16 data can also be used to derive lapse rates in the vertical (although ABI data gives scant information in the vertical). The animation below shows derived profiles at 4 locations in central Illinois at 1951 UTC. (GOES-16 profiles are created only in regions that are confidently clear — clouds were present over much of eastern IL on 1 May 2023 as shown in this Day Cloud Phase Distinction RGB animation from 1746 – 1921 UTC). The blowing dust was most apparent in satellite imagery between the two southern profiles. As with the NUCAPS profiles, dry-adiabatic conditions are present near the surface.

A benefit of GOES-R profiles is that they are produced every 30 minutes. Thus, one can view how things evolve with time in a way that is far more difficult with NUCAPS profiles. The animations below shows the profiles and the northern and southern points in the above figure. Both profiles show surface warming over the 5 hours plotted — with the southern station warming a bit more — and well-mixed boundary layers.

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GeoXO — the follow-on to the GOES-R satellite series — will carry a hyperspectral sounding (the GXS) that will provide much more accurate profiles than are available from GOES-R.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) Dust RGB images (above) showed areas of blowing dust (shades of magenta/pink) that reduced visibility to near zero along Interstate 55 south of Springfield, Illinois (station identifier KSPI) on 01 May 2023 — which caused multiple-vehicle accidents that resulted in dozens of injuries and several fatalities. As a result, parts of I-55 in southern Sangamon and northern Montgomery County were closed in both directions. Surface reports showed wind gusts as high as 54 mph, with some GOES-16 Derived Motion Winds in the 35-40 knot (40-46 mph) range across the region. The source of this blowing dust was nearby agricultural fields that had recently been plowed during Spring planting activities.

In plots of rawinsonde data from Lincoln, Illinois (METAR station identifier KAAA, near the top-center of the Dust RGB images) shown below, a deep boundary layer adiabatic-to-superadiabatic temperature lapse rate was evident, which increased in maximum height from 806 hPa (1748 m) at 1200 UTC to 714 hPa (2743 m) at 0000 UTC. This steep boundary layer lapse rate aided the downward transfer of momentum, bringing the stronger 35-45 knot wind speeds that existed at higher altitudes down to the surface. During the time period between these 2 Lincoln IL rawinsonde launches, steep boundary layer lapse rates were also seen in sounding profiles derived from NOAA-20 and GOES-16 (as shown in this blog post).

Massive pileup on I-55 south of Springfield, Illinois has closed the interstate for nearly 30 miles. Blowing dust off freshly plowed fields led to very low visibility#ilwx
?: Nathan Cormier pic.twitter.com/im7QLE8BTp

— Nick Hausen (@NickHausenWx) May 1, 2023

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