The Storm Prediction Center in Norman OK issued a Moderate Risk of severe weather over the lower Ohio River Valley/mid-Mississippi River Valley on 8 May 2024, as shown below. (Here are the storm reports for that day). The orbits for MetopC and NOAA-20 on the 8th sampled the region well, as shown in the toggle above of NUCAPS Sounding Availability with timestamps of 1605 UTC (Metop-C) and 1902 UTC (NOAA-20). Note the purple box in the toggle. Both MetopC NUCAPS and NOAA-20 NUCAPS retrievals at that location converged to a solution. How might the thermodynamic information within just those two profiles help?

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The toggle below compares the MetopC NUCAPS and NOAA-20 NUCAPS profiles within the purple box in the toggle at the top of this blog post. The atmosphere at this location destabilizes in these three hours: diagnosed MUCAPE has more than doubled, mid-level lapse rates have steepened, the LFC has dropped, total precipitable water has increased. These indicators (derived from satellite-sensed radiances) all suggest that development of strong convection might proceed.

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This blog post just shows you two profiles showing how a small volume of the atmosphere over southeastern Missouri is changing. Gridded thermodynanic fields derived from all the NUCAPS profiles are also available and are especially useful in diagnosing gradients and changes in stability over a large area.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed widespread thunderstorms that produced tornadoes, large hail and damaging winds (SPC Storm Reports) across parts of Nebraska, Kansas and Oklahoma (as well as far western Iowa, Missouri and Arkansas) on 06 May 2024. This was declared a rare High Risk day for severe weather by the SPC (as also discussed in this blog post).

A longer animation of 1-minute GOES-16 “Clean” Infrared Window (10.3 µm) images (below) extended several hours past sunset. The coldest overshooting top infrared brightness temperatures were in the -70 to -75ºC range (darker black to embedded shades of white). These thunderstorms produced the deadly EF4-rated tornado in Barnsdall, Oklahoma around 0240 UTC, hail as large as 4.00″ in diameter near Moonlight, Kansas around 0126 UTC and a wind gust as high as 82 mph near Chester, Oklahoma around 2209 UTC.

5-minute CONUS Sector GOES-16 Visible (and after 1911 UTC, Infrared) images combined with GOES-16 Convective Available Potential Energy (CAPE) and Lifted Index (LI) Derived Stability Indices and the Total Precipitable Water (TPW) derived product (below) showed the instability and moisture within the warm sector of a large midlatitude cyclone that was centered over the Northern Plains — ingredients which helped to fuel the development of the severe thunderstorms.

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The Storm Prediction Center has deemed 6 May 2024 as a day with a High Risk of severe weather over the central/south-central Plains:

...SUMMARY...
   A regional outbreak of severe weather with multiple intense (EF3+),
   long-tracked tornadoes, as well as very large hail and severe
   thunderstorm gusts, is expected over parts of the south-central
   Plains from this afternoon through evening.

By 2100 UTC, strong convection had developed from South Dakota southward to western Oklahoma, as shown in the radar animation below (source).

The Polar Hyperspectral Model (PHS) includes as its assimilated input Fusion Data, i.e., ABI “retrievals” that are matched to the latest observations from Low Earth Orbit (LEO) Hyperspectral Soundings. The ABI retrievals thus have the great spatio-temporal resolution of ABI data and the excellent spectral resolution of the LEO Sounders. The result is a better description of the initial moisture distribution in the model. How is this performing today? Imagery below was taken from the model website here; once there click on Forecast Plots and then on the calendar to the correct day. The toggle below compares the 6-h forecast and the 3-h forecast of the PHS-influenced model (a 4-km WRF simulation). A series of Supercellular-like storms arcs from Nebraska southward to Kansas, with strong storms in northwestern South Dakota as well. Compare the toggle below to the one from a 3-km HRRR simulation that has not been influenced by PHS data. The HRRR simulation shows weaker convection.

The toggle below compares the 3-h forecasts (valid at 2100 UTC) of 3-km HRRR (no PHS data) with the 4-km WRF (with PHS data). (Here is a similar comparison of 6-h forecasts valid at 2100 UTC) The PHS data has lead to a more accurate simulation of the convective strength over Nebraska, Kansas and South Dakota.

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PHS scientists have created maps that combine where the High Shear and High Instability regions into one ‘Vortex Prediction’ image, shown below for 1700 UTC (and available at this website). This image below shows hourly forecasts valid at 1700 UTC, from forecasts initialized from 1100 – 1500 UTC on 6 May 2024. At 1700 UTC, the consistently-forecast most favorable environment for strong convection is over western Nebraska. That region is very close to the location of the first tornado touchdown of the day, shown below in SPC storm reports from 1830 UTC. (Imagery below courtesy Bill Smith Sr and Anthony DiNorscia, Hampton University).

Note that the HRRR simulation (left, below) has no similar signal as the WRF simulation with assimilated PHS data.

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At the request of Pacific Region Headquarters, the LightningCast domain centered on American Samoa has increased. At 1840 UTC, the domain roughly doubled, as shown in the two screen shots below from the RealEarth site. The Red Box captures the size of the previous domain; note that at 1900 UTC the contours extend from 160^oW westward to the dateline. The north-south domain size has also increased. The 1940 UTC image at the bottom of this post includes the new domain.

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Users will note that contours that touch the dateline in RealEarth will be drawn incorrectly (as shown here). This is being investigated. The AWIPS screen-capture, below, courtesy Eric Jacobsen, NWS/PRH, shows the display in AWIPS.

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