Blizzard warning were hoisted over the high plains of Kansas, Nebraska, New Mexico, Texas and Oklahoma for a strong storm on 8 January 2024 (image from the weather.gov website). The animation above shows visible imagery overlain with LightningCast probabilities centered over Kansas. Convection occurring over the cold aid will lead to increased snowfall rates, worsening local conditions (as if northerly winds of 30-40 knots weren’t enough!). LightningCast probabilities (that suggest where GLM observations within the next 60 minutes are most likely) give an advance warning of where conditions might be the worst in the short term. Note that Flash Extent Density values are scaled in the imagery from 1-15 vs. the default of 1-260.

LightningCast is available online here. LightningCast is a tool created via machine learning that uses ABI Bands 2, 5, 13 and 15 (0.64 µm, 1.61 µm, 10.3 µm and 12.3 µm, repsectively) to ascertain the lightning probabilities. Band 2, 5 and 13 are also the components of the Day Cloud Phase Distinction RGB, and a 1-hour animation, 1801-1901 UTC, of that field, overlain with LightningCast probability and GLM observations is shown below. It’s hard to tease the information in LightningCast from the Day Cloud Phase distinction RGB.

MIMIC Total Precipitable Water fields, below, for the 24 hours ending 1900 UTC on 8 January 2024, show how the large-scale circulation is drawing moisture northward out of the Gulf of Mexico.

The large-scale circulation is also apparent in the Advected Layer Precipitable Water (ALPW) fields, below. (source) Data for the different layers suggest that moisture transport is most apparent below 500 mb.

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As is frequently the case with strong storms over the Southern Plains, strong surface winds on the south side of the storm have lofted dust, as shown in the toggle below between Visible and Dust RGB imagery at 2110 UTC on 8 January 2024 (available here as well). The pink/magenta enhancement in this RGB shows where dust is detected.

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GOES-18 (GOES-West) Mid-level Water Vapor (6.9 µm) images (above) revealed a well-defined Foehn gap (narrow ribbon of darker blue enhancement) near the spine of the Sierra Nevada range in California, along with a broad “orographic crest cloud” (darker green enhancement) that extended eastward across southeast California into southern Nevada on 06 January 2024.

The corresponding GOES-18 “Clean” Infrared Window (10.3 µm) images are shown below.

A toggle between GOES-18 Water Vapor and Infrared images at 2201 UTC + Topography (below) helped to illustrate that the location of the Foehn gap was immediately downwind (east) of the spine of the Sierra Nevada.

There were Pilot Reports of Mountain Waves in the vicinity of the Foehn gap, as well as a report of Moderate to Severe Turbulence within the crest cloud feature (below).

In a comparison of GOES-18 10.3 µm infrared brightness temperature, CLAVR-x Cloud Top Temperature derived product and CLAVR-x Cloud Top Height derived product within the crest cloud feature at 0021 UTC (below), the Cloud Top Temperature product was nearly 5C colder than the single-channel infrared brightness temperature, and the Cloud Top Height was around 45000 ft.

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From 1500 to 1900 UTC on 4 January 2024, GOES-16 was in Mode 4 (vs. the usual Mode 6) operations. Mode 4 scanning produces a full-disk image every 5 minutes. Mesoscale sectors and CONUS sectors are not scanned (although a CONUS sector can of course be subsected out of the Full Disk image). The mp4 animation above (from the CSPP Geosphere site) shows the transition. Before 1500 UTC, data are at 10-minute time-steps; after 1500 UTC, 5-minute time-steps occurs. Imagery is over Panama, a region where 5-minute images typically are not available. Indeed, regions outside of GOES-16 CONUS sector will enjoy the benefits of a 5-minute cadence until 1900 UTC on 4 January 2024. The Mode change has occurred to create simulated data for GOES-U, still scheduled for launch in late April of this year.

The data feed into the National Weather Service Advanced Weather Information Processing System (AWIPS) is not greatly affected by the change from Mode 6 to Mode 4, as shown below. Full Dis imagery changes from a 10-minute to a 5-minute cadence at 1500 UTC, and the timestamp for the CONUS sector changes from …/1446/1451/1456 to 1500/1505/1510… UTC.

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The ‘Time-Time’ charts (that show scanning strategies are available online here for Mode 4 and here for Mode 6 (or here).

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As of 1900 UTC 4 January 2024, GOES-16 is back in Mode 6 operations. The screenshot below is from the CSPP Geosphere site.

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10-minte Full Disk scan GOES-18 (GOES-West) Air Mass RGB images (above) showed a large cyclone as it deepened to a 936 hPa Hurricane Force Low while approaching the Aleutian Islands of Alaska on 02-03 January 2024 (surface analyses). The Sea Level Pressure dropped to at least 945.6 hPa at Dutch Harbor/Unalaska (METAR identifier PADU), which set a new record January minimum pressure for that site.

As the low passed near Buoy 46072 (located just east of PAAK), the pressure there dropped to 942.7 hPa at 1940 UTC on 02 January (below).

GOES-18 Air Mass RGB images with plots of Metop ASCAT winds at 2150 UTC on 02 January and 0730 UTC on 03 January (below) depicted wind speeds in the 50-60 knot range to the south and southwest of the low center.

A toggle between GCOM-W1 AMSR2 Wind Speeds (source) at 1332 UTC on 02 January and 0042 UTC on 03 January (below) showed several small pockets of Hurricane Force magnitude (>64 knots, shades of magenta) within the expanding field of strong winds south of the low center on 03 January.

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