Heavy rains have finally hit California, which declared a state of emergency on Wednesday January 4 due to extreme rainfall amounts. The GOES-West enhanced Band 9 imagery (6.9 µm, mid-level water vapor) illustrates how moisture associated with the recent similar Trans-Pacific atmospheric river generated heavy rainfall for much of California, Oregon, and Washington. Overlayed with NEXRAD radar reflectivity, the animation below paints a good picture of the rainfall that accumulated within the 21 hours shown.

The California Nevada River Forecast Center reports that some areas in northern California have already accumulated up to five inches of rain in the past 24 hours. Flooding has already created dangerous situations for the residents of California.  

Readers can recreate the above animation and explore other GOES data using RealEarth, a free web-based visualization tool for satellite and other remote sensing weather products.

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GOES-17 — and GOES-18, beginning at 1801 UTC on 04 January (after GOES-18 became the operational GOES-West satellite) — Air Mass RGB images (above) showed a rapidly-intensifying Hurricane Force low pressure system (surface analyses) over the East Pacific Ocean as it approached the US West Coast during the 03 January – 04 January 2023 period (brief periods with horizontal striping in the earlier GOES-17 images was due to that satellite’s Loop Heat Pipe issue).  As the crude oil tanker POLAR RESOLUTION was moving south-southeastward along the western periphery of the storm, it reported winds as strong as 50-60 knots which were frequently producing blowing spray (1001 UTC Air Mass RGB image) — and Buoy 46006 reported wind gusts of 60 knots (2001 UTC Air Mass RGB image) and wave heights of 41 feet.

With abundant illumination from the Moon (which was in the Waxing Gibbous phase, at 95% of Full), a Suomi-NPP VIIRS Day/Night Band (0.7 µm) image at 1004 UTC (2:44 AM PST) on 04 January provided an excellent “visible image at night” of the storm. Note the POLAR RESOLUTION report of 55 knot winds with blowing spray (near the western edge of the storm’s cloud shield).

GOES-17/GOES-18 True Color RGB (and Nighttime Microphysics RGB) images from the CSPP GeoSphere site (below) displayed the cloud features within the storm’s broad circulation, in addition to a long/narrow cloud band associated with its trailing cold front (which eventually moved south of all the islands of Hawai`i, except the Big Island — as shown in the surface analysis at 0000 UTC on 05 January).

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GOES-18 became the operational GOES-West satellite at 1800 UTC on 4 January. The toggle above shows the GOES-West (labeled as GOES-17, but the 1806 UTC image is using GOES-18 satellite information) IFR Probability Fields before/after the changeover. The IFR Probability field gives more useful information about surface visibility/ceiling restrictions than (for example) visible imagery (shown here) that shows widespread cloudiness at the time. There are noticeable changes between the 1756 and 1806 UTC fields, likely because the numerical model output used in GOES-R IFR Probability fields will change every hour, that is (in this case) at 1800 UTC.

The toggle below shows the airmass RGB from GOES-17 at 1756 and from GOES-18 at 1806 UTC over the same domain; note that stripes at 1756 UTC (an artifact of Loop Heat Pipe issues in GOES-17) are not present at 1806 UTC in the GOES-18 imagery.

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GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images with an overlay of GLM Flash Extent Density (above) covered part of a widespread winter storm event — which included thundersnow in parts of Nebraska, Iowa, South Dakota and Minnesota — that occurred on 03 January 2023. Areas that reported thundersnow experienced convectively-enhanced snowfall rates of 2-3 inches per hour; storm total snowfall amounts were as high as 27 inches in southeastern South Dakota and 18 inches in northeastern Nebraska (NWS Sioux Falls event summary | WPC storm summary).

Ahead of the cold front associated with this winter storm (surface analyses), severe thunderstorms produced tornadoes, large hail and damaging winds (SPC Storm Reports) from the Upper Midwest to the Deep South. Overlapping GOES-16 Mesoscale Domain Sectors provided imagery at 30-second intervals over parts of Mississippi, Alabama, Georgia and Tennessee where some of the severe weather occurred — “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images that include time-matched plots of SPC Storm Reports are shown below. With some of these thunderstorms, pulsing overshooting tops exhibited infrared brightness temperatures as cold as -70 to 75ºC.

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