GOES-18 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.3 µm, bottom) images, with and without an overlay of GOES-18 GLM Flash Extent Density [click to play animated GIF | MP4]

1-minute Mesoscale Domain Sector GOES-18 (GOES-West) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) included an overlay of GLM Flash Extent Density — which showed thunderstorms that produced flash flooding, hail and an EF-1 tornado (SPC Storm Reports) in the Central Valley of California on 11 March 2023. At 2236 UTC (1 minute prior to the Tornado Warning being issued), an overshooting top along the Calaveras/Tuolumne County line exhibited an infrared brightness temperature of -53.3ºC — which roughly corresponded to the altitude of a Most Unstable Maximum Parcel Level (MU MPL) as analyzed from the 0000 UTC Oakland rawinsonde (source).  Note that for the relatively low-topped convection over California on this day, the coldest value of the default infrared enhancement was modified to -70ºC, to aid in the identification of colder overshooting tops (shades of white embedded within dark black regions).

The corresponding GOES-18 Cloud Top Height derived product at 2236 UTC — just before the issuance of the Tornado Warning — was around 32,482 feet (below). For this storm, the maximum value of the default Cloud Top Height enhancement was set to 35,000 feet.

GOES-18 “Red” Visible image (0.64 µm, top) and Cloud Top Height derived product (bottom), with cursor sampling of the coldest 10.3 µm pixel along the Calaveras/Tuolumne County line at 2336 UTC [click to enlarge]

During the period leading up to convective initiation of the hail/tornado-producing thunderstorm, 1-minute GOES-18 Visible and Infrared images (below) include contours of LightningCast Probability — a >50% LightningCast Probability (green contour) over western San Joaquin County at 2009 UTC provided a 17-minute lead time to the start of a prolonged period of GLM-indicated lightning activity for that storm, which commenced at 2026 UTC (2000 – 0100 UTC animation).

GOES-18 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.3 µm, bottom) images, with an overlay of GLM Flash Extent Density and contours of LightningCast Probability [click to play animated GIF | MP4]

These thunderstorms developed in an environment of modest moisture and instability, as shown by 1-minute GOES-18 Visible and Infrared images combined with Total Preciptitable Water (TPW) and Convective Available Potential Energy (CAPE) derived products in cloud-free areas (below). Satellite-derived TPW values up to 0.90 inch and CAPE values as high as 400 J/kg were observed in the general vicinity of the strongest convection. Note that the default enhancements for TPW and CAPE were also modified for use with these particular storms — the maximum TPW value was set at 1.1 inches, while the maximum CAPE value was set at 500 J/kg.

GOES-18 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.3 µm, bottom) images, combined with Total Preciptitable Water and Convective Available Potential Energy (CAPE) derived products in cloud-free areas [click to play animated GIF | MP4]

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MIMIC Total Precipitable Water product during the period 0400 UTC on 06 March to 1200 UTC on 08 March 2023 [click to play animated GIF | MP4]

The MIMIC Total Precipitable Water product during the period 0400 UTC on 06 March to 1200 UTC on 08 March 2023 (above) displayed the poleward transport of an atmospheric river (AR) that moved across Alaska and then the North Pole — eventually passing over Svalbard (located between Norway and Greenland). As this AR was emerging from the north coast of Alaska and approaching the North Pole, Total Precipitable Water (TPW) value anomalies were as high as 5-6 standard deviations above normal (source).

As the AR moisture plume was moving over Utqiagvik (formerly “Barrow”; station identifier PABR) Alaska at 0000 UTC on 07 March, the rawinsonde-derived TPW value was 0.62 inch (which might have been a monthly record high TPW for PABR, according to this tweet). At that particular time there was good agreement with the MIMIC TPW product, whose value in the vicinity of PABR was 0.65 inch (below).

MIMIC Total Precipitable Water product at 0000 UTC on 07 March, along with a cursor sample showing the PABR surface report at that time [click to enlarge]

The NESDIS Snowfall Rate product from the CICS site (below) showed the AR plume of clouds that was likely producing snowfall at the surface as it moved northward from the coast of Alaska to the Arctic Ocean.

NESDIS Snowfall Rate product [click to play animated GIF]

As the AR was passing across the North Pole, the maximum MIMIC TPW value at that location was 0.25 inch at 0900 UTC on 07 March (below).

MIMIC TPW value over the North Pole at 0900 UTC on 07 March [click to enlarge]

As the leading edge of the AR eventually began moving over Svalbard (station identifier ENSB) — a distance of approximately 2000 miles from the northern coast of Alaska — light snow was observed at 2000 UTC (below) and 2100 UTC on 07 March, and then again at 0900-1000 UTC on 08 March.

MIMIC TPW product at 2000 UTC on 07 March, with a cursor sample of the METAR surface observation at Svalbard ENSB [click to enlarge]

Note the gradual increase in temperature and dew point as the AR continued to traverse Svalbard (below).

Time-series plot of surface report data from Svalbard Lufthaven [click to enlarge]

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Note: NOAA-21 data used in this blog post are preliminary and non-operational. Imagery was created using Polar2Grid v3.0.

The CIMSS Community Satellite Processing Package (CSPP) team has released Polar2Grid version 3.0, a software package that can be used (among many other things!) to create high-quality imagery from JPSS Sensor Data Record (SDR) files as might be produced at a Direct Broadcast site (or ordered/downloaded from NOAA CLASS). Polar2Grid v3.0 represents a significant change from Polar2Grid v2.3, and some of those changes are documented here. The latest Polar2Grid also has significantly faster processing. The three true-color images above were created using Suomi NPP, NOAA-20 and NOAA-21 VIIRS imagery. (Note that NOAA-21 data are still preliminary and non-operational, although Beta maturity has been reached. They are included here to show that Polar2Grid can produce NOAA-21 imagery every bit as stunning as imagery from Suomi NPP and NOAA-20!). An especial advantage of 3 Polar Orbiters is obvious in the imagery above: the capability to animate high-resolution JPSS data.

Polar2Grid linux-based software can be downloaded from this website in the form of a gzipped tar file (Documentation on Polar2Grid is also available.) After expanding the downloaded file, and setting an environment file, i.e., export POLAR2GRID_HOME = /directory/where/software/sits, the various packages within $POLAR2GRID_HOME/bin can be run. To create the imagery above, I first created a map on which to reproject the data. This required the use of the p2g_grid_helper.sh scripts that creates the required navigation information in a format Polar2Grid recognizes. I wanted to create something that covered the Great Lakes because all 3 JPSS satellites — Suomi-NPP, NOAA-20 and NOAA-21 — scanned the entire Great Lakes in one swath on a relatively clear day. How will the three scenes compare? After some trial and error, I used this command

./p2g_grid_helper.sh GreatLakes -84.0 45.0 500.0 -500.0 2880 1920 > GreatLakes.yaml

that created a grid (called ‘GreatLakes’) centered at 84^oW, 45^oN, with 500 m resolution in the N-S and E-W directions, with a grid size of 2880×1920. The information created was redirected into the file ‘GreatLakes.yaml’; Polar2Grid software by default now expects grid configuration files created by the p2g_grid_helper shell script to reside in files with a suffix of ‘yaml’.

To acquire data for Polar2Grid to process, I accessed the CIMSS real-time system holding files created from the Direct Broadcast site. Data are separated out by satellite, and by day/time. Multiple granules are within each day/time file, especially now that CIMSS is producing expanded files by using data from other Direct Broadcast sites! Suomi NPP data for this case, for example, are at this link from 1734 UTC on 7 March; data from NOAA-20 are from 1821 UTC; data from NOAA-21 are from 1846 UTC. I could also have requested data from NOAA CLASS by selecting ‘JPSS VIIRS Sensor Data Record Operational (VIIRS_SDR) — although this site only distributes Operational data: NOAA-21 data are not available (yet). Usually when I access JPSS data from NOAA CLASS, I first view the orbits (from this website) for the day in question (7 March in this instance) for NPP, NOAA-20 and (eventually) NOAA-21, so I can access specific times that cover the region of interest.

Once the data were on the machine that holds the Polar2Grid software, it was straightforward to create imagery, using these commands for Suomi-NPP, NOAA-20 and NOAA-21 data, respectively; all the data were in the same directory:

./polar2grid.sh -r viirs_sdr -w geotiff -g GreatLakes --grid-configs GreatLakes.yaml -p true_color -f ../../daydata/*npp*.h5
./polar2grid.sh -r viirs_sdr -w geotiff -g GreatLakes --grid-configs GreatLakes.yaml -p true_color -f ../../daydata/*j01*.h5
./polar2grid.sh -r viirs_sdr -w geotiff -g GreatLakes --grid-configs GreatLakes.yaml -p true_color -f ../../daydata/*j02*.h5

Polar2Grid’s viirs_sdr reader (the -r flag) is being used, as is the geotiff writer (the -w flag). This syntax is different from earlier versions of Polar2Grid, but more in line with that in Geo2Grid. The data are being regridded (the -g flag) to a ‘GreatLakes’ grid, and grid configurations are stored within the ‘GreatLakes.yaml’ file. The product (-p flag) being created is ‘true_color’ and the data files (the -f flag) are found in the relative directory specified. If a user is unsure of what products can be created given the data in the data directory, the –list-products-all instruction can be used in place of -p to find that out.

The three commands above create (spectacular!!) True-Color imagery from Suomi-NPP, NOAA-20 and NOAA-21, seen in the animation above. Polar2Grid can also be used to add maps to the imagery, but this blogger thought those weren’t necessary.

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Cyclone Freddy in the Indian Ocean continues to persist and is situated along the southwest coast of Madagascar. It is currently crossing the Mozambique channel for the third time. Freddy intensified to a Category 5 storm on 2023-02-15. It is now listed as a Category 2 storm.

A three-week animation made in RealEarth shows Cyclone Freddy’s long life and unusual path between Madagascar and Mozambique. The animation shows infrared satellite data every half day (every twelve hours) from 2023-02-14 to 2023-03-07. The storm first travels west across the Indian Ocean, changes in intensification once it makes landfall, and eventually gains its cyclonic structure back. The Global Infrared display product in RealEarth is archived quite far back compared to other display products, making it useful for tracking storms over multiple days or weeks. You can revisit this Cyclone Freddy animation in RealEarth and other weather data products.

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