Sentinel-1A orbits have a repeat cycle of 12 days, and the second observation in April over Samoan waters occurred on 13 April, as shown above (there were SAR winds created in this domain on 1 April as well, here, on a similar weak-wind day). Diagnosed winds are uniformly light (3-7 knots) in the absence of strong convection. The atmosphere is very moist, as shown in the MIMIC Total Precipitable Water animation (below) from 0000-0900 UTC on 13 April. Note that the region of strongest winds in the image above, to the west of Upolu and near the western edge of the domain, is likely an artifact from reflection of the SAR signal off of ice from the deep convective cloud at the western edge of the SAR domain. This toggle of winds and Normalized Radar Cross Section (NRCS) data shows the characteristic feathery structure in NRCS fields that arise when cloud ice is present.

Sentinel-1A will overfly Samoa again around 0552 UTC on 25 April.

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Clear skies over the upper Midwest allowed all 3 JPSS Satellites — Suomi NPP, NOAA-20 and NOAA-21 — to obtain excellent views of the Great Lakes on 11 April 2023. The Great Lakes are largely ice-free (with the exception of a few bays in northern Green Bay, over northern Lake Superior, and over northern Lake Huron). (Here are two images from 7 March for comparison). The CIMSS Direct Broadcast site includes imagery for each of the five Great Lakes (here’s Lake Erie, for example, from NOAA-20 at 1846 UTC on 11 April, via this direct link to this directory, valid for about a week); the animation below shows Suomi NPP, NOAA-20 and NOAA-21 images of the Great Lakes from the CIMSS Direct Broadcast website (link) with 5 images between 1705 and 1911 UTC. Multiple JPSS Satellites means that time animations are easily created.

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VIIRS imagery is also available at the VIIRS Today Site and at the CIMSS VIIRS Imagery Viewer. True-Color imagery is also available via an LDM feed from CIMSS.

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GOES-16 (GOES-East) Shortwave Infrared (3.9 µm), Fire Temperature RGB, and Fire Power / Fire Temperature derived products (above) showed thermal signatures from a recycling plant fire in Richmond, Indiana on 11 April 2023. The Fire Power and Fire Temperature derived products are components of the GOES Fire Detection and Characterization Algorithm (FDCA).

GOES-16 True Color RGB images from the CSPP GeoSphere site (above) provided a good portrayal of the contrast between the dark black smoke plume and the surrounding bare ground — which was also evident in True Color RGB images from GOES-18 (GOES-West), in spite of the rather large viewing angle from that satellite (below).

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JMA Himawari-9 Ash RGB images created using Geo2Grid (above) showed a complex volcanic cloud resulting from an eruption of Shiveluch that began just after 1300 UTC on 10 April 2023. Much of the volcanic cloud exhibited brighter shades of yellow (indicating a mixture of ash and SO2), but there were also areas of brighter green (indicating larger concentrations of SO2) along with more localized pink-to-magenta features (a signature of larger ash concentrations). 

Similar to what was seen during an eruption of Bezymianny on 07 April, GOES-18 (GOES-West) “Red” Visible (0.64 µm) images from the CSPP GeoSphere site (below) provided an oblique view of overshooting volcanic clouds produced during one of the eruptive pulses.

Another volcano has erupted in eastern Russia! This VOLCAT loop of IR satellite imagery and Ash height shows how the atmospheric circulation over the past 24-hours distributed ash from the #Shiveluch #volcano across nearly all of the #Kamchatka peninsula. https://t.co/XUISai5pTL pic.twitter.com/qmQipZfz8a

— UW-Madison CIMSS (@UWCIMSS) April 11, 2023

===== 14 April Update =====

GOES-18 SO2 RGB images during the 4-day period from 11-14 April (above) showed the eastward transport of high-altitude filaments of mixed SO2 and Ash (brighter shades of yellow) across the Bering Sea and Gulf of Alaska, eventually moving over parts of Alaska, British Columbia and Yukon. Given the large amount of SO2 produced by this Shiveluch eruption, the SO2 RGB was a very effective product for monitoring the long range transport of its volcanic cloud.

Large #eruption of #Shiveluch (#???????, #Kamchatka) w/ stratospheric plume, starting at ~12:00 UT on April 10 with paroxysmal phase at ~17:00 UT. #Sentinel5P #TROPOMI measures ~0.2 Tg SO? in the #volcanic cloud. Looks like the largest Shiveluch eruption of the satellite era. pic.twitter.com/EGle2BAbl0

— Prof. Simon Carn (@simoncarn) April 11, 2023

A number of Aviation Ash Advisories were issued within the Alaska region, including those on 14 April that are displayed below.

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