1-minute Mesoscale Domain Sector GOES-18 (GOES-West) Dust RGB images (above) showed a plume of resuspended ash (brighter shades of pink) from the 1912 Novarupta-Katmai eruption in Alaska, which was being transported offshore across the Shelikof Strait toward Kodiak Island on 27 September 2023. Surface volcanic ash within the Valley Of Ten Thousand Smokes.was being lofted by strong northwesterly winds.

Volcanic ash (VA) was reported at Kodiak Airport (PADQ) for 7.5 hours, from 2123 UTC on 27 September to 0453 UTC 28 September (below) — for example, see METAR cursor sampling at 2200 UTC, 2300 UTC and 0000 UTC — but the ash was not restricting surface visibility below 10 miles.

1-minute GOES-18 Nighttime Microphysics RGB + daytime True Color RGB images from the CSPP GeoSphere site (below) provided a more detailed view of the ash plume.

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New routine schedule

EWS-G1 (Electro-optical Infrared Weather System Geostationary) is a U.S. Space Force mission. The imager is now running a different routine scan schedule, as can be seen on the UW/SSEC geo-browser. This schedule includes scans of the Indian Ocean, the extended Indian Ocean and Full Disks. Previously only Full Disk images had been obtained every 30 minutes. An EWS-G1 “quick-guide (pdf).” EWS-G1 imagery has been available via the UW/SSEC since late 2020. The EWS-G1 was formerly NOAA’s GOES-13. EWS-G1 has employed the “XGOHI” remapping of data before GVAR generation, to handle larger inclination angles. This capability was first employed on GOES-10 (and then GOES-12) when their images provided special coverage of the Southern Hemisphere for a combined almost 7 years.

A loop of the coverage of three scans (mp4 and animated gif).

GOES-15 has become EWS-G2

It was recently announced by the Secretary of the Air Force that GOES-15 has become EWS-G2: “The U.S. Space Force accepted the transfer of a second geostationary weather satellite from the National Oceanic and Atmospheric Administration to extend persistent weather coverage of the Indian Ocean region until the 2030 timeframe. … As it currently does with EWS-G1, NOAA will operate EWS-G2 on behalf of the Space Force from the NOAA Satellite Operations Facility in Suitland, Maryland, and Wallops Command and Data Acquisition Station in Wallops Island, Virginia.”

EWS-G2 has the same spectral coverage as the EWS-G1. The EWS-G2 was formerly NOAA’s GOES-15. GOES-15 was launched in March 2010 and the first GOES-15 images were sent on April 6, 2010. A GOES-15 technical report which was written soon after launch.

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The posted near realtime imagery are free for public use (please credit UW-Madison/SSEC) and users can contact UW/SSEC Satellite Data Services for information on data access / subscription. Most of the above images were made using the McIDAS-X software. NOAA/NESDIS/STAR supplies some calibration support of this imager.

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GOES-18 (GOES-West) SO2 RGB and Ash RGB images (above) showed the complex transport of a volcanic cloud (shades of yellow in the SO2 RGB imagery) produced by an explosive eruption of Mount Shishaldin that began around 1340 UTC on 25 September 2023. The bulk of the cloud drifted to the southeast, while another part wrapped cyclonically across the far southeastern Bering Sea. There was also a small secondary eruption that began around 1610 UTC, sending a small volcanic cloud eastward (that moved just north of False Pass).

There were trace to minor amounts of volcanic ashfall reported in False Pass, King Cove, Cold Bay and Sand Point, occurring in conjunction with light rainfall. A 1912 UTC Pilot Report (PIREP) issued at Sand Point (below) mentioned that volcanic ash (VA) was falling in light rain (-RA), covering surfaces.

A radiometrically retrieved Volcanic Ash Height product from the NOAA/CIMSS Volcanic Cloud Monitoring site (below) indicated that parts of the volcanic cloud reached heights in the 18-20 km range.

In Nighttime Microphysics RGB  + daytime True Color RGB images from the CSPPGeoSphere site (below), after sunrise the leading edge of the southeast-moving volcanic cloud exhibited shades of tan to light brown (indicating significant ash content).

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Wave observations from the Aunu’u site just to the east of American Samoa, above, show waves exceeding 12 feet starting late in the day on 22 September and persisting through the weekend into the 25th. The National Weather Service office in Pago Pago issued High Surf Warnings during this event

ASZ001>004-251915-Tutuila-Aunuu-Manua-Swains Island-Rose Atoll-705 PM SST Sun Sep 24 2023

...HIGH SURF WARNING NOW IN EFFECT UNTIL MONDAY...

WHAT...Surf of 15 to 18 feet

WHERE...East and south shores

WHEN...Through Monday

IMPACTS...Expect ocean water occasionally sweeping across beaches,very strong breaking waves, and strong longshore and potentially deadly rip currents. Some strong coastal erosion is likely. Very large waves may bring some ocean debris onto roadways, impact small harbors, and make navigating the harbor channel dangerous.

PRECAUTIONARY/PREPAREDNESS ACTIONS...Residents in vulnerable locations may experience flooding. Some roads in vulnerable, low-lying areas may be closed from floodwaters. Stay tuned to local officials for any road closures or evacuations. Anyone in low-lying and vulnerable areas could be swept out to sea and face significant injury or death.

MetopB and MetopC Advanced Scatterometer plots (taken from this website), below, show a large region of strong (20-25 knot) east-southeast winds to the west and south of Samoa and American Samoa.

GOES-18 Derived Motion Wind vectors, below, similarly show a large region of 20-25 knot winds to the east and south of the Samoan Islands. These winds are helping to force the wave action.

Altimetry from satellites can also be used to determine wave heights, and a plot (also from this website, then click on ‘Altimeter’) is shown below. It is difficult to compare these values to the buoy values above; altimetry plots show the Significant Wave Height, namely the mean wave height of the highest 1/3 of all waves. The single swath shown below has Significant Wave Heights between 9 and 11 feet, at 1343 UTC on 23 September 2023.

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