GOES-18 (GOES-West) SO2 RGB and Ash RGB images (above) showed the northeastward drift of a volcanic cloud produced by an eruption of Mount Shishaldin that began shortly before 0730 UTC on 23 July 2023. The initial (higher-altitude) portion of the volcanic cloud likely contained moderate concentrations of SO2 (denoted by brighter shades of yellow in the SO2 RGB images) — while the trailing (lower-altitude) portion of the volcanic cloud likely contained concentrations of ash (shades of pink in the Ash RGB images). The ash signature dissipated after about 4 hours, while the SO2 signature persisted for the duration of the 11.5-hour animation.

A toggle between the SO2 RGB and Ash RGB images at 1000 UTC is shown below.

A pilot report issued at 0727 UTC (below) indicated that volcanic ash (VA) was rising to altitudes of 30000 feet (FL300).

===== 24 July Update =====

A longer animation of GOES-18 SO2 RGB images (above) showed the distinct SO2 signature (brighter shades of yellow) from the Shishaldin eruption, as it rotated counterclockwise within the circulation of a slow-moving middle tropospheric low in the Bering Sea — moving over far southwest Alaska and St. Lawrence Island on 23 July, and eventually becoming stretched into a long/narrow filament over far eastern Russia on 24 July.

View only this post Read Less

The animation below, showing GOES-16 Clean Window infrared imagery (Band 13, 10.3 µm; processed using geo2grid, v1.1), tracks the named storm Don, first named as Subtropical Storm Don at 0900 UTC on 14 July, reclassified as Tropical Depression Don at 1500 UTC on the 17th, and upgraded to a Tropical Storm at 0300 UTC on the 18th, and to a hurricane at 2100 UTC on the 22nd. The animation shows the storm periodically affected by shear (when the low-level circulation is separated from the deep convection), especially on the 14th of July.

A closer view using 10-minute GOES-16 Visible and Infrared images on 22 July (above) showed Tropical Storm Don developing a distinct eye, before being upgraded to a Hurricane at 2100 UTC. The coldest cloud-top infrared brightness temperatures were around -60ºC (darker shades of red).

---

On 24 July, Long-lived Don, devoid of convection, was deemed extra-tropical. This occurred while Don was moving north of the domains shown above. The last tropical advisory was issued at 1500 UTC.

For more information on Don, refer to the National Hurricane Center’s website. Don presents no current threat to land.

View only this post Read Less

GOES-18 (GOES-West) Day Land Cloud Fire RGB, Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.3 µm) and Visible images with an overlay of the Fire Power derived product — Fire Power is a component of the GOES Fire Detection and Characterization Algorithm FDCA — (above) showed thermal signatures associated with a wildfire that produced a pair of pyrocumulonimbus (pyroCb) clouds in Canada’s Northwest Territories late in the day on 21 July 2023.

At 2300 UTC, the 3.9 µm infrared brightness temperature reached 90.85C, with a Fire Power value of 3623 MW (below). Located at a latitude of 67.35N, this wildfire was only about 40 miles south of the Arctic coast.

The 2 pyroCb clouds began to form at 2340 UTC and 0010 UTC — when pyrocumulus jumps were evident in the RGB and Visible images. Cloud-top 10.3 µm infrared brightness temperatures eventually were as cold as -54.7C.

View only this post Read Less

Sentinel-1A overflew Hawai’i and Maui near sunrise on 20 July 2023, measuring the surface winds surrounding those islands. The mp4 animation above (click here for an animated gif) shows GOES-18 visible imagery (Band 2, 0.64 µm) from 1601 to 1801 UTC. The animation includes toggles at 1616 UTC when Sentinel 1A data resulted in wind measurements. (Sentinel-1A winds are available at this website — note that this is a new url!; this website shows global views of Normalized Radar Cross Section (NRCS) data.) The strong winds in the channel can be inferred by the swift motion of the clouds there compared to elsewhere during the animation. Note also how the high terrain of Hawai’i and Maui are effectively blocking the low-level flow around those islands.

The 1616 UTC imagery are shown side by side below (the visible image grey scale upper bound is reduced in the image from the default 130 to 25). The strong winds through the Alenuihaha channel (20-30 knots, and closer to 35 knots just south of Maui) are apparent, and many wind gradients in the SAR data are associated with GOES-18 visible imagery features.

SAR Satellites operate on a 12-day repeat cycle. Sentinel-1A will take observations in this same region 12 days after 20 July, i.e., on 1 August.

View only this post Read Less