1-minute Mesoscale Domain Sector GOES-19 (GOES-East) Visible images (above) showed Hurricane Humberto as it intensified from a Category 4 to a Category 5 storm on 27 September 2025 (Humberto became the second Category 5 storm in the Atlantic Basin this season — with Erin being the first). Low-altitude mesovortices were evident within the eye, along with cloud-top gravity waves in the surrounding eyewall region.

In an animation of 1-minute GOES-19 Infrared images (below), the eye began to exhibit a slight amount of trochoidal motion as Humberto intensified later in the day.

A DMSP-18 SSMIS Microwave image at 2013 UTC — shortly before Humberto was upgraded to Category 5 at 2100 UTC (below) displayed a fully-closed inner eyewall.

Humberto’s intensification to Category 5 occurred as the hurricane was moving through an environment of weak deep-layer wind shear (below) and traversing warm water.

Microwave, wind shear and sea surface temperature imagery was sourced from the CIMSS Tropical Cyclones site.

A RCM-2 Synthetic Aperture Radar (SAR) image (source) at 2214 UTC (below) sensed wind speeds as high as 126.94 kt in the NW quadrant of Humberto.

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10-minute Full Disk scan GOES-18 (GOES-West) daytime True Color RGB + nighttime Dust RGB images created using Geo2Grid (above) showed a plume of resuspended volcanic ash (hazy shades of tan in True Color RGB, and shades of violet in Dust RGB) from the 1912 Novarupta-Katmai eruption in Alaska — which was being transported offshore across the Shelikof Strait and over parts of Kodiak Island during 22-23 September 2025. Surface volcanic ash within the Valley Of Ten Thousand Smokes was being lofted by strong northwesterly winds that were being channeled through the valley.

According to this USGS Volcano Notice, the National Weather Service issued a SIGMET advising aviation interests that the maximum height of this resuspended ash was 6000 ft.

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This blog author loves posting about the seasons! They provide the opportunity to post some awesome full disk GOES images, but there’s more than that. The passing of the seasons has always been marked by humans, sometimes because of agricultural significance, spiritual significance, community bonding, or simply to mark time. The fall (or autumnal) equinox marks the time when the sun is directly above the equator, as we transition seasons from summer to fall in the northern hemisphere (and it’s going from spring to summer in the southern hemisphere). This year the fall equinox is September 22, 2025. It can be seen in GOES visible band imagery at satellite sunrise or sunset where the terminator (the dividing line between night and day) is aligned perfectly north & south in the middle of a full disk visible band image. For the people in the northern hemisphere, the autumnal equinox marks the end of summer and the beginning of autumn, which lasts until the winter solstice (around December 21 or 22). This is the astronomical definition of the changing of seasons as the tilt of the earth on its axis will lead to summer in the southern hemisphere as we head into winter up here in the northern hemisphere.

Sunset and sunrise time-lapse animations from space (below) show the progression of the terminator from spring equinox, through summer solstice, to fall equinox from the satellite’s point of view. For these times of day the disk is “half” illuminated so the terminator formed by the shadow of the night-side of earth is easy to track. GOES-East sits over the equator above 75 West (which is in Columbia, near where the borders of Peru, Ecuador, and Columbia meet) and GOES-West sits over the equator above 137 West (which is out in the Pacific Ocean away from any major land masses – maybe the closest thing is French Polynesia, 680 miles to the southwest; and for reference, Hawaii is over 1700 miles to the northwest of the GOES-West subpoint). These two views provide coverage of nearly two thirds of the earth and so in addition to the terminator you can see some of the things that affected life across our hemisphere from major storm systems to smoke and dust. Technically sunrise, sunset, and local noon vary from day to day, but these animations use a consistent time every day that is close to sunrise, sunset, or noon.

In this GOES-19 (GOES-East) animation in addition to seeing the terminator progress from equinox to summer solstice and back to equinox, there are multiple tropical storms visible, including Hurricane Erin in mid-August and Hurricane Gabrielle in the last few frames. One can also observe dust blowing off the African continent and the reflection of the sun migrating north from the equator and then back south to the equator.

In this GOES-18 (GOES-West) animation there are also multiple tropical storms visible. There have been 8 tropical storms and 8 hurricanes this year so far in the east Pacific, some of which caused major flooding in parts of Mexico. There was also plenty of wildfire smoke mixed in with the clouds over Canada and the northern half of the US during summer 2025, affecting air quality across wide areas of both countries.

In this GOES-18 (GOES-West) animation of local noon the seasonal transitions may be more difficult to spot. As the northern hemisphere transitions from spring equinox, through summer, to fall equinox, the earth’s tilt puts the southern hemisphere away from the sun. This can be seen at the bottom of these images at the south pole as it gradually gets darker and darker until the solstice (June 21) and then starts to get light again. That’s winter in Antarctica and there are days where it just stays dark all day for those scientists and support staff that work down there through their winter. Some of the tropical storms and hurricanes may be easier to watch in this animation as the whole disk is as well-illuminated as it gets at satellite noon.

This GOES-19 (GOES-East) animation is similar to the previous one, but now at sunset for the satellite (23:00 UTC).

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For the past few days, the eyes of the Philippines and Taiwan have been focused on a developing tropical system in the western Pacific. What began as a small group of convective cells northwest of Micronesia on 16 September 2025 has grown into the most intense tropical system up to this point in 2025. Super Typhoon Ragasa (called Nando in the Philippines as the Philippine national meteorological service maintains a separate list of typhoon names). A super typhoon is broadly equivalent to a strong category 4 hurricane on the Saffir-Simpson scale. For a storm to achieve super typhoon status, winds have to be in excess of 130 kts (the upper bound for a category 4 storm is 136 kts).

The rapid intensification of Ragasa can be seen in the Advanced Himawari Imager (AHI) view over the last three days starting at 0300 UTC in 19 September 2025. Using the Band 13 infrared view enables the consistent monitoring of the storm at all hours of the day.

We’ll discuss a few key moments from this loop. At the start of the animation (0300 UTC on 19 September), the system had just been classified as a tropical storm only a few hours earlier. Overall organization is weak and no eye is present.

However, this area was well-suited for tropical intensification. First, note the CIMSS MIMIC-2 total precipitable water (TPW) imagery from the same time as the above IR satellite view. TPW values are elevated in the western Pacific. Even outside of the storm itself (seen as the fuchsia area exceeding the top of the color scale), MIMIC indicates TPW of more than 60 mm west of the Philippines.

Second, the sea surface temperatures (SSTs)in this area were quite warm. The NCEP SST product, as mapped by SSEC, shows temperatures approaching 32 C (90 F).

In fact, these temperatures are 1-2 C above normal, as determined by the NOAA Coral Reef Watch daily SST anomaly plot, seen here for 19 September.

With lots of atmospheric moisture and significant amounts of warm oceanic water, the latent heat machine that drives tropical systems sprang into life, and the newly christened Ragasa quickly intensified. By 2100 UTC on the 19th, an eyelike structure could be seen at the center of rotation.

Over the next day, the eye structure strengthened and then went through an eyewall replacement cycle but retained its strength at teh conclusion of that process. Evacuations were ordered for parts of the Philippines and Taiwan in anticipation of landfall. Sustained winds in excess of 115 kts were reported at 0000UTC on the 21st as the storm exhibited a compact eye.

By 0000 UTC on the 22nd, those sustained winds had increased to 145 kts putting the storm solidly into Category 5 status. The large eye of Ragasa is passing north of the large Philippine island of Luzon, though that region will be battered by significant winds over the coming day. This can be seen in the 10 min Himawari target imagery, which is following Ragasa as it progresses westward.

At this point Ragasa is projected to continue west-northwest and pass very close to Hong Kong. The past and projected track can be seen on the forecast graphic product from the Joint Typhoon Warning Center, issued at 0000 UTC on 22 September.

Additional information pertaining to Ragasa is available in this blog post.

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