Overlapping 1-minute Mesoscale Domain Sectors provided 30-second GOES-18 (GOES-West) Infrared Window images of Hurricane Polo (above) as it rapidly intensified from a Category 1 to a high-end Category 3 storm late in the day on 21 September 2026. An eye became apparent by the end of the animation (the overlapping Mesoscale Sectors ended at 0438 UTC on 22 September, when Sector 1 was re-positioned over the Southwest US).

Following the period of 30-second imagery, a single GOES-18 Mesoscale Sector provided 1-minute Infrared Window imagery for the remainder of the day on 22 September (below), as Polo continued to rapidly intensify to a Category 4 (at 0600 UTC) and then to a Category 5 hurricane (at 1200 UTC). It is interesting to note that as Polo was progressing toward its maximum intensity (at 1900 UTC), an Enveloped Eyewall Lighting Signature was evident in the concentration of GLM Flash Points (for example, at 1445 UTC or at 1637 UTC); however, this eyewall lightning then abruptly ended after about 1900 UTC. (The ~2 hour GOES-18 data outage and subsequent image degradation/striping was due to a NOAA firewall maintenance issue.)

In terms of central pressure — with a minimum of 892 hPa (SATCON) — Polo became the second-most intense hurricane on record in the East Pacific.

Within an hour of Polo reaching Category 5 intensity at 1200 UTC, a Synthetic Aperture Radar (SAR) image (below) from Canada’s RCM-3 satellite (source) depicted wind speeds as high as 144.37 knots in the NW quadrant of the hurricane.

Products from the CIMSS Tropical Cyclones site showed two factors that were favorable for Polo’s rapid intensification on 22 September: (1) moving through an environment of low to moderate vertical wind shear (0900 UTC | 1800 UTC), and (2) traversing warm water (Sea Surface Temperature | Ocean Heat Content).

View only this post Read Less

10-minute Full Disk scan GOES-19 (GOES-East) Infrared Window images (above) showed the evolution of Tropical Storm Fay in the East Atlantic Ocean on 20 September 2026. As of 0300 UTC on 21 September — the last image of the animation — NHC rated Fay’s wind speed at 60 knots (just 4 knots below Category 1 Hurricane intensity). GLM Flash Points indicated the presence of intermittent lightning activity within areas of deep convection.

A 2238 UTC overpass of Metop-C provided a swath of ASCAT winds – which had velocities as high as 53 knots (below).

Fay was becoming embedded within an environment of unfavorably-high northwesterly deep-layer wind shear, as shown below (sourced from the CIMSS Tropical Cyclones site).

As a result of increasingly-unfavorable wind shear, the low-level circulation center eventually became exposed as it was displaced to the west and northwest of Fay’s deep convection (below).

View only this post Read Less

The GOES-18 (GOES West) Advanced Baseline Imager showed something interesting off of California’s Cape Mendocino on the morning of Saturday, 19 September 2026. This cape is the westernmost point in California and is characterized by significant terrain changes over a relatively short distance. The Pacific Ocean next to the coast of California is frequently covered in stratocumulus clouds due to the relatively cold sea surface temperatures caused by the California current and its associated upwelling. These cold temperatures are clearly visible in the NOAA Sea Surface Temperature maps derived from satellite observations. Here’s the map for the previous day, 18 September 2026; note how the temperatures around Cape Mendocino (the westward-poking nub near the intersection of 40 N and 124 W) are around 13 C or 55 F.

These cold sea surface temperatures cause the air above the ocean to also become quite cold, cooling to the dew point and forcing the formation of clouds. Since air is a poor conductor of heat, the air further away from the surface does not cool which causes a notable inversion to form and which limits the vertical extent of the clouds that develop. This can result in quite widespread deck of these clouds over cool ocean regions, as can be seen in this geocolor RGB image from GOES-18. Note how, outside of some valley fog, California is basically cloud-free while the ocean immediately adjacent is overcast with marine stratocumulus.

But there’s an exception to this idea that the entire west coast is socked in with clouds. Let’s zoom in on the area around Cape Mendocino with this animated true color loop. While it’s always fun to watch valley fog dissipate with the rising sun, here pay special attention to what’s happening south of the cape.

The winds are predominately northerly and it’s easy to see how the clouds are streaming southward because of that. But in the wake of the Cape, the skies are clear over the ocean. What’s going on here? To get a better idea, let’s take a look at the terrain of Cape Mendocino, courtesy of the US Geological Survey National Map. Here, there’s a topographic map with a transect drawn across the cape to give an idea of the terrain.

As you can see, over a short distance the terrain goes from the ocean at sea level to peaks near 3,000 feet. That’s quite a jump over a relatively short distance and the southerly flow is forced to deflect around the cape. In the wake of the northerly flow that is blocked by the terrain of the cape, drier continental air (enhanced by downsloping) is able to enter that region and prevent clouds from forming despite the quite cold sea surface temperatures. There even seems to be a hint of a terrain-forced mesolow with some southerly flow appearing right next to the coast in this region.

Note how difficult it is to see this clear spot in the infrared imagery, however. This is because the clouds are so shallow that there is very little difference between their temperature and the temperature of the ocean. Because we know what we’re looking for, we can probably identify the clearing region, but we’d likely have to resort to some other product to help discern between clear sky and cloud cover for a region that we hadn’t already been looking at.

View only this post Read Less

10-minute Full Disk scan GOES-19 (GOES-East) daytime True Color RGB + nighttime Dust RGB images created using Geo2Grid (above) showed a plume of blowing dust originating from the dry Lake Colhué Huapi in southern Argentina on 16 September 2026. The airborne dust appeared as shades of magenta to violet in the nighttime Dust RGB images. This blowing dust was lofted by strong westerly winds in the wake of a cold frontal passage (surface analyses).

During the same time period, GOES-19 daytime True Color RGB + Nighttime Microphysics RGB images (below) highlighted a curious difference in the nighttime appearance of the blowing dust plume — with parts of the plume exhibiting brighter shades of white.

The differences in appearance of both a narrow dust plume originating from the far northern tip of the dry lake bed and part of the leading (eastern) edge of the plume were highlighted in a comparison of Dust RGB and Nighttime Microphysics RGB images at 2320 UTC (below).

2-3 hours prior to the start time of the GOES-19 RGB image animations shown above, the plume of blowing dust was reducing the surface visibility to ~6 miles at Comodoro Rivadavia (METAR identifier SAVC) at 1700-1800 UTC (below). Lake Colhué Huapi lies within the lower-elevation (darker shades of green) area 50-60 miles west-northwest of SAVC.

A plot of surface report data from SAVC (below) indicated that westerly winds gusted as high as 43 knots at 2000 UTC on 16 September (the start time of the GOES-19 RGB image animations).

View only this post Read Less