5-minute CONUS Sector GOES-19 (GOES-East) Day Snow-Fog RGB images (above) displayed the signature of snow cover (shades of red) across parts of Montana on 13 October 2026. This was remnant snow cover that fell 2 days earlier, accumulating to depths as high as 8-9 inches — and snow depths on the morning of 13 October were generally in the 4-8 inch range at lower elevations. This remnant snow cover had the effect of keeping surface air temperatures several degrees cooler compared to nearby areas of bare ground.

Another satellite product that is useful for highlighting snow cover is the Day Cloud Phase Distinction RGB (below) — which depicts snow cover as brighter shades of green. In both RGB image types, low stratus and fog appear as pale shades of white.

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While many of the nation’s meteorological eyes have been along the Gulf Coast as Isaias made just the first Atlantic hurricane landfall of 2026, that wasn’t the only part of the continental United States to be impacted by a tropical system this weekend. In the evening of October 10, the storm formerly known as Hurricane Rachel made its landfall in the far northern part of Baja California, and San Diego experienced some of its impact.

Rachel had been as strong as a Category 3 storm while it was in the warm waters of the Pacific found to the south of the Gulf of California. However, as it propagated to the north, it moved over the relatively cool waters of the California Current. Even in an El Niño year, this current (which originates well to the north adjacent to British Columbia) runs cold. Water adjacent to southern California and Baja California in Mexico was around 22-24 C, or 72-75 F, as can be seen in the following map from the NOAA Physical Sciences Lab.

As a result, Rachel’s intensity peaked several days earlier, as captured by the CIMSS D-MINT satellite intensity product. By the time it reached the shore, it was well into tropical storm status.

The devolution of Rachel is quite easy to see from the satellite-based synthetic aperture radar (SAR) winds from Canada’s RADARSAT. Remember, these can only tell the speed of the wind, and numerical weather prediction analyses are used to overlay wind directions on top of the SAR imagery. Still, we can see that as of 8 October (Thursday) Rachel still had a notable eye.

By the time landfall was imminent, however, the structure was far more ragged and there was no obvious circulation pattern. Here’s the SAR wind imagery from 11 October 2026, three days later. Note the very different structure in the wind speed and the lack of a classic tropical shape to the wind field.

Here’s the Band 13 (10 micron) animation from GOES-18 (GOES West) for the afternoon and evening of Saturday, 10 October. Again, this looks far less like a tropical system than it did a few days earlier when it was at its maximum strength of Category 3.

The approach of Rachel caused the National Hurricane Center to issue a tropical storm watch for San Diego County, California, just the second ever tropical storm watch issued for the state of California (The first was Hurricane Hilary in 2023). Flooding has been a concern for the southeast United States with flash flood warnings issued for Las Vegas and southwestern and central Utah.

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Overlapping 1-minute Mesoscale Domain Sectors provided GOES-19 (GOES-East) images at 30-second intervals — and Infrared Window imagery (above) showed Hurricane Isaias moving toward the US Gulf Coast on 09 October 2026. Isaias reached Category 3 intensity at 1220 UTC (Infrared image | NHC advisory). The coldest cloud-top infrared brightness temperatures were in the -85 to -88 C range (darker shades of purple). GLM Flash Points displayed occasional lightning activity within the core of Isaias.

30-second sunrise-to-sunset GOES-19 CIMSS Natural Color RGB images created using Geo2Grid are shown below.

Although Isaias was moving through an environment of rather high southwesterly vertical wind shear (below), the shear direction generally aligning with the storm motion likely helped to mitigate unfavorable shear effects.

Isaias passed over a patch of fairly high Ocean Heat Content (below), which may have played a role in its intensification to Category 3.

While Isaias was still a Category 2 storm, a well-defined eye was depicted in microwave imagery from ATMS and DMSP-18 (below).

Later in the day, after Isaias had reached Category 3 intensity, microwave images from ATMS and DMSP-18 (below) continued to display an eye — although the eyewall had eroded along the southern edge.

In the GOES-19 Infrared imagery, a sustained and distinct eye was no longer evident after about 1400 UTC — but the MIMIC-TC product (below) showed the slowly-eroding eye structure for a longer period of time.

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A closer view of 30-second GOES-19 Infrared Window images (below) showed Category 3 Hurricane Isaias as it approached the Gulf Coast and eventually made landfall near Destin, Florida (METAR identifier KDTS) at 0130 UTC on 10 October (weakening to a high-end Category 2 storm just prior to landfall). After landfall, there was a rapid warming of GOES-19 cloud-top infrared brightness temperatures and a decrease in GLM-based lightning activity.

Shortly before landfall, Isaias produced a peak wind gust of 80 knots (92 mph) at Pensacola International Airport KPNS — and shortly after landfall Isaias produced a peak wind gust of 99 knots (114 mph) at Whiting Naval Air Station KNDZ (below). A list of wind gusts included 117 mph at Oriole Beach, Florida.

About 1.5 hours prior to landfall, northerly to northwesterly offshore Synthetic Aperture Radar (SAR) wind speeds (below) were as high as 109.1 knots in the NW quadrant of Isaias, and 110.3 knots in the SW quadrant of Isaias.

Noteworthy in this case was the occurrence of strongest surface winds on the *west* side of Isaias’s center — the SAR image above nicely showed the narrow corridor of high wind speeds associated with a sting jet (NWS Mobile forecast discussion), in agreement with a plot of peak wind gusts (below).

As Isaias was beginning its gradual transition to an inland post-tropical cyclone, GOES-19 Infrared Window imagery (below) exhibited the “scorpion tail” cloud signature that is often associated with a sting jet (the curved scorpion tail cloud feature was passing over Pensacola KPNS, which recorded a peak wind gust of 73 knots around that time).

Other cases where this “scorpion tail” satellite feature accompanied a sting jet are documented here on this blog.

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Tropical Storm Isaias reached hurricane intensity at 0330 UTC on 08 October 2026 — becoming the first Atlantic Basin (which includes the Gulf of Mexico) hurricane of the 2026 season. 1-minute Mesoscale Domain Sector GOES-19 (GOES-East) Infrared Window images (above) showed the deep convection in the vicinity of the surface storm center of Hurricane Isaias — with GLM Flash Points displaying lightning activity with many areas of deep convection. The coldest cloud-top infrared brightness temperatures associated with convective bursts near the storm center were in the -85 to -90 C range (darker shades of purple).

In an animation of 1-minute GOES-19 Visible images (below), a gradual thinning of high clouds over the storm center eventually revealed an eye for a few hours later in the day.

Isaias continued to intensify to a Category 2 storm by 1800 UTC, in spite of moving through an environment of moderate southwesterly vertical wind shear (below).

A DMSP-18 SSMIS Microwave image (below) depicted a large (albiet somewhat ragged) eye.

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