The residents of American Samoa found themselves in the early morning hours of 20 November 2025, as strong maritime convection moved into the region. There is no radar in the area, so satellite observations are critical for operational awareness and nowcasting. The Band 13 infrared view on GOES-18 showed a large array of vigorous convective storms stretching east-west across the near-equatorial Pacific.

While this product gives a solid qualitative view of where deep, moist convection is taking place, additional products can also further inform as to the intensity of the storms. One of these is the Day Convection RGB. The recipe for this product is designed to show red when clouds are high and green where cloud droplets are large. The combination of high clouds and large droplets is found in deep convective plumes, while the combination of red and green produces yellow. The following animation shows that relationship in action. You might note that this loop spans the sunrise. Since the product relies heavily on near-infrared and visible reflectance, it can only be used during the day. The lack of yellow at the start of the loop does not mean that there is no deep convection. Instead, it just means that the 3.9 minus 10.3 micron brightness temperature difference which comprises the green channel of this image in very small at night (unless something is on fire).

With no radar, satellites have to step in and help fill the gap. The GREMLIN product is a machine-learning retrieval of rainfall from satellite brightness temperature observations, designed to mimic the radars that forecasters find so familiar. The following loop is from GREMLIN as displayed on AWIPS for roughtly the same time as the previous animations. Note the pulses of yellow over and around the island of Tutuilia, corresponding with rain rates of 40 mm/hr (more than 1.5 inches per hour).

Satellites can also help judge the convective instability of the atmosphere. NUCAPS-retrieved thermodynamic profiles from polar-orbiting hyperspectral infrared and microwave sounding instruments provide valuable information about the atmosphere’s thermodynamic state. Since NUCAPS retrieves dozens of profiles simultaneously, it’s possible to analyze the profiles like a three-dimensional cube, taking horizontal slices and seeing how key parameters change horizontally as well as vertically. The next image shows the 850-500 mb lapse rate over the central Pacific as calculated by NUCAPS and displayed in AWIPS. The NUCAPS availability parameter is plotted on top as an array of red, blue, or green dots. The values in the middle of the convection are untrustworthy as neither the infrared nor the microwave sounders can penetrate the convective cores. Still, the reliable locations show lapse rates approaching 6 C/km. In the tropics, the moist adiabatic lapse rate is less than it is in the tropics as more latent heat lease means a slower lapse rate. Therefore, the observed lapse rates can still indicate instability

Clicking on any of the dots in AWIPS brings up the sounding and its associated stability indices. For one green dot near Pago Pago, American Samoa, the environment is clearly moderately unstable with CAPEs in the mid-to-upper 1000s and effectively no CIN to restrain convection.

This just continues a trend of record-setting precipitation in American Samoa, which has previously been discussed on the blog. The chart below shows the accumulated precipitation for so far in 2025 (blue), the wettest year before now (2020, magenta), and normal (brown). Already in 2025, the total rainfall has exceeded every single year save one despite still having a month to go.

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10-minute Full Disk scan GOES-19 (GOES-East) Water Vapor images centered over the southern Great Lakes (above) included contours of Moderate Or Greater (MOG) Turbulence Probability (yellow contour = 40%) and Pilot Reports of Turbulence on 20 November 2025. The yellow 40% MOG contour progressed eastward across the southern Great Lakes and toward the Northeast US during the day — note the appearance of one report of Extreme Turbulence over the southwest portion of Lower Michigan around 1500 UTC.

Products from the Aviation Weather Center allowed cursor samples of two closely-spaced Pilot Reports of Extreme Turbulence — apparently from the same aircraft, as it was flying southeast (below).

The second encounter of Extreme Turbulence occurred at 1505 UTC, causing minor injuries (below).

A toggle between the 1501 UTC GOES-19 Water Vapor image and a 3-hour NAM40 model forecast of 250 hPa winds valid at 1500 UTC (below) indicated that the initial 1450 UTC Pilot Report of Extreme Turbulence (red symbol) occurred in an area of strong speed shear just north of the axis of a 150-knot jet streak (shades of orange). There was also the characteristic dry/moist gradient in Water Vapor imagery along the axis of the upper-tropospheric jet streak.

An animation of 5-minute CONUS Sector GOES-19 Water Vapor images with Pilot Reports of Turbulence is shown below.

Thanks to Rick DiMaio for alerting us to this case!

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10-minute Full Disk scan GOES-19 (GOES-East) daytime True Color RGB + nighttime Dust RGB images — created using Geo2Grid (above) showed the offshore transport of significant amounts of blowing dust from the Patagonia region of southern Argentina on 17-18 November 2025.

A slightly longer period of GOES-19 Dust RGB images (below) displayed the plume of airborne dust (brighter shades of magenta) as it arced eastward then southward across the southern Atlantic Ocean.

The airborne dust also exhibited a similar magenta signature in Nighttime Microphysics RGB images from the CSPP GeoSphere site (below).

Strong boundary layer winds  — which lofted the areas of blowing dust — developed in the wake of a cold front associated with a low pressure system that was deepening off the coast of Argentina (below).

There was a wind gust to 75 kts (86 mph) at METAR site SAVC at 1500 UTC — and for several hours leading up to that time, blowing dust had reduced the surface visibility to less than 1 mile at that airport (below).

5 hours later there was a wind gust to 61 kts (70 mph) at METAR site SAVT at 2000 UTC — and just before that time, blowing dust reduced the surface visibility to about 1 mile at that airport (below).

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One of the most popular GOES products is the True Color RGB. There’s a lot to like about it: a constantly updating full color view of the planet, watching clouds swirl above sapphire seas and emerald forests. It can be positively mesmerizing to watch loops of this product, at least until the sun sets, the terminator arrives, and the visible reflectances go away.

There is an important cacceat to remember, though. The GOES true color product isn’t really a true color image of the planet. The GOES ABI instrument is not like a consumer digital camera, in which separate channels record the red, blue, and green reflectance and assemble those into an easily recognizable photograph. Instead, while ABI has a blue channel (Channel 1, 0.47 microns) and a red channel (Channel 2, 0.64 microns), it doesn’t have a green channel. Instead, ground processing does a little trickery. Channel 3, at 0.86 microns, is very sensitive to vegetation. What we can do instead is create an RGB product where red is red, blue is (wait for it…) blue, and green is a channel that is strongly representative of surfaces that are green. Most of the time this works just fine for the majority of users.

However, this all relies on the assumption that vegetation is green. But what happens if you have a lot of vegetation that isn’t green at all? How would that appear on the GOES True Color RGB? This image, taken on 17 November 2025, shows the southeastern United States as seen from GOES-19. Note how lush the forests in this region look. There’s lots of green throughout the region. If you were looking to identify where fall colors weer at their peak, it might be challenging to do so with this image.

VIIRS tells a different story. This image, obtained via direct broadcast, was taken at approximately the same time from the NOAA-21 satellite. The VIIRS instrument has true red, green, and blue channels, so a true color RGB is much closer to what our eyes would perceive if we were looking down from space. Note how the green areas of this image are much smaller in extent. Florida, southern Alabama, and the coastal regions of Georgia and South Carolina still retain much of their verdant colors as before. However, the hardwood forests of Appalachia, including the dense forests along the Tennessee / North Carolina border, are much browner than before.

The following slider allows you to directly compare the two images to see how they differ. Check out how the colors along the coasts, where trees are still green, are mostly the same between the two images, but they are very different in the forested regions where leaves have already turned.

This slider also does a good job of illustrating parallax and how cloud height exacerbates it. As you slide the bar back and forth, note that there’s very small displacements in the positions of the low clouds, like the popcorn convection throughout the Florida peninsula. However, the high cirrus (likely aged contrails) over Georgia and Alabama show a much greater horizontal displacement due to the very different scanning positions of the two instruments.

This simple example shows that it’s important to remember that the GOES ABI True Color product is really representing an idealized version of what we think the planet is supposed to look like, rather than a direct capture of what it actually looks like right now. Note that this is not as much of an issue with many other geostationary satellites. The Flexible Combined Imager (FCI) on EUMETSAT’s Meteosat-12, the Advanced Himawari Imager (AHI) on the Himawari series operated by Japan, and the Advanced Meteorological Imager (AMI) on South Korea’s GEOKOMPSAT-2a all have the necessary channels to produce full spectrum true color images. Note that this is not true for SEVIRI, still in operational use over the Indian Ocean on Meteosat-9 and in wide use in central and eastern Asia. EUMETSAT’s Natural Color RGB is a combination of 1.6 (red), 0.8 (green), and 0.6 (blue), which has even fewer visible channels than the GOES True Color.

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