CIMSS Satellite Blog, CIMSS

Thunderstorms prompt the issuance of Flash Flood Warnings in American Samoa

By Scott Bachmeier • 24 January 2026

Due to a lack of radar coverage over American Samoa, WSO Pago Pago requested a 1-minute Mesoscale Domain Sector over the islands to monitor convective development and the potential for flash flooding. GOES-18 (GOES-West) Clean Infrared Window (10.3 µm) images (above) showed rain showers and thunderstorms that developed in the general vicinity of the American Samoa... Read More

1-minute GOES-18 Infrared images with an overlay of GLM Flash Points (white dots) and METAR surface reports (cyan), from 1501 UTC on 24 January to 0000 UTC on 25 January [click to play MP4 animation]

Due to a lack of radar coverage over American Samoa, WSO Pago Pago requested a 1-minute Mesoscale Domain Sector over the islands to monitor convective development and the potential for flash flooding. GOES-18 (GOES-West) Clean Infrared Window (10.3 µm) images (above) showed rain showers and thunderstorms that developed in the general vicinity of the American Samoa island of Tutuila (where Pago Pago International Airport NSTU is located) on 24 January 2026. GLM Flash Points indicated that intermittent lightning occurred near Tutuila — and thunderstorms were occasionally reported at NSTU. The development of deep convection was enhanced by the presence of a surface trough of low pressure across the area (1500 UTC | 1800 UTC | 0000 UTC).

The coldest cloud-top infrared brightness temperatures were in the -85 to -89ºC range (darker shades of purple embedded within brighter white regions) — which represented a slight overshoot of the Most Unstable (MU) air parcel’s Equilibrium Level (EL), which was around 15 km (or 50 kft) according to a plot of rawinsonde data from NSTU at 0000 UTC on 25 January (below).

Plot of rawinsonde data from Pago Pago, American Samoa at 0000 UTC on 25 January [click to enlarge]

The GOES-18 Infrared image at 1850 UTC (below) included a sample of the corresponding NSTU METAR — which indicated that a thunderstorm with heavy rain showers was reducing the visibility to 3 miles at that time. Note that the coldest cloud-top infrared brightness temperatures of that particular thunderstorm (violet pixels) were displaced to the southwest of NSTU, due to a GOES-West parallax offset associated with a cloud-top altitude around 50 kft or 15.2 km.

GOES-18 Infrared image at 1850 UTC on 24 January, with a cursor sample of the 1850 UTC Pago Pago (NSTU) METAR surface report [click to enlarge]

The GOES-18 Infrared image at 2058 UTC (below) included a sample of the corresponding NSTU METAR — which indicated that a thunderstorm had earlier occurred from 1800-1856 UTC, and heavy rain showers had occurred from 1811-1951 UTC.

GOES-18 Infrared image at 2058 UTC on 24 January, with a cursor sample of the 2058 UTC Pago Pago (NSTU) METAR surface report [click to enlarge]

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Decoded surface reports from Pago Pago, with the precipitation reports for 24 January (local time) highlighted by a green box [click to enlarge]

Pago Pago recorded 2.76″ of rainfall during their calendar day of 24 January (above) — with most of that occurring during the ~2 hour period from 1811-1951 UTC (below). WSO Pago Pago issued Flash Flood Warnings at 1812 UTC and 2100 UTC on 24 January.

Pago Pago METAR reports, with the period of heavy rain showers (+SHRA) occurring within the red box [click to enlarge]

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Aircraft dissipation trails drift across Ohio

By Scott Bachmeier • 24 January 2026

5-minute CONUS Sector GOES-19 (GOES-East) Red Visible and Near-Infrared “Snow/Ice” images (above) displayed a cluster of aircraft dissipation trails or “distrails” (in contrast to aircraft condensation trails or contrails) that drifted eastward across Ohio on 24 January 2026.These distrail features were caused by aircraft that were either ascending through or descending through a... Read More

5-minute GOES-19 Red Visible images (0.64 µm, top) and Near-Infrared “Snow/Ice” images (1.61 µm, bottom), from 1601-1801 UTC on 24 January [click to play MP4 animation]

5-minute CONUS Sector GOES-19 (GOES-East) Red Visible and Near-Infrared “Snow/Ice” images (above) displayed a cluster of aircraft dissipation trails or “distrails” (in contrast to aircraft condensation trails or contrails) that drifted eastward across Ohio on 24 January 2026.

These distrail features were caused by aircraft that were either ascending through or descending through a cloud layer composed of supercooled water droplets — cooling from wake turbulence (reference) and/or particles from the jet engine exhaust acting as ice condensation nuclei caused the small supercooled water droplets to transform into larger ice crystals (many of which then often fall from the cloud layer). The darker gray appearance of the distrails in 1.61 µm imagery confirmed that those features were composed of ice crystals (since ice is a strong absorber of radiation at that wavelength).

The corresponding GOES-19 Day Cloud Phase Distinction RGB images created using Geo2Grid (below) provided another view of the distrails — the brighter shades of green were indicative of glaciating cloud features. Interestingly, numerous long/narrow contrails were also apparent over the supercooled cloud layer (shades of white) to the south and east of the distrails.

GOES-19 Day Cloud Phase Distinction RGB images, from 1601-1801 UTC on 24 January [click to play animated GIF]

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Havasu Fire in Arizona

By Scott Bachmeier • 21 January 2026

A prescribed burn in far western Arizona’s Havasu National Wildlife Refuge became uncontrolled as northerly winds unexpectedly increased (gusting to 36 mph at RAWS site QHAA3 just north of the fire, and gusting to 28 mph at Needles Airport just west of the fire around 2300 UTC) — and grew to become the Havasu Fire... Read More

5-minute GOES-18 Microphysics RGB images with an overlay of NGFS Fire Detection polygons and plots of surface reports, from 1501 UTC on 19 January to 1501 UTC on 21 January [click to play MP4 animation]

A prescribed burn in far western Arizona’s Havasu National Wildlife Refuge became uncontrolled as northerly winds unexpectedly increased (gusting to 36 mph at RAWS site QHAA3 just north of the fire, and gusting to 28 mph at Needles Airport just west of the fire around 2300 UTC) — and grew to become the Havasu Fire on 19 January 2026. The fire’s thermal signature was evident in a 2-day animation of 5-minute PACUS Sector GOES-18 (GOES-West) Microphysics RGB images and Next Generation Fire System (NGFS) Fire Detection polygons from 19-21 January (above).

Although the initial fire detection signal was seen in the GOES-18 Microphysics RGB image at 1521 UTC, the initial NGFS Fire Detection polygons appeared at 1606 UTC (below).

GOES-18 Microphysics RGB image at 1606 UTC on 19 January, with the initial detection of NGFS Fire Detection polygons [click to enlarge]

A probe of the NGFS Fire Detection polygons at 0451 UTC on 20 January (below) revealed a 3.9 µm infrared brightness temperature of 137ºC — which is the saturation temperature of GOES-18 ABI Band 7 detectors.

GOES-18 Microphysics RGB image at 0451 UTC on 20 January, with a probe of NGFS Fire Detection polygons [click to enlarge]

On 20 January, GOES-18 GeoColor RGB images (below) showed the south-southeast transport of smoke from the Havasu Fire — hazy conditions were reported in Lake Havasu City during the day. The smoke affected school activities: students were kept inside for recess that day, and the evening Lake Havasu High School Boys Soccer game was postponed for another date.

5-minute GOES-18 GeoColor RGB images with an overlay of NGFS Fire Detection polygons and plots of surface observations, from 1546-2001 UTC on 20 January [click to play MP4 animation]

The southward transport of Havasu Fire smoke could be seen in True Color RGB images from both GOES-18 (GOES-West) and GOES-19 (GOES-East), sourced from the CSPP GeoSphere site (below).

5-minute True Color RGB images from GOES-18 (left) and GOES-19 (right), from 1516-2006 UTC on 20 January [click to play MP4 animation]

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Ice in southern Lake Michigan

By Scott Bachmeier • 20 January 2026

1-minute Mesoscale Domain Sector GOES-19 (GOES-East) True Color RGB images from the CSPP GeoSphere site (below) showed ice that had formed in far southern Lake Michigan (within the nearshore waters of Wisconsin, Illinois and Indiana) on 20 January 2026.1-minute GOES-19 Visible images with plots of surface winds and surface air temperatures (below) depicted... Read More

1-minute GOES-19 True Color RGB images, from 1349-1629 UTC on 20 January [click to play MP4 animation]

1-minute Mesoscale Domain Sector GOES-19 (GOES-East) True Color RGB images from the CSPP GeoSphere site (below) showed ice that had formed in far southern Lake Michigan (within the nearshore waters of Wisconsin, Illinois and Indiana) on 20 January 2026.

1-minute GOES-19 Visible images with plots of surface winds and surface air temperatures (below) depicted the cold air temperatures — from single digits below 0ºF to single digits above 0ºF — that were present near the Lake Michigan coast shortly after sunrise. Along the eastern coast of the lake, surface air temperatures were in the 10-16ºF range, and lake effect cloud bands were producing snowfall in far southwestern Lower Michigan.

1-minute GOES-19 Visible images, with hourly plots of surface wind barbs and 20-minute plots of surface air temperature, from 1336-1745 UTC on 20 January [click to play MP4 animation]

The GOES-19 Visible image at 1510 UTC (below) included an overlay of Metop-C ASCAT wind barbs — which showed westerly winds of 20-25 kts that were causing the ice to slowly drift away from the coast.

GOES-19 Visible image at 1510 UTC on 20 January, with an overlay of Metop-C ASCAT wind barbs [click to enlarge]

A toggle between the 1500 UTC GOES-19 Visible image with and without an overlay of the 1500 UTC GOES-19 Sea Surface Temperature (SST) derived product (below) indicated that SST values were as warm as 3.54ºC in the open waters just east of the sea ice.

GOES-19 Visible image at 1500 UTC, with/without an overlay of the GOES-19 Sea Surface Temperature derived product [click to enlarge]

A 30-meter resolution Landsat-8 Natural Color RGB image visualized using RealEarth (below) provided a more detailed view of the lake ice in the vicinity of Chicago.

Landsat-8 Natural Color RGB image at 1628 UTC on 20 January [click to enlarge]

On the following day, ice analyses from the Canadian Ice Service (below) showed that the Ice Concentration along the southern shoreline of Lake Michigan was 9/10 to 10/10 (red) and the Ice Stage was “New Lake Ice” (pink).