Himawari-9 clean window (Band 13, 10.4 µm) infrared imagery, below, (created using geo2grid software and HSD files from the SSEC Data Center) shows strong convection developing in the Philippine Sea between the Philippines to the southwest, the Ryuku Islands to the west, Japan to the north, and Guam far to the east. The structure of the the convection in the infrared imagery at the start of the animation strongly suggests development along an outflow boundary that persists through much of the animation.

The toggle below shows where the outflow might exist at 0800 UTC.

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This area of the western Pacific Ocean falls under the view of the Direct Broadcast antenna in the back yard of the National Weather Service on the island of Guam. What does the information downloaded from that antenna show? Three derived rain-rates from MetopC, NOAA-20 and NOAA-21 are shown below (imagery courtesy Douglas Schumacher, SSEC/CIMSS). The convection persisted for these five hours.

Day Night Band imagery from NOAA-21 shows that the strong convection was electrified. Lightning streaks are obvious in the Day Night band imagery.

Ground-based lightning observations, below (Courtesy Brandon Aydlett, Science/Operations Officer in Guam), also show extensive lightning with this convective system.

GCOM AMSR-2 imagery, below (also processed at the Direct Broadcast site on Guam, and ingested into the AWIPS machine, and also courtesy of Brandon Aydlett, WFO Guam), shows the strong microwave signal and the winds diagnosed to exceed 40 knots (and the region where wind diagnostics failed because of rain contamination). The wind speeds are also available at this NOAA/NESDIS site.

Himawari-9 Full Disk airmass RGB imagery (source) from late in the day on 10 April, below, shows that this convection was to the south of a developing cyclone moving into the northwest Pacific Ocean.

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Given all the lightning observed at 1700-1730 UTC, a natural question might be: what did LightningCast probabilities (computed with Himawari-9 data and CSPP Geo LightningCast software) show an hour earlier? Very large probabilities centered near 25^oN, 134^oE! A LightningCast animation (here) from 0000 to 2000 UTC on 10 April shows large value moving eastward through the domain below.

Thanks to Brandon Aydlett, WFO Guam, for kick-starting this blog post!

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The Campbell Mesa prescribed burn occurred just east of Flagstaff, Arizona on 09 April 2025. Given that this location is approximately midway between the views of GOES-18 (GOES-West, with a satellite zenith angle for Flagstaff of 48.72 degrees) and GOES-19 (GOES-East, with a satellite zenith angle for Flagstaff of 56.13 degrees), this fire served as a good opportunity to compare detection using the Next Generation Fire System (NGFS) and the currently-operational Fire Detection and Characterization Algorithm (FDCA).

Beginning with GOES-18/GOES-West NGFS imagery (above), the initial detection of a thermal anomaly for this prescribed burn occurred at 1726 UTC — with the maximum Feature Fire Radiative Power (674.67 MW) and Pixel 3.9 µm Temperature (174 ºF) being detected 4.8 hours later at 2216 UTC. With the corresponding GOES-19/GOES-East NGFS imagery (below), the initial detection of a thermal anomaly for this prescribed burn occurred at 1806 UTC — with the maximum Feature Fire Radiative Power (623.83 MW) and Pixel 3.9 µm Temperature (163 ºF) being detected 4.2 hours later at 2216 UTC. This fire produced a rather dense smoke plume, which drifted over parts of Interstate 40 east of Flagstaff.

GOES-19 True Color RGB images created using Geo2Grid (below) provided a larger-scale view of the smoke created by this prescribed burn.

Now taking a look at fire detection using the FDCA Fire Mask from GOES-18/GOES-West and GOES-19/GOES-East (below), the initial detection from GOES-19 was at 1806 UTC (in agreement with the NGFS initial detection) — but the initial detection from GOES-18 was not until 2156 UTC (nearly 4 hours later!). South/southwest winds at Flagstaff (KFLG) occasionally gusted as high as 23 kts, which may have played a role in fire’s longevity and dense smoke production.

Images of Topography with an overlay of the GOES-18/GOES-19 FDCA Fire Mask (below), showed that there was some higher terrain (darker shades of tan to brown) west of the prescribed burn. Did this terrain play a role in the large discrepancy between GOES-18 and GOES-19 initial detection times? The answer is probably not — and we can’t separate that from where the GOES detector samples actually fall on the fire. What we do know is that the NGFS is more sensitive than the FDCA, which is by design, and we see that demonstrated in this case (with the much earlier GOES-18 NGFS initial detection).

Thanks go out to Chris Schmidt (CIMSS) for providing input on aspects of NGFS vs FDCA that applied to this case.

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Advanced Scatterometry (ASCAT) plots derived from MetopB and MetopC, above, shows a pulse of winds associated with a Gulf of Tehuantepec wind event. Gales are widespread, and winds up to 45 knots are plotted. When Tehuano Gap Winds occur in clear skies (as in this example), the effect on the sea state can become apparent in visible imagery. On 9/10 April, high clouds masked the view of the ocean as shown in the animation of CSPP Geosphere true color imagery on 9 April 2025, below. You can see, however, the rapid motion of the clouds over the narrow Isthmus of Tehuantepec and the dissipation of those clouds in their descent towards the ocean.

The strong winds forced the development of large waves, as shown below in the plot of Significant Wave Heights.

Scatterometry plots and altimetric wave heights are available at this website. These are derived from microwave observations that are not affected by the widespread clouds.

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GOES-18 True Color imagery during the day on 7 April, above, shows the development of a standing wave downwind of the elevated topography on the Aleutian peninsula between King Salmon and Perryville. (Note also the faint signal of volcanic ash as discussed here) What atmospheric conditions support the development of these clouds? Soundings from King Salmon AK at 1200 UTC/7 April and 0000 UTC/8 April, below, taken from the University of Wyoming Sounding site, show very strong northerly winds at low-levels and near dry-adiabatic conditions at 1200 UTC. At 0000 UTC, the low-level winds are relaxing but the steep low-level lapse rate persists. By 0000 UTC, Aleutians are starting to be affected by a system dropping down from the north as evidenced by changes in the cloudiness in the animation shown above. The inversion is between 850 and 900 mb, around 1000 m above Sea Level. Only a few peaks in this area of the Aleutians reach above 1 km (link).

Day Cloud Phase Distinction imagery during the day on 7 April, below, suggests that the standing wave cloud is glaciated.

Mid-level Water Vapor infrared imagery (6.95 µm), below, also shows the development of the standing waves. Surface observations show very strong northerly winds off the Bering Sea.

The toggle below between VIIRS and GOES-18 ABI visible (0.64 µm) imagery highlights the importance of VIIRS data at high latitudes. There is a significant parallax shift in the GOES-18 imagery such that the standing wave is shown to be over the mountains, rather than displaced to the south as in the VIIRS imagery (and, likely, in reality). VIIRS data also allows the use to see the shadow of the higher clouds on the terrain below; the oblique view from GOES-18 misses that feature.

The animation below compares zoomed-in VIIRS imagery from Visible (I01, 0.64 µm), shortwave infrared (I04, 3.87 µm) and longwave infrared (I05, 11.45 µm) channels. Solar reflectance of 3.74 µm energy means the clouds and surface are warm — but note how the shadow of the clouds — where little solar reflection occurs — are relatively cold!

VIIRS data can be used to create Day Cloud Phase Distinction RGBs, as shown in the animation below (courtesy Carl Dierking, GINA), and the multiple JPSS Satellites (Suomi NPP, NOAA-20 and NOAA-21) means excellent temporal resolution.

JPSS Satellites carry infrared and microwave sounders, and data from those sounders are used to create vertical profiles of moisture and temperature, i.e., NUCAPS soundings. The animation below shows three soundings near the standing wave. There is a strong inversion upstream of the standing wave cloud, and the inversion is not so pronounced downstream of the cloud. The boundary layer in all three soundings is dry adiabatic.

My thanks to Aaron Jacobs, WFO Juneau and Carl Dierking, GINA, for alerting me to this interesting case, and supplying imagery and suggestions. Aaron also forwarded along the following screen captures of FAA Webcams at Chignik Bay and Perryville shown below.

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