1-minute Mesoscale Domain Sector GOES-19 (GOES-East) Visible images (with an overlay of the FDCA Fire Mask derived product), Shortwave Infrared images and Infrared Window images (above) showed the thermal anomaly associated with a wildfire in the far western Oklahoma Panhandle that produced a small pyrocumulonimbus (pyroCb) cloud shortly before sunset on 14 May 2026. Note that a RAWS site just southwest of the pyroCb-producing wildfire reported a wind gust to 63 mph (during the 30-minute period ending at 2330 UTC), followed by a wind gust to 47 mph (during the 30-minute period ending at 0030 UTC).

A cursor sample of the GOES-19 Infrared Window image at 0005 UTC on 15 May (below) showed when the pyroCb cloud first exhibited a cloud-top 10.3 µm brightness temperatures of -40ºC (dark blue enhancement) or colder — a necessary condition to be classified as a pyrocumulonimbus cloud. The coldest pyroCb cloud-top 10.3 µm infrared brightness temperature was -47.41ºC, which occurred as early as 0040 UTC.

1-minute GOES-19 GeoColor RGB images with NGFS Fire Detection polygons (below) revealed that the smoke-laden pyroCb cloud top exhibited subtle shades of tan (0037 UTC image) — in contrast to the brighter-white cloud tops of adjacent convection.

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5-minute CONUS Sector GOES-19 (GOES-East) True Color RGB and Ash RGB images created using Geo2Grid (above) showed plumes of blowing dust that were lofted by strong winds on the back side of a midlatitude cyclone on 12 May 2026. The surface source of much of this blowing dust was recently-plowed agricultural fields in North Dakota, South Dakota and Minnesota.

Note that the leading edge of one of the blowing dust plumes was beginning to move over the “4 lakes” area of Madison in southern Wisconsin near the end of the day (0036 UTC images). A vertically-pointing lidar on the University of Wisconsin-Madison campus depicted an increase in boundary layer aerosol loading (shades of orange) from 2300 UTC on 12 May to 0200 UTC on 13 May (below).

GOES-19 Ash RGB images that included outlines of counties affected by a NWS-issued Wind Advisory and/or Blowing Dust Advisory are shown below. At times the Blowing Dust Advisories covered parts of I-29 in North Dakota as well as I-94 and I-90 in Minnesota.

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1-minute Mesoscale Domain Sector GOES-19 (GOES-East) GeoColor RGB images with an overlay of Next Generation Fire System (NGFS) Fire Detection polygons (above) provided a view of the thermal signature, pyrocumulus clouds and smoke associated with the Max Road Miramar Fire Fire  —  which began burning in the Florida Everglades (just west of the Miami – Fort Lauderdale metro area) during the early afternoon hours on 10 May 2026 (the initial NGFS detection was at 1636 UTC or 12:36 PM EDT). A great deal of smoke was transported eastward across the Miami metro area and out over the adjacent offshore waters. By the end of day, the fire had burned 4800 acres. Vegetation fuels were dry, since that portion of southeast Florida had been experiencing Moderate to Extreme Drought conditions.

At 1822 UTC, the wildfire first exhibited a 3.9 µm shortwave infrared brightness temperature of 138ºC (below) — which is the saturation temperature of GOES-19 ABI Band 7 detectors. The fire continued to intermittently exhibit this saturation temperature during the remainder of the day, even not long before sunset at 2300 UTC.

A larger-scale view of GOES-19 True Color RGB images from the CSPP GeoSphere site (below) better showed the offshore transport of smoke. Overshooting tops were occasionally seen with pyrocumulus clouds generated by the fire (such as at 1934 UTC).

The fire continued to flare up again on the following day (below) — with the most of the smoke drifting to the north-northwest. By the end of the day on 11 May, the burned area had increased to 11090 acres.

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Edit: NWS Honolulu Science and Operations Officer (SOO) Robert Ballard graciously provided some insight into this case, and this post has been updated with his input. Thanks, Bob!

In the morning hours of 8 May 2026, some interesting low level cloud plumes appeared over or near the Hawaiian island of Oahu. The presence and cause of these clouds sparked some discussion around the Honolulu Forecast Office (who were gracious hosts of this blogger this past week) as it wasn’t immediately clear what was happening instance. Fortunately, satellites can provide some clues as to what was going on. This was mostly an overnight event, so we’ll start with the GOES-18 (GOES West) Band 13 (10.3 micron) loop. Here we see cloud blooming over the central Hawaiian island of Oahu as well as to the northeast and southwest. The leading edge of these clouds also exhibits noticeable clearing as the clouds propagate outward.

So what’s going on here? Let’s see how satellites might provide some insight. Our first clue is that this is a fairly warm set of clouds. The contrast in the above loop isn’t great using the default color settings in AWIPS. Switching color maps and changing the limits brings out some more detail. Here’s a static image with a data readout. Our suspicions appear to be correct: the cloud at its coldest was still above freezing. The royal blue parts of the image that represent the expanding cloud shield are around 5-7 C, while the green areas represent the ocean surface and are around 19-20 C.

Next, let’s take a look at the Night Microphysics RGB product. According to the RGB Quick Guide, these pink and purple colors are associated with cloud-free regions. Obviously, that’s not happening here. However, the standard interpretations of these products were crested with the midlatitudes in mind, and in regions further afield the standard interpretations may not apply due to very different environmental temperatures and water vapor concentrations.

Perhaps a look at the 12 Z radiosonde launch from Lihue may help. Lihue is on the very eastern edge of the island of Kaua’i, the island on the left side of the loop above. It’s around 100 miles from Honolulu (on the bay of the island at the enter of the image) and thus reasonably representative of the environment. Shown below, it’s a fairly typical sounding for Hawaii this time of year, with a prominent trade wind inversion between 650 and 800 hPa caused by the large-scale subsidence found at the boundary between the tropics and sub-tropics. Below that is a nearly-saturated and well-mixed boundary layer. Looking at the raw data, we can see that the inversion started around 780 hPa (2250 m) with the freezing level around 570 hPa (4850 m).

Adding in the surface observations from Honolulu brings some additional insight. The observations show the base of the cloud deck was 7500 feet (2300 m) which means that in essence the base of the clouds was at the base of the inversion. Contemporaneous radar-derived rain accumulation indicate that precipitation remained on the northeast side of the island, and no rain was recorded at Honolulu. At the time the clouds initiated (around 10 PM local or 0800 UTC), the surface temperature at Honolulu was 76 F (24 C) with a dew point of 66 F (19 C). That temperature might be the key to all of this. Let’s zoom in on the bottom of that sounding. I’ve added the Honolulu temperature and dew point observations in red and green respectively, and approximated a parcel trace in blue.

If we assume that the vertical profile at Lihue is reasonably representative of the conditions over Honolulu, then it could be possible that surface-based parcels would be positively buyoant. If we look at the start of the start of the cloud formation, it appears to form on the northeastern edge of Oahu, as marked in the figure below.

Winds on the north side of the island were weak and from the north at the time that the convection initiated around 10 PM local time. The last bit of the puzzle is the terrain. Oahu is dominated by two significant mountain ranges, the Wai’anae range in the west and the Ko’olau Range in the east, which are the remnants of shield volcanoes of geological ages past. Courtesy of Open Street Map, here is a topographical map of Oahu.

Note how the initial cloudiness seems to parallel the Ko’olau Range, and the observed rain did the same. NWS SOO Robert Ballard notes the following, lightly edited for context:

At 10 pm, if the background flow is light enough (usually something like 8 knots or less background flow), you’d expect to see offshore/downslope land breezes, rather than onshore/upslope sea breezes dominate.  From the Night Microphysics loop, the low level background flow in the low cloud field seems to be fairly light and from the east-southeast, which is a favorable flow pattern to pin showers to the windward side of the Ko’olau mountain range, especially if you have some sort of mid-to-upper support coming near or over the islands.  This type of overall pattern, when a little more favorable aloft, can produce impactful rainfall and even flash flooding.

We may finally have enough information to put everything together. It appears that upslope flow in a relatively warm and saturated environment was enough to initiate what would normally be deep, moist convection. However, the strong cap of the trade wind inversion was high enough to allow convection to initiate but low enough to limit it to the 600-700 hPa level. This meant the clouds stayed relatively warm, and since everything stayed below freezing there was no lightning. In essence, these were cumulonimbus anvils at 1/3 the height of normal.

A few other “anvils” can be seen in locations over the ocean. These aren’t as vigorous as the main anvil over Oahu, but then again, they didn’t have the benefit of terrain enhancement. Given how warm the surface was and how saturated the air was, it’s very possible that there was surface based localized convection that didn’t need orographic lift to inititate.

The final question is the clearing that we see around the edges of the anvils as they propagate outward. That is likely subsidence compensating for the vertical lift. As the updraft slams into the trade wind inversion and the anvil spreads out, there has to be sinking motion elsewhere to maintain mass continuity. That subsidence means warming and drying, creating a clear band around the anvils.

Now that we’ve got all of this context, scroll back up and look at the second image again. Because, after all, how often do you see an overshooting top below the freezing level?

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