1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed Ophelia for a few hours after it became a Tropical Storm at 1800 UTC on 22 September 2023. The low-level circulation center (LLCC) was initially exposed, but deep convection just to the west began to increase in coverage and intensity as it wrapped around and soon obscured the LLCC. Ophelia was becoming better organized as it traversed the warm water (Sea Surface Temperature | Ocean Heat Content) of the Gulf Stream.

1-minute GOES-16 Infrared images with/without an overlay of GLM Flash Extent Density (below) indicated that lightning activity began to increase around 1900 UTC, as smaller-scale pulses of embedded convection started to exhibit cloud-top infrared brightness temperatures around -70ºC. A notable lightning jump was evident from 1925-1945 UTC.

A closer look at the aforementioned lightning jump is shown below, using 5-minute GOES-16 Infrared images and GLM Flash Extent Density — a brief pulse of convection with cold overshooting tops (brightness temperatures around -70ºC, brighter shades of white embedded within darker black regions) occurred from 1916-1931 UTC, with the Flash Extent Density then ramping up from 1926-1946 UTC (reaching a peak at 1936 UTC).

In comparisons of GOES-16 Infrared (10.3 µm), CLAVR-x Cloud Top Height (CTH) and Operational CTH derived products at 1921 UTC (above) and 1926 UTC (below), it can be seen that the CIMSS-derived CLAVR-x CTH (having a 2-km resolution) was far superior to the Operational CTH (having a 10-km resolution, as is currently available in AWIPS) in terms of determining both the areal coverage and the magnitude of cloud heights associated with the cold overshooting tops that immediately preceded the lightning jump. In fact, at 1926 UTC, the CLAVR-x CTH value was nearly 10 kft higher than the Operational CTH (57384 ft vs 47687 ft).

Several hours later, a closer look at 1-minute GOES-16 Infrared images with/without an overlay of GLM Flash Extent Density (below) showed Ophelia approaching the coast of North Carolina, making landfall at 1020 UTC or 6:20 AM EDT on 23 September (producing strong winds and heavy rainfall). The center of Ophelia passed between Buoy 41037 to the southwest (which recorded a peak wind gust of 72 knots) and Buoy CLKN7 to the northeast (which recorded a peak wind gust of 67 knots).

Hourly MIMIC Total Precipitable Water images (below) depicted the tropical moisture that was transported inland across the Mid-Atlantic states, resulting in heavy rainfall and flooding.

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10-minute Full Disk sector GOES-18 (GOES-West) Day Land Cloud Fire RGB, Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.3 µm) and “Red” Visible (0.64 µm) + Fire Power derived product (a component of the GOES Fire Detection and Characterization Algorithm FDCA) images (above) showed signatures of multiple wildfires across northeastern British Columbia (BC) and northwestern Alberta (AB), some of which produced numerous  pyrocumulonimbus (pyroCb) clouds late in the day on 22 September 2023. Several of these fires burned very hot, exhibiting 3.9 µm shortwave infrared brightness temperatures of 137.88ºC (the saturation temperature of GOES-18 ABI Band 7 detectors) — and for the large wildfire near Rainbow Lake AB (CWSH), Fire Power values intermittently reached the 6400-6405 MW range (which are the highest GOES Fire Power values sampled by this author for any wildfire).

True Color RGB images from the CSPP GeoSphere site (below) displayed the BC/AB pyroCb development, as well as widespread dense smoke from the many wildfires across the region.

A longer animation of GOES-18 Infrared images covering a larger area (below) showed that while two of the largest BC fires produced 1 to 4 pyroCb clouds each — pyroCb clouds are defined as having cloud-top 10.3 µm infrared brightness temperatures of -40ºC and colder, shades of blue — one of the two largest AB fires produced an amazing string of 7 pyroCb clouds (between 2300 UTC on 22 September and 0800 UTC on 23 September). About 100 miles downstream (northeast) of that prolific pyroCb-producing AB wildfire, smoke reduced the surface visibility to 1/2 mile for several hours at Hay River (CYHY) in the Northwest Territories.

The coldest cloud-top 10.3 µm infrared brightness temperature exhibited by the largest of the AB pyroCbs was -60.6ºC — placing it at an altitude near 12 km (just below the tropopause) as seen in a plot of rawinsonde data from Fort Nelson BC (CYYE) (below).

On the following day, the leading edge of high-altitude BC/AB pyroCB smoke plumes could be seen moving southeastward across Hudson Bay in True Color RGB images from both GOES-18/GOES-West (above) and GOES-16/GOES-East (below).

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The National Weather Service forecast office on Guam (at 13.4^oN, 144.7^oW) is paired with an L/X band satellite receiver that can download data from Polar Orbiting satellites, which data can subsequently be processed by Polar2Grid software to produce useful products. The animation above shows 4 different Himawari-9 Band 13 images on 21 September, a day when Guam was experiencing intermittent rains as a feature moved northward. When do you think the rain was heaviest? Did you choose 1130 UTC? That is what the microwave-derived rainrate suggests (see below). A side-by-side comparison of the Himawari Band 13 imagery and Microwave-derived rain rate is here. A meteorogram for Guam International airport is here: Heaviest observed rains were around 1200 UTC; rains ended around 1500 UTC. That is in agreement with the microwave diagnoses.

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What was the environment around Guam? Microwave estimates of Total Precipitable Water, below, (source), show Guam near the northern edge of a moisture-rich band of tropical origins. Advanced Scatterometer winds, at bottom, from MetopB and MetopC (times as noted in the caption), show a convergence line nearing Guam on 20 September (on 21 September, ASCAT did not sample over Guam).

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Thanks to Douglas Schumacher, CIMSS, for supplying the imagery from the Guam Direct Broadcast antenna!

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CSPP Geosphere, often featured on this blog, is a website which allows users to view near-real-time imagery of GOES-East and GOES-West ABI data. All sixteen spectral bands on the ABI are available to view, along with RGB imagery. Full disk products are available, along with Continental United States (CONUS) and the two mesoscale sectors. Every ten-minute Full disk frame of data is included on CSPP Geosphere. The data is archived back approximately two weeks, allowing users to look at past events. The interface of the CSPP site allows the user to select specific time frames they are interested in viewing. CSPP allows users to save animations with 144 or fewer frames, making the frame selection tool very useful.

To create an animation like the one below, the user can select a frame every third hour, going back seven days. This creates a weekly animation, showing frames every three hours (0000Z, 0300Z, 0600Z, 0900Z, etc.) for each day.

The video shows a fairly active week for cyclones in the Atlantic. Hurricane Lee made landfall on 2023-09-16 as a post-tropical cyclone on the western coast of Nova Scotia. There is also Hurricane Margot, which has veered to the east to the mid-Atlantic, far away from any coastline.

On 2023-09-17, the structure which will become Hurricane Nigel becomes quite apparent. It is designated a hurricane on 2023-09-18 at 0900Z. By 2023-09-19 at 0300Z, the rotational structure is clear and an eye is apparent. On 2023-09-20 around 1200Z, Nigel’s path begins to move eastward. It is forecast to devolve into an extratropical cyclone and currently poses no threat to human populations.

The full disk animation from CSPP Geosphere allows users to view many interesting weather phenomena over the Atlantic Ocean. Along with the lifecycles of hurricanes, one can see large amounts of dust blowing off of the Sahara Desert in West Africa. At the mouth of the Amazon River, there is visible river sediment outflow from the Amazon’s delta and estuary.

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