11 hours of 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed Post-Tropical Cyclone Lee as it approached Atlantic Canada and Maine on 16 September 2023. PTC Lee made landfall in far western Nova Scotia around 2000 UTC, and produced strong winds and heavy rainfall across much of Maine.

A longer animation of 5-minute CONUS Sector GOES-16 Air Mass RGB images (below) portrayed the large size of Lee, which transitioned from a Category 1 Hurricane to a Post-Tropical Cyclone by 0900 UTC. Shades of orange in the RGB imagery indicated that dry air had wrapped into the southern and eastern quadrants of Lee.

Hourly MIMIC Total Precipitable Water (TPW) images (below) showed the moisture associated with Lee as it moved northward across parts of New England and the Canadian Maritimes. Darker shades of red represented TPW values of 2.5 to 3.0 inches.

A plot of rawinsonde data (source) from Caribou, Maine KCAR at 0000 UTC on 17 September (below) indicated that the TPW value of that very moist sounding was 1.51 inches — which was not much less than the record value for all 17 September / 0000 UTC soundings (source) for Caribou, which was 1.63 inches (bottom).

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10-minute GOES-18 (GOES-West) “Red” Visible (0.64 µm) + Fire Power derived product (a component of the GOES Fire Detection and Characterization Algorithm FDCA), Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.3 µm) and Day Land Cloud Fire RGB images (above) showed a wildfire east of Fort Nelson (CYYE) in far northeastern British Columbia that produced 3 consecutive pyrocumulonimbus (pyroCb) cloud pulses late in the day on 15 September 2023. This wildfire burned very hot — 3.9 µm shortwave infrared brightness temperatures reached 137.88ºC (the saturation temperature of GOES-18 ABI Band 7 detectors) at 2350 UTC, with a Fire Power value at that time of 6282.52 MW (below).

A closer look at GOES-18 Shortwave Infrared images (below) showed the rapid east-southeastward run of the pyroCb-producing British Columbia wildfire. For nearly 4 hours, the peak 3.9 µm brightness temperature of that large fire remained at 137.88ºC (from 2350 UTC on 15 September to 0340 UTC on 16 September).

In a longer animation of GOES-18 Infrared Window images covering a larger area (below), a total of 5 distinct pyroCb clouds were produced by the British Columbia wildfire — while farther to the east, another fire in northwestern Alberta (located just south of Rainbow Lake, CWSH) later produced 2 pyroCb clouds. Strong surface winds (with gusts as high as 35 knots at Fort Nelson) associated with the approach and passage of a cold front likely played a role in intensifying wildfire behavior that led to these pyroCb formations.

The first (and largest) of the Alberta pyroCb clouds passed near/over the High Level Airport (CYOJ), where a thunderstorm was reported from 0603-0652 UTC (below). In addition, smoke from the nearby wildfire restricted surface visibility at CYOJ to 2-1/4 miles at one point.

A toggle between VIIRS Infrared Window (11.45 µm) images from NOAA-20 at 0828 UTC and Suomi-NPP at 0919 UTC (below) showed the northward transport of the first (large, elongated) Alberta pyroCb as it crossed over the Alberta / Northwest Territories border just ahead of the approaching cold front. The second (much smaller) Alberta pyroCb was apparent in the earlier NOAA-20 image, just behind the cold front. VIIRS data used to create those 2 images were downloaded and processed by the CIMSS/SSEC Direct Broadcast ground station.

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After sunrise, a cyclonic gyre of dense wildfire smoke (shades of tan to light brown) was seen moving eastward across the Northwest Territories toward Nunavut in True Color RGB images (source) from both GOES-18 (above) and GOES-16 (below). Boundary layer smoke from widespread fires on the previous day became entrained into the circulation of a low pressure system (surface analyses).

A Suomi-NPP VIIRS True Color RGB valid at 1912 UTC — viewed using RealEarth — is shown below.

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JMA Himawari-9 True Color RGB images created using Geo2Grid (above) showed the motion of a plume of discolored water — located between Saipan and Anatahan in the Northern Mariana Islands — which was the result of an eruption of the Ruby submarine volcano late in the day on 14 September 2023 (Volcanic Activity Notice). The plume was semi-circular in shape on Day 1 of the 2-day animation, but had become more oblong on Day 2. No atmospheric volcanic clouds were created by this eruption.

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The eruption of Mt. Shisaldin late in the day on 15 September (Blog Post) was accompanied by lightning. Shishaldin’s latitude is 54.75^oN, very near the northern edge of the GOES-18 Geostationary Lightning Mapper’s (GLM’s) field of view, as shown in this Quick Guide; although most of Alaska is not sampled by the GLM instrument, parts of the Aleutians are, including the land surrounding Shishaldin. The toggle below shows the SO₂ RGB at 0220 UTC and 1-minute Flash Extent Density at 0219 UTC on 16 September 2023. This case is a good reminder that GLM can give lightning information, even in Alaska!

Similarly, GLM observed lightning at 0151 and 0152 UTC 0n 16 September 2023, as shown below.

GLM imagery for this blog post was created using CSPP’s Gridded GLM software that operates on Level 2 LFCA files; resultant GLMF files were then placed into AWIPS.

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