GOES-16 “Red” Visible (0.64 µm) images from 1100-2200 UTC, with 15-minute METAR surface reports plotted in yellow and hourly Fixed Buoy reports plotted in cyan [click to play animated GIF | MP4]

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.

GOES-16 Air Mass RGB images, from 0101-2201 UTC [click to play animated GIF | MP4]

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.

MIMIC Total Precipitable Water images, from 0400 UTC on 16 September to 0000 UTC on 17 September; rawinsonde sites are plotted in blue [click to play animated GIF | MP4]

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).

Plot of rawinsonde data from Caribou, Maine at 0000 UTC on 17 September [click to enlarge]

Plot of annual rawinsonde-derived Total Precipitable Water climatology for Caribou, Maine — highlighting values for 0000 UTC on 17 September [click to enlarge]

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