Imagery from the CSPP Geosphere site (link), above, shows an area of disturbed tropical weather to the south of Mexico in the eastern Pacific Ocean. The National Hurricane Center (link, and below) notes a lack of organization with slow development forecast over the next few days. (Note that GOES-West Mesoscale Sector #2 is monitoring this region. Here’s a 1-hour animation.)

Metop-B overflew the system at 0400 UTC on 27 May, as shown below (source). A possible circulation center — or perhaps better stated as a center of cyclonic vorticity — is apparent at the southwestern edge of the domain near 11^oN, 100^oW.

In what kind of environment does this disturbed weather find itself? Imagery from the SSEC/CIMSS Tropical Weather site, below, shows relatively low values of wind shear, and very warm Sea-Surface Temperatures. In addition, low-level convergence and upper-level divergence are very close to the vorticity maximum at 850mb. A second set of scatterometery, from HY-2C (also available at this KNMI website), shows the broad center of circulation.

A 24-hour animation of MIMIC Total Precipitable Water, below, shows that this system is embedded within the abundant moisture of the Intertropical Convergence Zone.

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This invest is in a moisture-rich environment, with warm sea-surface temperatures and fairly low shear. Slow development is forecast. For more information on this system, refer to the SSEC Tropical Website, or the website of the National Hurricane Center.

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Clear skies over the Gulf of Maine close to midnight early on 27 Man 2025 allowed for the VIIRS instrument on NOAA-20 to capture a crisp view of the sea surface temperatures over that body of water. Temperatures are cooler than 50^oF over the entire Gulf of Maine, with low 40s (magenta in the color table used) hugging the coast of eastern Maine and Atlantic Canada. The coldest temperatures — in the 30s, still! — are over Lake Ontario. At the very southern edge of the scene, the warm waters of the Gulf Stream (just a bit warmer than 80^oF) are apparent.

JPSS data used in this blog post downloaded at the SSEC/CIMSS Direct Broadcast antenna and processed into AWIPS-ready tiles by CSPP software.

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1-minute Mesoscale Domain Sector GOES-18 (GOES-West) Infrared and Visible images (above) showed the development of thunderstorms that moved southwestward across the Fairbanks North Star Borough during the early afternoon hours on 26 May 2025 — producing small hail and heavy rainfall at several locations. The coldest cloud-top infrared brightness temperatures associated with these thunderstorms were around -55ºC. It bears mention that thunderstorm activity in the Fairbanks area is very unusual during the month of May.

A sequence of Suomi-NPP VIIRS Infrared Window and Visible images (below) displayed 3 views of these thunderstorms — and without the parallax (from this site) that is inherent with GOES-18 imagery at the high latitudes of Alaska, the storms were situated more directly over the locations that reported hail (Fox, Fairbanks, North Pole and Moose Lake). The coldest cloud-top infrared brightness temperatures sensed with VIIRS instrument were around -60ºC.

According to a plot of rawinsonde data from Fairbanks at 0000 UTC on 27 May (below), the GOES-18 cloud-top 10.3 µm brightness temperature of -55ºC closely corresponded to the altitude of the tropopause — while the Suomi-NPP cloud-top 11.45 µm brightness temperature of -60ºC represented a tropopause overshoot of approximately 1 km.

It is notable that the Total Precipitable Water (PW) value of 0.64″ on the Fairbanks sounding was in the 90th percentile of all 0000 UTC soundings on 27 May (below).

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5-minute CONUS Sector GOES-19 (GOES-East) GeoColor RGB images with an overlay of Next Generation Fire System (NGFS) Fire Detection polygons (above) showed the dense smoke plumes and thermal signatures associated with the ongoing Nopiming Provincial Park wildfire on 22 May 2025 (this wildfire exhibited extreme behavior and also produced numerous pyrocumulonimbus clouds on 13 May).

GOES-19 Visible images with an overlay of the FDCA Fire Mask derived product (below) also displayed the wildfire smoke plumes and thermal anomalies.

10-minute Full Disk scan GOES-19 True Color RGB and Aerosol Optical Depth (AOD) derived product images from the CSPP GeoSphere site (below) depicted AOD values as high as 1.0 (dark red) within the dense smoke plumes. Smoke from the previous day of Nopiming wildfire activity was also seen drifting across western Manitoba and crossing the Manitoba/Saskatchewan border.

Toggles between VIIRS True Color RGB and False Color RGB images from Suomi-NPP and NOAA-20 (as visualized using RealEarth) are shown below. Active fires along both the western and eastern periphery of the large Nopiming Fire burn scar showed up as brighter shades of pink in the False Color RGB images — and although none of the individual fires were particularly large, because of the dry fuels being being burned the resulting smoke plumes were quite dense.

As the smoke drifted southwestward across the US/Canada border a few hours after sunset, a plot of surface observation data from Cavalier (K2C8) in far northeast North Dakota (below) showed that the surface visibility at that site was reduced to 6 miles with haze at 0435 UTC and 0515 UTC on 23 May (the base of the smoke layer at those 2 times was 300 ft above ground level).

A NOAA-20 VIIRS Day/Night Band image valid at 0912 UTC (4:12 AM local time) on 23 May revealed the bright nighttime glow of fires that continued to burn overnight along/near the edges of the darker-gray Nopiming Fire burn scar. Faint smoke plumes (light shades of gray) could be seen drifting W-NW away from several of the active fires.

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