10-minute Full Disk scan GOES-18 (GOES-West) images (above) showed notable signatures of the strong reflection of solar radiation off either open water or mixed water/ice across the Chukchi Sea and Beaufort Sea north of Alaska on 08 July 2026.

Cursor samples near the center of strong reflection at 0900 UTC and 0910 UTC (below) revealed shortwave infrared brightness temperatures of 137.88 C — which is the saturation temperature of GOES-18 ABI Band 07 detectors. Even the Infrared Window brightness temperatures were as warm as 68.18 C.

Looking at a 16-panel display of all GOES-18 ABI spectral bands (below), it could be seen that bright reflectance signatures were evident in all Visible and Near-Infrared bands (01-06, including the Cirrus band 04), and warm thermal signatures were apparent in all Infrared bands 07-16 (although the signatures were rather subtle in the Water Vapor bands 08-10).

A sequence of Suomi-NPP VIIRS Visible images (below) displayed the widespread ice that remained throughout much of Chukchi Sea and Beaufort Sea on 08 July.

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5-minute CONUS Sector GOES-18 (GOES-West) images (above) showed the development of a large wildfire southeast of Lytton, British Columbia (CWLY) — which produced multiple pyrocumulonimbus (pyroCb) clouds on 07 July 2026. Each pyroCb exhibited cloud-top infrared brightness temperatures in the -40s C (shades of blue) to -50s C (shades of red) — temperatures cold enough to ensure that heterogeneous glaciation had occurred at the cloud top.

As smoke from the wildfire drifted northeast, it eventually reduced the surface visibility to 3/4 mile at Kamloops CYKA (below).

This wildfire burned very hot, with the GOES-18 Fire Mask displaying Saturated Fire (yellow) pixels at 2211 UTC and 2216 UTC (below).

The coldest cloud-top infrared brightness temperature associated with these pyroCbs was -56.57 C at 0046 UTC on 08 July, after one of the clouds had drifted far northeast of the source fire (below).

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Social media lit up on 4 July 2026 with video of a strong rotating condensation funnel from Cantwell, Alaska, on the southern edge of the Alaska Range. You can see the video in this news story from KTUU-TV in Anchorage. This funnel was seen around 5 PM local time, or around 0100 UTC on the 5th. It didn’t didn’t quite reach tornado status as it never appeared to come into contact with the surface, and thus no damage was associated with this event. The NWS Weather Forecast Office in Fairbanks released the following public information statement about the event (reproduced here for accessibility and permanence:

498
NOAK41 PAFC 060027
PNSAFC
AKZ701>704-711>714-721>729-731-732-735-741>757-761>766-771>773-781-785-787-
791-795-061227-

Public Information Statement
National Weather Service Anchorage AK
427 PM AKDT Sun Jul 5 2026

NWS Anchorage received a report of a funnel cloud spotted south of the
Alpine Creek Lodge along the Denali Hwy on July 4, 2026 at about 5pm;
the report was received at about 5:49pm. The funnel was visible for
about 15 mins by onlookers, extending from the base of a towering
cumulus. Referencing videos and photos, there are no visible signs
that the funnel was in contact with the ground. Radar shows that the
parent cloud reached about 30kft and produced a single cloud-to-ground
lightning strike at 5:14pm. Based on area observations and local
topography, this funnel was likely generated by Susitna Valley winds
flowing against storm motion winds, creating enough wind shear to
generate a funnel cloud. If more information is provided that confirms
contact with the ground, this event could be reclassified.

$$

PP/AB

Geostationary satellite observations are challenging at this latitude. Cantwell is at 63.4 degrees north. The geostationary spatial resolutions are defined at the sub-satellite point over the equator. As long as you’re close to the equator the 2 km infrared resolution is pretty close. However, as the satellite scans further north, the pixels become more elongated. By the time it reaches Cantwell, the pixels are stretched to almost 6 km in the north/south direction. We can see the effects of this in the relatively coarse pixels of the visible imagery in the following loop. This is Band 2 from GOES-18, so its nominal resolution is the best we have at 0.5 km. However, at Cantwell the pixels are about 3 times the nominal resolution. Cantwell is in the center of the map, due east of the Denali National Park.

It may be challenging to interpret this loop as we’re seeing low convective clouds over a snowy mountain range, and thus we’ve got white on top of white. This is why it’s worth looking at different products to gain a fuller understanding of what’s going on. This next loop shows the Day Convection RGB, which is used to discern if convective clouds are actively growing deep. In this case, the Day Convection product is useful because it’s helping to discriminate the clouds from the snowy surface.

From this, we can see that this is becoming quite an interesting case. Normally, we’d expect deep convection to drive such a well-defined funnel cloud. But this is Alaska, and things are different up there. Prior to this event there have been only six recorded tornadoes over Alaskan land (Wikipedia has a list of tornadic events in Alaska, and the 19 April 2024 event was documented on this blog). The typical Great Plains supercell driven by the intersection of warm, moist Gulf airmasses and the edge of cooler, dry air masses generally doesn’t form in Alaska. Instead, the driving force for this particular event, as the NWS statement above describes, is atmospheric motion interacting with the local terrain. Take a closer look at the motion of the clouds, using this image as a key. The Alaskan Range arcs across the middle of the loop. There’s some lower level easterly flow that appears to be trapped by the terrain while the deeper flow is coming up from the south. This creates some significant localized wind shear that can force rotating storms even in the absence of deeper convection.

There was a VIIRS overpass a few hours before this event (around 22:30 UTC), and that true color view of that is shown here. Note how there is much greater detail in the VIIRS view, although there’s nothing in this image that makes it obvious that such an unusual event will be shortly taking place. Still, it is good for forecasters to consult the VIIRS imagery when it’s available so that one can evaluate the coarser geostationary imagery with some better context as to what’s going on.

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Super Typhoon Bavi rapidly intensified to a Category 5 tropical cyclone (ADT | SATCON) east of Guam on 03 July 2026. Bavi was moving through a very favorable environment characterized by low values of deep-layer wind shear (above) as it was traversing progressively warmer water (Sea Surface Temperature | Ocean Heat Content). Shear, ADT, SATCON, SST and OHC products were sourced from the CIMSS Tropical Cyclones site.

10-minute Full Disk scan JMA Himawari-9 AHI Visible and Infrared images (below) provided a post-sunrise view of Bavi.

Himawari-9 Visible images (below) revealed the presence of low-altitude mesovortices within the eye of Bavi.

A daytime NOAA-21 VIIRS Day/Night Band image (below) also displayed the signature of low-altitude mesovortices within the eye.

===== 05 July Update =====

A Himawari-9 Target Sector was positioned over Super Typhoon Bavi on 05 July, providing imagery at 2.5-minute intervals. Himawari-9 Infrared Window images (above) showed Bavi — which had reached an intensity of 155 knots at 1200 UTC (JTWC discussion | ADT | SATCON) — as its eye approached the small island of Rota, located between Saipan to the north and Guam to the south. Bavi remained in a very favorable environment for intensification, with factors such as low deep-layer wind shear and warm water (SST | OHC).

The coldest cloud-top infrared brightness temperatures within the eyewall region of Bavi were around -80 C (violet pixels) — which roughly corresponded to the Most Unstable (MU) air parcel’s Equilibrium Level (EL) at a pressure of 100 hPa, according to a plot of rawinsonde data from Guam (below).

A nighttime NOAA-20 VIIRS Day/Night Band image (below) displayed the large eye of Bavi as it was southeast of the island of Rota. Peak wind gusts just prior to the image time included 67 knots at Andersen Ar Force Base, 63 knots at Guam International Airport and 55 knots at Saipan International Airport. “Side-lighting” from the Moon — which was in its Waning Gibbous phase, at 72% of full — was brightly illuminating the western eyewall’s interior vertical edge.

In a side-by-side comparison of 2.5-minute Himawari-9 Visible and Infrared Window images (below), low-altitude mesovortices were very apparent within the eye as its center passed just north of Rota.

A daytime NOAA-21 VIIRS Day/Night Band image (below) showed Bavi after its center had moved northwest of Rota. Peak wind gusts shortly before the time of the image included 96 knots at Guam International Airport, 80 knots at Andersen Air Force Base and 67 knots at Saipan International Airport. The overall peak wind gusts at those 3 METAR sites during the passage of Bavi were 96 knots at Guam, 96 knots at Saipan and 83 knots at Andersen.

The remarkably strong winds of Bavi induced large waves on the ocean surface — in fact, at 1246 UTC on 06 July the Jason-3 satellite sensed Significant Wave Height values as high as 58.70 feet west of the Mariana Islands (below).

===== 09 July Update =====

An analysis of Sea Surface Temperature from late in the day on 09 July (below) revealed a swath of cold water upwelling (brought about by the aforementioned large waves) along a portion of the track of Bavi — most notably in the area of of the Mariana Islands just north of Guam, where SST values had cooled from around 30 C on 05 July to around 27 C on 09 July.

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