Much of the time when we look at weather satellites, we’re using them to look at clouds: where are they, how fast are they moving, are they growing or dissipating, things like that. Right now, however, the dominant story across much of the continental United States is a persistent heat wave. In the past couple of days, several locations in the western US have broken their all time high temperature records, with multiple sites in Montana reporting temperatures in excess of 110 F (43 C).

Heat waves, of course, are often typified by a lack of clouds. After all, if there are clouds present, some of the sun’s incoming shortwave radiation is bounced back to space where it can’t heat the surface. Therefore, you might not think that satellites have a lot to see when you’re in the middle of a heat wave. However, there’s still much that our constellation of satellites can do to help diagnose what’s currently happening and how people are being affected by it.

First, let’s get a big picture view of southern Canada and the continental United States on the afternoon of 14 July 2026, as depicted by the True Color product from GOES-19 (GOES East). There’s lots to see here. Most of the central part of the US is clear except for further south, where Gulf-influenced dew points are sufficiently high to support the development of cumulus clouds; those will most likely dissipate as solar heating diminishes later in the day. Numerous fires in Ontario, Saskatchewan, and elsewhere are producing smoke that is joining with the output of Minnesota’s fires (which we discussed in a blog post yesterday). This smoke is forecasted to A large low pressure system east of Hudson Bay is drawing in flow to the northeast of this loop. We also see strong southerly flow over the western United States that takes a sharp turn to the east along the US/Canada border.

Of course, there’s also lots to see when you look at the infrared wavelengths, too. Here’s the Band 9 (6.9 micron) loop for the same scene. Now we start to see some interesting things. First off, we have a good view of the general upper level flow that clearly shows warm, moist Pacific ocean air from off the coast of California being advected northward into the Pacific Northwest and western provinces of Canada. We also see a strong plume of moisture penetrating the central US from the southeast, likely contributing to the development of the cumulus clouds we saw above. Much of the Great Plains appears dry, too.

It’s that ability to quickly identify the characteristics of the large scale flow that really makes a product like the water vapor loop useful on a day like today. This is especially true for the current observational environment in the United States, where many of the 1200 UTC radiosondes have disappeared from the central and western part of the country. Consider the 500 mb analysis from this morning. This chart is one of the most common tools that a forecaster uses for assessing the general state of the atmosphere and what the overall flow is going to be. And yet, there’s hardly any observations on the west side of this figure which really limits how much it can be trusted. The water vapor satellite loops help forecasters identify how the flow is behaving in the absence of the observations and fill in the gaps created by the change in radiosonde observation times.

Of course, we can also use the satellites to track the temperature of the surface itself. The MODIS land surface temperature product provides a global land surface temperature for both the daytime and nighttime overpasses. This image shows that the far western parts of South Dakota and northeastern Wyoming are approaching temperatures of around 116 F (47 C)! You can access this product at the NASA Worldview website, an excellent one-stop shop for polar orbiting level 2 products.

Of course, the standard Band 13 infrared can also tell us a good deal about how surface temperatures are distributed. Here’s a loop of that band displayed in AWIPS with surface weather conditions displayed. This is an alternative color scale designed to exploit the temperature characteristics and to lnot look so much like clouds. Note something interesting here: Iowa is further south than Minnesota, but the Land of 10,000 Lakes is actually a little warmer than the Hawkeye State. Some potential reasons for this: Iowa had some pop-up cumulus to help bring some intermittent relief from the sun, and the smoke from the Canadian fires has wrapped around and is infiltrating Iowa from the east while leaving Minnesota clear. Take another look at the water vapor loop to see the kind of flow pattern that can lead to such a result.

Despite the fact that much of the central United States is experiencing clear skies, there’s still lots to see from satellites. They’re an important part of understanding the weather, regardless of what type of weather there is.

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1-minute Mesoscale Domain Sector GOES-19 (GOES-East) Visible images with an overlay of the Fire Mask derived product (above) showed the smoke plumes and thermal signatures associated with numerous wildfires across far northeastern Minnesota and southern Ontario on 13 July 2026. An elevated fire risk was in place, due to very warm surface air temperatures (near to above 100 F), low relative humidity and winds occasionally gusting over 20 mph. With the recent trend of increasing wildfire activity across the immediate area, a decision was made to close all entrances to the Boundary Waters Canoe Area Wilderness at the end of the day on 13 July (this was only the third time that the BWCAW has been completely closed).

As the smoke drifted eastward across the airport at Thunder Bay, Ontario (METAR identifier CYQT), the surface visibility was reduced to 2.5-3.0 miles at times (below).

A closer view using 1-minute GOES-19 GeoColor RGB images with an overlay of Next Generation Fire System (NGFS) Fire Detection polygons (below) displayed the hot thermal signatures and dense smoke plumes of these wildfires. Over 33000 acres were burned in northeastern Minnesota on this day, with some of the wind-driven fires crossing the border into Ontario.

One example of the rapid rate of wildfire intensification is shown below — just 1.7 hours after initiation, a fire northeast of Ely, Minnesota exhibited the GOES-19 Band 7 detector saturation temperature of 138 C.

Farther to the north over Ontario, one of the wildfires produced 3 pyrocumulonimbus (pyroCb) clouds (below), which exhibited cloud-top infrared brightness temperatures in the -40s C (shades of blue to cyan) and -50s C (shades of red) — and some GLM-detected lightning activity was seen with the 2 larger pyroCbs.

The largest pyroCb (which appeared to be a merger of the initial 2 pyroCbs) eventually exhibited a minimum cloud-top infrared brightness temperature of -58.96 C at 0030 UTC (below).

The cloud-top temperature of -58.96 C was not far below the tropopause, according to a plot of rawinsonde data from Pickle Lake, Ontario (below).

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Earlier this week, we discussed the rapid development of Super Typhoon Bavi, a major tropical cyclone in the western Pacific Ocean. It delivered a strong hit to the island of Rota, part of the American territory known as the Commonwealth of the Northern Mariana Islands. You can read more about Rota’s devastation and see photos of the aftermath in this article from the Stars and Stripes. Even for a typhoon, Bavi was an extraordinary event. Note how the Joint Typhoon Warning Center described Bavi in one of its warnings:

TYPHOON 09W (BAVI) REMAINS A GARGANTUAN TYPHOON, WITH A WIND FIELD SIZE RANKING
IN THE TOP 3 PERCENT OF ALL WESTERN PACIFIC TYPHOONS OF THE PAST DECADE.

The National Weather Service forecast office in Tiyan, Guam was even more direct with its language when it issued an extreme wind warning issued in anticipation of Bavi’s landfall on Rota:

THIS IS AN EXTREMELY DANGEROUS AND LIFE-THREATENING SITUATION! TAKE COVER NOW! Venturing outside can result in DEATH from flying projectiles.

Their warnings weren’t unwarranted. By some estimates, this was the most powerful tropical storm to hit a part of the territory of the United States. In this post, we’re going to delve into some additional products that could be used to assess the storm and how it was evolving over time. This is a bit of a deeper dive that we normally post to the CIMSS Satellite Blog, but an extraordinary storm deserves an extraordinary analysis.

First, we’ll look at a standard product in a somewhat unique way. This movie shows the Band 13 infrared view from Himawari-9, but instead of having a fixed field of view it follows Bavi’s center of rotation. We can see most of the life cycle of this cyclone, from its initial identification as a tropical depression until it loses its clearly discernible eye. Watch as the circulation organizes then forms a tight, clear eye as it intensifies. The storm categorization is visible in the lower right of the animation.

The infrared loop is the classic way of monitoring tropical systems, but there’s so much more that satellites can tell us. For one, it’s helpful to know about the environment in which a tropical system is forming. Here’s a map of some sea surface temperatures, courtesy of NOAA’s Coral Reef Watch. Remember, the Pacific is currently experiencing an El Niño. That’s easy to see when you look at a sea surface temperature anomaly map, which shows how far above or below normal the observed temperatures are. While the greatest sea surface temperature (SST) anomalies are centered right at the equator, the tropical western Pacific is experiencing temperatures that are 1-1.5 C above normal. The figure below shows the satellite-observed sea surface temperature anomaly map for 25 Jun 2026, the first day that the Joint Typhoon Warning Center issued an alert for a new invest in an area where cyclogenesis was favorable. The location of that invest is depicted with a purple star on the SST anomaly map.

Following several days of favorable shear and warm tropical waters, the storm intensified into a tropical depression on 1 July, and after that, further intensification was quite rapid. Analyzing the intensification of tropical systems is one of the applications where polar orbiting satellites excel. Geostationary satellites give us a nice, consistent view of particular place over time. However, geostationary platforms can’t support microwave antennas; the energy emitted from the earth and its atmosphere is so low in the microwave band compared to infrared emission and visible reflectance that it is effectively impossible to collect from the much larger geostationary altitude (22,000 miles vs 500 miles).

The CIMSS Tropical Cyclone Group has developed tools and products to monitor each tropical storm in every basin to help forecasters determine the strength and evolution of these powerful systems. Many of these products leverage the unique strengths of microwave imagers. Microwave has some particular advantages for tropical observations that are worth investigating here. One of the big ones is that microwaves are so long compared to infrared waves that they are generally unaffected by clouds and thus can tell us information about the precipitation structure within the cloud. This allows us to see some interesting things. Much of the time, the top of a tropical cyclone can be obscured by thick cirrus: as low level flow converges it ascents and condenses to form upper level clouds. This can really obscure where the center of circulation is, especially for developing storms. For example, the rightmost image is the Band 13 IR window view of Bavi from Himawari-9 on 2 July. The system really just looks like a large blob of convective cloud. However, looking through the cloud with several different microwave channels (the left three panels) shows us exactly where the eye of the storm is. Correctly identifying the center is critical for a number of reasons, including determining motion and properly assessing the storm’s intensity via the Dvorak technique (which we’ll discuss later).

The microwave images above are from a special data source. These datasets are produced via public-private partnership between NOAA and Tomorrow.io. Seeing the utility of microwave observations, Tomorrow.io has designed relatively low-cost sensors and put them into orbit to help fill in the temporal gaps between NOAA and EUMETSAT observations. NOAA, on the other hand, recognizes that these observations have many uses for numerical models, operational forecasting, and other applications, so they purchase these data on behalf of the public.

Microwave imagery also helps us understand the thermodynamic structure of the storm. Here’s an animation of the Advanced Microwave Sounding Unit (AMSU) Band 6, at 54.46 GHz. These are storm-centric images that follow the known center of rotation as it progresses westward. As the storm gets stronger, the temperature in the middle gets warmer. This is because hurricanes are warm core storms, a fundamental characteristic that separates them from the cold core wintertime low pressure systems that dominate weather in the midlatitudes. All of the humid (but unsaturated) air that flows into the center of a hurricane releases extreme amounts of latent heat as it condenses which causes the air at the center to be warmer. Just look at how the warm core emerges over the course of several days of microwave observations. The stronger the system, the greater the difference between the core and the surrounding environment.

Note that the temperatures outside of the core are on the order of -28 C. Clearly, this channel isn’t seeing all the way to the surface but instead is only seeing partway down, to around 350 mb or so. If we look at a different channel, we’ll see a horizontal cross section at a different depth of the atmosphere. Here’s channel 7, 54.94 GHz, for the same period as the earlier loop. Environmental temperatures are much cooler here, signifying that our cross section is much higher in the atmosphere (in this case around 200 mb).

We can put the various channels from AMSU together, in fact, to create a vertical cross section of the storm. This next plot shows the temperature anomalies relative to normal for 6 July. Here, we see that the warm core gets warmer with height from the surface up to around 150 mb or so. Clearly, the higher up an air parcel goes, the more condensation takes place and the more latent heat gets released. This only stops once the tropopause is reached, when the air collides with that super-stable layer and moves outward instead. You can even see that effect with the elevated temperatures between 100 and 200 mb.

As we’ve already discussed, the microwave images are the best tool for diagnosing where the eye of the storm is and how strong the eyewall is. But we’ve also discussed how the microwave pictures aren’t continuous like the geostationary ones are. The ability to monitor the eye characteristics like you can with the microwave imagers but at a geostationary like cadence would be a huge asset to forecasters. This is where the CIMSS MIMIC product comes in. MIMIC takes the irregularly-spaced microwave satellite swaths and applies image morphing techniques to them to, well, mimic the effects of a rotating tropical cyclone, including increasing angular velocity closer to the eye and increasing rotational speed with increasing observed wind speed. It focuses on the 85 to 89 GHz channels from the various microwave radiometers in orbit, as these channels are highly sensitive to precipitation and can be used to create a radar-like product for locations where radar observations are impossible. This animation shows MIMIC in action for all of 4 July 2026 in UTC time. MIMIC stays focused on the center of the storm’s rotation and tracks it across the ocean. Note how the islands of Guam and Saipan appear to move in from the left as the typhoon tracks westward.

Something very interesting is happening at the end of the above loop: we’re seeing an eyewall replacement cycle. Note how the eye gets bigger and the brighter colors disappear right at the end. During a hurricane’s life cycle, the outer bands are robbing the center of energy and momentum as they move inward, causing the original eye wall to die out. The new eye is bigger and the storm is less intense as the pressure gradients are reduced, but it distributes the storm’s heavier impacts over a larger area. Strong cyclones can also re-intensify after an eyewall replacement. The above loop cuts off right as the diameter of the eye is rapidly growing. Let’s see what happens over the next 24 hour period:

The eye seems to decrease in diameter, causing the gradients to reintensify and the winds to increase. This happened right before the storm passed between Guam and Saipan, enabling the typhoon to hit Rota with such ferocity.

Products like these can help us identify the position of the storm and assist in qualitatively assessing its strength. But CIMSS also has a long history in using satellites to quantitatively measure storm intensity. The earliest such products were based on the Dvorak technique. In principal, the Dvorak technique is simple: tropical cyclones of similar intensity all have similar appearance on satellite. Thus, if you can use a satellite to identify what stage a storm is in, you can then correlate that to a reasonable estimate of wind speed and central pressures. This is especially useful in the Pacific, where hurricane hunter flights are much more rare than they are over the Atlantic and thus remotely sensed techniques are desired. Even in places where aircraft reconnaissance is more common, Dvorak enables forecasters to fill in the temporal gaps. The primary issue with the original Dvorak technique is that it reqires human inspection for satellite images which can bring subjectivity and bias. CIMSS developed the Advanced Dvorak Technique (ADT) to automate this process and correct for some biases that became known after the original technique was developed. But CIMSS didn’t stop there: they have continued to develop new techniques that include artificial intelligence and machine learning to better assess tropical cyclone intensity from satellite imagery.

The CIMSS D-MINT product is the culmination of decades of automated tropical cyclone intensity estimates from CIMSS. Here is a time series of D-MINT wind speed estimates that combine the always present geostationary infrared images with observations from the polar orbiting microwave radiometers. The black line shows the JTWC’s estimate of wind speed, which looks to be slightly overestimating the wind speed relative to the D-MINT observations. Of special interest in this plot are the periwinkle observations, which are from the Tomorrow.io satellites discussed above. Here we can see how the storm rapidly intensified from a high end tropical storm to a Category 5 super typhoon in about 24 hours. It stayed at or above Category 5 status for about three days, including its overpass over Rota, before starting to weaken. It’s really interesting to note the fluctuation in cyclone intensity right around 0000 on 5 July, which is the same time as the eye wall replacement we saw above! Given the paucity of aircraft reconnaissance in this basin, these observations are critical for determining the strength of Pacific typhoons, and CIMSS is at the forefront of developing and distributing these observations.

Of course, as we’ve alluded to already, there are other ways of measuring tropical cyclone intensity by satellite. The CIMSS SATCON product blends a number of these different estimates together to produce a best-estimate of satellite-derived tropical cyclone strength. This next figure shows the time series of SATCON for Bavi over the last several days. The thick red line shows the SATCON best estimate while the thin red lines give a measure of the uncertainty about that measurement.

These products are critical for operational forecasting, especially in the Pacific. Models can often struggle in these data-sparse regions, and these satellite-based tools are often the only way that forecasters can validate how well a model has been doing and if it can be trusted in the future. There’s many more products to explore, and this blog post could easily be twice as long if we described them all. Instead, we encourage you to visit the CIMSS Tropical Cyclones website at tropic.ssec.wisc.edu, click on a storm (if one is active) and explore all the products that then come up.

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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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