1-minute Mesoscale Domain Sector GOES-19 (GOES-East) Visible images (above) showed fog/stratus that was moving southward across the far southern part of Lake Michigan on 25 April 2026. Plots of METAR surface observations highlighted how areas near the coast — where a lake breeze advected the fog/stratus inland — stayed significantly cooler (temperatures in the 40s F) than cloud-free areas farther inland (temperatures in the 50s and 60s F). Water temperatures in southern Lake Michigan were still in the upper 30s to low 40s F.

5-minute CONUS Sector GOES-19 Cloud Thickness derived product images (below) depicted how variable the thickness of the fog/stratus layer was as it drifted southward across the lake.

Cursor samples (below) indicated that the maximum Cloud Thickness of the Lake Michigan stratus was just over 1000 ft (lighter shades of orange).

View only this post Read Less

In the afternoon and evening of 23 April 2026, numerous tornadoes touched down across the Great Plains of the continental United States. The storm reports gathered by NOAA’s Storm Prediction Center show a line of tornadoes extending from central Iowa down to north central Oklahoma, accompanied by numerous reports of large hail and damaging winds. While full damage surveys are pending, it appears that some of the most destructive storms were on the south end of the line. The Oklahoman newspaper in Oklahoma City has video of the tornadoes, including one that damaged structures on Vance Air Force Base near Enid in the north central part of the state. Fortunately, as of press time, no fatalities have been reported.

The storms were initiated by a particularly strong dry line. In fact, we’ll begin by highlighting just how intense this dry line was: it was so strong you could see it from space! The dry line was clearly visible on the GOES-19 (GOES West) Band 13 Infrared Window Channel, which isn’t a channel where you’d expect to see a dry line. Under clear sky conditions, you would think that two locations with the same surface temperature would have the same brightness temperature. However, look at the following image from 2100 UTC (4:00 PM CDT). There is a definite boundary running along from north-northeast to south-southwest. However, temperatures on either side of this boundary are a consistent 86 F. It turns out that there is so much water vapor in the east that it’s causing the brightness temperature in the east to be a little colder than in the bone-dry west, causing the right side of the image to be a little lighter than the left side.

Dry lines serve as a useful trigger for convective initiation as the dry air is denser than humid air. Compare a pair of special radiosonde launches from 1800 UTC (1:00 PM CDT) from Amarillo, TX (in the heart of the Texas Panhandle) and Lamont, OK (in the north central part of the state) as depicted on the SPC’s Observed Sounding Archive. This is a slider, so you can drag the center line back and forth to compare the differences between the two. (It may be challending to see the light gray slider handle in the middle of the image, but it’s there; drag it back and forth to see how conditions change and to ensure that you’re not seeing the Lamont hodograph with the Amarillo skew-T). Both show nearly identical profiles between 850 mb and the tropopause but they have very different low level structure. In Amarillo, on the dry side of the dry line, the surface dew point depression is a whopping 62 F! That results in clear skies and very little chance for convective development. But in Lamont, by contrast, convection is much more likely. That profile is a classic “loaded gun” sounding, with a low-level capping inversion separating a modestly moist planetary boundary layer from dry air aloft. If an external trigger can hoist those moist parcels above the cap, then they’ll accelerate upward on their own. Note also that both sites have clockwise curved hodographs, indicating wind shear that is favorable for supercell development.

Let’s take a look at the cell initiation. To start with, we’re going to being a couple of hours before the IR satellite image above to gauge what the preconvective environment was like. Seen below is Band 2 (visible red) from GOES-19. Remember, this is the band with the highest spatial resolution of any of the bands on the GOES Advanced Baseline Imager (ABI). Here we see a single frame at 1900 UTC (2:00 PM CDT). The northern part of this view is covered by so-called fair weather cumulus. There are a couple of indicators that things may be preparing to change. The first is the clear gradient in the dew point. Just left of center of the image below is Enid, OK, which at this time is reporting 84/66. But just 50 miles to the northwest is Alva, OK, which is reporting 91/43. That’s a drop in the dew point of nearly 1 F for every 2 miles. The winds are generally southerly in the south and east parts of the image, but they’re more westerly in the west and north parts. This is intensifying the moisture gradient as the southerly winds are advecting moist Gulf air while the westerly winds are bringing in air from the arid high plains. (In fact, you can see this play out in the advected layer precipitable water product provided by our friends at CIRA).

As we advance forward two hours, our guess about the intensification of the water vapor gradient was correct. Enid got a little moister at 87/65, but Alva got a whole lot drier and is now 93/28. That’s now a 37 degree change in the dew point over just a 50 mile difference. We’re also starting to see a little more convergence along the dry line as the Alva winds have veered slightly while the Enid winds have backed just a bit. This is starting to focus convection along the moisture boundary which can be seen as a line of cumuli stretching northeast to southwest across the image.

If some of these parcels can penetrate high enough, we’re going to see some explosive development. One of the GOES-19 mesoscale sectors was trained on this area, so we have a minute-by-minute view of the evolution of the environment. This loop of Band 2 runs from 2000 UTC (3 PM UTC) all the way to 0100 UTC (8 PM UTC) giving us the highest possible spatial and temporal resolution view of the initation and development of this event. The long shadows of the setting sun help make the overshooting tops readily apparent.

The cell that produced the Enid tornado formed at the very south of the line just as the sun was setting. Here’s the same time period as the above loop, but this time as seen by Band 13, the infrared window. Here, the overshooting tops are clearly evident as cold (red) spots against the slightly warmer (yellow/orange) anvils. We also see evidence of enhanced v signatures as the upper level winds divert around the overshooting tops.

One of the easiest ways to identify where the initiation boundary is via satellite imagery is the Air Mass RGB product. In the loop seen below, the warm, moist air mass that originated over the Gulf is green while the dry air of the high plains is purple. In this loop, which focused on the 1900 to 2300 UTC (2:00 PM to 6:00 PM CDT) run, you can see the boundary tighten and intensify before the cells even initiate. This is the area to target which monitoring where initiation will take place.

The Day Convection RGB can also be used to monitor where cells are initiating and undergoing rapid development. Areas of yellow highlight regions where active convective development is taking place. However, users have to be careful as this is a daytime-only product and this event straddles the transition from day to night. The following loop shows the issues with this as it stretches from 2130 UTC to 0100 UTC (4:30 PM to 8:00 PM CDT), and the clouds generally all become the same shade of magenta as the sun sets. The GOES-19 Geostationary Lightning Mapper (GLM) five minute flash density is overlaid on the top of this product to highlight where lightning is taking place.

____________________

1-minute GOES-19 Infrared images that included an overlay of 1-minute GLM Flash Points (above) provided a closer view of the lightning activity associated with the severe thunderstorms in southern Kansas and northern Oklahoma. Also included at the end of the animation are plots of METAR surface reports; the two METAR sites in the vicinity of Enid OK are Vance Air Force Base (KEND) just south-southwest of the city center, and Enid Woodring Regional Airport (KWDG) just east-southeast of the city center (map). Of note was the Peak Wind of 93 kts (107 mph) at KEND, which occurred at 0111 UTC (this was also the start time of the EF4-rated Enid tornado that was on the ground for about 37 minutes). The coldest cloud-top infrared brightness temperature during the Enid tornado was -79.15ºC at 0138 UTC — which represented a ~2.0 km overshoot of the Most Unstable (MU) air parcel’s Equilibrium Level (EL), according to a plot of 0000 UTC rawinsonde data from Norman OK.

1-minute GOES-19 Infrared images with time-matched plots of SPC Storm Reports (below) included a report of 4.00 inch diameter hail in southern Kansas, 3.75 inch diameter hail in far northern Oklahoma, and the tornado with a 107 mph wind gust near Enid.

____________________

Of course, the CIMSS ProbSevere product was tracking this event as it evolved. Here’s a snapshot at 0115 UTC (8:15 PM CDT) depicting how ProbSevere assessed the storm that produced the Enid tornado. Note the high confidence that ProbSevere has in the presence of severe activity: overall severe probability is 92% while tornadic probability is 65%.

Today, Friday 24 April, is another severe weather day in Oklahoma, so it may be a few days before the damage survey crews are able to assess the number and severity of these tornadoes. Regardless, it was an intense day that was well-captured by a variety of satellite products.

View only this post Read Less

April 22, 2026: Happy Earth Day! The first Earth Day was celebrated on April 22, 1970. The idea was conceived by then Wisconsin Senator Gaylord Nelson and an estimated 20 million Americans participated on that first day, which was approximately 10% of the US population back then. You can read more about the first Earth Day celebration on the Nelson Institute’s web page: Tracing Earth Day’s Origins.

To celebrate we are going to show off some full-disk GOES imagery. Here’s a selfie of almost everyone in North and South America today at 17:00 UTC (roughly local noon to the satellite) from GOES-19 (GOES-East) ABI:

If you weren’t in the GOES-East image maybe you can find yourself in the GOES-West (GOES-18) full disk image at local satellite noon (21:00 UTC)…

Here is an animation of GOES-19 (GOES-East) from satellite sunrise (11:00 UTC) to satellite sunset (23:00 UTC). GOES-East sits over the equator at 75W, so in the same timezone as the United States east coast.

Here is a similar animation of GOES-18 (GOES-West) from satellite sunrise (15:00 UTC) to satellite sunset (03:00 UTC the next day). GOES-West sits over the equator at 137W, which would put it roughly in Alaska’s timezone (noon for that location on this day was 21:06 UTC and that is -9 hours from UTC noon and that’s Alaska Standard Time), though 137W is somewhat east of the Alaska/Canada border.

Where were you at noon on Earth Day 2026? Unless you were off planet or in the Arctic or Antarctic Circle, you must be somewhere in this next image. A true color, local-noon composite from five geostationary imagers, thanks to the SSEC Satellite Data Services (SDS), including two from the USA, one from Japan, and two from Europe:

View only this post Read Less

Islands in warm tropical seas can create convection through a combination of factors that work together to foster deep convection. A recent example from the island of Guadalcanal in the Solomon Islands during the day of Monday 20 April 2026 illustrates this. Guadalcanal is famous as the site of a pivotal campaign of land and naval battles during World War II but today is known as a lush island of tropical rainforests, beaches, and the home of the nation’s capital city Honiara.

There are multiple ways that an island can foster convection. First and foremost, during the day, the island heats up faster than the surrounding ocean. Hot air rising, of course, is at the heart of deep moist convection. But this is enhanced by two additional factors: coastal breezes and orographic lift. Coastal breezes are a frequent byproduct of daytime island heating. Intro to Meteorology textbooks and popular media often simplify this as the air over the land gets warm causing it to rise while cooler ocean-based-air rushes in to fill the gap. The truth is more complex but more interesting; if you really want to know more it’s at the end of this post (be warned, though, it’s pretty technical). For now, though, we’ll note that as the island heats up it causes an offshore breeze to form. For a large continental landmass, this breeze can penetrate inland dozens of kilometers. For a small island, the breeze can’t penetrate that far because it will soon collide with the breeze coming from the other side of the island. This creates a low level convergence zone which enhances the upward lift caused by the daytime heating. Finally, the terrain of the island also has an impact. Many of these tropical islands are quite rugged, which means that as the wind rushes onshore it undergoes orographic lifting by the many mountains. This enhances the upward motion even more. This map of the terrain of Guadalcanal (courtesy of Wikipedia) shows that the island is dominated by an east-west ridge. Any flow from the north or the south is going to be enhanced by this vertical lift.

We’ll take a look at Guadalcanal on this day, starting with the true color view from the Himawari-9 Advanced Himawari Imager (AHI). Guadalcanal is the island at the center of this animation. The loop starts at 2130 UTC, which is 8:30 AM local time. The island starts clear, and is a beautiful deep green. For those of you who are mostly familiar with looking at GOES satellite imagery, you might think it is green because of the tropical vegetation that isn’t normally seen over the continental United States. However, it’s important to remember that the AHI has a true green channel unlike the US geostationary satellites and so its colors are going to appear a little more saturated. Shortly after the start of this loop localized convection forms across the island. However, if you watch the animation to the end, howver, you see that the convection starts to get squeezed into the middle of the island by the sea breezes on either side, forming a band of clouds that runs alongside the island’s mountainous spine.

It may be good to evaluate the kind of environment in which this convective development is taking place. Here’s a plot of the NOAA Physical Sciences Laboratory satellite-observed sea surface temperatures (SSTs). The Solomon Islands are circled in yellow, and it’s clear from this map that SSTs are a toasty 29-30 C (84-86 F). As such, there’s a lot of latent heat available to support convection.

Furthermore, the vertical structure of the atmosphere is also supportive of convection. Here is a skew-T plot of a nearby NUCAPS-retrieved vertical profile at 0338 UTC (2:38 PM local time), provided courtesy of the NUCAPS Savvy tool maintained by NASA SPoRT. The profile is generally well-mixed, with a near dry-adiabatic low level and a largely moist-adiabatic environment aloft. The instability is large, however, with CAPE values ranging from over 3200 to nearly 4300 J/kg depending on the values used. If low-level air parcels can ascend to around 1400-1600 m, they’ll breach the level of free convection and ascend on their own.

However, remember that terrain map above? That central mountainous spine has an elevation of around 1000-1200 m, so much of the work is already being done by orographic lift. The convergence and daytime heating doesn’t have to be very strong at all to unlock deep moist convection. Let’s see what happens over the next few hours. This loop is the same True Color RGB product as earlier, but now runs from 0100 to 0500 UTC (noon to 4:00 PM local) and covers the initiation of the deep convection.

Looking at the same period but through the Band 13 (10 micron) infrared channel helps to show how deep this convection was in a way that’s not possible with the true color alone. Here we see a burst of cold brightness temperatures as the convection ascends to the tropopause.

Additional RGB products can provide useful insight as well. The Day Convection RGB shows bright yellow plumes where the vertical growth is the most extensive while the red clouds are where ice particles can be found.

The Day Microphysics RGB also highlights some useful information. The salmon and golden areas indicate thick clouds with small water droplets (salmon) or ice particles (golden) which are commonly associated with deep convection. The green clouds are high-level ice clouds, which show that the cloud top is glaciating and thus the storm is transitioning rapidly to the mature stage.

Despite the strong forcing and favorable thermodynamics, this storm didn’t last very long. One possibility is that the deep convection to the south created an outflow boundary, which can be seen in the satellite loops as lines of clouds propagating northward. This cold, dense air would be kryptonite to any deep convection and cut it off just as it was getting going. At the same time, the day was getting late and the natural solar heating was dying out. Here’s the Band 13 view of the end of this event, from 0500 to 0900 UTC (4:00 PM to 8:00 PM local time). Sunset is around 0715 UTC (6:15 PM local time).

As promised, here is a more detailed description of coastal breeze formation. This post’s author has a special interest in coastal breeze formation (as depicted in this paper published in the Journal of Atmospheric Sciences) so he’s happy to take the time to offer a more precise explanation. As is well-known, the land heats up more readily than the water does due to differences in thermal heat capacity. This means that the air that is adjacent to the land also gets warmer than the air over the water. This creates a density gradient from land to sea, which in turn results in localized baroclinicity (we weren’t kidding when we said this was going to be a technical explanation) as the isobars remain largely static while the isopycnals tilt from parallel to the isobars before the heating to crossing them afterward. According to Kelvin’s Circulation Theorem, circulation in a baroclinic fluid is constant with time, but a barotropic fluid is going to cause a change in the circulation. Therefore, as the environment transitions from baroclinic to barotropic, it goes from zero circulation to a measurable one. That circulation is the coastal breeze.

View only this post Read Less