5-minute CONUS Sector GOES-19 (GOES-East) Nighttime Microphysics RGB + daytime True Color images from the CSPP GeoSphere site (above) showed a remnant Mesoscale Convective Vortex (MCV) that migrated eastward from southeastern Montana to northwestern South Dakota — where it helped to force the rapid development of a slow-moving Mesoscale Convective System (MCS) during the afternoon hours on 01 August 2025.

The MCS eventually began to produce periodic hail and damaging winds after 2100 UTC, as shown by 1-minute Mesoscale Domain Sector GOES-19 Visible images (above) and Infrared images (below) that included time-matched plots of SPC Storm Reports. The visible imagery revealed numerous pulses of overshooting tops, as well as intricate patterns of cloud-top gravity waves.

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Significant convection across the northern continental United States has had some notable impacts on the aviation network over the past few weeks. On Wednesday, 30 July, Delta Flight 56 was en route from Salt Lake City, UT, with an intended destination of Amsterdam. Shortly after takeoff at 4:30 PM local time (22:30 UTC), this Airbus 330-900neo encountered a thick band of vigorous convection over Wyoming. The GOES-18 Band 13 (10 micron infrared window) imagery for this period shows just how intense the convection was, with numerous cells featuring overshooting tops and enhanced v signatures.

While the plane attempted to avoid the worst of the convection by skirting to the south of the main area of severe thunderstorms, rapidly infilling developed made it very challenging to avoid the turbulence. The loop above covers the period from 2200 UTC (30 minutes before takeoff) to 2350 UTC (about 20 minutes after the severe turbulence was reported). ADS-B data courtesy of Flight Aware shows just how sudden the altitude changes were: over the course of just three minutes, the plane pitched upward approximately 1000 feet (300 m), them dropped sharply 1700 feet (510 m) before returning to its planned altitude of 37000 feet (11.3 km).

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A sequence of 5-minute CONUS Sector GOES-19 (GOES-East) Visible, Infrared and Water Vapor images (above) displayed the rapid development of a distinct cluster of thunderstorm overshooting tops about 20 miles NNW of the Cherokee, Wyoming VOR site (identifier CKW) — which became apparent near the location of the Extreme Turbulence encounter (which was 10 miles NNW of CKW, according to the Pilot Report):

RWL UUA /OV CKW340010/TM 2342/FL370/TP A339/TB EXTREME TURB FL370/RM COULD NOT HOLD ALTITUDE +/- 900FT ZDVWC-34

Note that there was a time lag between the turbulence event (2323-2325 UTC) and the time that the Pilot Report was transmitted (2342 UTC), as the pilots regained control of the aircraft and assessed the extent of any damage and injuries to passengers and crew.

1-minute Mesoscale Domain Sector GOES-19 True Color RGB images (above), which included time-matched plots of the DL56 aircraft location, provided a better view of the rapid development of thunderstorm overshooting tops.

A closer view using 1-minute GOES-19 Visible and Infrared images (below) included cyan * symbols that represented the surface-based location of DL56 at the time of each image — while the yellow + symbols represented the “parallax-corrected” location of DL56 over the cloud features at that time (using the 37000-ft nominal cruising altitude to calculate the parallax adjustment). Judging from the parallax-corrected points, it appears that the aircraft flew directly over (or very near to) the cluster of rapidly-developing convective overshooting tops. (Rapid convective development has been the cause of other severe turbulence events: for example, here, here and here.)

An AWIPS cursor sample of the GOES-19 Infrared image at 2326 UTC (above) showed that the coldest thunderstorm overshooting top (near the extreme turbulence encounter) exhibited an infrared brightness temperature of about -63ºC. According to a plot of rawinsonde data from Riverton, Wyoming (below), that infrared brightness temperature represented a ~1 km overshoot of the Most Unstable (MU) air parcel’s Equilibrium Level (EL) — reaching an altitude around 11.5 km or 37730 ft (above the 37000 ft cruising altitude of DL56).

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The CIMSS Turbulence product is a machine learning product that analyzes geostationary satellite imagery to identify areas where turbulence is likely. The contours on the animation below show the probability of moderate or greater turbulence at least once during a ten minute period as determined by this tool. The state of Wyoming (along with most of the Rockies) was clearly an environment in which turbulence could be expected.

A closer view of the MOG turbulence probability product, centered over southern Wyoming, is shown below (courtesy Sarah Griffin, CIMSS). A moving trace of the DL56 flight path is also plotted on the imagery — note the northward jog at the point of the Extreme Turbulence encounter (that red PIREP location is plotted on the last 2 images of the animation). As the areal extent of thunderstorm activity increased during that 4-hour period, so did the coverage of higher MOG turbulence probability.

Unfortunately, numerous injuries occurred during this flight. The plane made an emergency diversion to Minneapolis, and 25 passengers and/or crew were taken to local hospitals.

This was not the only high profile turbulence event in the last week of July 2025. On Sunday 27 July, the Boston Red Sox started their first leg of a road trip by boarding a plane bound for Minneapolis so they could take on the Minnesota Twins. The flight initially diverted to Detroit to allow time for conditions to settle, but then it pushed onward into Minnesota where convection was severe. The plane finally landed around midnight local time (0500 UTC). Once again, the GOES ABI Band 13 is an excellent took for diagnosing vigorous convective storms, with overshooting tops and wave patterns easily discernable.

Numerous players reported experiencing nausea and other impacts from the heavy turbulence, with one player being unable to play the next day due to lasting effects. Sox pitcher Lucas Giolito said, as quoted by MassLive, “It was the worst sustained turbulence I’ve ever experienced. Forty-five minutes straight of left, right, dropping down. At least on a roller coaster, you know when the drop is coming, or you know when you’re rolling right or you’re rolling left. You can see it. But sitting on a plane, it was like, oh boy. At one point, I kind of flew up out of my seat.” Shortstop Trevor Story echoed those comments, saying to MLB “It was awful. It was one of the worst, probably the worst flight I’ve been on turbulence-wise.” With 9 seasons and 10 years respectively in the major leagues for Giolito and Story, these players speak from significant experience with airplane flights.

However, the ordeal has inspired the Red Sox and they have embraced the adversity. Witness their turbulence-inspired celebration, seen here by Ceddanne Rafaela after he hit a triple. While the Sox lost their first post-turbulence game, they won the next two to take the series from the Twins.

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5-minute PACUS Sector GOES-18 (GOES-West) Nighttime Microphysics RGB and daytime True Color RGB images (above) revealed the cyclonic circulation of an actinoform cloud feature as it passed just north of the Hawaiian Islands on 30 July 2025.

GOES-18 Visible images (below) included plots of Ship and Fixed Buoy reports — unfortunately, the actinoform cloud feature avoided all of those reports, so any effects on sensible weather could not be ascertained (another case near Hawai`i provided evidence of rain showers associated with an actinoform feature).

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In the evening of 28 July 2025, residents of the Samoan island of Upolu experienced an intense thunderstorm which produced hail, a very rare event for maritime tropical Pacific environments. Social media videos show 1 – 2 cm hailstones falling around residents excited to see such novel conditions. The forecasters at the National Weather Service office in neighboring Pago Pago, American Samoa (approximately 50 mi or 80 km away), requested and received a mesoscale sector from GOES-18, which easily covered both the US territory of Amercian Samoa as well as the independent nation of Samoa.

Since American Samoa doesn’t have a radar, the CIMSS ProbSevere algorithm is not well-suited for deployment in that location. However, the CIMSS LightningCast product was available, and it is seen superimposed on the 1 minute mesoscale Band 13 (10 micron data). LightningCast uses AI and machine learning techniques to quantify the probably of a particular storm producing lighting based on its satellite signatures, and here it is clear that this particular storm is capable of producing substantial lightning.

Zooming in on a single frame of the above animation, at 0653 UTC, shows the presence of a very cold brightness temperature at the center of the storm. This is indicative of an overshooting top and is a hallmark of deep, moist convection. Given the storm’s location in the tropics (around 14 degrees south) the troposphere is naturally quite deep and thus the overshooting top indicates the tip of an updraft that penetrates through a very thick layer of the atmosphere.

In fact, the 0000 UTC sounding from Pago Pago, AS, shows a tropopause height well over 12 kilometers above the ground, which is a reasonable estimate of the height of the anvil of the cumulonimbus cloud. The overshooting top is soaring even higher above the surface, and thus it is clear that this storm has substantial vertical lift. A classic rule of thumb in the midlatitudes for enhanced hail growth is steep lapse rates in the -10 C to -30 C layer of the atmosphere as this is where hail growth is at its greatest. (Warmer than -10 means water is less likely to freeze on contact, colder than -30 means supercooled droplets are rare). This event exhibits strong instability in the hail growth zone with lapse rates that are much steeper than the moist adiabatic lapse rate (blue lines) between those temperatures.

With no radar at Pago Pago, satellite-based estiamtes of precipitation intensity are required. This animation shows a loop of the CIMSS GREMLIN product, which aims to simulate radar reflectivity from satellite observations. GREMLIN was trained using GOES ABI and GLM inputs over the continental United States, and while its accuracy may be highest there, it can still provide useful information in other parts of the GOES domains about the intensity of a storm and its evolution.

The Night Microphysics RGB also can provide some insight. Here, the presence of large areas of red cloud help verify that we are looking at thick ice anvils associated with deep convection, and really helps separate the deep convective clouds from the low level ones. This also makes the vertical shear of the wind profile easy to recognize, with the low level clouds moving to the west with eastward moving anvils superimposed on top of them.

Hail is rare in the tropics for a variety of reasons. The first is that it is quite warm. In the above skew-T, the freezing level is approximately 580 mb. While deep, vigorous convection may be producing hail storms more frequently, they melt by the time they reach the surface. A second factor is that humidity and precipitable water values are high. This inhibits evaporative cooling by the rain (helping to lower the temperature below the cloud and giving the hailstones a greater opportunity to reach the surface). This storm appears to buck that trend with a strong updraft and particularly strong buoyancy in the layer of the atmosphere where hail is most likely to form. Whatever the reason, the people of Samoa will remember this event for a long time to come.

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