1-minute Mesoscale Domain Sector GOES-19 (GOES-East) Visible and Infrared Window images (above) included time-matched plots of SPC Storm Reports — most notably the EF3-rated tornado that moved through the Appleton/Menasha area in northeastern Wisconsin, beginning around 1656 UTC — produced by clusters of thunderstorms on 27 July 2026. Very large hail also occurred in Wisconsin with these storms, including a few reports of 3.00 inches in diameter (and one report of 4.50 inches in diameter, which did not get plotted). Separate thunderstorms also produced large hail, damaging winds and a few tornadoes in the Chicago area.

1-minute GOES-19 Visible and Infrared Window images with an overlay of surface fronts (below) depicted the presence of a surface trough / developing warm front across eastern Wisconsin — the severe thunderstorms were moving southward near or just east of that surface boundary.

A closer look centered near Appleton — airport METAR identifier KATW (below) showed very high dew points across that area, with KATW reporting a dew point of 81 F at 1545 UTC (surface report plot), about an hour before the tornado. As the parent thunderstorm was approaching from the north, pulses of overshooting tops exhibited infrared brightness temperatures as cold as -75 to -78 C (brighter white pixels embedded within dark black regions).

According to a plot of rawinsonde data from Green Bay (below), infrared brightness temperatures of -75 to -78 C represented a significant overshoot of the Most Unstable (MU) air parcel’s Equilibrium Level (EL). The sounding also portrayed a very unstable atmosphere having a MUCAPE value of 4770 J/kg and a Lifted Index of -12 C.

Also of note was the Total Precipitable Water (PW) value of 2.12 inches — according to the SPC Sounding Climatology site, this was a record high PW value for all 27 July 1200 UTC soundings at Green Bay (below).

It is uncommon to see strong tornadoes in the morning in Wisconsin. Looking back from 1950 through April 30 of this year, the prime time for strong tornadoes in Wisconsin is between 2 and 7 pm (CST). Yesterday's tornado began at 10:56 am CST, making it just the 10th to start during that hour.

— Wisconet (@wisconet.bsky.social) 2026-07-28T14:44:03.051Z

===== 29 July Update =====

In toggle between before/after (13 July vs 29 July) Landsat-8 Natural Color RGB images as visualized using RealEarth (above), a faint signature of the tornado damage path (a transition from green shades to tan shades, due to tree/vegetation damage and an increase of structural debris on the ground) could be seen in the vicinity of Appleton, Fox Crossing and Menasha on 29 July.

Similarly, an image slider comparison between Sentinel-2 Optimized Natural Color RGB images on 13 July vs 28 July is shown below — which provided a better view of the vegetation damage swath (most notably near the bottom-center portion of the 28 July image, which is the Menasha area).

BEFORE AND AFTER: A great job by @nearmap showing the damage caused by the EF-3 Appleton-Menasha tornado on Monday. #wiwx pic.twitter.com/J7sw9TvURk

— Scott M (@EODWX5) July 29, 2026

View only this post Read Less

1-minute Mesoscale Domain Sector GOES-19 (GOES-Eas)t Visible images (above) showed Hurricane Genevieve as it was rapidly intensifying to become a Category 4 storm on 26 July 2026. Low-altitude mesovorticies were very apparent within the eye — and GLM Flash Points depicted intermittent lightning activity within the eyewall of the hurricane.

The corresponding 1-minute GOES-19 Infrared Window images (below) displayed cloud-top infrared brightness temperatures as cold as -75 to -80 C surrounding the eye.

Products from the CIMSS Tropical Cyclones site indicated that Genevieve was moving through an environment of low deep-layer wind shear, and traversing warm water. These favorable factors allowed the hurricane to reach a 135-knot intensity by 0300 UTC on 27 July (ADT | D-MINT | SATCON).

===== 27 July Update =====

Hurricane Genevieve continued to intensify after sunset, reaching 140-knot Category 5 intensity by 0600 UTC on 27 July (0900 UTC NHC discussion).

View only this post Read Less

1-minute Mesoscale Domain Sector GOES-19 (GOES-East) Visible images (above) and Infrared Window images (below) showed clusters of thunderstorms that produced hail as large as 2.50″ in diameter and wind gusts as high as 92 mph (SPC Storm Reports) across parts of South Dakota on 25 July 2026.

Pulses of overshooting tops exhibited infrared brightness temperatures as cold as -83 C (above) — which represented a significant overshoot of the Most Unstable (MU) air parcel’s Equilibrium Level (EL), according to a plot of rawinsonde data from Aberdeen, South Dakota (below).

1-minute GOES-19 Infrared Window images with plots of GLM Flash Points (below) displayed the abundant lightning activity associated with these severe thunderstorms.

View only this post Read Less

Earlier this week, we discussed the development of Fausto, a Pacific tropical system that formed south of Mexico. As expected, the storm has intensified to hurricane strength. Current projections (as of 1500 UTC, 5:00 AM HST) are for it to pass directly over the Hawaiian islands on Tuesday 28 July into Wednesday 29 July. Fortunately, the forecasts show the system weakening to a tropical storm before it reaches Hawaii, but the potential impacts for such a system are still quite significant given the potential for heavy rainfall. Here’s the most recent cone plot from the National Hurricane Center depicting Fausto’s expected track over the next five days.

The GOES-18 (GOES West) Band 13 infrared window imagery shows how Fausto has organized since the Blog last looked at it a few days ago. On Monday the 20th, it had a well-defined circulation but no eye was present in the infrared and even in the microwave it was somewhat challenging to identify exactly where the circulation was centered. Here on Friday 24 August, that’s no longer the case, as can be seen in the loop below.

If we take a close look at that loop, we seen that the eye is a little ragged and irregular. Compare this to when Bavi was at its greatest strength two weeks ago: its eye was almost perfectly symmetric. The strong correlation between hurricane form and its intensity is the heart of the Dvorak Technique for tropical cyclone intensity estimation. CIMSS has been a pioneer in developing automated methods of obtaining cyclone strength from satellites. The Advanced Dvorak Technique (ADT) assesses key parameters of the cyclone from infrared satellite imagery and thus can produce a continuous time series of cyclone intensity so long as there’s an accurate assessment of the position of the center of circulation. Here’s a time series of Fausto’s strength as calculated by ADT. Based on this, Fausto was a borderline Cat 2/Cat 3 event in during teh time shown in the above animation.

Since the development of ADT, CIMSS has continued to develop more advanced methods of retrieving tropical cyclone intensity from satellite observations. The D-MINT product is a deep learning algorithm that combines geostationary satellite data with microwave imagers and sounders from polar-orbiting satellites. Because it relies on the more temporally-infrequent microwave observations it doesn’t have the temporal continuity of ADT, but the enhanced inputs can contribute to a more accurate and reliable estimate, and each observation has an associated uncertainty with it. Here’s the D-MINT time series for Fausto.

With many different automated methods for cyclone strength estimation, it is convenient to see these methods together. The CIMSS SATCON product takes estimates from several different sources and produces a weighted average consensus value. Here, we see a consensus of around 95 knots as of the most recent estimates.

Scatterometry and synthetic aperture radars also provide compelling views of the structure of tropical cyclones. The wide spacing of the scatterometer swaths in the tropics can sometimes prove frustrating as the center of a cyclone can frequently be in the gaps. However, the most recent MetOp-C ASCAT scatterometer overpass was dead on and captured the wind structure perfectly. Note that the observed wind speed tops out at 50 kts, much lower than the automated wind speed estimates described above. This is a limit of the instrument itself and thus we cannot rely on it for exact measurements of wind speed within the core of a tropical storm. However, it is still quite valuable to see the overall distribution of winds and the general flow patterns around the center of circulation.

Synthetic aperture radar (SAR) winds can provide much more detail on the wind speed of a tropical system, with higher maximum values and much higher spatial resolution than the ASCAT method seen above. Below is a plot we see courtesy of NOAA STAR. Here we see winds approaching 100 kts on the north side of the eye. This provides an excellent depiction of somethingwe expect: in the northern Hemisphere, winds on the right side of the eye relative to the direction of motion are faster than those on the left side. This is because the winds on the right side are abetted by the motion of the storm itself while those on the south side are counteracted by storm motion. Note that the SAR product doesn’t directly show wind direction; the SAR technique can only be used for the magnitude of the wind, not its direction. The STAR plot embeds modeled wind vectors to bring context about wind direction to the plot.

Current forecasts show that Fausto is near its peak intensity and weakening is expected over the next few days. Some additional notes from the National Hurricane Center said in its 5:00 AM HST (1500 UTC) discussion:

However, it is worth noting that the guidance has 
struggled to capture the trends in Fausto's intensity over the past 
few days.  Nonetheless, decreasing water temperatures and drier air 
should cause the cyclone to gradually lose strength, and an increase 
in westerly vertical wind shear early next week will likely aid in 
that weakening trend.  The NHC intensity forecast lies near the 
middle of the guidance envelope, and shows steady weakening through 
the period.  There is relatively high confidence that Fausto will be 
a tropical storm when it is in the vicinity of the Hawaiian Islands.

View only this post Read Less