Overview: Week 3, Day 4

The final operations day of the testbed began with our last daily debrief session, and we talked a bit about the applications sounding information with respect to the future GeoXO mission. The forecast for today was...meh? We had storms in the forecast, but the environment during our operations was marginal for severe weather overall. One office was localized to Billings, MT (BYZ) to capture developing thunderstorms closer to the jet streak, while a second office was localized to Topeka, KS (TOP) close to a remnant MCV that was kicking off convection already by 16 Z. Both offices got two mock-DSS events again today. If thunderstorms were looking unlikely to form in the Billings CWA by ~20Z we planned to move them to the Miami, FL office. Thank you Florida for being our safety net for thunderstorms.

Two MDs were issued by SPC during the afternoon for our forecast areas, with one resulting in a severe thunderstorm watch.

With Jonny's help I made a 'test RGB' from the Synthetic GXI imagery. There's no physical basis to the RGB (yet!), but it was a proof of concept that we could do it. An example and the recipe is shown below. What features can we pull from this new imagery relative to water vapor at low levels and through the entire column? Maybe we can figure it out in future testbeds!

During operations, I showed forecasters another example of SZA imagery over California with the impacts of the marine layer with low clouds and fog. Forecasters also compared this imagery against the Nighttime Microphysics to see how long the 'gap' was between the two, and what features you could identify with each product. Additionally I found a case from a fire from sunrise through the lens of the Day Fire RGB.

Kevin

Soundings Capture Unstable Atmosphere over Northeastern South Dakota

1. Satellite Evolution and Pre-Frontal Forcing (2030 UTC)

The afternoon of June 3, 2026, presents a classic setup for convective development across northeastern South Dakota.

Surface Features: A cold front moving eastward, combined with an outflow boundary from a preceding Mesoscale Convective System (MCS), is serving as the primary surface focus for thunderstorm initiation.

Pre-frontal Monitoring: The 2030 UTC composite satellite image captures an area of concern for downburst winds, particularly near Aberdeen, SD.

Cloud Phase Distinction: At this time, the GOES-19 SZA Day Cloud Phase Distinction product in Figure 1 below highlights pre-frontal cumulus development as distinct, blue-shaded "Cu streets," indicating the initial vertical growth of liquid-water clouds before they transition to ice-phase convection. 

Figure 1: Composite SZA cloud phase distinction, MRMS reflectivity, and LightningCast probability product image at 2030 UTC 3 June 2026.

2. Thermodynamic Analysis: The Miller Type 1 Profile (1800 UTC)

Sounding data from 1800 UTC in Figure 2 reveals a volatile environment characterized by a classic severe weather profile.

Sounding Structure: A comparison between the GOES-19 sounding retrieval and the Aberdeen, SD (KABR) radiosonde observation shows a prominent "narrow hourglass" structure.

The "Loaded Gun": This signature closely resembles a Miller Type 1 profile—often referred to as a "loaded gun" sounding—where a moist boundary layer is capped by a warm, dry layer (capping inversion) and steep lapse rates aloft.

Potential Energy: The environment features large CAPE (1694 J/kg on G19 and 2138 J/kg on RAOB) and a calculated Wind Gust Potential (WGP) of 43 to 45 knots.

Figure 2. Comparison between the GOES-19 (G19) sounding retrieval (left) and the Aberdeen, SD (ABR) RAOB sounding at 1800 UTC 3 June 2026 (right).

Figure 3. Comparison between the 1900 UTC NOAA-21 NUCAPS sounding retrieval 40 km NW of Aberdeen, SD (left) and the Aberdeen (ABR) RAOB sounding at 1800 UTC 3 June 2026 (right).

3. Regional Validation: NUCAPS vs. KABR RAOB (1900 UTC)

The regional thermodynamic environment is further validated by satellite-derived sounding retrievals.

Profile Consistency: The 1900 UTC NOAA-21 NUCAPS sounding, retrieved approximately 40 km northwest of Aberdeen, shows excellent structural agreement with the KABR radiosonde.

Downburst Ingredients: Both profiles exhibit favorable wet-bulb zero heights positioned near the 700-mb level, a key factor for maximizing evaporative cooling and subsequent downburst strength.

Forecast Outlook: Thunderstorm downburst occurrence will be most favorable during the late afternoon hours as the eastward-advancing cold front impinges on this highly unstable air mass over the Aberdeen area.

StormRangerWX

Actual WVT Data from FCI

 One of the products demonstrated at this year’s HWT is synthetic water vapor transmittance (WVT) imagery.  The product, a ratio of 0.91 μm to 0.86 μm reflectances, is based on the existence of water vapor absorption at 0.91 μm.  Dividing by 0.86 μm helps to highlight the water vapor signature.  As NOAA does not yet operate a satellite channel at 0.91 μm, synthetic imagery is created for HWT from the High-Resolution Rapid Refresh model run through the Community Radiative Transfer Model.  However, EUMETSAT’s latest geostationary satellite, Meteosat-12, does contain 0.91 μm and 0.86 μm channels on its Flexible Combined Imager (FCI), and is used to augment the synthetic imagery during HWT.

Figure 1 shows an FCI WVT loop over northeastern Africa and the Arabian Peninsula from 3 June 2026.  The darker regions are indicative of higher amounts of total precipitable water (TPW).  Noteworthy regions of higher TPW can be seen along the west and south coasts of Saudi Arabia and Yemen as moisture moves onshore from the Red Sea and the Gulf of Aden.  The greater moisture along and equatorward of the Sahel is also very apparent.  Protruding from this reservoir of high TPW is a stream of moisture moving north to southern Algeria and then northeast towards Israel.  The existence of these high moisture areas can be confirmed by the corresponding TPW loop (Figure 2) created from blending retrievals from multiple polar-orbiting satellites.  Additional confirmation of the moisture protrusion over Algeria can be seen in the surface dewpoints at the reporting stations (Figure 3).  The stations in southeast Algeria have dewpoints above 40°F, whereas further north the dewpoints are 30°F or lower.

Figure 1.  WVT product loop over Africa on 3 June 2026.

Figure 2. Corresponding TPW product created from multiple polar-orbiting satellites.

Figure 3.  Surface observations over Algeria around 1300UTC 3 June 2026.  Dewpoint temperature (°F) is shown in blue.  Zooming in may be necessary to read the numbers.

Geogxi

Every Cloud Has a Silver Lining - Satellite-Based Mesoanalysis

Satellite-based observations have become a larger part of an operational forecaster’s toolshed with each passing decade. Over the past 10 or so years since the launch of the GOES satellites over North America, forecasters now have access to extremely high-resolution, high-quality data. That data can be used for a wide array of potential benefits, and this satellite HWT is designed in large part to show us how we can widen out that repertoire even more.

With that in mind, I’d like to start out this Hump Day blog post by discussing one of the products that has not been featured as prominently in my previous blogs - GXI water vapor data. In essence, the next generation of weather satellites (GEO-XO) will have the kind of sensitivity that lets us really drill down into the absorption bands to see some neat stuff. That kind of capability won’t arrive until the 2030s, so for this week we are taking a look at what the data could look like via HRRR simulated satellite data.

Figure 1: WVT Ratio from the HRRR (left) compared to Split Window Moisture on GOES-East (right).

As you can see above, there are limitations to this analysis. For one thing, even perfectly initialized models are going to struggle to carry cloud cover forward given its sensitivity. And for another, models are not going to perfectly initialize.

Still, if you squint and look across the eastern portions of NWS Aberdeen's CWA, there is an area of somewhat lighter grey feeding into the cloud band on the HRRR. This is suggestive of a potential moist pool in the region. Actual observations of this would help forecasters dominate the mesoanalysis space like never before.

Perhaps one of the most powerful uses of mesoanalysis tools came from the OCTANE speed-direction tools today. I have spoken at length about those tools, so won’t spend too much time on them. This gif just does a great job of summarizing what we might be able to do:

Figure 2: OCTANE Speed (top left), Direction (top right), Cloud Top Cooling (bottom left), and Day Cloud Phase (bottom right)

Here we have a storm on the north end of the cluster (yellow OCTANE speed, purple OCTANE cloud tops) and developing updrafts to its south-southwest. Those updrafts are occurring in an area of boundary-layer cumulus (shown well by their northeast or yellow motion in the Direction panel). Further to the east, there are clouds oriented along two axes: an area of HCRS (red in the Direction tool), and an area of stable billow clouds (yellow in the Direction tool). Knowing your mesoanalysis, this provides a tell that the northern updraft is likely to wither as it enters a stable boundary layer, which it did. It’s also a tell that further south, updrafts won’t have the same issue. As of the time of this writing, a supercell has developed out of that southern cluster.

This author would be remiss if they didn’t mention the in-person IDSS potential offered by the Lightning Stoplight tool. This has also been discussed previously, so I won’t belabor the details too much. But the ability to display a dashboard from your browser with basically a color-coded area showing how long it has been since the last lightning strike will go a long way toward helping partners understand when DSS activities may restart.

Figure 3: Lightning Stoplight in its web-browser-based glory.

Sabrina Carpenter

FGF CTC CTD Testing

Today's DSS event brought us to the wonderful state of North Dakota in the FGF CWA. Unfortunately with no lightning at either DSS event today, I did not get to use the GOES Stoplight product, so I used Octane again. I continue to be highly impressed by the utility of the OCTANE products. You know the saying “A picture is worth a thousand words”? Well, to me, that is exactly what the cloud top cooling and divergence product embodies. There are so many features that can be picked out from this. Near the bottom left, there are multiple updraft attempts that try but most fail. It shows multiple storms developing in McPherson and Dickey Counties with cooling cloud tops and increasing cloud top divergence. Further to the west in Emmons county it shows a cloud top cooling signal but it ends up disappearing and subsequently the cloud top divergence decreases. Pairing all of the imagery with a visible band really gives some nice textures to the picture where you can easily point out quickly developing features. I find myself continually migrating back to the Octane products for situational awareness as storms approach the DSS event.

Figure 1: East Meso1 Cloud Top Cooling and Cloud Top Divergence with ENTLN lightning data overlaid.

Dry Thunderstorms

LTG DSS with LTG Cast and Stoplight

 Upon starting the shift we had a supercell that was about 1 hr out from our first event. In operations our DSS forecaster would have immediately informed our partner that the cell (which had 1” hail report) is barreling in from the southwest.

Both versions of the LTG cast were providing a 70% chance of LTG within the next hour as well, with convection out ahead of the main supercell the heads up notification would also have included this information.

45minutes later we had our first lightning strike onsite ahead of the main supercell.

—---------------------------------------------------------------------------------------------------------------------------

Activity began to wind down by 2030Z

An all clear call would have been made at 2100Z with the stoplight product largely vacant of any lightning detection. MRMS-10C was also outside of the 8mile range ring with little build up expected upstream. Lightning cast had also dropped to around 10%.

IsthataTOR

GEOXO storm development and LightningCast DSS

 The GEOXO Sim 5.15um band and WVT ratio showed supercell or at least thunderstorm development near Gettysburg by 21Z. However the initialization of the upper level cirrus was underdeveloped and the main severe warned thunderstorm was farther north than observed. The lower level cumulus also appeared to be underdeveloped. There is a clear region in the sims where higher moisture is present and dryer air exists on either side, with the thunderstorms developing on the western boundary line.

Figure 1: GEOXO Sim 5.15um band and WVT ratio on top with observed GOES-19 IR an visible imagery on bottom. First frame shows Observations at around 20Z compared to the model and the second frame is in the future on the top an hour later.

While not severe or as intense as the Sim suggested, storms did develop and provided an interesting borderline case where LightningCastv1 showed barely 10% and v2 showed barely 30% chance of lightning in the next hour within 5 miles of the Gettysburg DSS location. A lightning strike occurred roughly miles from Gettysburg that was detected by the ENTLM and the Stoplight tool maybe 2 miles to the east. In this case, the addition of MRMS was clearly helpful in detecting the initial nearby convection.

Figure 2. LightningCast comparison between version 1 and 2 and parallax vs no parallax adjustment.

Cloudius

Overview: Week 3, Day 3

Day 3 started with our debrief from Tuesday, along with a focus group activity for GeoXO lightning mapper capabilities. I showed forecasters SZA imagery near sunrise during a period of glare from the GOES-East perspective near sunset. Overall forecasters felt the cloud tops were more 'washed out' by the brighter visible channels, but mentioned the important feature from the Day Cloud Phase Distinction is often the cloud phase before the overspreading anvil cloud begins. 

Traditional Day Cloud Phase Distinction RGB

SZA Day Cloud Phase Distinction RGB

Wednesday targeted the Northern Plains again, with the cold front being are only source of lift and deep layer shear that we can pull from this week. We decided to localize the forecasters to NWS Grand Forks, ND (FGF) and Aberdeen, SD (ABR), and each had two DSS events so they could leverage the LightningCast SuperDashboards.

1PM

Storms were slow to develop early in the forecaster period with a bit of cloud cover making the Synthetic GXI imagery less usable, so the product developers took both offices on a 'tour of Europe' showing off the Water Vapor Transmittance product from the Meteosat-12 FCI. This led us back to the states where we talked more about colormaps for WVT and what forecasters preferred. I made a display as part of that discussion. Upper left is WVT with 'flipped' colormap, upper right is WVT with the origional colormap, lower left is WVT with a red-green colormap made by a forecaster in the previous week, and the lower right is PWATs from the most recent HRRR run (18Z).

 2 PM

Forecasters in both offices focused mostly on DSS tasks early in the forecast period, along with comparing OCTANE's CONUS and MESO products. Additional discussion centered around the Lightning Stoplight tool and debating the 'optimal' color table to convey the intended actions from those viewing the product.

As thunderstorms approached the mock-IDSS events forecasters interrogated LightningCast data and discussed its applications, along with the desire to have variable ranges for the dashboard web display. We did run into an interesting case where a thunderstorm initiated over a narrow band of cirrus clouds, which may have impacted signals from OCTANE and LightningCast.

To end the day, I spammed AWIPS looking for sunrise imagery to show off SZA (thanks Justin for turning on the feed so early!)

Fog and low clouds from the marine layer along the California coast from the Day Cloud Phase Distinction RGB (SZA left/traditional right)

Valley fog over the Appalachian Mountains in the morning from the Day Snow Fog RGB (SZA left/traditional right).

Kevin

Persistent Severe MCS and Downbursts in Southwestern South Dakota

 1. Convective Initiation & MCS Evolution (1900 UTC)

The early afternoon of 2 June 2026 was marked by the development of a persistent mesoscale convective system (MCS) over Fall River County, SD as shown in Figure 1 below.

Satellite Observations: The 1900 UTC composite satellite image shows the system advecting east-northeastward, exhibiting rapidly increasing ice-phase cloud tops and a significant rise in lightning flash rates.

Structural Signatures: At this stage, the MCS already exhibits a well-defined bow echo complex and a prominent rear-flank dry-air notch. These features indicate
that the system is efficiently processing dry mid-level air to generate strong surface outflows.

Figure 1: Composite SZA cloud phase distinction, MRMS reflectivity, and LightningCast probability product image at 1900 UTC 2 June 2026.

2. System Intensification and Dual Bow Echoes (2030 UTC)

By 2030 UTC, Figure 2 shows the convective complex underwent further intensification and expansion as it tracked across southwestern South Dakota.

Complex Organization: The system evolved into a more formidable MCS consisting of two distinct bow echo complexes.

Severe Potential: Each bow echo was accompanied by its own rear-flank dry-air notch. This dual-notch presentation signaled a marked increase in downburst potential, as the system became increasingly organized and capable of producing widespread damaging winds.

Figure 2: Composite SZA cloud phase distinction, MRMS reflectivity, and LightningCast probability product image at 2030 UTC 2 June 2026.

Figure 3. Comparison between the GOES-19 (G19) sounding retrieval 90 km SSE of Rapid City, SD (left) and the Rapid City (UNR) RAOB sounding at 1800 UTC 2 June 2026 (right).

3. Thermodynamic Environment: Rapid City (1800 UTC)

An analysis of the 1800 UTC environment in Figure 3 explains the high-end wind potential observed.

Sounding Profile: A comparison between the GOES-19 sounding retrieval and the Radiosonde observation (KUNR) at Rapid City, SD, reveals a textbook "hourglass-inverted-V" profile.

Instability & Wind Potential: The environment was characterized by large CAPE (1014 to 1584 J/kg). Correspondingly, the Wind Gust Potential (WGP) was calculated between 41 and 47 knots, providing strong evidence for the severe gusts that followed.

4. Regional Validation & Surface Verification

Regional sounding data further confirmed the widespread nature of this volatile environment.

NUCAPS Comparison: A NOAA-21 NUCAPS sounding retrieved at 1919 UTC approximately 150 km southeast of Rapid City showed excellent structural agreement with the UNR radiosonde (RAOB).

Key Ingredients: Both profiles highlighted favorable wet-bulb zero heights for evaporative cooling and robust downburst generation.

Ground Truth: This thermodynamic setup culminated in a significant surface event: a severe 55-knot downburst wind gust was recorded at Cactus Flats, SD, at 2043 UTC— aligning well with the high WGP and structural signatures identified earlier in the afternoon.

Figure 4. Comparison between the 1919 UTC NOAA-21 NUCAPS sounding retrieval 150 km SE of Rapid City, SD (left) and the Rapid City (UNR) RAOB sounding at 1800 UTC 2 June 2026 (right).

StormRangerWX

Moisture advancing east in pre-convective Wyoming environment

 Simulated GeoXO Imager (GXI) imagery revealed the westward extent of higher moisture in the pre-convective environment of eastern Wyoming this afternoon.

Figure 1 shows the water vapor transmittance (WVT, derived from the 0.91 µm channel) in the left panel and the 5.15 µm brightness temperature in the right panel over a five hour period from 16-20 UTC..  A dashed green line indicates the approximate westward extent of the deeper moisture as estimated from the WVT imagery. In this “inverted” color scheme, drier areas appear darker in WVT (as does higher terrain), and moister areas appear whiter; high-topped clouds generally appear dark.  In the last frame of the loop, convection initiates near Douglas along this moisture boundary on the southern end of this green line.

While WVT is sensitive to the total column water vapor, the 5.15 µm channel is only sensitive to water vapor in lower levels, where lower brightness temperatures generally coincide with higher low-level moisture.  It is interesting to note that the WVT and 5.15 µm gradients do not always align with each other, possibly suggesting an evolving vertical distribution of water vapor.  Our future plans include developing methods to utilize these differences to derive information about depth of moisture in the column.

Figure 1: WVT (left panel; inverted color scale so whiter colors=more moist). The green dashed line indicates the approximate westward extent of deeper moisture as estimated from WVT. 

VortexTilting