Overview: Week 2, Day 2

10 AM

Tuesday began with a group discussion and first impressions for the five experimental products. Topics included how forecasters applied LightningCast and the Lightning Stoplight, OCTANE Cloud-Top Cooling for monitoring updraft strength, and the value of SZA imagery near sunrise to observe low clouds and fog. I showed an example of the SZA Day Cloud Phase Distinction RGB on CIRA-SLIDER, with clouds and storms across Florida around sunrise. I asked the forecasters to identify what time the imagery became 'usable' for them, and compared it against the traditional imagery of the same scene. Here were the results:

• Traditional imagery:
• SZA imagery:

I'm hoping to run a similar experiment with SZA imagery near sunset tomorrow. Here's the imagery I showed today. When do you think each imagery becomes 'usable'?

Traditional Day Cloud Phase Distinction RGB

SZA Day Cloud Phase Distinction RGB

We jumped into our forecast discussion, which asked the question 'Can we avoid going back to Florida again?' Unfortunately that answer was NO, so we localized to NWS Melbourne, FL and NWS Miami, FL.

1 PM

Shortly after ops started SPC issued an MD for the Florida peninsula.

Forecasters in the MFL office talked about providing DSS with LightningCast and Lightning Stoplight, and noticed in the OCTANE MesoAnywhere product how cirrus motions aloft cloud interfere with low cloud motions. MesoAnywhere is on the left, ABI MESO imagery is on the right.

Forecasters in the MLB office issued a handful of warnings, and we had a discussion about the OCTANE-CONUS Cloud-Top Cooling product. While the OCTANE MESO products showed more information, forecasters still found the OCTANE-CONUS products useful if a MESO wasn't availalble in this case.

Late in the day we viewed the frontal boundary in KS where storms might initiate this evening through the Synthetic GXI products, namely the 5.15 µm and WVT products. We compared them with the ABI split window moisture field (10.3-12.2 bands) and the ALPW from JPSS. In talking with another developer, we got the idea to create a 'sandwich' product that meshes the WVT and ABI Split Window products.

-Kevin

Monitoring LC V1 and V2 in Florida

At the beginning of week #2, forecasters were over Florida getting used to the products that they would be looking at for the week. For the Lightningcast product, one of the questions that was being asked by developers was differences between Version 1 (V1) and Version 2 (V2). V1 included 4 ABI inputs (channel 2 [the red band], channel 5 [the snow/ice band], channel 13 [the IR-window], and channel 15 [the dirty IR-window]), with V2 also including Muli-Radar Multi-Sensor (MRMS) reflectivity at -10C. Contours for both versions are shown in figure 1. Both versions looked fairly similar in the spatial extent and timing of the contours.

Figure 1: Lightningcast contours for V1 (left panel) and V2 (right panel) over Florida on 11 May 2026 from 2026Z to 2121Z. Satellite imagery in the background is the Day Cloud Phase Distinction RGB from GOES-19.

While not examined by forecasters today (but will be for fictional DSS events later in the week), the lightning dashboard for the Gainesville Regional Airport (KGNV) showed that V2 had a better handle on lightning cessation than V1 for that particular location (figure 2). V2 showed a ~5% probability of lightning within the next hour at 2050 UTC, while V1 reached that same probability at 2118 UTC, roughly 30 minutes later.

Figure 2: Lightning dashboard for KGNV. V1 probabilities at that location are shown by the red line and V2 probabilities at that location are shown by the green line. The GLM flash counts within 5-miles/5-min (8-miles/5-min) are shown by the dark (light) blue circles.

-Aurora

GXI 0.91 µm-based WVT Imagery of a Florida Sea Breeze

Figure 1: GeoXO/GXI water vapor transmittance (WVT).  At 20 UTC (last frame), the subtle darker shading near the coast shows the extent to which the sea breeze has moved inland.

Figure 2: Associated 20 UTC dewpoint from HRRR. Image from pivotalweather.com.

Today’s operations focused on convection moving across Florida with an associated sea breeze on the eastern coast. This provided an opportunity to see how this feature might appear in future GeoXO GXI imagery.  We looked at synthetic GXI imagery based on the 00 UTC HRRR output from the same day.

Figure 1 shows a short loop of synthetic water vapor transmittance (WVT) imagery.  WVT is the reflectance ratio of the 0.91 to 0.86 µm channels, and oftentimes better highlights areas of moisture than the 0.91 µm channel alone.  Darker areas (i.e. lower values) of WVT generally represent areas with higher total column water vapor.

At the end of the loop, as the sea breeze establishes itself inland (as demonstrated by the forecast dewpoints in Figure 2), a subtle area of darker shading in WVT is visible near the coast, delineating the extent to which the sea breeze has moved inland.

The dewpoint gradient across the sea breeze is only a few °F, which explains the subtleness of this feature.  Stronger sea breezes with larger moisture gradients will be much easier to identify than what is seen in this example (as regularly demonstrated in WVT from EUMETSAT’s Flexible Combined Imager (FCI) over Europe).  It is also noteworthy that the synthetic 5.15 µm did not identify the sea breeze, mostly due to the limited vertical extent of the sea breeze circulation.  WVT, by contrast, is sensitive to water vapor anywhere in the column.

-VortexTilting

 

Monitoring Downburst Potential with Sea-breeze Convective Storms in Florida

In accordance with Mesoscale Discussion #705 issued by NWS/Storm Prediction Center at 1724 UTC, the main area of focus for thunderstorm downburst wind generation was set as the Atlantic coastal region of Florida from south of Jacksonville to Palm Beach County.

The initial analysis highlights a primary area of concern for severe downburst winds situated along the east-central Florida coast. This region is characterized by strong ambient instability, creating a highly favorable thermodynamic environment for robust convective updrafts. Furthermore, the convergence of lingering thunderstorm outflow boundaries with the advancing Atlantic sea-breeze front serves as a potent mesoscale lifting mechanism. This boundary interaction is anticipated to force explosive convective initiation, setting the stage for intense downward momentum transport as heavy precipitation cores develop and rapidly descend.

Figure 1: Composite of SZA day cloud convection, LightningCast lightning probability, and MRMS radar reflectivity at 1906 UTC 11 May 2026

To assess the vertical thermodynamic structure within this concern area, we examine NOAA-21 NUCAPS (NOAA Unique Combined Atmospheric Processing System) sounding profiles. These satellite-derived soundings exhibit a classic "hourglass" profile, featuring dry sub-cloud and mid-tropospheric layers flanking a moist low-level convective layer. This signature is strongly indicative of sufficient potential instability and rapid evaporative cooling. Driven by this thermodynamic structure, the NUCAPS profiles suggest a large downburst wind gust potential in the vicinity of 50 knots, placing the environment right at the threshold for severe convective wind generation.

Figure 2. Comparison of NOAA-21 NUCAPS sounding profiles in the Cape Canaveral area during the afternoon of 11 May 2026.

Corroborating the polar-orbiting data, a GOES-19 derived sounding at 1740 UTC shows excellent agreement with the NUCAPS profiles. The high-temporal-resolution geostationary sounding captures the same inverted-V, dry-adiabatic lower troposphere. Complementing the sounding data, the corresponding GOES-19 Brightness Temperature Difference (BTD) microburst risk product highlights the Cape Canaveral area as a localized maximum for severe downdrafts. The BTD product calculates a Wind Gust Potential (WGP) of 40 to 50 knots, tightly aligning with the NUCAPS assessment and emphasizing the imminent threat to the Space Coast.

Figure 3. GOES-19 sounding profile near Titusville, FL at 1740 UTC compared to an eastern U.S. sector IR BTD product image during the afternoon of 11 May 2026.

To validate the satellite-derived observations against high-resolution numerical weather prediction, we evaluate the 1800 UTC Rapid Refresh (RAP) model sounding at Cape Canaveral. The RAP model profile definitively confirms the thermodynamic signatures identified in both the NUCAPS and GOES soundings. It displays significant Convective Available Potential Energy (CAPE) coupled with substantial mid-level dry air, yielding a high computed Wind Gust Potential (WGP). This strong consensus across multiple platforms—polar satellite, geostationary satellite, and mesoscale modeling—renders a clear and consistent picture of an environment primed for significant downburst activity.

 

Figure 4.RAP model analysis sounding profile retrieved over Cape Canaveral, FL at 1800 UTC 11 May 2026.

-StormRangerWX

Florida Convection - May 11 2026

 Today we examined several experimental satellite products, LightningCast V2, Synthetic GXI, and Solar Zenith Angle - Adjusted (SZA) Imagery, OCTANE, and Lightning Stoplight over north central Florida. It was a relatively quiet convective day across the CONUS, especially for mid May with the only area of significant convection over north central Florida.

While I was already very familiar with the LightningCast V2, the Stoplight and the SZA imagery, the product that sparked the most interest to me or was most excited about its future capabilities  was the synthetic GXI imagery, which uses the 0.91 µm and the Water Vapor Transmittance (WVT) or the ratio of the 0.91 µm/0.86 µm channels.  Once these two new channels become available on the Next Generation of GOES satellites, GeoXO, I believe these two new products will become extremely useful in determining moisture gradients or moisture pooling and it would be of greater utility than the current Split Window Difference (SWD) product available from the current GOES Advanced Baseline Imager (ABI). In particular, the WVT image below (top right panel) clearly showed a moisture gradient (darker colors representing higher TPW vs brighter color colors representing lower TPW) associated with a cold front sinking into the Gulf Coast states.

Figure 1 (above): Four Panel Display of GeoXO imagery showing the 5.5 µm and the WVT products at the top left and right respectively, and the “Clean” Window IR and VIS channels at the bottom left and right respectively.

Figure 2. WPC Surface Analysis valid 18 UTC Mon May 11 2026 showing cold front extending from the Carolinas southwestward to the Gulf Coast states to along the U.S.- Mexico border.

Hurricane Specialist

SPG Blog Post Florida Convection 05-11-2026

Deep convection was hard to come by in Florida on May 11th, 2026 but a weakening storm did move over a land breeze boundary along the coast during the late afternoon and into the evening. The land breeze was visible on the GeoXO viewer and can be seen as a buildup of moisture along the coast which then dissipates around 2200z. Figure 1 shows this buildup of moisture very well.

Figure 1: Land breeze moisture build up along the East Coast of Florida.

As a weakening thunderstorm traversed over the boundary, it was reinvigorated and strengthened rapidly. This can be seen below on Figure 2. A thunderstorm moved over the boundary, seemingly absorbed the moisture at the boundary and developed deep convection over the ocean.

Figure 2: A thunderstorm moved over a land breeze boundary and restrengthened.

Batman

SPG Blog Post Day 1

Today, the group learned about the suite of satellite products that we will be testing. Below I will include some notes on two of the products we learned about during the operations portion of the day.

Figure 1: LightningCast-ECONUS-compare product

• During this exercise, we were placed into two different CWAs: MLB and JAX. I was in the MLB CWA, monitoring developing convection over the FL peninsula, as a frontal boundary moves through to the north. There was a marginal risk, per SPC guidance.
• Above is the LightningCast ECONUS comparison product. The top two panels used GOES-19 satellite imagery, while the bottom two panels used MRMS data. The left panels are V1 of LightningCast, and the right panels are V2.
• I noticed that V2 improved on noise reduction, with low percent chances of lightning being more confined to developing storms. V1 seemed to have some low percentages over clouds that looked like low level cumulus, but V2 fixed that.
• I really liked how this product highlights areas of active storms, and where the best chances of thunder are next. I find the extent of the LightningCast product to help for DSS purposes, as I have an idea on what areas ahead of the storm should prepare to see lightning.
• The color scale, following SPC categories, works nicely and is easy to interpret, from a forecaster point of view.

Figure 2: Octane CTC

• Figure 2 shows the OCTANE Cloud Top Cooling product.
• This suite of products became helpful as I began to understand their use.
• The CTC product seems to be very informative on convection development, and differentiating between the various thunderstorm phases. The color scale changes from green, yellow, to red to indicate cloud tops beginning to cool, and are colored at the rate at which they cool every 5 minutes. This way, the user can see where cloud tops are rapidly cooling, and thus where convection is developing/strengthening.
• The colormap is relatively easy to understand, from my perspective.
• Playing around with the color scale may help to really hone in on developing storms, as from looking around the CONUS, there is a lot of blues and greens. If someone wanted to narrow the scale a little, to reduce the amount of data to sift through, that could help make things a little easier to navigate. I personally don’t mind it, because I think it’s a good way to see general cloud coverage and cloud types.

Kelvin-Helm

Overview: Week 2, Day 1

10 AM 

Week 2 of the Satellite Experiment kicked off this morning, with a fresh batch of forecasters and a recharged group of developers. Convection was difficult to find unless you were along the Gulf or Atlantic coasts, and with marginal deep layer shear the potential for severe weather was also also categorized as Marginal from SPC in its 13Z outlook. After our orientation session, the forecast discussion today was focused on western Louisiana, Florida, and the Carolinas. Ultimately we decided to localize to the NWS offices in Jacksonville, FL (JAX) and Melbourne, FL (MLB) with the expectation that upstream convection and land-sea breeze interactions could initiate and sustain convection throughout our operations window (18-22 Z).

1 PM

Operations kicked off with the developers providing hands-on demonstrations and walk-throughs with the forecasters. With a slower severe weather pattern on the first day, we encouraged everyone to think of today as a 'training day'. Forecasters asked several questions about the synthetic GXI imagery, such as the heights sampled by the 0.91 and 5.15 µm bands, the impacts of snow cover, and how the synthetic products compare to the real 0.91 µm imagery from FCI. We also talked about making RGB products from the synthetic imagery, and realized that the imagery specialists at CIRA had taken the liberty of remapping the products to the ABI 2km grids (kudos!). I'm hoping to create some RGBs this week that we can play with and improve on. What would forecasters like to see in an RGB? Moisture by height? Low level boundaries?

2 PM

We got an MD from SPC! Not a great chance for a watch, but good to know some severe risk exists in our CWAs.

4 PM

The rest of the operations day was pretty slow, so I spent some time working (arguing?) with AWIPS to make an RGB for the Synthetic GXI data. It's a work in progress...

Found an interesting case of dissipating and initiating convection form the perspective of LightningCast v2 and Lightning Stoplight v2 further west near the Alabama coast. You can watch the probabilities drop and the stoplight transitions from red to green for the dissipating storm, while probabilities increase shortly before the first lightning flashes. Lots of anvil debris to obscure the signal of initiating convection in this example, but there appeared to be at least some lead time by LightningCast before the first lightning flashes appeared from the Lightning Stoplight.

A nice thunderstorm went up east of Jacksonville, with a notable cooling signature from the OCTANE-CONUS Cloud-Top Cooling product. I compared that with the OCTANE-MESO product, and may encourage forecasters to do the same later this week.

To wrap up, I decided to explore all the flavors of the Day Cloud Phase Distinction RGB with a procedure I called 'oops-all-dcpd'. 

• Upper Left: GOES-19 CONUS
• Upper Right: OCTANE MesoAnywhere (from GOES-19 CONUS)
• Lower Left: SZA (from GOES-19 CONUS)
  
• Lower Right: GOES-19 MESO

Kevin

Boundary-Initiated Thunderstorms over southern Louisiana

To begin the assessment of severe wind potential, we look at an AWIPS composite analysis at 1830 UTC in Figure 1 below. This display seamlessly integrates LightningCast lightning probabilities and OCTANE cloud phase distinction imagery overlaid with Lake Charles, LA (KLCH) NEXRAD base reflectivity. This composite clearly highlights a primary area of concern for downburst activity over southwestern Louisiana. We can observe the active development of a cluster of intense thunderstorms firing along a cold front boundary situated just north of Lake Charles. The combination of rapidly increasing radar reflectivity, distinct cloud top phase changes, and high lightning probabilities indicates robust updraft pulses capable of generating dense precipitation cores—the necessary precursor for severe downdraft initiation. Advancing two hours to 2030 UTC, the AWIPS composite reveals a significant shift in the convective focal point. While the initial cluster along the cold front has progressed, a new, rapidly developing convective complex is visible in the Beaumont-Port Arthur, Texas area. Crucially, this new activity is tracking eastward toward Lake Charles, propagating along the outflow boundary laid down by the earlier storms. Outflow boundaries act as mesoscale lifting mechanisms; as the dense, rain-cooled air surges forward, it forces the ambient unstable, moist Gulf air upward, continuously regenerating intense convective cells capable of producing new downbursts.

Figure 1: Composite of OCTANE MESOANYWHERE day cloud phase, LightningCast lightning probability, and Lake Charles, LA (KLCH) NEXRAD reflectivity at 1830 UTC (top) and 2030 UTC 30 April 2026.

To quantify the threat posed by this advancing convection, we analyze the thermodynamic environment near Lake Charles using both GOES satellite-derived soundings and Rapid Refresh (RAP) model profiles in Figure 2. There is strong agreement between the observational and modeled data. Both soundings reveal a convectively unstable environment characterized by a classic, lower-tropospheric "hourglass" profile. This includes a distinct surface-based "inverted-V" signature—a thermodynamic structure highly favorable for the generation of wet microbursts due to the rapid evaporation and cooling of precipitation as it falls through the dry sub-cloud layer. Based on these thermodynamic profiles, the Wind Gust Potential (WGP) is calculated to be between 42 and 47 knots.

Figure 2. Comparison of RAP model and GOES soundings over southwestern Louisiana at 1900 UTC 30 April 2026.

The "Low-End" Downburst Threat in Southern Louisiana

While a Wind Gust Potential of 42 to 47 knots falls just shy of the National Weather Service threshold for a Severe Thunderstorm Warning (50 knots / 58 mph over land), it is imperative to classify this as a significant "low-end" downburst threat. As established in earlier research, a horizontal surface gust of 34 knots implies that a negatively buoyant downdraft accelerated toward the surface at a comparable velocity of roughly 34 knots. A localized vertical air current impacting the surface with speeds in the 40-knot range represents an anomalous and highly hazardous transfer of kinetic energy. Therefore, as these new storms move from the Beaumont-Port Arthur area toward Lake Charles, they carry a highly elevated threat for aviation and marine interests. A 40+ knot downburst produces intense low-level wind shear that can severely destabilize general aviation aircraft during approach and departure. Furthermore, it easily exceeds the 34-knot criteria required for the issuance of Special Marine Warnings, posing an immediate capsize threat to recreational boaters and passenger vessels navigating the waterways of southern Louisiana and the nearby Gulf Coast.

 -StormRangerWX

A Tour of Today’s 0.91 µm Imagery over Europe from FCI

 

Figure 1: FCI satellite loop from 11:30 to 12:10 UTC 2026/04/30 showing GeoColor (top) and WVT (bottom).

Figure 2: GFS 12 UTC 2-meter dewpoint analysis. Source: pivotalweather.com

On a fairly inactive weather day over the continental United States, forecasters took a virtual tour of the European meteorological scene, viewing actual 0.91 µm-based water vapor transmittance (WVT) imagery from the MeteoSat Third Generation (MTG) Flexible Combined Imager (FCI) over Europe. This is analogous to information that will be available to U.S. forecasters after the launch of GeoXO. GeoXO Imager (GXI) synthetic imagery is currently being evaluated in the current Hazardous Weather Testbed.

Comparing the GeoColor imagery (Figure 1, top) to the WVT imagery (Figure 1, bottom), it is apparent that there is information about column water vapor in WVT that is not present in other visible/near-infrared channels.  For comparison, a GFS dewpoint analysis is shown in Figure 2.  A cyclone is present over the North Atlantic with an associated front trailing across Central Europe, west of Italy.

Some notable features in the WVT imagery:

• The dark “shadow” advancing northeastward across central France is indicative of moisture advecting in advance of the front.
• Moisture from the Mediterranean Sea is working its way inland in eastern Spain and northern Morocco.
• Low-level northeasterly flow can be seen as motion in the WVT clear-sky imagery over Germany.
• Clouds complicate interpretation of WVT imagery.  Higher clouds tend to be bright (for example along the front) while low clouds are often dark (for example over the western Mediterranean Sea off the Spanish coast).  For this reason, comparison of WVT imagery to GeoColor or visible imagery is a logical step in interpretation of the imagery.

The imagery from this blog can be viewed on CIRA SLIDER (with the left/right slider tool enabled) at https://col.st/ecye9.

-VortexTilting