May 8, 2025 was an interesting day for the experiment because “WFO GSP” was not allowed to utilize radar to issue severe thunderstorm warnings. I relied heavily on OCTANE Speed and CTD/cooling products and GREMLIN for making these decisions. At first, I struggled a bit with mentally shifting everything to the southeast due to parallax. After I began to utilize the ENTLN data as a proxy for storm core, it was better to estimate storm location and movement (although still not perfect). By the end of the day, I ended up issuing seven severe thunderstorm warnings. I found myself relying more on the CTD and cloud top cooling panel than the speed sandwich. Since it was my second day using the OCTANE products, I was quicker at picking up on signals in the CTD panel that suggest the presence of stronger thunderstorms. Having the CTD in one number compared to having to mentally calculate it while using the speed sandwich was helpful when working in simulated operations when a couple seconds does make a difference. I also found GREMLIN useful as a situational awareness tool to help distinguish which cells should potentially be interrogated more.
Here is a loop of OCTANE Speed Sandwich and the CTD and CTC products from two severe thunderstorm warnings I issued. The severe thunderstorm warnings were issued for the same storm, with the second one being issued as the first one was expiring. Looking at the OCTANE data combined with ENTLN (Image 1), it was clear that the storm was taking a turn to the right. I don’t know the specific values that CTD was showing, but I do believe this storm had values of 4+.
Image 1: Two severe thunderstorm warnings in OCTANE SS and CTD/CTC with Lightning Cast v1 and v2 overlaid. ~21:20Z to 21:56Z
GREMLIN (Image 2) also subtly shows this change in direction. What is interesting is that GREMLIN using ECONUS actually maxed out with a value of 60.4 dBZ.
Image 2: GREMLIN loop for the same two severe thunderstorm warnings in Image 1.
Image 3: Severe thunderstorm warning with OCTANE SS and CTD/CTC. ~21:56Z-22:22Z.
Image 4: Severe thunderstorm warning for the same time but with GREMLIN.
Another severe thunderstorm warning I issued, was showing CTD values of 4+ that prompted a warning. In GREMLIN, the strength of this cell was not as obvious in the ECONUS version, but slightly more prominent in EMESO-2. GREMLIN shows these cells basically merging, but I don’t know if that was reality. Looking at these loops compared to the movement of the lightning data, I don’t think my strom track was very good. In cases where radar is unavailable, I could see other novice warning forecasters also struggling with identifying storm track and motion when using strictly satellite data and also trying to mentally correct for parallax. This may not be an issue for more experienced warning operators though.
– Golden Retriever Lover