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Looking at PHS overlayed on the visible satellite imagery with regards to convective initiation – PHS lines up with satellite from Garrett (CYS) to Pingree Park (BOU) especially by 19Z, but does show the beginnings of CI at 18Z as well.
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| GOES Visible and PHS Composite Reflectivity 18-19Z 20 May 2024 |
Forecaster Cumulus
At 1910Z on May 20, OCTANE picked up a good signal on convection developing just northwest of Chicago, IL. On the Speed Direction product, there was a well-defined difference in direction vector on the southeast flank of the anvil (250deg) versus the western flank of the anvil (200deg).
There is also a subtle signal on the OCTANE speed sandwich product, though not as pronounced. Regardless, for a fresh storm just reaching severe levels, it was worth noting.
–Insolation
Viewing CI and LightningCast (LC). LC probabilities on the SW portion of the storm (in the center) at 1958Z ranged between 70-75%. Just before GLM signatures pop up at 2007Z, LC probabilities jump up to around 82%. Not included in the animation, but at 1951Z, LC probabilities were around 50%. The overall trend upward would give me confidence that I can use this product to tell an emergency manager the potential for lightning is medium to high within the next 10-20 minutes (using this case, hypothetically starting at 1951Z).
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| Lightning Cast product overlaid on Cloud Phase Distinction on the left and radar reflectivity on the right. 20 May 2024 |
Forecaster Cumulus
Overall, GREMLIN performs fairly well with the zoomed out shape of the precipitation returns compared to radar, but perhaps a bit larger extent. Picks up on a few heavier cells moreso versus heavier stratiform rain. Since the overall radar mosaic of GREMLIN looks so close to current radar, it would increase my confidence in using it for the big picture (especially if the radar data were to go out for some reason).
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| GREMLIN vs radar reflectivity 2010Z through 2058Z 20 May 2024 |
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| Zoomed in GREMLIN vs radar reflectivity 2010Z through 2058Z 20 May 2024 |
Forecaster Cumulus
While looking for thunderstorm initiation, my eyes are turned towards anything that informs me whether convection will develop further or decay. There have been several things to note while waiting for instability to move into the region.
The main forecast challenge is the favorable ingredients to produce severe convection has to be advected into the region. The WRF with PHS data demonstrates that initial convection intensifies later in the day as better instability arrives across the region on the bottom right panel. This also corresponds with better dynamics noted across the others entering eastern Colorado. Model reflectivity on the bottom right increases as a result of better forcing over time. Until then, it’s monitoring at what point things actually start turning the corner and using the new tools available to find that point.
And so far, the things found have been what it’s not. So here are some things being observed in this period of waiting. At the beginning of the day, one of the things I noticed was related to the OCTANE detecting warming and cooling. As clouds moved off snowy foothills, it was apparent on the viewer where water clouds appeared warmer than the snow surface, and caused a pocket of cooling to appear on the eastern foothills once satellite could see the frozen snow, and warming whenever a cloud layer shifted overhead obscuring the snow. In the middle of convection, this would probably be irrelevant, but just a thing to note while we wait.
That’s all I have today!
Found an example showing the application of OCTANE using IR – convective initiation and eventually divergence. Can see this in the color differences in the speed (NE) and direction (NW/SE) IR panels in the top left and top right in the image below, but also the cloud top divergence panel (bottom left). Could use the products alone (especially the direction panel), but I like seeing all three together to have the whole picture.
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| OCTANE (from AWIPS) using IR showing CI and divergence (20 May 2024) |
Forecaster Cumulus
While more intense convection has been slow to develop in southeastern, the LightningCast probability for >10fl started to increase as synoptic forcing improved. About 13 minutes later (image below), the GLM flash extent density increased to around 30 flashes per 5 minutes, which was well signaled by LightningCast. While the probability depicted by LightningCast wasn’t terribly high (to around 15 percent initially), the upward trend in probability did signal the potential.
-Joaq
OCTANE Night Direction and Speed Products
Today’s challenge was to try and see if we could draw out features better in both the OCTANE Night direction and speed products. The night products rely on IR satellite imagery and the lower resolution washes out a lot of the features we can normally see in daytime imagery. The easiest way to try and attain this was to first play around with the color curves in the IR brightness temp (CH-13-10.35um) overlay. Adjusting the colormap starting with black at 40 to white at -45 back to black at -80 then interpolating the ‘Alpha’.
Original OCTANE Night Color Curve – Direction
New OCTANE Night Color Curve – Direction
Original OCTANE Night Color Curve – Speed
New OCTANE Night Color Curve – Speed
Supercells of Midland, TX
As always, the first thing I did when I sat down this afternoon is AWIPS is immediately start fooling with the color tables. Today’s chimera was a combination of OCTANE Cloud Top Divergence and Cooling with MRMS Reflectivity at -20° C. MRMS was modified to only show values that exceeded 40DBZ to interrogate the relationship between cloud top divergence and highest reflectivity. At this point in the week, I’m throwing science against the wall to see what sticks.
My primary radar was MAF with MESH overlay for estimated hail size greater than two inches. Taking a look at MAF sounding this morning, it’s giving me big hail vibes and I wanted to see how MESH correlated with the convergence signatures from OCTANE.
Spice Level: Cayenne 🌶🌶🌶
At first glance of the Midland sounding I’m drawn to the fact that we have a substantial amount of CAPE (~3000J/KG). A little bit of a CAP at 700MB should be quickly overcome as there is a pretty good clearing in the clouds over most of Midland’s CWA. Lapse rates from 7-500MB is nearly 9C/KM, with a pair of dry layers from 8-500MB and between 5-300MB. Our hodograph, while not perfect, is generally a straight line from left to right. Effective shear is around 45kts. My conclusion: hail. Possibly big hail, and we may have a chance of some splitting cells at some point today.
One of the cool things we noticed that the OCTANE Divergence/Cooling product picked up a splitting super cell around 15 minutes before the radar did. This was really cool and could be an excellent way of identifying splitting supercells and getting out warnings with an extra 10 minutes of lead time.
The inverted images on the OCTANE DIV/COOL product I think does a good job of highlighting areas in which those storms have entered an environment in which they are ready to split. Studying splitting supercells using sat imagery may give us abetter understanding of when storms are more likely to split.
Thanks for accepting me into this HWT! I got a lot out of it and am excited for what satellite can do for ops in the future!
-Charmander
