Cyclone Biparjoy in the Arabian Sea began a period of rapid intensification late in the day on 09 June 2023, reaching Category 3 intensity by 12 UTC on 10 June (SATCON) — EUMETSAT Meteosat-9 Visible (0.64 µm) and Infrared Window (10.8 µm) images (above) showed Biparjoy during the 0100-1330 UTC period on 10 June 2023. A somewhat cloud-contaminated eye signature was evident in both the Visible and Infrared Meteosat-9 images, in addition to a Suomi-NPP VIIRS True Color RGB image (viewed using RealEarth) valid at 0747 UTC (below).

The Category 3 intensity of Biparjoy was supported by 2 overpasses of RADARSAT Constellation Mission (RCM)-3 at 0125 UTC (above) and 1337 UTC (below) — with peak Synthetic Aperture Radar (SAR) radial wind velocities of 106 knots in the SE quadrant at 0125 UTC and 105 knots in the SE quadrant at 1337 UTC (source).

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The animation above shows a strong convective system between Austin and San Antonio moving southeastward on 8 June 2023 . SPC storm reports note that this complex dropped hail in Bulverde (in Comal County, 13 miles northeast of San Antonio) around 1900 UTC, and in various locations in Bexar County (of which San Antonio is the county seat) between 1900 and 1930 UTC). Why are GLM observations of Flash Extent Density sparse in this severe storm with obvious overshooting tops and a warm trench?

GLM observations are clustered on the trailing edge of the system at the beginning of the animation. It’s likely that optical detection of lightning flashes is being inhibited by the thickness of the cloud (and suspended hydrometeors) in this case. GLM observations of Total Optical Energy (in this case with a 1-minute sampling) at 1840 UTC, below, from GOES-16 shows very little activity in this convective complex. Compare that to GOES-18 observations of the GLM TOE at the same time, at bottom (click here for a toggle)!

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When using the GLM, remember that it is detecting an optical signal of lightning. Consider what might lie between the lightning emissions and the satellite. For this case, absorption by thick cloud, rain and perhaps suspended hail was preventing the optical signal from reaching GOES-16 (over the Equator at 75.2^o W, to the east of the storm). GOES-West (over the Equator at 137^o W) had a view of the lightning from the west that was less affected by the thick cloud and whatever was inside it.

Thanks to John Cintineo, CIMSS, and Kevin Thiel, SPC for alerting me to this event during the Hazardous Weather Testbed. Blog posts created by NWS forecasters that discuss HWT demonstration products can be found here.

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Added, 11 July 2023: GLM Engineers have determined that the GOES-16 GLM did detect flashes during this event in the region where GOES-18 also detected flashes. However, a blooming filter in the GLM processing screened out the signal (erroneously). The blooming filter activates when the BGMSB (background most significant bits) that is related to background brightness increases too quickly. That can happen during explosive development.

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NOAA’s Hazardous Weather Testbed is an annual evaluation (by National Weather Service forecasters) of experimental satellite-based products that provide useful information during convective weather events. One of the demonstration products this year is a model with initial conditions that have assimilated fused polar hyperspectral soundings from NOAA-20/NOAA-21 and MetOp satellites. The animations above and below compare the simulated Composite Reflectivity (at hourly intervals from the 1500 UTC model run) with observed LightningCast probabilities (used here as a proxy for convection). In both cases, the Composite Reflectivity grossly captures the evolution and development of convection.

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The image above shows a 7-h forecast of Composite Reflectivity over North Dakota, valid at 2300 UTC on 8 June 2023 (Note: your blogger mistakenly saved this one instead of the 6-h forecast at 2200 UTC, but the two were similar). Convection is predicted for an east-west line across the southern part of the state, with convective complexes stretching north and east of the western terminus of the line. Additional convection appears in western Montana, and over northern South Dakota. How does that compare to the observations shown below? The east-west line of observed convection is a bit farther south than predicted. The convective complexes stretching northeastward from the western terminus of that east-west line are a bit farther east than predicted. There is less convection in South Dakota than predicted. (The convection in Montana is not displayed in this particular radar sector, but it’s inferred by the satellite imagery! Overall, the predicted and observed convection match to some extent.

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The slider below compares a 6-h forecast valid at 1100 UTC on 9 June with the infrared imagery. The PHS model accurately captured the development of the southward-propagating Mesoscale Convective System over southeast South Dakota.

PHSnMWnABI model output are available at this link.

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GOES-18 (GOES-West) SO2 RGB, Shortwave Infrared (3.9 µm) and Fire Power derived product images (above) showed the SO₂ plume and thermal signature of an eruption of Kilauea that began at 4:44 AM HST or 1444 UTC on 07 June 2023. As of 1451 UTC (only 7 minutes after the onset of the eruption), the 3.9 µm infrared brightness temperature reached 137.88ºC — which is the saturation temperature of the GOES-18 ABI and 7 detectors — and Fire Power values peaked around 2100 MW (cursor sample). The Fire Power derived product is a component of the GOES Fire Detection and Characterization Algorithm (FDCA).

The thermal signature was also evident in Nighttime Microphysics RGB imagery from the CSPP GeoSphere site — and after sunrise the hazy SO₂-rich volcanic plume could be seen in True Color RGB images, drifting southwestward away from Kilauea and the Big Island of Hawai`i.

GOES-18 Ash RGB images created using Geo2Grid (below) showed the SO₂-rich volcanic cloud (shades of cyan) as it drifted southwest. According to the Hawaiian Volcano Observatory, a sulfur dioxide (SO₂) emission rate of approximately 65,000 tonnes per day was measured between approximately 8 and 9 a.m. local time (1800-1900 UTC).

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