Singapore Airlines Flight SQ321 encountered severe turbulence over Myanmar (flightradar24 blog) while en route from London to Singapore on 20-21 May 2024 — which resulted in dozens of injuries and 1 fatality. 10-minute interval JMA Himawari-9 AHI Visible and Infrared images (above) showed areas of deep convection developing over Myanmar, near the estimated location of the turbulence encounter at 0749 UTC on 21 May (southwest of Yangon International Airport, identifier VYYY). The main cluster of rapidly-developing convection in the vicinity of the turbulence event exhibited cloud-top infrared brightness temperatures as cold as -81.6ºC by 0800 UTC (violet-enhanced pixels); VYYY later reported a thunderstorm from 1030-1100 UTC.

A rocking animation of Himawari-9 Visible and Infrared images at 0740/0750/0800 UTC (below) helped to emphasize how rapidly the area of convection (that the aircraft likely flew over) was developing — from no apparent infrared signature at 0740 UTC to exhibiting minimum cloud-top infrared brightness temperatures of -72.3ºC at 0750 UTC and -81.6ºC at 0800 UTC. However, it is important to note that the Himawari-9 AHI instrument was actually scanning the Myanmar area about 3 minutes after the time stamp of each image — so on the 0740 UTC and 0750 UTC images, a cyan * symbol marked the approximate aircraft position at 0743 UTC and 0753 UTC (when the satellite was scanning that region; Flight SQ321 had exited the image scene by 0803 UTC).

The 0750 UTC Himawari-9 Visible and Infrared images are shown below (a toggle between the individual Visible and Infrared images is available here). While the cyan * symbol making the approximate aircraft location at the 0753 UTC satellite scan time appeared to be well southeast of the rapidly-developing convection, another important consideration is parallax — for cloud tops of 30 kft and 50 kft over Myanmar, the parallax adjustments for those cloud tops would be toward the southeast at distances of 10 km (6.2 mi) and 17 km (10.6 mi), respectively.

Himawari-9 Water Vapor images with contours of Moderate Or Greater (MOG) Turbulence Probability (source) began to display pockets of 50% or higher MOG probability over that area of Myanmar (yellow contours, just west of the top center portion of the images) at least an hour before the Flight SQ321 severe turbulence event.

A more zoomed-in view is shown below, with a plot of the flight path of SQ321 (here’s the loop as an animated gif).

Cloud Heights

An animation of the Himawari-9 Cloud Top Height (CTH) derived product is shown below — CTH values of several convective clouds reached 40-50 kft as Flight SQ321 was flying over that portion of Myanmar.

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Stereoscopic visible imagery over the region of turbulence from Himawari-9 (left in the animation below) and GEOKOMPSAT-2A or GK-2A (on the right in the image below) shows the rapid vertical growth around the time of turbulence. To view the imagery in 3-dimensions, cross your eyes so that 3 images are present, and focus on the image in the center, as described here, where this technique is called ‘cross-viewing’.

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GK2A imagery cropped from Full Disk imagery from this site, shown below from 0700 to 0800 UTC on 21 May, similarly show the development of strong convection over Myanmar.

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A WRF model run that includes assimilated Low-Earth-Orbit (LEO) satellite sounder data (fused with ABI data) is being evaluated at the Hazardous Weather Testbed (Blog posts from forecasters at HWT are here). On 20 May 2024, the PHS model output included convective development over the eastern Plains of Colorado, as shown in the animation below of model Composite Reflectivity at hourly time-steps. The screenshots below are from AWIPS; model output is also available here.

The PHS model accurately predicted convective initiation, as shown in the (hourly) animation below of GOES-East visible imagery.

The three toggles below compare the forecasts of Composite Reflectivity and Visible Imagery at 2000, 2100 and 2200 UTC.

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Based on the forecast, a LightningCast monitoring point was created where the model forecast initiation (approximately 39.7^oN, 104.7^oW; National Weather Service forecasters have the ability to request monitoring points to supplement the airports/stadiums that are done routinely and are available at this website). That LightningCast probabilities are shown below for the point.

The animation below shows the Day Cloud Phase Distinction RGB and the LightningCast Probability contours over eastern CO (figure above and animation below courtesy John Cintineo, NSSL).

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While much of Kansas was under a “Particularly Dangerous Situation” Severe Thunderstorm Watch, 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) Visible/Infrared Sandwich RGB images (above) showed thunderstorms that produced tornadoes, large hail (to 3.00 inches in diameter) and damaging winds (gusts of 90-100 mph) (SPC Storm Reports) across parts of Kansas on 19 May 2024. Some flash flooding was also reported, with water covering portions of Interstate 70 and other nearby roads. The discrete supercell thunderstorms that initially developed during the late afternoon hours eventually consolidated into a larger organized Mesoscale Convective System / squall line by about 0000 UTC on 20 May.

1-minute GOES-16 Visible/Infrared Sandwich RGB images combined with the Total Precpitable Water derived product (above) and the CAPE derived stability index (below) revealed a plume of moisture (TPW values to 1.6 in) and instability (CAPE values to 2200 J/kg) that was spreading northward along the I-35 corridor, feeding into the tornado/hail/wind/flash-flood-producing supercell thunderstorm that was propagating eastward along the I-70 corridor.

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Overlapping 1-minute Mesoscale Domain Sectors provided 30-second interval GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) — which showed thunderstorms that produced two EF1-rated tornadoes as well as damaging winds (resulting in some fatalities) across the Houston area (SPC Storm Reports) on 16 May 2024. Widespread structural damage occurred in downtown Houston — and there were also power outages across much of the area. The Infrared images revealed numerous pulses of thunderstorm overshooting tops that exhibited infrared brightness temperatures of -80ºC or colder (shades of violet embedded within brighter white regions).

Larger-scale views of 30-second GOES-16 Visible and Infrared images are shown below.

Taking a closer look at the Houston metro area, 30-second GOES-16 Visible images with/without an overlay of GLM Flash Extent Density (below) showed the lightning activity associated with these thunderstorms, which included a few brief lightning jumps.

Survey reports from severe storms 5/16:
– EF-1 tornado near Cypress (peak winds 110mph).
– Straight-line wind damage in downtown Houston. Winds peaked ~ 100mph.
– Widespread straight-line winds near Baytown/Galena Park area. Wind peaked 90-100mph.

More details to be shared later

— NWS Houston (@NWSHouston) May 17, 2024

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