Severe thunderstorms move from southern Missouri into northeastern Arkansas

April 15th, 2022 |

GOES-16 “Clean” Infrared Window (10.35 µm) images, with time-matched SPC Storm Reports plotted in white [click to play animated GIF | MP4]

Overlapping 1-minute Mesoscale Sectors provided 30-second GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) images (above) — with time-matched plots of SPC Storm Reports — of thunderstorms that produced straight-line wind damage and hail as large as 4.25 inches in diameter across far southern Missouri and northeastern Arkansas after sunset on 15 April 2022. These storms intensified in the vicinity of a warm front that become quasi-stationary across the area (surface analyses). Following a storm damage survey (NWS Little Rock PNS), it was determined that damage at the reported tornado locations was caused by straight-line winds and wind-driven large hail.

Around the time of the first tornado/wind damage report (below), an area of warmer cloud-top infrared brightness temperatures (shades of orange) began to appear immediately downwind (southeast) of the cold overshooting top (cluster of black pixels) — suggesting the presence of an Above-Anvil Cirrus Plume (reference | VISIT training).

GOES-16 “Clean” Infrared Window (10.35 µm) image at 0030 UTC, with time-matched SPC Storm Report plotted in white [clic to enlarge]

The coldest GOES-16 cloud-top infrared brightness temperatures were around -70oC, which was about 10oC colder than the tropopause / equilibrium level temperature, as seen in a plot (source) of 00 UTC rawinsonde data from Little Rock, Arkansas (below).

Plot of rawinsonde data from Little Rock, Arkansas at 00 UTC on 16 April 2022 [click to enlarge]

Blowing snow across the North Slope of Alaska

April 15th, 2022 |

Suomi-NPP VIIRS Visible (0.64 µm) and Shortwave Infrared (3.74 µm) images [click to play animated GIF | MP4]

A sequence of Suomi-NPP VIIRS Visible (0.64 µm) and Shortwave Infrared (3.74 µm) images (above) revealed a long east-to-west oriented swath of horizontal convective roll (HCR) clouds associated with blowing snow and blizzard conditions across parts of the North Slope of Alaska on 15 April 2022. The plume of supercooled water droplet HCR clouds appeared warmer — lighter shades of cyan — due to enhanced reflection of incoming solar radiation   At reporting sites within the northern portion of the HCR clouds and blowing snow, winds were gusting in the 35-40 knot range and the visibility was often 1/2 to 1/4 mile.

A Suomi-NPP VIIRS SnowCloud RGB image at 1624 UTC (below) showed that this plume of HCR cloud features — which was mixed with blowing snow — crossed the coast of northwestern Alaska and extended several miles westward  across nearshore waters of the Chukchi Sea.

Suomi-NPP VIIRS SnowCloud RGB image at 1624 UTC (credit: Jason Ahsenmacher, NWS Fairbanks) [click to enlarge]

GOES-17 Near-Infrared Snow/Ice (1.61 µm) images created using Geo2Grid (below) showed how the HCR cloud plume evolved during the day.

GOES-17 Near-Infrared Snow/Ice (1.61 µm) images [click to play animated GIF | MP4]

Thanks to Jason Ahsenmacher, NWS Fairbanks, for bringing this interesting case to our attention!

ACSPO SSTs from Himawari-8 in AWIPS

April 15th, 2022 |
Himawari-8 Band 3 (0.64 µm) visible imagery overlain on top of ACSPO SSTs derived from Himawari-8 data, toggled with Himawari-8 Band 13 (10.41 µm) infrared imagery, 0800 UTC on 15 April 2022 (Click to enlarge)

The image above toggles between Advanced Clear-Sky Processor for Ocean (ACSPO) sea-surface temperatures (created with AHI data from Himawari-8) overlain with AHI Band 3 (0.64 µm) visible imagery, and AHI Band 13 (10.41 µm) clean window infrared imagery. Sheared tropical Storm Malakas — in the midst of transition to an extratropical storm — is apparent in the upper center of the imagery. The SST color enhancement is such that violet temperatures show were SSTs exceed 27o C. Malakas is now over ocean water with a temperatures of around 20o C.

GOES-17 Image Degradation due to a warmer Set Point temperature

April 15th, 2022 |
GOES-17 Band 10 (7.34 µm), Band 12 (9.61 µm) and Airmass RGB imagery over the PACUS sector, 0001 UTC on 15 April 2022 (Click to enlarge)

During the current warm period for GOES-17, when the sun’s position leads to excessive heat build-up on GOES-17 because of the poorly-functioning Loop Heat Pipe, the Set Point temperature has been increased from 92.8 K. This change occurred on 11 April 2022 and it is scheduled to last for one week — the daytime ‘stripiness’ should relax on 19 April when the Set Point temperature changes back to a cooler temperature (90 K). The figure below (from this NESDIS/STAR link) shows Focal Plane Temperatures at different time scales. The Set Point change is apparent in the figure showing the last 10 days; a second Set Point temperature occurred on 9 April, but that one did have such a big effect on imagery. Note how the warmest Focal Plane Temperature has been increasing in the past 10 days.

GOES-17 Focal Plane Temperature at different timescales (Click to enlarge)

You might ask: What is the Set Point temperature and why is it affecting these two bands? The cryocooler is a secondary cooling mechanism on GOES-R satellites (the Loop Heat Pipe is another cooling mechanism). Heat from the cryocooler’s operation actually warms up the satellite. So, warming the cryocooler set point decreases that thermal load. That warmer setpoint, however, means the focal plane of the ABI is warmer (as evidenced in the image above), and that warmer focal plane degrades select bands for all 24 hours. The benefit of a warmer cryocooler is that the number of nightly images completely missing related to the Loop Heat Pipe is not quite so long. In other words, for Band 10, all of the daytime images have some degradation, but the number of completely missing night-time images is decreased (compared to what would happen if the Set Point were cooler!). This pdf shows predictions for how warm the Focal Plane Temperature might get over the course of this year; note (on page 5) that the April heating period is the warmest, and that (page 6) Bands 10, 12 and 16 are the most affected bands.

Because Band 10 (and Band 12) data are used in some RGBs — such as the airmass RGB shown above — those RGBs will also be affected for this week.