10-minute Full Disk sector GOES-18 (GOES-West) Day Land Cloud Fire RGB, Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.3 µm) and “Red” Visible (0.64 µm) images with an overlay of the Fire Mask derived product (a component of the GOES Fire Detection and Characterization Algorithm FDCA) (above) displayed signatures of a wildfire in far northeastern British Columbia, which produced 2 pyrocumulonimbus (pyroCb) clouds — exhibiting cloud-top infrared brightness temperatures in the -40s to -50s C, denoted by shades of blue to red in the 10.3 µm images — late in the day on 29 May 2024 (Canada’s first pyroCb clouds of their 2024 wildfire season were observed on 13 May).

A similar animation that includes GOES-18 Visible images with an overlay of the Fire Power derived product — another component of the FDCA — is shown below.

GOES-18 True Color RGB images from the CSPP GeoSphere site (below) displayed several plumes of low-altitude wildfire smoke, followed by the explosive development of the 2 high-altitude pyroCb clouds (which then drifted to the northwest).

The coldest 10.3 µm infrared brightness temperature sensed for each of the 2 pyroCb clouds was -52ºC. According to rawinsonde data from nearby Fort Nelson, BC (CYYE), this represented a pressure level of 307 hPa or an altitude around 8.9 km (below).

This wildfire burned very hot, exhibiting a peak 3.9 µm shortwave infrared brightness temperature of 137.88ºC (which is the saturation temperature of GOES-18 ABI Band 7 detectors) — at 2250 UTC (below).

The GOES-18 Fire Power value reached 6057.70 MW at 2310 UTC (below) — values over 6000 MW are only seen with very hot fires.

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GOES-16 (GOES-East) Nighttime Microphysics RGB images (above) showed a thunderstorm that moved southeast from the New Mexico / Texas border across the southern Texas Panhandle Plains on 29 May 2024. A narrow northwest-to-southeast oriented hail swath produced by this storm  — from south of Clovis, New Mexico (KCVN) to south of Lubbock, Texas (KLBB) — showed up as pale shades of beige.

GOES-16 “Clean” Infrared Window (10.3 µm) images with/without an overlay of the hourly Land Surface Temperature (LST) derived product (in cloud-free areas) (above) indicated that the LST within the hail swath was as much as 10-12ºF cooler than adjacent bare ground (even after sunrise). A cursor sample of LST values within and immediately adjacent to the hail swath at 1401 UTC is shown below.

In a comparison of GOES-16 Infrared, Infrared + Land Surface Temperature, Day Land Cloud RGB and CIMSS Natural Color RGB images at 1401 UTC (below) note that the hail swath signature was not evident in the CIMSS Natural Color RGB image.

Hat tip to NWS Midland and NWS Lubbock for pointing out this interesting feature!

*NERD POST*

Our satellites captured a swath of hail that fell from a t'storm across the TX Panhandle!

Tracks of real-time estimated hail are in the blues and greens and then the satellite shows a thin yellow-organe line detailing the ice that has collected on the ground! #txwx pic.twitter.com/apL4ICCnau

— NWS Midland (@NWSMidland) May 29, 2024

Here's a satellite image this morning where we've outlined a narrow swath of hail that fell from a mini bow-echo that produced large hail and destructive winds along its path including Levelland and Tahoka. #txwx #lubwx pic.twitter.com/clNexHk8aB

— NWS Lubbock (@NWSLubbock) May 29, 2024

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) widespread showed thunderstorms that produced tornadoes (resulting in a number of fatalities), large hail (up to 3.5 inches in diameter in Oklahoma) and damaging winds as high as 78 mph in Kansas (SPC Storm Reports) across the southern and central Plains during the daytime hours on 25 May 2024. Pulses of overshooting tops were apparent in the Visible imagery.

In the corresponding 1-minute GOES-16 “Clean” Infrared Window (10.3 µm) images (below), the coldest overshooting top infrared brightness temperatures were in the -70 to -79ºC range (shades of black to white).

In a closer view of a deadly supercell thunderstorm that was moving across North Texas, 1-miinute GOES-16 Infrared images (below) showed pulses of overshooting tops exhibiting cloud-top infrared brightness temperatures of -80ºC or colder (violet pixels) as it produced tornadoes (one of which produced fatalities at Valley View, Texas around 0346 UTC), hail to 3.00″ in diameter and damaging winds to 70 mph.

In addition, a closer view of another deadly tornado-producing supercell thunderstorm (below) similarly showed numerous pulses of overshooting tops as it moved across northeast Oklahoma (including the communities of Claremore and Pryor) and continued across northwest Arkansas (where it produced several more fatalities).

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One focus on day 4 of HWT in Norman was the North Platte, Nebraska (WFO LBF) County Warning Area (CWA) over western Nebraska. This was near a gradient in the Storm Prediction Center Convective Outlook that had an enhanced risk over central Nebraska and a Slight risk over western Nebraska. The first concern was when would convective initiation occur? The 1600 UTC PHS model run had convective initiating at 2000 UTC and building from then on.

The distribution of moisture modeled in the MUCAPE field above was very similar to the Split Window Difference field (here, from this link).

The PHS model runs hourly. The data above shows the 2000 UTC forecast from 1600 UTC (that is, a 4-hour forecast). The 3-h forecast valid at 2000 UTC (from the PHS run at 1700 UTC) did not include initiation until after 2000 UTC. Compare the two fields below, 3-h and 4-h forecasts for 2000 UTC and 2100 UTC from 1600 UTC and 1700 UTC, respectively.

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PHS Model Forecasts are available at this website. HRRR model forecasts are available here (and elsewhere). The following six figures compare the forecasts for 2200 UTC in forecasts initialized at 1600, 1700, 1800, 1900, 2000 and 2100 UTC, that is 6-h, 5-h, 4-h, 3-h, 2-h and 1-h forecasts. (Click here for an animation of the forecasts; For views of what was occurring between 2000 and 2220 UTC on 23 May, click here for the North Platte WFO and here for the Aberdeen WFO). The WRF model with assimilated PHS data showed stronger convection forming earlier, closer to the actual time of convective initiation, than was predicted by the HRRR model that does not include PHS information.

The image below also shows HRRR model output (initialized without any Polar Hyperspectral Sounding information) as available at this website. The forecast was too slow in initiating convection over Nebraska.

The stepped animations below show the hourly GOES-East Day Cloud Phase Distinction RGB over the northern High Plains from 2000-2300 UTC on 23 May, and the GOES-East Day Cloud Phase Distinction RGB overlain with the PHS forecasts of Composite Reflectivity at 2100, 2200 and 2300 UTC on 23 May. Strong convective growth is apparent in both fields. Severe weather was reported in both the North Platte and Aberdeen CWAs from this convection (SPC Storm Reports).

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