1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) include time-matched (+/- 3 minutes) plots of SPC Storm Reports, and showed thunderstorms that produced tornadoes and damaging winds across southeast Texas and southwest Louisiana on 24 January 2023. One tornado caused EF3 damage in the Houston, Texas area. This severe convection developed along and ahead of an advancing cold front — and also produced heavy rainfall (image | text), including a new daily record of 4.05″ at Downtown Houston.

A comparison of GOES-16 Infrared, Cloud Top Temperature and Cloud Top Height at 2124 UTC is shown above — cursor sampling (below) showed that the Cloud Top Temperature derived product value was about 1ºC colder than the 10.3 µm cloud-top infrared brightness temperature at that particular time (the Cloud Top Temperature product values are typically 1ºC to 4ºC colder).

1-minute GOES-16 Infrared and Visible images with/without an overlay of GLM Flash Extent Density (below) revealed a series of lightning jumps (rapidly-growing clusters of bright white FED pixels) during the 1854-2319 UTC period — with FED values as high as 414 at 2019 UTC (minutes after a tornado began to produce damage in the Houston area) and 445 at 2110 UTC.  To match the images shown above, a modified version of the default AWIPS infrared enhancement was used which helps to more easily identify brief pulses of thunderstorm overshooting tops — some of which exhibited cloud-top infrared brightness temperatures as cold as -75ºC.

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Two more animations were created over a larger spatial domain than shown above. Here’s is the GOES-16 Mesoscale 2 Sector Band 2 (0.64 µm) from 1620 – 2229 UTC (as an mp4 animation), and here is the same mp4 animation but with GLM 5-minute Flash Extent Density overlain.

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A strength of the Night Microphysics RGB in the tropics is that it’s pretty easy to use it in regions of mostly clear skies to diagnose wind shear, because high clouds will show up as dark red, and low cloud show up as pale pink or cyan (see this annotated image). In the animation above (from the CSPP Geosphere site), low clouds around and to the west of the Samoan Islands are moving towards the west-northwest. High clouds are moving in the same direction: Wind shear values are low. In contrast, in the northeastern part of the domain above, low clouds are (also) moving towards the west-northwest — but high clouds are moving off to the east: Wind shear values are high.

A wind shear analysis from 1200 UTC, below, taken from the SSEC/CIMSS Tropical Weather website (direct link to shear plot) confirms what the Night Microphysics RGB suggests.

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Northern California enjoyed a clear day on 23 January, and the animation above, from the CSPP Geosphere site, (click here for a direct — but not permanent — link to the animation) shows the shadow of Mount Shasta (see the still image below identifying both the mountain and the shadow) shortening over the course of the morning. Note that clouds are also present around the mountain peak as well, although this webcam screen capture from 2100 UTC (source) shows only clear skies. Also of interest in the animation above: the sloshing of the low clouds within the valleys of southern Oregon.

Click here and here for similar blog posts on the shadow of Denali. Thanks to Mike Stavish, SOO at WFO MFR for drawing our attention to this event.

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Monthly means of full disk GOES-17 brightness temperatures¹ for Bands 8, 10, and 13 have been computed from 2019 to 2021, totaling 36 months. This is an expansion of similar work that had been done for Band 13 for a single year. Band 8, centered on 6.2 µn, is sensitive to upper-level water vapor. While Band 10, centered on 7.3 µn, is sensitive to low-level water vapor. Band 13 is the clean longwave infrared window channel and observes at 10.3 µn.

Brightness temperature can be thought of as the amount energy (radiance) being reflected or emitted from Earth and measured by satellite sensors. These fields of averaged brightness temperature are useful for assisting forecasters in knowing what can be expected from satellite retrievals on monthly timescales, especially in remote Pacific regions where forecasters are heavily reliant on satellite data.

While a large amount of smoothing is expected for a monthly average, the resulting full disk fields are not homogenous. Certain patterns appear. The ITCZ is noticeable. Also, an area of warmer brightness temperature is visible west of Hawaii during winter months in the animations for Bands 8 and 10. This is likely associated with a synoptic high pressure for that region.

Reference to a Climatic Atlas created by Sadler et al. (1987) from the School of Ocean and Earth Science and Technology confirms potential for a synoptic high pressure region that is usual for that time of year. However, because the Sadler fields are derived surface measurements (temperature, pressure, wind, and stress), comparing them to GOES-17 ABI brightness temperatures is not exactly an “apples to apples” situation.

¹ Brightness temperatures are computed from radiances.

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