GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images that included an overlay of GLM Flash Extent Density (above) revealed intermittent clusters of lightning activity across parts of north-central Illinois — many of which occurred in the general vicinity of METAR sites that were reporting moderate to heavy snow — during the hours prior to and around sunrise on 12 January 2024. Near the end of the animation period, isolated lightning signatures were also seen along the Iowa/Illinois border and in the Chicago area. Although a few METAR sites occasionally reported lightning in the distance, none of the sites explicitly reported thundersnow.

GOES-16 Infrared + Flash Extent Density images that also included contours of LightningCast Probability (below) showed that the LightningCast tool generally performed fairly well, with probability values frequently in the 25-50% range in advance of many of the larger Flash Extent Density episodes across Illinois.

A closer view of GOES-16 “Red” Visible (0.64 µm) and Infrared images centered over the Chicago area (below) showed the isolated GLM Flash Extent Density event that occurred around 1311 UTC (just before sunrise). Again, no nearby METAR sites explicitly reported thundersnow.

LightningCast Probability values in the Chicago area rose to around 50% at 1241 UTC (below), 15 minutes prior to the observed GOES-16 GLM Flash Extent Density event.

Toward the end of the day, a few bursts of GLM Flash Extent Density were observed over the Detroit, Michigan area (below).

In this case, thundersnow (TSSN) actually was reported at one METAR site: KDET (Coleman A. Young International Airport, located 6 miles northeast of downtown Detroit), as shown below.

However, LightningCast Probability values were lower for these Flash Extent Density events over the Detroit area — generally remaining at or below 10-25%.

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Upper-air rawinsondes at station 74455 (Davenport, Iowa, above) show the response at that point to the approach and development of a potent winter storm (See the Airmass RGB animation below). The lowest levels of the atmosphere have saturated in the 12 hours between upper air observations. Model soundings, after the RGB animation, (from the Tropical Tidbits website) show that the GFS predicted the saturating that was observed. What kind of observations (independent of the model) might be available before the 1200 UTC upper air sounding to check to see if the actual atmosphere is behaving as the GFS predicts?

NOAA-20 overflew the Mississippi River valley shortly after 0800 UTC on 12 January 2023. NUCAPS profiles derived from the CrIS and ATMS instruments on NOAA-20 give valuable asynoptic information about the state of the atmosphere. The image below shows a toggle of ABI Band 13 image (without and with the 0.5 NEXRAD radar reflectivity overlain) along with the NUCAPS Sounding availability plot. The Green Points of the NUCAPS Soundings availability are where the infrared and microwave retrievals converged to a solution. Yellow points are where only the microwave retrieval converged. Red points denote retrievals that did not coverge. Of particular note: the slot of warmer brightness temperatures over central Iowa. Note that there are green points associated with that feature (including a green point in southwestern Wisconsin).

What do some of the 0800 UTC profiles show? That is shown in the animation below that includes profiles from green and yellow points over the mid-Mississippi River valley. The retrievals from the green points over Wisconsin and Iowa both show the same kind of thermal structure below 650-700 mb as is predicted in the forecast shown above, and as observed in the 1200 UTC sounding at Davenport. This is also true in some way for the yellow point in extreme northwest Illinois; for the one in in eastern Iowa, and especially the one near Davenport, the effects of falling snow lead to progressively less reliable information in the retrieval. Microwave-only retrievals that converge to a solution are far more likely to converge to a sensible solution if precipitation is not ongoing, so refer to radar imagery when using NUCAPS profiles.

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You can use NUCAPS profiles, even in cloudy regions surrounding precipitation, to assess model performance in an ongoing event. In this case, NUCAPS profiles suggested that the atmosphere was evolving in a manner consistent with model predictions. Other kinds of observations that give useful model-independent thermal profiles (ACARS observations, for example) are unlikely to be present at this time of day over Iowa.

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In regions without radar, satellite estimates of rainfall intensity are vital in understanding precipitation. Microwave estimates have an advantage in that microwave energy is not strongly affected by clouds, so the internal structure of the cloud that can affect rainfall distribution can be detected. (However, microwave data has poorer spatial resolution than infrared.) Rain Rates shown above are generally less than 1″/hour. Microwave estimates do require a knowledge of the surface emissivity. Over the ocean, that emissivity is fairly well-known. Microwave rainfall estimates above show no rainfall along the coast of southern/eastern New England, an artifact, perhaps, of changes in the surface emissivity estimates that is affecting the Rain Rate algorithm. The GsMap site (from Japan’s JAXA), shows computed rain rate as well, using a variety of satellite sources. The toggle below compares the 0600-0659 and 0700-0759 UTC estimates on 10 January, bracketing the observation above (derived, incidentally, from data downloaded at the Direct Broadcast antenna at CIMSS and processed using CSPP software). The 0700-0759 UTC image does a much better job of matching the 0622 UTC Rain Rate shown above. Values off the east coast of the US are 10-15 mm/hour. The region of missing data along the coast is absent.

NOAA produces CMORPH2 estimates of precipitation as well, available at this website. The image below shows a screen-capture of rain rate at 0630 UTC on 10 January 2024. A zoomed-out view, it nevertheless shows the heaviest precipitation is offshore.

CMORPH2 is also available at RealEarth (link — then enter ‘CMORPH2’ in the Search Box). 1-hour precipitation rates 10-25 mm/hour are shown (25 mm/hr, of course, is 1 inch/hour)

GOES-R data are also used to create Rain Rate estimates, and the estimate from 0620 UTC, below, shows the original GOES-R algorithm output. Close inspection of the field will show a correlation with the cold cloud tops. However, the product algorithm has been modified considerably in the past five years, and output from the new ‘Enterprise’ algorithm (courtesy Bob Kuligowski, NOAA), not yet implemented in AWIPS, is shown at bottom. The Enterprise algorithm shows much less of a relationship with the very cold cloud tops, in agreement with the microwave estimates above.

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10-minute Full Disk scan GOES-18 (GOES-West) “Clean” Infrared Window (10.3 µm) + Total Precipitable Water (TPW) images (above) showed the colder clouds associated with rain showers (with isolated embedded thunderstorms) and the clear-sky TPW field in the vicinity of Hawai`i during the 08-09 January 2024 time period. Surface analyses depicted a cold frontal boundary — which became more diffuse with time — that moved southeast across the island chain as a Storm Force Low intensified NW of Hawai`i.

A closer view using 5-minute PACUS Sector GOES-18 Infrared images (below) included 15-minute METAR plots — which showed periodic moderate to heavy rain; Local Storm Reports mentioned some flooding (and wind damage).

Of note was the issuance of a Tornado Warning at 0515 UTC on 09 January for the far western portion of Molokai island (below).

In a comparison of GOES-18 10.3 µm infrared brightness temperature, CLAVR-x Cloud Top Temperature derived product and CLAVR-x Cloud Top Height derived product for a portion of the tornado-warned storm (below), the Cloud Top Temperature value was nearly 3C colder than the single-channel infrared brightness temperature, and the Cloud Top Height was around 30800 ft.

Later in the day, a Severe Thunderstorm Warning was issued at 2044 UTC for the far southern portion of Hawai`i (below).

In a comparison of GOES-18 10.3 µm infrared brightness temperature, CLAVR-x Cloud Top Temperature derived product and CLAVR-x Cloud Top Height derived product for a portion of the severe-warned storm (below), the Cloud Top Temperature value was about 3.6C colder than the single-channel infrared brightness temperature, and the Cloud Top Height was around 29800 ft.

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Microwave estimates of Rain Rate (derived using the MiRS algorithm within the CSPP software package) are available at this website. The animation below shows seven observations on 8 January 2024, from 07 UTC to 23 UTC. The axis of the heaviest rain was over Oahu starting at 1900 UTC on 8 January.

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