Every-minute true-color imagery from the CSPP Geosphere site (above) shows the quick development of the Hughes Fire in Los Angeles county. This event developed during a time of Red Flag Warnings over Los Angeles and Ventura Counties, as shown in the screenshot image from NWS Los Angeles below.

How did NGFS detections do with fire initiation with this event? The Alerts Dashboard that includes a notification of Los Angeles County is shown below. A user would click on the caret at the right edge of the ‘Los Angeles County, CA’ banner at the top to see the county-specific detections.

Those detections specific to Los Angeles county are below. Lines 2-4 in the Alerts Dashboard below show the initial detections of a fire 50 minutes ago (GOES-16 CONUS data), 51 minutes ago (GOES-18 CONUS data) and 57 minutes ago (GOES-18 Mesoscale-1 Sector data). The notifications for this fire all show that the development is in a region with Critical Risk from SPC, and a Red Flag Warning from the Los Angeles forecast office^{1 (see below)}. It should not surprise you that the more rapid observations from the mesoscale sector leads to earlier detections of the fire!

If you click on the blue ‘Satellite Imagery’ button in the GOES-18 ABI, Mesoscale Sector 1, you’ll see NGFS Microphysics with thermal anomalies outlined. The 1834 UTC image shows the first instance of a probable fire detection. You can probe the imagery as shown (by mousing over) There is a slider on the right-hand side to change the time of the image.

The animation below shows the evolution of the imagery in the five minutes surrounding the initial detection.

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AWIPS imagery, above, showing imagery from 1806 to 1845 UTC indicate a rapid development of the fire. The slow animation showing 1833, 1834 and 1835, below, show similar detections as in NGFS; the first detections are at 1834 UTC. Surface observations show very low dewpoints over southern California, and that dryness will affect the growth of the fire.

The imagery below (NGFS Microphysics, FIre Temperature RGB, GeoColor and the Basemap image) from 2034 UTC — just two hours after initiation, show a large, hot fire with a smoke plume.

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Here is the WatchDuty page on this fire. The first entry on this fire is at 1842 UTC.

¹Note: Typically a Red Flag Warning will cause a magenta banner. For this case, parts of Los Angeles county — a county with a large area — were not in a Red Flag Warning. The most recent detection in Los Angeles County is not in the part of that county that has a Red Flag Warning (note how the alert shown above does identify that more recent risk as ‘Nominal’); that is controlling the coloring of the county banner. CIMSS Scientists are working on a fix to this so that Los Angeles County will retain its Magenta Banner even if a fire develops in a part of the county where Red Flag warnings are not present.

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Regarding the initiation time of the Hughes Fire, by using a color enhancement that is well-suited for fire detection, it can be seen that an unambiguous increase in 3.9 µm infrared brightness temperature (darker green pixels) occurred at 1833 UTC near the northeast tip of Castaic Lake (above). Then at 1834 UTC the Fire Mask derived product displayed a “High Probability Fire” pixel (orange).

A 7-hour animation of 1-minute GOES-18 Shortwave Infrared and Visible + Fire Mask (below) showed the rapid increase in areal coverage and intensity of the Hughes Fire — the fire exhibited a peak 3.9 µm infrared brightness temperature of 137.88ºC from 1855-2014 UTC. Wind gusts at a RAWS site just north of the fire perimeter (WMSC1, Hughes Lake) reached 45 mph at 2300 UTC, a factor that aided rapid fire growth. As the southwest flank of the fire approached Interstate 5, a section of I-5 was closed. In addition, smoke from the fire reduced surface visibility to 4 miles near the coast at Naval Air Station Point Mugu (KNTD). By sunset, a marked decrease in the fire’s thermal signature was evident.

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GOES-16 Upper-level water vapor infrared imagery for the 2.5 days ending at 1331 UTC on 22 January 2025, above as an mp4 (click here for a 125-megabyte animated gif) shows an active subtropical jetstream initially across the Gulf States. The jet deforms as an impulse drops south through California. Note the development on 21 January of cold cloud tops (white and green in the enhancement used) especially after 1100 UTC over east Texas and Louisiana in response to the eastward propagation of that digging shortwave indicated by yellow (warmer brightness temperatures) moving across northern Mexico into west Texas at that time. The combination of this storm and an unusually cold and dry airmass over the deep south (and the rest of the country east of the Rockies) has resulted in a near-unprecedented snowstorm over the Gulf Coast states into the south Atlantic states. Numerous locations set all-time record snowfalls!

Webcam Imagery from just before Noon Central Time (1800 UTC) on 21 January included this Traffic Cam shot from Lake Charles, LA, this view of Galveston TX (from here) and this view of Bourbon Street in New Orleans (source).

GOES-16 Day Cloud Phase Distinction from 1816-1951 UTC, below, shows the strengthening storm. You can use the cloud texture over Louisiana to infer regions where precipitation is occurring (all in the form of snow!). Day Cloud Phase Distinction also highlights — in green — snow that is on the ground in Kansas and Oklahoma, and also in southeast Texas that becomes apparent as the deeper clouds (orange/yellow in this RGB) pull away. That snow on the ground in southeast Texas is inhibiting the development of cumulus clouds (white/cyan).

The toggle below includes annotations highighting regions of snow and low clouds.

A zoomed-in Day Cloud Phase Distinction RGB over Louisiana at 2001 UTC, below, shows how one might use this RGB, both the color and texture, to infer regions where precipitation is occurring.

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A closer look at the Gulf Coast — from Bay City, Texas across Louisiana to Gulfport-Biloxi, Mississippi — using GOES-16 Infrared (10.3 µm) images (above) showed the eastward progression of snow observations (which were occasionally moderate to heavy at some sites) during the 16.5 hours ending at 2201 UTC. Cloud-top infrared brightness temperatures became increasingly colder (-40s to -50s C, shades of green to yellow) as snowfall rates increased across the region. A corresponding animation with overlays of Winter Watches, Warnings and Advisories is available here — which included the first-ever Blizzard Warning issued by the NWS Lake Charles forecast office (that extended all the way to the coast!).

NWS Lake Charles has issued it's first ever Blizzard Warning for Jefferson and Orange counties as well as Cameron, Calcasieu, Jeff Davis, Acadia, Vermilion and Lafayette parishes until noon today. pic.twitter.com/JlyJpIxRcw

— NWS Lake Charles (@NWSLakeCharles) January 21, 2025

Two features of note occurred during that time period: (1) a brief cluster of GOES-16 GLM Flash Extent Density (FED) pixels over southwest Louisiana at 1511 UTC (above), suggesting that thundersnow may have occurred (none of the 3 nearby METAR sites explicitly reported lightning or thundersnow, although the southernmost site was reporting heavy snow) — however, the heaviest storm total snowfall amounts occurred near the eastern edge of the FED signature; it is also interesting that a small packet of cloud-top Kelvin-Helmholtz waves traversed that same area immediately preceding the FED signature (possibly an indicator of enhanced snowfall rates), and (2) a Ship Report of moderate to heavy freezing rain off the coast of Louisiana at 1800 UTC (below); there was quite a difference between that ship report air temperature (32ºF) and sea surface temperature (61ºF)!

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GOES-16 Land Surface Temperatures at 1301 UTC on 22 January 2025 showed sub-zero (^oFahrenheit; the region in white in the toggle highlights values between -5 and 0) values over Florida, Alabama and Louisiana. Surface observations (recorded at 1.5 m) were in the single digits above zero.

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An hour earlier, at 1201 UTC, the coldest GOES-16 Land Surface Temperature (LST) in southern Louisiana was -8.12ºF (the darker purple pixel west-southwest of Baton Rouge, KBTR) (below). That morning, the coldest air temperatures in that area were -1ºF near Lafayette, KLFT (there were 2 dark purple LST pixels northeast of KLFT, with a value of -6.4ºF). The coldest LSTs generally corresponded with the area that received the highest snowfall amounts.

GOES-16 daytime True Color RGB images (source) on 21 January and 22 January (below) provided a good view of the areal coverage of snow cover across northeast Texas, southern Louisiana and southern Mississippi. The southwest and south-central portion of Louisiana that received the most snowfall exhibited a brighter white appearance.

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Early morning satellite imagery, below, shows the snowband across the south. The toggle below between Band 2 (visible, 0.64 µm, at which wavelength snow is highly reflective) and Band 5 (near-infrared, 1.61 µm, at which wavelength snow absorbs energy and therefore appears dark) helps to highlight the snow band. You will be able to watch the snow area decrease in size on satellite imagery as the southern Sun shines soothingly.

Because of the reflectivity difference over snow in GOES-R Bands 2 and 5, any RGB that includes those two channels will produce a snowband with a different color than low cloud or adjacent land. That’s demonstrated in the toggle below. I chose 1441 UTC rather than 1401 UTC as shown above to take advantage of increased solar reflectance. In AWIPS, I could have used the 1401 UTC and adjusted the RGB bounds — via ‘Composite Options’ accessed by left-clicking on the product legend — to create a brighter image.

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Sentinel-2A True-Color imagery of the snow over western Lousisiana/northeast Texas on 22 January 2025 (from this link) is shown below.

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The Satellite Liaison Blog also discussed this storm here.

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While Wisconsin endures a very cold airmass without the brightening benefit of snow, various satellites continue to take spectacular imagery.  The GOES-16 True Color imagery above, from the CSPP Geosphere site, shows a clear scene and snowless features over southern Wisconsin (except over Racine and Kenosha counties in far southeast WI where lake-effect snow fell earlier this month).  The resolution of the GOES-16 Visible channel (Band 2, 0.64 µm) is 0.5 km at the sub-satellite point, meaning an effective resolution of around 1 km over Wisconsin.  NOAA-20 overflew Wisconsin on 19 January and the scene below, from the VIIRS Today website, shows a similar view, but with nominally better resolution:  the visible channels (M03, M04, M05) used to create true-color imagery have 750-m resolution.  The ‘true color’ views do not look the same because of the different wavelengths that are used to create them.

Even better resolution imagery occurred when Sentinel-2A overflew Wisconsin on 17 January 2025 (link; to reproduce the imagery below, change the date at the website that opens; this site also allows a user to view southern California and the effects of recent fires).  The MSI (Multi-Spectral Imager) on Sentinel-2A has 10-m resolution at 0.49, 0.56 and 0.67 micrometers), so it can produce pictures with far higher resolution, but its temporal coverage is restricted.  Madison was lucky on the 17th: full coverage on a clear day. It really is that brown in Wisconsin without snowcover! Your blogger also finds the ice patterns on the lakes fascinating.

A zoomed-in view over Madison’s isthmus, below, includes the UW-Madison campus and the State Capitol.

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Thermal signatures of the still-unfrozen water of Lake Oahe reservoir (along the Missouri River, in central South Dakota) were evident in GOES-16 (GOES-East) Infrared, Low-level Water Vapor and Mid-level Water Vapor images on 19th January 2025 (above). As a result of cold arctic air (morning low temperatures across western/central SD were generally in the -10 to -20F range) flowing across the open water of Lake Oahe, there were also 2 brief periods of light lake effect snow at Pierre (KPIR), each which reduced the surface visibility to 2.5 miles (below).

With a cold/dry arctic air mass in place over the region, the GOES-16 Mid-level Water Vapor (Band 09) and Low-level Water Vapor (Band 10) weighting functions peaked at lower than normal altitudes (below) — with significant amounts of radiation from the surface reaching the satellite detectors (thereby enabling a signature of Lake Oahe in the Water Vapor imagery).

In fact, the Total Precipitable Water value derived from 1200 UTC Rapid City rawinsonde data (0.03 in) (above) was a record low value for 1200 UTC soundings on 19 January (below).

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