Night Microphysics RGB imagery from the CSPP Geosphere site (link) show the blossoming of high clouds (deep red in the RGB) north of the Samoan Islands, clouds that subsequently sag southward. Careful inspection of the animation also shows clouds that are more pink than deep red; these are likely mid-level clouds that might be developing in the vertical. Water vapor imagery (below, from this site) also show the development of cold cloud tops north of the Samoan Islands, part of a region of colder cloud tops that extends to the east of American Samoa (circled in this annotated water vapor image from 1320 UTC).

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As you’re pondering the satellite imagery, perhaps you recall the numerical models from the previous days. The animation below (taken from the tropicaltidbits website) shows precipitation moving towards the Samoan Islands (in the upper right quadrant of the domain) from the east and northeast. This animation shows a nine sequential forecasts all valid at 0600 UTC on 28 January 2025. The forecasts were consistent in bringing rain towards the Samoan Islands (near 12^oS, 170^oW). And the satellite imagery above shows convection dropping southward.

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A timely Metop-C overpass provided ASCAT sea-surface winds at 0930 UTC over the Samoan Islands. Strong winds to the north of Samoa, and lighter winds near Samoa, suggest surface convergence that might be helping to force the convection. (Image from this website).

LightningCast Probabilities (available here) show the likelihood of a GLM observations within the next 60 minutes. The animation below shows LightningCast increasing to the north of the Samoan Islands overnight on early 28 January; those probabilities move southward as convection continues, and eventually lightning (in the form of GLM Observations) occurs over Independent and American Samoa. The lightning is north of American Samoa at 1040 UTC, and overspreads the islands from 1140-1410 UTC, when the animation stops. (Click here for an animation with a faster timestep). The increasing LightningCast probabilities suggest strong convection .

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Pago Pago, American Samoa reported light rain at 1600 UTC on 28 January. When you try to determine if rain is imminent, use as many satellite products as you can!

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5-minute CONUS Sector GOES-16 (GOES-East) Visible images (above) showed ice across much of Lake Erie on 27th January 2025. The far western and far eastern parts of the lake were covered in fast ice — while the motion of drift ice within the central portion of the lake was being influenced by strong SW winds gusting to 30-40 kts (near the east end of Lake Erie, there was a peak wind gust of 51 kts at Niagara Falls KIAG at 1921 UTC). Lake Erie average ice cover had quickly risen above the historical average during the preceding week, as cold temperatures prevailed across much of the eastern US.

GOES-16 True Color RGB images from the CSPP GeoSphere site (below) provided better contrast between the lake ice and areas of open water.

A closer look at GOES-16 True Color RGB images centered over the fast ice covering the far western part of the lake (below) revealed that some of that ice began to become detached from the shoreline later in the day, due to wind stress.

A closer look at GOES-16 True Color RGB images centered over the fast ice covering the far eastern part of the lake (below) displayed a large section of the western ice edge that was abruptly pushed eastward by strong winds late in the day. As that rapid deformation of the fast ice occurred, the pressure appeared to force a small segment of ice northward up the Niagara River.

RCM-1 and RCM-2 SAR Normalized Radar Cross Section imagery (source) at 1137 UTC and 2331 UTC (below) provided a detailed view of the intricate ice structure across the western portion of Lake Erie — in addition to linear channels created by icebreaker ships.

A toggle between Sentinel-2 Optimized Natural Color RGB and Normalized Difference Water Index images (below) demonstrated that the NDWI product was more useful for highlighting ice leads as well was the linear channels created by icebreaker ships.

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GOES-18 Upper Level water vapor infrared imagery, above, (source) shows a stream of upper-level moisture moving over southeastern Alaska on the east side of a cyclonic system over western Alaska on 27 January 2025. This large storm moved warm and moist air northward into Alaska; several stations tied record warm temperatures on 26 January (albeit weak records, compared to the days before the 26th), including Fairbanks and Anchorage and Kodiak Island. GOES-18 Airmass RGB images, below (from here), show the characteristic red/orange enhancement over central Alaska and the northern Gulf of Alaska expected when a strong potential vorticity anomaly is present. The green enhancement over southeast Alaska is more typical of an airmass with at least some tropical origins. (You can find a Quick Guide for the airmass RGB here, or here).

MIMIC Total Precipitable Water for the 24 hours ending 1400 UTC on 27 January 2025, below, shows a concentrated ribbon of northward-moving enhanced moisture (one might call this an atmospheric river) moving eastward, from south-central Alaska at the start of the animation to southeast Alaska at the animation’s end. The south coast of Alaska had generous rains on the 26th as this moisture source moved through.

The atmosphere river resulted in Total Precipitable Water amounts that were well above normal. The NOAA/NESDIS/OSPO Percent Of Normal field for 1200 UTC on 27 January 2025, below, from this source, showed values near 200% of normal.

The 1200 UTC/26 January 2025 sounding from Anchorage (from the handy Wyoming Sounding site) showed a TPW at 17.31 mm, 0.68 inches. (Here’s the blended TPW percent of normal for 1200 UTC on 26 January — note the exception moisture to the west of where it occurs above 24 hours later). The plot below is from the SPC Sounding Climatology page, and shows the observed maximum/mean/minimum sounder TPWs at Anchorage. The values with this system although not record breaking are certainly on the high side of the distribution for January.

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This website shows microwave estimates of snowfall rate from the many polar-orbiting satellites that give excellent coverage over Alaska. Data from 0444 through 1342 UTC on 27 January 2025, below, shows heaviest snows along the coast of southeastern Alaska, and considerable snow along the Brooks Range in northern Alaska as well.

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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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