10-minute Full Disk scan Dust RGB images from GOES-18 (GOES-West), GOES-17, GOES-19 (Preliminary/Non-operational) and GOES-16 (GOES-East) created using Geo2Grid (above) showed vivid signatures of blowing dust (brighter shades of magenta) that originated over parts of northern Mexico and southwestern New Mexico — and was subsequently transported northeastward across southern New Mexico and southwestern Texas on 11th February 2025.

The respective satellite locations over the Equator are: GOES-18 (137.0 W longitude), GOES-17 (104.7 W longitude), GOES-19 (89.5 W longitude) and GOES-16 (75.2 W longitude). However, GOES-17 has been temporarily brought out of storage and is drifting slowly from 12th-15th February 2025, approximately 0.3 degrees of longitude in total. All ABI imagery during this “Longitude Test” will be resampled to the nominal 105 W location. GOES-17 products will be analyzed for any potential impacts that this shift in longitude might cause. The overall goal of the Longitude Test is to determine what product impacts (if any) there might be when GOES-16 (currently operational as GOES-East) is moved to 75.5 W in March, ahead of GOES-19’s arrival (GOES-19 is then scheduled to become operational as GOES-East on 4th April). Tangentially, this also tests our ability to track a GOES-R series satellite as it moves (and still receive data).

5-minute CONUS Sector GOES-16 daytime True Color and Nighttime Microphysics RGB images from the CSPP GeoSphere site (below) highlighted the hazy tan-colored appearance of the blowing dust during the hours leading up to sunset, followed by the brighter shades of magenta dust signature at night (the Nighttime Microphysics RGB makes use of the 10.3-12.3 µm “Split Window Difference“, which is effective for dust detection).

A GOES-16 Visible image (below) included plots of the strong winds that were creating the blowing dust — which at that time was restricting the surface visibility to 1/2 mile at El Paso, Texas (KELP).

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One of the first things that meteorologists learn in their Intro to Weather class is that low pressure means cloudy skies and rain while high pressure means clear skies and sun. Of course, the second thing that meteorologists learn is that weather often doesn’t behave in a textbook way. The southeastern United States today is a good example of that.

Looking just at the surface observations from the Weather Prediction Center, one would think that the Atlantic southeast is under fairly quiescent conditions. A strong high pressure system is centered over southeastern Pennsylvania, but an arm of this high extends south all the way into northeastern Georgia. A stationary front parallels the northern border of Florida. Even the low pressure system in northern Mississippi is quite weak, with a central pressure that is higher than the average mean sea level pressure. All in all, it looks to be a fairly ordinary day.

But the satellite on SSEC’s Real Earth tells a different story. Here’s a loop of true color imagery from GOES-16 this morning.

Obviously, the Atlantic southeast is dominated by clouds, which seems to stand in opposition to what the surface map indicates should be happening. Some of the cloudiness is due to overflow from the midwestern cold front. But a good deal of the cloudiness is caused by the cyclonic flow around the high pressure in the northeast. The flow is coming from over the ocean, where is becomes laden with moisture. As it moves ashore, it runs into the southern extend of the Appalachian Mountains where orographic uplift forces it aloft and clouds and rain ensue.

One of the localized phenomena that arises from this kind of flow in northeastern Georgia has been dubbed the “wedge.” In wedge events, a shallow, stable layer of cold air forms due to cold air damming against the Appalachians. A sounding from the 1500 UTC RAP analysis shows this clearly:

This time of year is historically home to the strongest cold air damming events in this region, and their effects can be significant. Low level inversions like the one seen today can contribute to hazardous wintertime precipitation like freezing rain, as snow formed in a saturated layer aloft melts as it falls through the elevated warm layer then freezes again when it contacts the surface. In April 2023, a wedge event received national attention: the Masters golf tournament was interrupted by a backdoor cold front that formed from the wedge of cold air flowing southward along local terrain. During that event, winds exceeded 30 mph, trees were felled near spectators, and play was interrupted due to these hazardous conditions.

Days like today are a reminder that it’s always a good idea to get a bird’s-eye view of the weather using the wealth of observations that satellites can provide.

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GOES-16 (GOES-East) Upper-level Water Vapor (6.2 µm) and Mid-level Water Vapor (6.9 µm) images (above) displayed leeside cold frontal gravity waves (reference) as they propagated southward across Oklahoma, Texas and far eastern New Mexico on 8th February 2025.

In a corresponding animation that included plots of surface wind barbs, peak wind gusts and frontal analyses (below), it could be seen that the gravity waves were generally present along or just behind the western portion of the surface cold front — while farther to the east, the gravity waves advanced ahead of the cold front.

Plots of GOES-16 Water Vapor (6.2 µm / Band 08 and 6.9 µm / Band 09) Weighting Functions derived using rawinsonde data from Fort Worth, Texas (KFWD) (below) indicated that the peak contribution of upwelling radiation for both spectral bands was originating from the middle troposphere (at pressure levels of 516-460 hPa) — with no contributions from the surface.

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The leeside cold frontal gravity waves were also apparent in GOES-19 (Preliminary/Non-operational) Upper-level Water Vapor (above) and Mid-level Water Vapor images (below).

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10-minute JMA Himawari-9 AHI “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.4 µm) images (above) showed the formation of a pyrocumulonimbus (pyroCb) cloud that was spawned by a bushfire in Grampians National Park in far southeast Australia on 4th February 2025. The pyroCb exhibited cloud-top 10.4 µm infrared brightness temperatures (IRBTs) in the -40s C (denoted by shades of blue to cyan), attaining a minimum IRBT of -49.9º C at 0430 UTC. This temperature roughly corresponded to an altitude around 11 km — not far below the tropopause — according to rawinsonde data from Melbourne: (plot | text). The pyroCb cloud drifted southeast, eventually passing just south of Melbourne Airport (YMML).

Himawari-9 True Color RGB images created using Geo2Grid (below) displayed the pyroCb cloud that was being transported southeastward — and dense smoke (shades of tan) was evident in the vicinity (and immediately downwind) of the Grampians bushfire.

As a surface trough of low pressure was moving east-northeastward across the state of Victoria during that time period (surface analyses), strong southerly winds behind the trough axis (surface observations at Melbourne) helped to intensify the Grampians fire complex — and the pyroCb cloud developed just after the trough passed through the area. Himawari-9 Fire Temperature RGB images (below) revealed (1) the northward expansion of the Grampians bushfire following the ~0300 UTC trough passage (along with flare-up of new fires to the NW), and (2) the pyroCb formation just after the time of the trough passage (0340 UTC image). Note that in the Himawari-9 True Color RGB images shown above, the trough passage also initiated a northward transport of boundary layer smoke from the bushfire source region.

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