A dryline over the United States High Plains will serve as a focus for convective development later in the day on 22 April. (Click here for the 1300 UTC Convective Outlook). What tools are available to view gradients of Total Precipitable Water, and how do they compare? The toggle above compares Gridded NUCAPS fields of TPW and roughly coincident GOES-16 derived Total Precipitable Water. (TPW can be viewed online here). A zoomed-in version of the image above is shown below (including an image showing NUCAPS Sounding Availability points). Note that NUCAPS gives values in regions of clouds. GOES-R has a higher spatial resolution. A user might use both to take advantage of the strengths of both sensors.

Of course, a benefit of GOES-R over NUCAPS values is that GOES-R estimates can animate. The 2-hour animation below shows a relatively stationary gradient over the High Plains from Texas northward through Kansas.

SPC Mesoanalyses at 0800 and 1000 UTC, below, similarly show a relatively stationary gradient. Perhaps the strength of the gradient is different in the analysis below compared to the satellite-based esimates above, but the different enhancements and map projections makes it difficult to make a direct comparison!

The NAM-12 image of TPW below also shows a tight gradient over the High Plains.

Gridded NUCAPS fields of TPW are also available at this RealEarth-driven site, and at this SPoRT site. The RealEarth field is shown below.

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The GOES-16 Total Precipitable Water at 1716 UTC, above, is a bit less concentrated over western Kansas. The image is also toggling with the Split Window Difference (10.3 µm- 12.3 µm) enhanced such that dark regions have more moisture. No appreciable gradient in moisture that might focus convection is apparent. (The 1630 UTC Convective Outlook has not appreciably changed from 1300 UTC). Note below how well the surface dewpoint gradients and TPW gradient match!

Continue to monitor the evolving moisture distribution using the resources above as the afternoon progresses.

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The Tunnel Fire north of Flagstaff offers an excellent example of why knowledge of Parallax with satellite features is important. In the animations above, note how the location of the warmest pixels are shifted: GOES-17 has the warmest pixels very close to US Highway 89 leading northeast away from Flagstaff; GOES-16 has the warmest pixels just to the west of that road! Which is correct?

Even with surface-based features such as fires, parallax (see other blog posts dealing with parallax here, here, here and here) is an issue with GOES imagery. (Click here to see parallax with lakes) The perceived location is shifted away from the sub-satellite point. So for this example, the true fire location might be somewhere between the satellite-indicated locations. Note also that the FDCA values from GOES-17 differ from those GOES-16; for this fire, GOES-17 values were warmer.

NOAA-20 overflew this fire at 20:50, 20:30 and 20:10 on 19, 20 and 21 April, and imagery from the NASA Worldview site is shown below (Click here for a direct link to the 20 April scene) VIIRS imagery typically has smaller parallax shifts than GOES (and in fact, as detailed here, considerable effort has gone into better georeferencing of VIIRS imagery, as discussed in this blog post and shown in this toggle), and the fire location is therefore more accurate. The 20 April view from NOAA-20 occurred shortly after the end of the animation above, and shows a fire straddling the highway.

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A toggle between Suomi-NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images at 0954 UTC or 3:54 am local time (above) displayed the nighttime glow and thermal signatures of actively-burning portions of the Tunnel Fire on 20 April 2022. As noted in the Inciweb report, a 10-mile section of the north-south U.S. Highway 89 was closed (from milepost 425 to 435) as the fire crossed that road.

After sunrise, GOES-17 (GOES-West) Fire Temperature RGB, Shortwave Infrared (3.9 µm), Fire Power and Fire Temperature images (below) showed how the fire intensified during the day (the Fire Temperature and Fire Power derived products are components of the GOES Fire Detection and Characterization Algorithm FDCA).

A longer animation of GOES-17 Fire Temperature RGB images created using Geo2Grid is shown below. The less-intense signature of the Crooks Fire is also apparent, to the southwest of the more prominent Tunnel Fire.

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JMA Himawari-8 “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.4 µm) images (above) showed signatures of a rapidly-spreading grassland fire in eastern Mongolia’s Numrug National Park (near the border with China) on 19 April 2022. The fast rate of northeastward growth of the dark burn scar in Visible imagery was particularly striking. Strong winds aided the rapid expansion of this fire, due to the tight pressure gradient between a high over central China and a deepening low that was moving from Siberia to northeastern China (surface analyses).

Consecutive NOAA-20 VIIRS Infrared image valid at 0401 UTC and 0541 UTC — viewed using RealEarth (below) — showed the eastward drift of individual small pyrocumulonimbus (pyroCb) clouds, which exhibited cloud-top infrared brightness temperatures of -40ºC and colder (brighter green color enhancement).

A toggle between NOAA-20 VIIRS True Color RGB and Infrared images at 0541 UTC (below) depicted the dark burn scar as well as the smoke plume with embedded pyroCb clouds.

30-meter resolution Landsat-8 False Color RGB imagery valid at 0252 UTC (below) provided an even more detailed view of the dark burn scar — in addition, the active fire front appeared as brighter shades of pink to red along the eastern and southeastern flanks.

After sunset, the northern flank of the fire continued to burn at an intense rate, judging from the thermal signature seen in Himawari-8 Shortwave Infrared images (below). Dense layered clouds began to move over the region before sunrise the next day, which then acted to mask the fire’s thermal signature.

A toggle between NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images valid at 1757 UTC (below) showed the bright nighttime glow of active fires — especially along the aforementioned northern flank — in addition to the associated smoke plume that was moving eastward, as illuminated by the Moon (which was in the Waning Gibbous phase, at 90% of Full). This smoke did not exhibit a signature in the corresponding 11.45 µm Infrared image, since relatively thin smoke layers are generally transparent to upwelling surface radiation at longer wavelengths.

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