GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) revealed a curious pattern of waves moving east-northeastward across a patch of mid-level clouds over central Lake Michigan during the morning hours on 23 June 2018.

In an effort to determine the vertical extent of these waves, a look at GOES-16 Low-level Water Vapor (7.3 µm), Mid-level Water Vapor (6.9 µm) and Upper-level Water Vapor (6.2 µm) images from the UW-Madison AOS site (below) showed a signature of waves propagating northeastward across the region during the 0802-2102 UTC time period.

There also were scattered pilot reports of light to moderate turbulence across the region as these waves were moving through, including one report of continuous Clear Air Turbulence at 36,000 feet over eastern Wisconsin.  Due to the subtle nature of these waves, their signature was not as obvious in the 8-bit McIDAS-X Water Vapor images shown below as they were in 16-bit imagery displayed above (or what would be displayed using AWIPS II).

The waves were passing over eastern Wisconsin around the time of ascent of the 12 UTC sounding balloon launched from Green Bay (and continuous turbulence was reported at 38,000 feet) — a plot of weighting functions for the three GOES-16 Water Vapor bands (below) showed peak pressures in the 424-328 hPa (22,800-28,885 feet) range, although significant contributions of energy were still evident from the 300 hPa pressure level (31,000 feet) or higher.

About an hour prior to the start of the 2-km resolution (at nadir or sub-satellite point) GOES-16 Water Vapor animations, 1-km resolution Aqua MODIS Water Vapor (6.7 µm) imagery at 0801 UTC (below) showed a long narrow wave packet (oriented northwest to southeast) from far western Wisconsin to central Illinois — and these waves were also apparent along the tops of mid-level clouds along the Iowa/Illinois border. Was this the leading edge of the waves seen farther northeast over the Great Lakes during the subsequent morning and afternoon hours?

All things considered, the lack of a clear forcing mechanism for these waves qualifies this case to be placed into the “What the heck is this” blog category until a coherent explanation can be put forward…

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A nighttime Aqua MODIS Water Vapor (6.7 µm) image (above) showed the well-defined circulation of a midlatitude cyclone that was centered over northwest Iowa at 0814 UTC (3:14 am local time) on 21 June 2018. Contours of RUC model equivalent potential temperature along the 310 K isentropic surface indicated that a Trough of Warm Air Aloft (TROWAL) existed just to the north of the occluded surface frontal boundary, curving cyclonically from northeastern Iowa across southern Minnesota into southeastern South Dakota, then southward across eastern Nebraska. 24-hour precipitation totals in excess of 2-3 inches had already been observed at that time.

Suomi NPP VIIRS Infrared Window (11.45 µm) images (below) displayed minimum cloud-top brightness temperature values of -50 to -55ºC (yellow to orange enhancement) near the TROWAL axis.

An animation of GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (below) revealed that the storm system moved very slowly during the 00-20 UTC time period, while moderate to occasionally heavy rainfall was observed beneath the TROWAL air stream. 24-hour precipitation amounts reached 4-6 inches by 12 UTC in parts of southwest Minnesota, northwest Iowa and southeast South Dakota (FSD PNS) — and a number of river gauges were reporting minor to major flooding by the afternoon hours. This system was part of a prolonged flooding event (FSD summary).

It should be noted that TROWAL formation is rather unusual over this region during the summer months — but during the cold season a TROWAL can help to produce heavy snowfall (some examples are documented here, here and here).

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GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images (above) showed the smoke plume and thermal anomaly or “hot spot” (dark black to red pixels) associated with the Trail Mountain Fire in Utah on 20 June 2018. Once the smoke was lofted to higher altitudes (in 2 distinct pulses) it quickly fanned out southeastward toward the Utah/Colorado border, transported by northwesterly winds around the periphery of a ridge of high pressure that was building into the Southwest US.

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Until today, GOES-16 Data that flowed into AWIPS was remapped twice: First, from the observational perspective (that is, how the satellite views it) to a spherical fixed-grid projection that approximates the Earth, and then to a Lambert Conformal projection with (for infrared data) 2-km resolution over the Globe. That Lambert Conformal data was then shipped to AWIPS, where the data were again re-projected into the observational perspective desired by the meteorologist.

The 2-km resolution of the data shipped to AWIPS before today is applicable only at the sub-satellite point (nadir) for GOES-16. Thus, the second remap was suggesting better resolution than was warranted by the data. Additionally, the number of data points needed to be sent was very big.

At 1532 UTC on 19 June, the first fixed-grid format data were directly shipped to AWIPS; remapping to a Lambert Conformal projection is no longer done upstream of AWIPS. The toggle above shows the difference in the 7.34 µm “Low-Level” Infrared Water Vapor imagery over the coast of Oregon, near 46º N, 124º W (very far from the GOES-16 sub-satellite point at 0º N, 75.2º W), in the AWIPS CONUS projection.  At 1532 UTC, after the double remap is removed, the pixels are more distinct, and as expected they splay away from the sub-satellite point.

Removing a remapping in the data processing means that pixel-sized extremes — such as overshooting tops, or fires — and gradients will be better represented in the data.  Consider the Clean Window (10.3 µm) Infrared imagery below of strong convection over the Gulf of Mexico east of Texas.  Overshooting tops Brightness Temperatures are colder and the tops themselves more distinct after 1532 UTC than at 1527 UTC.

 

See also this blog post.  This training also discusses the remapping.  And here (or here) is the National Weather Service announcement on the change.

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