Fixed-Grid Format Data flowing in AWIPS

June 19th, 2018 |

AWIPS imagery of GOES-16 Low-Level Water Vapor (7.34 µm) at 1527 and 1532 UTC on 19 June (Click to enlarge)

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.

AWIPS imagery of GOES-16 Clean Window Infrared Data (10.3 µm) from 1347 to 1612 UTC on 19 June. The animation pauses on the last double-remapped image at 1527 UTC, and the first fixed-grid format image at 1532 UTC (Click to enlarge)

 

See also this blog postThis training also discusses the remapping.

High cloud shadow over eastern Iowa

June 18th, 2018 |

It’s always good to get a question that lends itself well to the “What the heck is this?” blog category. The answer, as is often the case, relied on an examination of imagery from a few different GOES-16 ABI bands.  To begin, note the darker feature on 1-minute Mesoscale Domain Sector GOES-16 “Blue” Visible (0.47 µm), “Red” Visible (0.64 µm) and Near-Infrared “Vegetation” (0.86 µm) images (below), which was moving northeastward and passing just to the west of Waterloo, Iowa (KALO) on the morning of 18 June 2018.

GOES-16 "Blue" Visible (0.47 µm), "Red" Visible (0.64 µm) and Near-Infrared "Snow/Ice" (1.61 µm) images

GOES-16 “Blue” Visible (0.47 µm, left), “Red” Visible (0.64 µm, center) and Near-Infrared “Vegetation” (0.86 µm, right) images [click to play animation | MP4]

To explore the initial hypothesis that this might be a shadow from a higher-altitude cloud feature, GOES-16 Near-Infrared “Cirrus” (1.37 µm), Mid-level Water Vapor (6.9 µm) and Upper-level Water Vapor (6.2 µm) images were examined (below), which did indeed reveal a small cloud element aloft that was drifting in the same direction as the darker feature seen above.

GOES-16 Near-Infrared

GOES-16 Near-Infrared “Cirrus” (1.37 µm, left), Mid-level Water Vapor (6.9 µm, center) and Upper-level Water Vapor (6.2 µm, right) images [click to play animation | MP4]

Finally, a comparison of GOES-16 Near-Infrared “Cirrus” (1.37 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.3 µm) images (below) showed that this small (and likely thin) high-altitude cloud exhibited no signature in the Shortwave Infrared, but did exhibit a 10.3 µm brightness temperature as cold as -20ºC (cyan enhancement) at times.

GOES-16 Near-Infrared

GOES-16 Near-Infrared “Cirrus” (1.37 µm, left), Shortwave Infrared (3.9 µm, center) and “Clean” Infrared Window (10.3 µm, right) images [click to play animation | MP4]

12 UTC rawinsonde data from Davenport, Iowa (below) showed southwesterly winds and an air temperature just below -20ºC at an altitude of around 9.6 km.

12 UTC rawinsonde data from Davenport, Iowa [click to enlarge]

12 UTC rawinsonde data from Davenport, Iowa [click to enlarge]

Thanks to Andrew Ansorge (NWS DMX) and Rich Mamrosh (NWS GRB) for alerting us to this interesting feature!

Severe weather in southern Wisconsin

June 16th, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.3 µm, right) images, with SPC storm reports plotted in red/cyan and surface station identifiers plotted in yellow [click to play MP4 animation]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed the development of thunderstorms over southern Wisconsin during the afternoon and evening hours on 16 June 2018. There were reports of hail, damaging winds and 1 brief tornado (SPC storm reports | NWS MKX summary). The pulsing of short-lived overshooting tops is evident in both Visible and Infrared imagery; above-anvil cloud plumes can also be seen in Visible imagery, drifting southeastward from the more robust overshooting tops. Note at 2000 UTC the boundary that was oriented approximately north-to-south, with widespread cumulus clouds to the west and generally cloud-free conditions to the east: this was a lake breeze boundary that had migrated inland from Lake Michigan. Many of the storms appeared to intensify as they interacted with this boundary.

Severe thunderstorms in North Dakota

June 14th, 2018 |

GOES-16 Mid-level Water Vapor (6.9 µm) images, with SPC storm reports plotted in red [click to play MP4 animation]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with SPC storm reports plotted in red [click to play MP4 animation]

GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) revealed the circulation of a shortwave aloft (500 hPa analyses) that was moving from the northern Rockies to the southern Canadian Prairie Provinces on 14 June 2018. The approach of this shortwave was helping to enhance large-scale forcing for ascent, as an occluded surface low developed over western North Dakota (surface analyses) — at 1630 UTC, SPC issued a Moderate Risk for severe thunderstorms across far northern North Dakota.

A Mesoscale Domain Sector was positioned over that region, providing images at 1-minute intervals; a comparison of “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (below) showed the development of this severe convection, which produced hail as large as 3.0 inches in diameter and 4 tornadoes (NWS Bismarck | NWS Grand Forks). The images include plots of SPC storm reports — just across the US/Canada border, storm reports in southern Saskatchewan/Manitoba can be seen here. Some of these storms exhibited very high radar reflectivity values, as shown here and here.

GOES-16

1-minute GOES-16 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.3 µm, bottom) images, with SPC storm reports plotted in red/cyan [click to play MP4 animation]

A larger-scale view of 1-minute GOES-16 Visible images (below) showed well-defined parallel inflow feeder bands moving into the southern flank of the storm approaching Minot (KMOT) and Minot Air Force Base (KMIB) during the 1600-1900 UTC time period. Distinct above-anvil plumes were seen with a number of the stronger storms.

1-minute GOES-16

1-minute GOES-16 “Red” Visible (0.64 µm) images, with SPC storm reports plotted in red [click to play MP4 animation]

The corresponding larger-scale view of 1-minute GOES-16 Infrared images (below) extended past sunset, and showed the final tornado that began around 0324 UTC.

1-minute GOES-16

1-minute GOES-16 “Clean” Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play MP4 animation]