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.  And here (or here) is the National Weather Service announcement on the change.

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, relies on an examination of imagery from a variety of GOES-16 ABI bands.  To begin, note the darker feature seen 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 across eastern Iowa and passing just to the west of Waterloo (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!

Lava flows continue from Kilauea’s Lower East Rift Zone

June 18th, 2018 |

NOAA-20 VIIRS Day/Night Band (0.7 µm), Shortwave Infrared I04 (3.75 µm), Shortwave Infrared M13 (4.05 µm) and Longwave Infrared (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm), Shortwave Infrared I04 (3.75 µm), Shortwave Infrared M13 (4.05 µm) and Longwave Infrared (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm), Shortwave Infrared I04 (3.75 µm), Shortwave Infrared M13 (4.05 µm) and Longwave Infrared (11.45 µm) images (above) showed signatures of the ongoing lava flows from the Lower East Rift Zone of the Kilauea volcano on the Big Island of Hawai’i at 1225 UTC (2:25 am local time) on 18 June 2018.

Note how the central ribbon of hottest lava flow (which continues its active ocean entry) saturated the I04 3.75 µm image, causing a “wrap-around” effect to display cold brightness temperatures (white pixels) — although the M13 4.05 µm band has a lower spatial resolution, it saturates at much higher temperatures, and sensed brightness temperatures in the 480 to 557 K range. The Infrared images also showed evidence of steam clouds flowing southward over the adjacent offshore waters.

A webcam image from near Kapoho (PGcam) around the time of the NOAA-20 VIIRS images is shown below. The active Fissure 8 is near the center of the image.

Webcam image from near Kapoho [click to enlarge]

Webcam image from near Kapoho [click to enlarge]

VIIRS imagery and webcam capture courtesy of William Straka (CIMSS).

Convection and Flooding over northern Wisconsin

June 17th, 2018 |

GOES-16 ABI Clean Window (10.3 µm) Infrared Imagery, 0200-0559 UTC on 17 June 2018 (Click to animate)

Persistent convection over northern Wisconsin, Minnesota and upper Michigan late Saturday (16 June)/early Sunday (17 June) caused significant flooding.  The animation above shows GOES-16 ABI “Clean Window” Infrared Imagery from 0200-0600 UTC on 17 June.  Note the persistence of the cold overshooting tops over western Bayfield County in northwestern Wisconsin! A longer Infrared animation (0110-1200 UTC) which includes hourly plots of precipitation type (yellow) and SPC storm reports of damaging winds (cyan) is available here.

This link from Wisconsin Emergency Management shows aerial pictures of the flood damage. Of note is the break in US Highway 2 to the west of Ashland WI.

The heavy rains also affected runoff into Lake Superior. MODIS imagery, below, from the MODIS Today site (also available from RealEarth: Link), shows considerable offshore flow of sediment on 19 June (a similar image from 18 June is here, with a toggle between the 2 days here).

True-Color Imagery from Aqua MODIS on 19 June 2018 (Click to enlarge)