Midwest derecho

July 19th, 2017 |

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

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

* GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing *

A long-lived mesoscale convective system (MCS) known as a derecho produced swath of damaging winds — as well as some large hail and a couple of tornadoes — that stretched from north-central South Dakota to northwestern Indiana on 19 July 2017 (SPC storm reports | TWC summary). GOES-16 “Clean” Infrared Window (10.3 µm) images (above) showed the southeastward propagation of the storm system.

Closer views of the early stages of the derecho as it moved across central and eastern South Dakota are shown below, using GOES-16 “Red” Visible (0.64 µm) and Infrared Window (10.3 µm) images. The highest measured wind gust was 100 mph near Polo (1522 UTC), with 83 mph recorded at Huron (1636 and 1730 UTC). Hail of 2.50 inches in diameter fell near Cavour (1703 UTC). Note that most of the severe reports were in the general vicinity of the persistent cold overshooting top (black to white enhancement) seen on the Infrared imagery; due to parallax, the apparent location of this storm-top feature was shifted slightly north of its true location.

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

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

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

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

1-km resolution Terra MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images at (below) showed the MCS over the Huron (KHON) area at 1656 UTC. Since there is minimal parallax associated with polar-orbiter satellite imagery, the cluster of SPC storm reports (occurring within +/- 30 minutes of the time of the MODIS image) was much closer to the cold (-70 to -73º C, lighter gray enhancement) overshooting top. Another feature of interest seen on the Infrared image was a “warm trench” (exhibiting brightness temperatures as warm as -60º C, red enhancement) immediately surrounding the cold overshooting top — perhaps a result of compensating subsidence?

Terra MODIS Visible and Infrared Window (11.0 µm) images, with SPC storm reports [click to enlarge]

Terra MODIS Visible and Infrared Window (11.0 µm) images, with SPC storm reports [click to enlarge]

375-meter resolution Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images at 1846 UTC (below) provided a detailed view of the MCS as it was centered near the South Dakota / Minnesota border. The coldest cloud-top IR brightness temperature was -83º C (violet enhancement).

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images, with SPC storm reports [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images, with SPC storm reports [click to enlarge]

Large iceberg breaks off the Larsen-C ice shelf in Antarctica

July 12th, 2017 |

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

A comparison of Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images on 12 July 2017 (above; courtesy of William Straka, SSEC) shows the large iceberg (named A-68) that had separated from the Larsen-C ice shelf in Antarctica (Project MIDAS).

===== 13 July Update =====

A 12 July vs 13 July comparison of VIIRS Infrared Window and Day/Night Band images (below) revealed a slight expansion of the ice fracture, as Iceberg A-68 slowly drifted away from the Larsen-C ice shelf.

12 July vs 13 July Suomi NPP VIIRS Infrared Window (11.45 µm) images [click to enlarge]

12 July vs 13 July Suomi NPP VIIRS Infrared Window (11.45 µm) images [click to enlarge]

12 July vs 13 July Suomi NPP VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

12 July vs 13 July Suomi NPP VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

Using GOES-16 Baseline Products to anticipate where heavy rain might fall

July 10th, 2017 |

GOES-16 10.3 µm “Clean Window” Superimposed on the Clear-Sky Baseline Total Precipitable Water Product, 0107 – 1337 UTC on 10 July (Click to play large animated gif)

GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing

Very heavy rain (4-5″) fell over parts of southwestern Wisconsin early on 10 July 2017 as a Mesoscale Convective System traversed the Upper Midwest (0831 UTC VIIRS Infrared vs Day/Night Band). The animation above blends the Clean Window (10.3 µm) from GOES-16 with the Total Precipitable Water Baseline Product (This product is available online — with a time delay — here). Note that the largest values of Precipitable Water are diagnosed to be over southern and western of Wisconsin. Looking at the animation of the 10.3 µm imagery, can you decide where the heaviest rain fell?

A screen capture from this website, below, shows 24-hour precipitation over the Upper Midwest, with a northwest-to-southeast oriented maximum near the northwest-to-southeast gradient of diagnosed total precipitable water field shown in the animation above. (This summary from the National Weather Service in Milwaukee shows accumulated precipitation ending at 0900 Central Time).

The Hazardous Weather Testbed at the Storm Prediction Center evaluates GOES-16 (and other satellites, such as Suomi NPP) products. There have been many instances that noted convection was most intense along the gradient of the moisture (See this summary, for example, or this one.) When GOES-16 Baseline Products indicate a gradient, pay close attention when strong convection develops upstream.

24-hour Precipitation over the Upper Midwest ending at 1200 UTC on 10 July 2017 (Click to enlarge)

Added: One day later, again, convection initiated (and/or persisted) north of the diagnosed Total Precipitable Water maximum over Illinois and Iowa (link), i.e., in the gradient of Total Precipitable Water.

GOES-16: wildfires in southern California

July 8th, 2017 |

GOES-16 Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images, with hourly surface plots [click to play MP4 animation]

GOES-16 Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images, with hourly surface plots [click to play MP4 animation]

* GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing *

As southern California experienced a record-setting heatwave, 2 large wildfires were burning in San Luis Obispo and Santa Barbara counties on 08 July 2017: the Alamo Fire and the Whittier Fire. GOES-16 “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images (above) showed the smoke plumes and hot spots (red pixels) associated with these 2 fires.

The dense smoke plumes also exhibited a signature on the Near-Infrared “Cirrus” (1.37 µm) images (below), even though they were not composed of ice crystals (note that 10.3 µm Infrared Window brightness temperatures of the smoke plumes were warmer than -20º C, cyan color enhancement, the entire day). This example demonstrates that in a dry atmosphere, the “Cirrus” imagery will also be able to detect the presence of any airborne particles that are efficient scatterers of light (which includes smoke, dust and volcanic ash).

GOES-16 Visible (0.64 µm, left), Near-Infrared Cirrus (1.38 µm, center) and Infrared Window (10.3 µm, right) images, with station identifiers plotted in yellow [click to play MP4 animation]

GOES-16 Visible (0.64 µm, left), Near-Infrared Cirrus (1.37 µm, center) and Infrared Window (10.3 µm, right) images, with station identifiers plotted in yellow [click to play MP4 animation]

During  the nighttime prior to sunrise, with the benefit of ample illumination from a Full Moon, a long smoke plume streaming southwestward from the Alamo Fire was clearly seen on Suomi NPP VIIRS Day/Night Band (0.7 µm) imagery at 0910 UTC or 2:10 am local time (below). A very bright glow — larger than that of some nearby city lights — was co-located with the large hot spot on the corresponding Shortwave Infrared (3.74 µm) image.

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.74 µm) images [click to enlarge]