Flooding along the Red River of the North

April 27th, 2022 |
ABI/VIIRS Flood/Inundation Product valid 0000 UTC 26 April 2022 (Click to enlarge)

The above image (from here; other flood product are available here) shows inundation occurring around the Red River of the North on the North Dakota/Minnesota border. The image combines the excellent spatial resolution of VIIRS on NOAA-20/Suomi-NPP with the excellent temporal resolution of the GOES-16 ABI) Precipitation over the past 7 days ending at 1200 UTC, below, from this site, shows an axis of heavy (>4″!) precipitation just south of Grand Forks. Flood gauges on 27 April (here, from “River Observations” at this site), show major flooding occurring over eastern North Dakota.

7-day precipitation ending 1200 UTC on 27 April 2022 (Click to enlarge)

The toggle below compares Band 2 and Band 5 (and the Day Land Cloud RGB) on 27 April 2022 at 1646 UTC. The 1.61 µm imagery has a very dark signal over the flooded region between Oslo and Drayton — because water absorbs energy at that wavelength (that is, it doesn’t reflect much back to the satellite) — so there is excellent contrast between land and water. Snow (and cirrus clouds) also absorb energy with a wavelength of 1.61 µm, so the reflectance differences between visible/0.64 µm (very bright) and the 1.61 µm (darker) can be used to identify regions of snow on the ground (for example between McClusky and Karlsruhe at the western edge of the image; between Langdon and Petersburg over the central part of the image); features that are bright in both the 0.64 µm and 1.61 µm imagery (for example, the feature stretching east-southeastward from between McClusky and Harvey to near Pingree) are clouds. Any RGB that includes both the 1.61 µm and the 0.64 µm (or 0.87 µm) imagery will highlight snow on the ground. The Day Land Cloud, shown in the toggle below, shows cyan in regions of snow (or cirrus).

GOES-16 Band 2 (0.64 µm), Band 5 (1.61 µm) and Day Land Cloud RGB, all at 1646 UTC on 27 April 2022 (Click to enlarge)

The series of webcam images below, spanning 21-27 April (with no 23 April image), from this website, shows the changes in the river at the Sorlie Bridge in East Grand Forks.

Webcam imagery showing the Red River of the North under Sorlie Bridge in East Grand Forks, Minnesota, 21-27 April 2022 (Click to enlarge)

Cyclone Batsirai in the southern Indian Ocean

February 1st, 2022 |
MIMIC Total Precipitable Water estimates, 2100 UTC 31 January – 2000 UTC 1 February 2022 (click to enlarge)

MIMIC Total Precipitable Water esimates over the Indian Ocean for the 24 hours ending at 2000 UTC on 1 February 2022, above, show the strong cyclonic circulation associated with Cyclone Basirai. Its forecast motion is westward towards Madagascar, as shown in the toggle below that also includes sea-surface temperatures and Window Channel (showing a well-structured storm; all images are from the SSEC/CIMSS Tropical Website). A wind shear analysis (also from the SSEC Tropical Website and valid at 1800 UTC on 1 February) for the Indian Ocean shows low shear values over the storm, but relatively high shear between the storm and the island of Madagascar.

Forecast Path for Batsirai, sea-surface temperature analysis, and window channel satellite imagery, times as indicated (Click to enlarge)

Batsirai’s path moves it close to Mozambique/Malawi, two countries that are still being flooded as a result of rains from Tropical Storm Ana a week ago. A VIIRS flood analysis (from this website), below, diagnoses active flooding occurring along the Shire River (south of Lake Malawi) and along the Zambezi River on 31 January 2022.

River Flood Analysis from VIIRS imagery, 5-day composite endings 31 January 2022 (click to enlarge)

For more information on Batsirai, consult the RSMC at La Réunion (click ici) or the SSEC Tropical Website.

Atmospheric River affecting Alaska

January 21st, 2022 |
MIMIC Total Precipitable Water estimates, 1800 UTC on 20 January – 1700 UTC on 21 January 2022 (Click to enlarge)

MIMIC Total Precipitable Water fields for the 24 hours ending 1700 UTC on 21 January, above, show abundant moisture flowing into southern Alaska. Hourly GOES-17 infrared imagery (Band 13 clean window infrared imagery at 10.3 µm), below, shows a large cyclonic circulation to the south and west of Alaska that is helping to draw moisture towards the state. Level 2 Total Precipitable Water (TPW) is overlain on the imagery and two things stand out: because it is a clear-sky only product, and because the north Pacific Ocean is very cloudy on the 21st, there is little TPW information. Also, GOES-R Total Precipitable Water is not completely Full Disk; TPW is computed to a Local Zenith Angle of 67o (ATBD) and you can see the cut-off for the product in northwestern Canada. Those two things argue for the utility of microwave detection of moisture over Alaska, as shown above.

GOES-17 Clean Window (10.3 µm, Band 13), hourly from 1200 – 1700 UTC on 21 January 2022, overlain with GOES-17 Level 2 Total Precipitable Water (Click to enlarge)

Much of Alaska Southeast from Yakutat to Wrangell is under a Flood Watch. (Image, taken from this site)

Kona low produces record rainfall and flooding in Hawai’i

December 7th, 2021 |

MIMIC Total Precipitable Water product [click to play animation | MP4]

As an anomalously-deep Kona low moved northwest of and then west of Hawai’i during the 04-07 December 2021 period, it began to tap moisture from the Pacific ITCZ and channel it northward across the islands — setting the stage for a prolonged heavy rainfall event (which produced the wettest December day on record at Honolulu). Hourly MIMIC TPW images viewed using RealEarth (above) showed the convergence of 2 northward-moving streams of ITCZ moisture, that then flowed across various portions of Hawai’i (located at the center of the images) from 00 UTC on 04 December to 00 UTC on 08 December.

Air Mass RGB images created using Geo2Grid (below) highlighted the southwestward migration of the Kona low (darker shades of red) as well as the northward motion of deep convection within the stream of ITCZ moisture.

GOES-17 Air Mass RGB images [click to play animated GIF | MP4]

In addition to the heavy rainfall across many of the islands, the high-elevation summits of Mauna Kea and Mauna Loa on the Big Island of Hawai’i also received accumulating snowfall — a signature of this snow cover (darker shades of magenta) was evident in GOES-17 Day Snow-Fog RGB images shown below.

GOES-17 Day Snow-Fog RGB images [click to play animated GIF | MP4]