Re-suspended ash from the Katmai volcano in Alaska

February 28th, 2021 |

GOES-17 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-17 “Red” Visible (0.64 µm) images [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm) images (above) showed the hazy signature of a plume of re-suspended ash from the 1912 Katmai volcanic eruption. Strong surface winds gusting to 50-55 knots — caused by a strong pressure gradient along the western periphery of a Storm Force low in the Gulf of Alaska (surface analyses) — lofted some of the thick layer of ash that has remained on the ground in the vicinity of the volcano. The most dense portion of the aerosol plume was  moving across the Barren Islands (between Kodiak Island to the south and the Kenai Peninsula to the north); near the northern edge of the aerosol plume, surface visibility was reduced to 5 miles at Homer and 7 miles at Seldovia.

A sequence of Suomi NPP VIIRS Day/Night Band (0.7 µm) images (below) showed that the plume had formed before sunrise — ample illumination from a Full Moon provided vivid “visible mages at night” (at 1131 UTC and 1311 UTC).

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

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

ASCAT winds from Metop-C at 0743 UTC and 2124 UTC (source) are shown below — they indicated a dramatic increase in surface wind speeds  of 50 knots or greater emerging from the Barren Islands into the Gulf of Alaska later in the day.

ASCAT winds from Metop-C, at 0743 UTC and 2124 UTC [click to enlarge]

ASCAT winds from Metop-C, at 0743 UTC and 2124 UTC [click to enlarge]

GOES-17 True Color RGB images created using Geo2Grid (below) provided a clearer view of the re-suspended ash plume. North of the plume, note the tidal ebb and flow of ice within Cook Inlet and Turnagain Arm leading into the Anchorage area.

GOES-17 True Color RGB images [click to play animation | MP4]

GOES-17 True Color RGB images [click to play animation | MP4]

Blowing dust across New Mexico. Texas and Oklahoma

January 30th, 2021 |

GOES-16 True Color RGB images [click to play animation | MP4]

GOES-16 True Color RGB images [click to play animation | MP4]

GOES-16 (GOES-East) True Color RGB images created using Geo2Grid (above) revealed multiple plumes of blowing dust — which had their sources in drought-stricken portions of New Mexico and the Texas/Oklahoma Panhandles — moving across Texas in the wake of a cold frontal passage on 30 January 2021. Other features of interest included an undular bore that developed ahead of the advancing cold front in Texas, and smaller plumes of blowing dust that originated from a cluster of dry lake beds in central New Mexico late in the day. Surface wind gusts in the 50-60 knot range were seen, and visibility was restricted to less than 1 mile at some locations.

1-minute Mesoscale Domain Sector GOES-16 Dust RGB and Split Window Difference (10.3 µm – 12.3 µm) images (below) showed that the dust signatures (brighter shades of magenta in the Dust RGB images, and brighter shades of yellow in the SWD images) diminished as the winds began to subside during the late afternoon hours.

GOES-16 Dust RGB and Split Window Difference (10.3 µm – 12.3 µm) images [click to play animation | MP4]

GOES-16 Dust RGB and Split Window Difference (10.3 µm – 12.3 µm) images [click to play animation | MP4]

Blowing dust across the High Plains (Part 2)

January 15th, 2021 |

GOES-16 Dust RGB images, with and without hourly surface reports [click to play animation | MP4]

GOES-16 Dust RGB images, with and without hourly surface reports [click to play animation | MP4]

As discussed in this blog post, GOES-16 (GOES-East) Dust RGB images (above) displayed the distinct signature of a large blowing dust plume (brighter shades magenta/pink) that initially developed over drought-stricken areas of eastern Colorado and far western Kansas on 15 January 2021. Surface wind gusts in excess of 60 knots were seen in eastern Colorado near the source of the dust plume, with a peak gust of 63 knots or 72 mph — in fact, the anomalously-strong 925 hPa wind speeds were 5-6 sigma above the climatological mean (source). Pilot reports near the edges of the plume indicated visibility restrictions due to dust at altitudes of 5,000 feet over southwestern Kansas and 10,000 feet over northeastern New Mexico.

GOES-16 True Color RGB and Dust RGB images (created using Geo2Grid) are shown below.

GOES-16 Dust RGB and True Color RGB images [click to play animation | MP4]

GOES-16 True Color RGB and Dust RGB images [click to play animation | MP4]

Due to the presence of very dry throughout the lower/middle troposphere (Amarillo, Texas rawinsonde data), a signature of the dust plume was also evident in GOES-16 Near-Infrared “Cirrus” (1.37 µm) images (below).

GOES-16 Dust RGB and Near-Infrared

GOES-16 Dust RGB and Near-Infrared “Cirrus” (1.37 µm) images, with plots of Ceiling and Visibility [click to play animation | MP4]

After sunset, the plume signature persisted in GOES-16 Dust RGB images (below) as the blowing dust continued to move southeastward across Texas.

GOES-16 Dust RGB images, with and without hourly surface reports [click to play animation | MP4]

GOES-16 Dust RGB images, with and without hourly surface reports [click to play animation | MP4]

===== 16 January Update =====

GOES-16 Dust RGB and True Color RGB images [click to play animation | MP4]

GOES-16 Dust RGB and True Color RGB images [click to play animation | MP4]

On the following day, the dust plume began to flow off the Texas coast and over the Gulf of Mexico by 06 UTC — and although the plume signature began to diminish in the GOES-16 Dust RGB images after sunrise, it was very apparent in True Color RGB imagery (above). Note that the True Color images revealed some recirculation of dust which began to move inland toward the end of the day, as surface winds near the coast shifted to southeasterly (surface analyses).

GOES-16 Natural Color RGB images with plots of Ceiling and Visibility (below) showed that the dust reduced the visibility to 2.5 miles at a site located just off the Texas coast at 14 UTC, and to 5 miles at a site located about 100 miles offshore at 15 UTC.

GOES-16 Natural Color RGB images, with plots of Ceiling and Visibility [click to play animation| MP4]

GOES-16 Natural Color RGB images, with plots of Ceiling and Visibility [click to play animation| MP4]

In a toggle between VIIRS True Color and False Color RGB images from Suomi NPP (below), the dust plume was very evident over the Gulf of Mexico (where its lighter appearance stood out against the dark background of the water).

VIIRS True Color and False Color RGB images from Suomi NPP [click to enlarge]

VIIRS True Color and False Color RGB images from Suomi NPP [click to enlarge]

Tehuano wind event

December 24th, 2020 |

GOES-16

Topography + GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) indicated that a strong arctic cold front (surface analyses) had plunged southward across Mexico, through the Chivela Pass, and emerged as a Tehuano (or “Tehuantepecer“) gap wind into the Gulf of Tehuantepec on 24 December 2020. Along the Gulf of Mexico coast, a few sites in Mexico reported blowing dust and/or blowing sand with onshore winds gusting to 40 knots.

GOES-16 True Color RGB images created using Geo2Grid (below) showed the hazy signature of blowing dust/sand as it was transported off the south coast of Mexico and spread out across the Gulf of Tehuantepec.

GOES-16 True Color RGB images [click to play animation | MP4]

GOES-16 True Color RGB images [click to play animation | MP4]

===== 25 December Update =====

GOES-16 "Red" Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

On the following day, GOES-16 Visible images (above) showed that the leading edge of the gap wind flow — marked by a broad arc cloud — was approaching the ITCZ / Monsoon Trough in the Pacific Ocean. Ship reports of 30-35 knot winds were seen within the offshore flow — and ASCAT surface scatterometer winds revealed speeds as high as 44 knots.

GOES-16 True Color RGB images (below) showed the hazy signature of blowing dust from Mexico as it spread out across the Pacific Ocean.

GOES-16 True Color RGB images [click to play animation | MP4]

GOES-16 True Color RGB images [click to play animation | MP4]

Aided by enhanced forward scattering during the morning hours, True Color RGB images from GOES-17 (GOES-West) showed the hazy signature of airborne dust from Mexico a bit better (below).

GOES-17 True Color RGB images [click to play animation | MP4]

GOES-17 True Color RGB images [click to play animation | MP4]