Gale-force low in the Gulf of Alaska

November 19th, 2018 |
GOES-17 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images [click to play animation | MP4]

GOES-17 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images [click to play animation | MP4]

* GOES-17 images shown here are preliminary and non-operational *

GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) showed the circulation associated with an occluded gale-force low in the Gulf of Alaska (surface analyses) which moved northward to a position just south of the Kenai Peninsula on 19 November 2018.

The 3 GOES-17 ABI Water Vapor bands sample radiation from different layers within the troposphere — the height and depth of these individual layers varies with changes in (1) the temperature/moisture profile of the atmosphere and (2) the satellite viewing angle (or zenith angle). The 3 water vapor weighting functions — calculated using 12 UTC rawinsonde data from Anchorage (PANC) — provide information on the height and depth of the radiating layers in the vicinity of the storm  (below).

GOES-17 Water Vapor weighting function plots for Anchorage, Alaska [click to enlarge]

GOES-17 Water Vapor weighting function plots for Anchorage, Alaska [click to enlarge]

Eruption of Volcán de Fuego in Guatemala

November 19th, 2018 |

GOES-16 Upper-level (6.2 µm, top), Mid-level (6.9 µm, center) and Low-level (7.3 µm, bottom) Water Vapor images [click to play animation | MP4]

GOES-16 Upper-level (6.2 µm, top), Mid-level (6.9 µm, center) and Low-level (7.3 µm, bottom) Water Vapor images [click to play animation | MP4]

Following several days of unrest, there was a moderate eruption of Volcán de Fuego in Guatemala beginning around 0630 UTC on 19 November 2018. GOES-16 (GOES-East) Upper-level (6.2 µm), Mid-level (6.9 µm) and Low-level (7.3 µm) Water Vapor images (above) displayed a signature of the volcanic plume, which drifted slowly northward and eastward for several hours. Since the 7.3 µm spectral band is also affected by SO2 absorption, the longer-lasting signal in the Low-level Water Vapor imagery suggests the plume contained SO2 as well as ash (since the 7.3 µm band is also sensitive to SO2 absorption).

A GOES-16 multiispectral Ash/Dust Cloud Height product from the NOAA/CIMSS Volcanic Cloud Monitoring site (below) indicated that the ash reached a maximum height of 7-8 km in the general vicinity of the summit between 1100-1200 UTC. A low-altitude plume of ash was seen drifting westward at heights of 1-5 km.

GOES-16 Ash Height product [click to play animation | MP4]

GOES-16 Ash/Dust Cloud Height product [click to play animation | MP4]

Along the southern coast of Guatemala, a 1400 UTC METAR from San Jose (MGSJ) reported a surface visibility of 5 statute miles with Volcanic Ash in the vicinity (VCVA) as the current weather type (below). At that time, the GOES-16 Split Window (10.3-12.3 µm) Brightness Temperature Difference was highlighting  concentrations of middle-tropospheric volcanic ash (yellow enhancement) farther inland closer to the volcano.

GOES-16 Split Window difference (10.3-12.3 µm) image, with METAR surface reports [click to enlarge]

GOES-16 Split Window difference (10.3-12.3 µm) image, with METAR surface reports [click to enlarge]