Hurricane Eta in the Caribbean Sea

November 2nd, 2020 |

GOES-16 “Clean” Infrared Window (10.35 µm) images (with and without an overlay of GLM Flash Extent Density) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images (with and without an overlay of GLM Flash Extent Density) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm), GLM Flash Extent Density and “Red” Visible (0.64 µm) images (above) showed Hurricane Eta as it was rapidly intensifying from a Category 2 to a Category 4 storm on 02 November 2020. For a few hours there was notable lightning activity within the inner eyewall of Eta.

GOES-16 Longwave Infrared (11.2 µm) images, with contours of 02 UTC deep-layer wind shear from the CIMSS Tropical Cyclones site (below) showed that the hurricane was moving through an environment of low shear, which favored intensification.

GOES-16 Longwave Infrared (11.2 µm) images, with contours of 18 UTC deep-layer wind shear [click to enlarge]

GOES-16 Longwave Infrared (11.2 µm) images, with contours of 02 UTC deep-layer wind shear [click to enlarge]

GOES-16 Infrared – Water Vapor Brightness Temperature Difference images (below) indicated that cloud tops within much of the central dense overcast surrounding the eye were likely above the local tropopause.

GOES-16 Infrared - Water Vapor Difference images [click to enlarge]

GOES-16 Infrared – Water Vapor Difference images [click to enlarge]

===== 03 November Update =====

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (credit: William Straka, CIMSS) [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (credit: William Straka, CIMSS) [click to enlarge]

A toggle between NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (above) displayed Eta at 0729 UTC. Illumination from the Moon — in the Waning Gibbous phase, at 93% of Full — provided a distinct visible image at night.

Eta made landfall along the Caribbean coast of Nicaragua as a Category 4 hurricane around 2100 UTC;1-minute GOES-16 Infrared and Visible images during the period 1000-2100 UTC (below) showed that the overall appearance of Eta had deteriorated somewhat compared to the previous day, with warming cloud-top infrared brightness temperatures and a cloud-filled eye. There was no GOES-16 GLM-detected lightning activity during those 11 hours leading up to landfall.

GOES-16 “Clean” Infrared Window (10.35 µm) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

Re-suspended ash from the Novarupta eruption in Alaska

November 2nd, 2020 |

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

GOES-17 Dust RGB and “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) and Dust Red-Green-Blue (RGB) images (above) showed the signature of a plume of re-suspended volcanic ash — originating from the region of the Novarupta volcano in Alaska — being transported southeastward across the Shelikof Strait toward Kodiak Island on 02 November 2020. The 1912 eruption of Novarupta left a very deep deposit of volcanic ash, which occasionally gets lofted by strong northwesterly terrain-enhanced winds in the Autumn months (before snowfall covers the ash). Another interesting aspect was a mesolow which had formed in the Shelikof Strait — it appeared as if some of the ash plume was becoming entrained into the western edge of the mesolow’s circulation. Note that Buoy 46077 was located near the center of this meslow, which led to frequent changes in the wind direction.

VIIRS True Color RGB images from NOAA-20 and Suomi NPP viewed using RealEarth (below) provided 2 high-resolution snapshots of the ash plume. The tan-colored surface source region of the Novarupta ash was evident in these True Color images.

VIIRS True Color RGB images from NOAA-20 and Suomi NPP [click to enlarge]

VIIRS True Color RGB images from NOAA-20 and Suomi NPP [click to enlarge]

Goni in the South China Sea

November 2nd, 2020 |

Himawari-8 Target (every 2.5 minutes) Infrared (10.41 µm) and visible (0.64 µm) Imagery, 0122 to 1352 UTC on 2 November 2020 (Click to animate)

Typhoon Goni hit the Phillipines as a major typhoon on 31 October.  Since then, an increase in shear and the topography of Luzon have both weakened the storm significantly.   The mp4 animation above (click here as an mp4) shows 2.5-minute Himawari-8 Target imagery Infrared (10.41 µm, left) and visible (0.64 µm, right) imagery from 0122 through 1352 UTC on 2 November.  Although significant convection continues, especially after dark near the center, suggesting strengthening, strong easterly shear, shown below, from this website, is present.  Convection in the animation above is displaced to the west of the surface circulation, as expected given the shear.  In addition, sea surface temperatures become progressively cooler along the projected track.  Environmental factors do not favor significant strengthening.

Past and predicted storm path/intensity for Goni in the South China Sea, along with 1200 UTC 2 November Tropospheric Shear (850-200 mb), click to enlarge)

A two-day animation of MIMIC Total Precipitable water (imagery from this ftp site) shows the change in circulation as Goni moved over Luzon.

MIMIC Total Precipitable Water, 0000 UTC on 31 October through 0000 UTC 2 November 2020 (Click to animate)