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Hurricane Willa

By Scott Bachmeier •

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images (above) showed Willa during the 48 hours that it rapidly intensified (ADT | SATCON) from a Tropical Storm at 15 UTC on 20 October to a Category 5 Hurricane at 15 UTC on 22 October 2018. Willa  — which became the third Category 5 hurricane of the 2018 season in the northeast Pacific basin (east of 180º longitude) — formed and had been moving over very warm water, with Sea Surface Temperatures of 29-30ºC. Deep-layer wind shear was also light during the 15 hour period lead up to Category 5 intensity.

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (below; courtesy of William Straka, CIMSS) showed Category 4 Willa off the west coast of Mexico at 0852 UTC on 22 October. The Moon was in the Waxing Gibbous phase (at 95% of Full), providing ample illumination for a “visible image at night” using the VIIRS Day/Night Band. Intricate cloud-top gravity waves were seen propagating radially outward from the storm center.

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]

1-minute Mesoscale Domain Sector GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window images (below) revealed the small eye of the Category 5 hurricane after sunrise, with multiple convective bursts that erupted along the western edge of the eyewall. A continuous series of storm-top waves could be seen propagating radially outward away from the eye on Visible imagery. However, the eye eventually became cloud-filled as Willa began to undergo an eyewall replacement cycle — the formation of a larger-diameter outer eyewall was evident on the MIMIC-TC product — and weaken to a Category 4 intensity.

GOES-16 "Red" Visible (0.64 µm) and "Clean" Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.3 µm, right) images [click to play MP4 animation]

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

GOES-17 “Red” Visible (0.64 µm) images (below) provided a more direct view of the storm, since the satellite was positioned over the Equator at 89.5º W longitude while in its post-launch testing location.

GOES-17

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

October 23 is the last full day, for a while, to use GOES-16 and GOES-17 data to produce stereoscopic imagery. GOES-17 is set to cease data transmission on 24 October around 1500 UTC as it starts its motion towards its operational GOES-West position of 137.2º W Longitude. The animation below, starting at 1307 UTC on 23 October, (click here for an animated gif) shows the occasional appearance of an eye within the storm center on 23 October as it approached the coast. To view the image in three dimensions, cross your eyes until 3 images are apparent, then focus on the image in the middle.

GOES-16 "Red" Visible (0.64 µm) and "Clean" Infrared Window (10.3 µm) images [click to play MP4 animation]

“Red” Visible (0.64 µm) images from GOES-16 (right) and GOES-17 (left) [click to play mp4 animation]

Categories: GOES-16, GOES-17, Satellite winds, Suomi NPP, Tropical cyclones, VIIRS