Tropical Depression Flossie near Hawai’i

August 5th, 2019 |

GOES-17

GOES-17 “Red” Visible (0.64 µm), “Clean” Infrared Window (10.35 µm) and Upper-level Water Vapor (6.2 µm) images [click to play animation | MP4]

An animation that cycles through GOES-17 (GOES-West) “Red” Visible (0.64 µm), “Clean” Infrared Window (10.35 µm) and Upper-level Water Vapor (6.2 µm) images (above) showed Tropical Depression Flossie just northeast of Hawai’i on 05 August 2019. Note that (1) the exposed low-level circulation center (LLCC) was very apparent in the visible imagery, (2) deep convection offset to the east/northeast of the LLCC exhibited cloud-top infrared brightness temperatures as cold as -83ºC , and (3) a series of gravity waves were propagating westward away from the convection, moving toward Hawai’i.

GOES-15 Infrared imagery and deep-layer wind shear data from the CIMSS Tropical Cyclones site (below) showed that the tropical cyclone was in an environment of strong shear, which was responsible for the displacement between the exposed LLCC and the convection. In addition to the wind shear, the weakening trend of the system was also due to its motion over cold Sea Surface Temperatures and low Ocean Heat Content.

GOES-15 Infrared Window (10.7 µm) images, with contours and streamlines of deep-layer wind shear [click to enlarge]

GOES-15 Infrared Window (10.7 µm) images, with contours and streamlines of deep-layer wind shear at 18 UTC [click to enlarge]