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Actinoform cloud produces light rain in Hawai`i

By Scott Bachmeier •

GOES-18 Nighttime Microphysics RGB and daytime True Color RGB images [click to play MP4 animation]

GOES-18 (GOES-West) Nighttime Microphysics RGB and daytime True Color RGB images from the CSPP GeoSphere site (above) displayed the cyclonic circulation of an actinoform cloud feature as it moved westward toward Hawai`i on 03 July 2023.

A closer view using GOES-18 “Red” Visible (0.64 µm) and Day Cloud Phase Distinction RGB images (below) showed the actinoform cloud as it approached the island of Oahu. 15-minute METAR surface reports revealed that one of the actinoform’s “spiral bands” produced brief (20-30 minute) periods of light rain and/or drizzle — first at Kaneohe Bay (PHNG) beginning around 0201 UTC, and then at Wheeler Air Force Base (PHHI) beginning around 0331 UTC — as it passed over the island.

GOES-18 “Red” Visible (0.64 µm) and Day Cloud Phase Distinction RGB images [click to play animated GIF | MP4]

According to the Day Cloud Phase Distinction RGB Quick Guide, shades of green generally denote cloud tops that are beginning to glaciate — but in this case, a GOES-18 Day Cloud Phase Distinction RGB image at 2301 UTC (below) included cursor-sampled values of RGB components along with the corresponding Cloud Top Phase and Cloud Top Height derived products at that same location. Since cloud-top 10.3 µm infrared brightness temperatures at that cursor location were quite warm (15.27ºC), derived products indicated that the Cloud Top Phase was Water (as opposed to a Mixed water/ice phase, which is often associated with cloud features exhibiting similar shades of green in this particular RGB).

GOES-18 Day Cloud Phase Distinction RGB image at 2301 UTC, with cursor-sampled values of RGB components along with the corresponding Cloud Top Phase and Cloud Top Height derived products [click to enlarge]

AWIPS Users: a variety of GOES RGB types combined with Derived Product Readouts is available under the Satellite -> Local Menu Items menu (below).

GOES RGBs with Derived Product Readouts menu structure [click to enlarge]

Categories: GOES-18, Level 2 Product Readouts, Red-Green-Blue (RGB) images