Cloud-top waves producing turbulence north of Hawai’i

February 6th, 2019 |
GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images [click to play MP4 animation]

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

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

Transient pockets of cloud-top waves were evident on GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) north of Hawai’i on 06 February 2019. Some of the waves were located along the tops of convective cloud features, while others appeared to be randomly distributed.

Plots of rawinsonde data from Lihue, Hawai’i (below) showed that winds within the middle to upper troposphere had a general westerly component — so these mesoscale cloud-top wave features were oriented perpendicular to the flow.

Plots of rawinsonde data from Lihue, Hawai'i [click to enlarge]

Plots of rawinsonde data from Lihue, Hawai’i [click to enlarge]

There was only 1 pilot report of turbulence within the broad region exhibiting these waves, occurring at 2304 UTC at an altitude of 33,000 feet — and this appeared to coincide with a discrete wave packet that was propagating eastward (below).

GOES-17 Upper-level Water Vapor (6.2 µm) images within 30 minutes of the 2304 UTC pilot report of turbulence [click to enlarge]

GOES-17 Upper-level Water Vapor (6.2 µm) images within 30 minutes of the 2304 UTC pilot report of turbulence [click to enlarge]

While the more robust wave packets could also be seen in GOES-17 “Clean” Infrared Window (10.3 µm) images (below), their complete areal coverage was more obvious in the Water Vapor imagery — particularly where the wave features were more subtle.

GOES-17 Upper-level Water Vapor (6.2 µm) and “Clean” Infrared Window (10.3 µm) images at 2302 UTC [click to enlarge]

Aviation advisories for Significant Weather (SIGWX) had been issued for that region (below), which included a Moderate risk for Clear Air Turbulence (CAT) from 28,000-39,000 feet and the possibility of isolated/embedded Cumulonimbus (CB) clouds with tops to 38,000 feet, along with a west-northwest high-level jet stream from 290º at 90 knots. The pilot report of turbulence at 33,000 feet included winds from 261º at 81 knots.

GOES-17 Upper-level Water Vapor (6.2 µm) image, with plots of aviation Significant Weather advisories [click to enlarge]

GOES-17 Upper-level Water Vapor (6.2 µm) image, with plots of aviation Significant Weather advisories that were in effect at that time [click to enlarge]

The cloud-top waves were also seen in a sequence of VIIRS Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP, viewed using RealEarth (below).

VIIRS Infrared Window (11.45 µm) images from NOAA-20 (at 2230 and 0030 UTC) and Suomi NPP (at 2320 UTC) [click to enlarge]

VIIRS Infrared Window (11.45 µm) images from NOAA-20 (at 2230 and 0030 UTC) and Suomi NPP (at 2320 UTC) [click to enlarge]