Mountain waves and a banner cloud over the Northeast US

October 25th, 2018 |

GOES-16 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-16 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-16 (GOES-East) Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) revealed 2 types of terrain-induced features — mountain waves, and a banner cloud (reference 1| | reference 2) — across the Northeast US on 25 October 2018.

The mountain waves were more widespread and long-lasting, while the banner cloud formed to the lee of the White Mountains in New Hampshire and Maine (extending downwind as far as 100 miles). Mountain waves are often associated with turbulence; pilot reports of Moderate turbulence appeared in the vicinity of mountain waves over far eastern New York at 1202 UTC1417 UTC and 1742 UTC. A toggle between a 1009 UTC 6.9 µm Water Vapor image with the banner cloud and Topography is shown below; a later comparison at 1802 UTC showing widespread mountain waves can be seen here.

GOES-16 Mid-level Water Vapor (6.9 µm) image + Topography [click to enlarge]

GOES-16 Mid-level Water Vapor (6.9 µm) image + Topography [click to enlarge]

Strong winds were prevalent across that region in the wake of a storm centered over the Gulf of Saint Lawrence at 12 UTC — this storm produced as much as 5-12 inches of snow on the previous day in Vermont, New Hampshire and Maine:  NWS Burlington | NWS Gray | NWS Caribou — and the approach of a mid/upper-level jet streak (below). Winds gusted to 74 knots at Mount Washington, New Hampshire.

GOES-16 Mid-level (6.9 µm) Water Vapor images, with RAP40 wind isotachs at 300 hPa [click to play animation | MP4]

GOES-16 Mid-level (6.9 µm) Water Vapor images, with RAP40 wind isotachs at 300 hPa [click to play animation | MP4]

A comparison of 1-km resolution Aqua MODIS Water Vapor (6.7 µm) and Infrared Window (11.0 µm) images at 0648 UTC (below) showed that there were some areas where the mountain waves existed in clear air, with no clouds as an indicator of wave presence (for example, over western Maine).

 Aqua MODIS Water Vapor (6.7 µm) and Infrared Window (11.0 µm) images [click to enlarge]

Aqua MODIS Water Vapor (6.7 µm) and Infrared Window (11.0 µm) images [click to enlarge]

A general lack of wave clouds over western Maine around that time was also evident on VIIRS Day/Night Band (0.7 µm) images (below) from Suomi NPP (at 0603 UTC) and NOAA-20 (at 0650 UTC). In this case, with ample illumination from the Moon — in the Waning Gibbous phase, at 99% of Full — the “visible image at night” capability of the Day/Night Band was fully realized.

Suomi NPP (0603 UTC) and NOAA-20 (0650 UTC) VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

Suomi NPP (0603 UTC) and NOAA-20 (0650 UTC) VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

Regarding the banner cloud which was present from about 0830-1700 UTC, the GOES-16 Cloud Top Height  and Cloud Top Phase products (below) indicated that the tops of the feature were around 24,000-25,000 feet (or 7.6 km, where the temperature was -43.1ºC on the 12 UTC Gray ME sounding: plot | text) and composed of ice crystals.

GOES-16 Cloud Top Height product [click to play animation | MP4]

GOES-16 Cloud Top Height product [click to play animation | MP4]

GOES-16 Cloud Top Phase product [click to play animation | MP4]

GOES-16 Cloud Top Phase product [click to play animation | MP4]