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]

Aerolineas Argentinas Flight 1303 encounters severe turbulence over South America

October 18th, 2018 |

ARG-1303 flight path (from FlightAware.com) [click to enlarge]

ARG-1303 flight path (from FlightAware.com) [click to enlarge]

Aerolineas Argentinas Flight 1303 encountered severe turbulence while flying from Miami, Florida to Buenos Aires, Argentina on 18 October 2018 (media report). The flight track (above) and flight log data indicated that the aircraft rapidly gained then lost over 2000 feet in altitude around 1823 UTC while over far western Brazil.

GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images (below) showed a cluster of rapidly-developing thunderstorms at that location and time (within the red circle) — cloud-top infrared brightness temperatures were colder than -80ºC (shades of violet).

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

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

Leeside frontal gravity wave moves southward across the Plains

October 4th, 2018 |
GOES-17 Upper-level Water Vapor (6.2 µm) images, with surface frontal analyses [click to play MP4 animation]

GOES-17 Upper-level Water Vapor (6.2 µm) images, with surface frontal analyses [click to play MP4 animation]

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

A strong cold front (surface analyses | max/min temperatures) moved southward across the Plains states during the 03 October – 04 October 2018 period — and GOES-17 Upper-level Water Vapor (6.2 µm) images (above) revealed a distinct leeside frontal gravity wave as it propagated from southern Colorado and southern Kansas at 05 UTC to southeastern New Mexico and the southern Texas Panhandle by 20 UTC. Thunderstorms formed along the stalled residual wave along the New Mexico/Texas border after 1930 UTC.

Pilot reports of high-altitude “mountain wave” turbulence (below) were seen at 1559 and 1721 UTC, along the north-to-south oriented portion of the gravity wave that had become stationary over eastern New Mexico.

GOES-17 Upper-level Water Vapor (6.2 µm) images, with pilot reports of turbulence [click to enlarge]

GOES-17 Upper-level Water Vapor (6.2 µm) images, with pilot reports of turbulence [click to enlarge]

A 1-km resolution Aqua MODIS Water Vapor (6.7 µm) image at 0807 UTC (below) showed detailed gravity wave structure over Oklahoma.

Aqua MODIS Water Vapor (6.7 µm) image [click to enlarge]

Aqua MODIS Water Vapor (6.7 µm) image [click to enlarge]

A 3-panel comparison of GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images with plots of surface wind barbs (below) showed how the winds changed to northerly/northeasterly as the cold front passed.

GOES-17 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images, with plots of surface wind barbs [click to play MP4 animation]

GOES-17 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images, with hourly plots of surface wind barbs [click to play MP4 animation]

Additional images of this event can be found on the Satellite Liaison Blog.

Upper-tropospheric gravity waves in the wake of a decaying MCS

September 1st, 2018 |

GOES-16 Upper-level Water Vapor (6.2 µm) images [click to play MP4 animation]

GOES-16 Upper-level Water Vapor (6.2 µm) images [click to play MP4 animation]

A series of large Mesoscale Convective Systems (MCS) developed across Nebraska and Iowa during the nighttime hours before sunrise on 01 September 2018, which produced large hail and damaging winds (SPC storm reports). Storm-scale anticyclonic outflow aloft around the periphery of the decaying convection acted as a short-term barrier to the upstream southwesterly winds within the middle/upper troposphere, creating quasi-stationary gravity waves along their rear (westward) edges which persisted for several hours. These waves were most evident over eastern Nebraska and northeastern Kansas on GOES-16 Upper-level Water Vapor (6.2 µm) images (above).

6.2 µm Water Vapor images with plots of GOES-16 Derived Motion Winds (below) intermittently showed these high-altitude anticyclonic winds along the western edges of decaying convection — for example, at 0842 UTC, 0922 UTC, 0957 UTC, 1127 UTC, 1212 UTC and 1312 UTC.

GOES-16 Upper-level Water Vapor (6.2 µm) images, with plots of Derived Motion Winds [click to play MP4 animation]

GOES-16 Upper-level Water Vapor (6.2 µm) images, with plots of Derived Motion Winds [click to play MP4 animation]

The quasi-stationary waves appeared to coincide with a few pilot reports of high-altitude turbulence: Clear Air Turbulence (CAT) was mentioned over northeastern Kansas at 37,000 feet and 39,000 feet, and “mountain wave action” was reported over southeastern Nebraska at 43,000 feet.

Pilot reports of turbulence [click to play animation]

Pilot reports of turbulence [click to play animation]

Higher resolution views of the convection were provided by VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images from Suomi NPP at 0755 UTC and NOAA-20 at 0845 UTC (below). With ample illumination from the Moon (in the Waning Gibbous phase, at 67% of Full), the “visible image at night” capability of the Day/Night Band was well-demonstrated. The coldest cloud-top infrared brightness temperature associated with the MCS in western Iowa was -84ºC — and the effect of a similar “blocking wave” along the western/northwestern edge of that storm could be seen, which was effectively eroding the approaching high-altitude anvil cloud material from the Nebraska MCS. Note that the 0845 UTC NOAA-20 VIIRS images are incorrectly labeled as Suomi NPP.

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images, with plots of SPC storm reports [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images, with plots of SPC storm reports [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]