Orographic standing wave cloud over the Mid-Atlantic states

December 17th, 2018 |

Topography + GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images, with pilot reports of turbulence [click to play MP4 animation]

Topography + GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images, with pilot reports of turbulence [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) showed the development of an orographic standing wave cloud — downwind of the Appalachian Mountains (topography) — over the Mid-Atlantic states on 17 December 2018. North of the wave cloud, widespread short-wavelength mountain waves were seen at lower elevations over and to the lee of the high terrain (even extending out over the Atlantic Ocean off the coast of New Jersey and New York). There were scattered pilot reports of turbulence across the region, with Severe turbulence being reported around 18 UTC and 00 UTC.

A comparison of GOES-16 Mid-level Water Vapor, Cloud Top Phase and Cloud Top Height products at 2007 UTC (below) indicated that this wave cloud was composed of Cirrus with maximum cloud tops around 30,000 feet.

GOES-16 Mid-level Water Vapor (6.9 µm), Cloud Top Phase and Cloud Top Height products [click to enlarge]

GOES-16 Mid-level Water Vapor (6.9 µm), Cloud Top Phase and Cloud Top Height products [click to enlarge]

GOES-16 Mid-level Water Vapor (6.9 µm) image at 2102 UTC, showing the orientation of a nortwest-southeast cross section [click to enlarge]

GOES-16 Mid-level Water Vapor (6.9 µm) image at 2102 UTC, showing the orientation of a northwest-southeast cross section [click to enlarge]

A GOES-16 Water Vapor image at 2102 UTC (above) showed the orientation of a northwest-to-southeast cross section of RUC40 model Relative Humidity, Wind Speed and Adiabatic Omega fields (below). In the middle of the cross section, a couplet of downward/upward motion aloft was seen over the Glen Allen VA area, with higher relative humidity values (shades of blue) above the 500 hPa pressure level corresponding to the wave cloud.

Northwest-southeast cross section of RUC40 model Relative Humidity, Wind Speed and Adiabatic Omega [click to enlarge]

Northwest-southeast cross section of RUC40 model Relative Humidity, Wind Speed and Adiabatic Omega [click to enlarge]

The standing wave cloud developed in the exit region of a branch of the polar jet stream that was diving southeastward across the Great Lakes — strong deceleration created an axis of deformation oriented from southwest to northeast (below), helping the stretch the wave cloud  feature as it slowly pivoted toward the southeast and along the coast. The strong downward motion component of the Omega couplet seen in the cross section was responsible for the relatively sharp upwind (northwest) edge exhibited by the wave cloud.

GOES-16 Mid-level Water Vapor (6.9 µm) images, with RAP40 model 250 hPa isotachs and deformation vectors [click to play animation | MP4]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with RAP40 model 250 hPa isotachs and deformation vectors [click to play animation | MP4]

A toggle between NOAA-20 VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images viewed using RealEarth (below) provided a detailed view of the wave cloud at 1825 UTC. The coldest cloud-top infrared brightness temperatures were around -50ºC (bright yellow enhancement), which was just above the 300 hPa pressure level on 00 UTC soundings at Roanoke/Blacksburg and Wallops Island Virginia.

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images [click to enlarge]

As pointed out by Jonathan Blaes (NWS Raleigh), these standing wave clouds can have an effect on surface temperatures beneath the feature:



A comparison of 1812 UTC Aqua MODIS Visible (0.65 µm), Infrared Window (11.0 µm), Near-Infrared “Cirrus” (1.37 µm) and Water Vapor (6.7 µm) images with plots of maximum temperatures on 17 December (below) revealed that high temperatures were confined to the upper 50s F beneath the wave cloud, in contrast to low 60s F on either side where incoming solar radiation was not diminished.

Aqua MODIS Visible (0.65 µm), Infrared Window (11.0 µm), Near-Infrared "Cirrus" (1.37 µm) and Water Vapor (6.7 µm) images, with plots of maximum temperatures on 17 December [click to enlarge]

Topography + Aqua MODIS Visible (0.65 µm), Infrared Window (11.0 µm), Near-Infrared “Cirrus” (1.37 µm) and Water Vapor (6.7 µm) images, with plots of maximum temperatures on 17 December [click to enlarge]

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.