Shear vortices over the Great Lakes and Ohio River Valley

June 7th, 2017 |

GOES-16 Water Vapor (6.2 µm, top; 6.9 µm, middle; 7.3 µm, bottom) images [click to play animation]

GOES-16 Water Vapor (6.2 µm, top; 6.9 µm, middle; 7.3 µm, bottom) images [click to play animation]

A well-defined train of wind shear vortices was revealed on GOES-16 Water Vapor images — Upper-level (6.2 µm), Mid-level (6.9 µm) and Lower-level (7.3 µm) — propagating westward over the Great Lakes on 07 June 2017 (above).

A larger-scale view using Mid-level 6.9 µm images (below) showed additional (and larger) vortices which were moving eastward over the Ohio River Valley. Pilot reports of turbulence are plotted on the water vapor images, and many of those reports appeared to be in the general vicinity of the vortices.

GOES-16 Water Vapor (6.9 µm) images [click to play animation]

GOES-16 Water Vapor (6.9 µm) images [click to play animation]

A 3-hour-interval Mid-Level Wind Shear product derived from GOES-13 (GOES-East) atmospheric motion vectors (AMVs) is shown below. An elongated cyclonic shear axis was present from the Northeast US to the Ohio River Valley, and the location of the water vapor vortices appeared to correspond to the wind shear gradients along the northern and southern edges of this axis.

GOES-13 Mid-Level Wind Shear product [click to enlarge]

GOES-13 Mid-Level Wind Shear product [click to enlarge]

Middle/upper-level deformation zone over the East Pacific Ocean?

May 23rd, 2017 |

GOES-15 Water Vapor (6.5 µm) images, with pilot reports of turbulence [click to play animation]

GOES-15 Water Vapor (6.5 µm) images, with pilot reports of turbulence [click to play animation]

An interesting linear feature appeared over the East Pacific Ocean on GOES-15 (GOES-West) Water Vapor (6.5 µm) images (above) on 23 May 2017, which at first glance immediately nominated it for the “What the heck is this?” blog category. A contrail was ruled out, since it was not oriented along a common or busy flight route — so potential large-scale dynamic processes were briefly investigated. Since the linear feature was perpendicular to the busy California/Hawaii flight route, pilot reports of turbulence are plotted on the water vapor images; two reports of light turbulence at altitudes of 33,000-34,000 feet (at 0918 and 1109 UTC) appeared to be close enough to have possibly been related to the linear feature.

GOES-15 Water Vapor (6.5 µm) images, with contours of satellite wind derived upper-level divergence [click to enlarge]

GOES-15 Water Vapor (6.5 µm) images, with contours of satellite wind derived Upper-Level Divergence [click to enlarge]

Satellite atmospheric motion vector (AMV) derived products such as Upper-Level Divergence (above) calculated at 3-hour intervals (source) revealed an area of divergence focused near the area of the linear satellite image feature — around 30º N, 140º W, at the center of the images — which reached its peak intensity at 12 UTC; this suggested that the feature may have formed along the axis of the sharp deformation zone between two upper-level lows over the East Pacific Ocean (mid/upper level winds | 200 hPa Vorticity product).

GOES-15 sounder Water Vapor (6.5 µm, top; 7.0 µm, middle; 7.5 µm, bottom) images [click to enlarge]

GOES-15 sounder Water Vapor (6.5 µm, top; 7.0 µm, middle; 7.5 µm, bottom) images [click to enlarge]

Unfortunately, this region was not within the view of Himawari-8 or GOES-16 (each of which provide 2-km resolution water vapor imagery at 3 atmospheric levels). However, the GOES-15 sounder instrument has 3 similar water vapor bands (above) — albeit at a more coarse 10-km spatial resolution at satellite sub-point — which showed the linear “deformation axis cloud signature” at all 3 levels of the atmosphere. The GOES-15 sounder water vapor weighting functions for a “typical” US Standard Atmosphere are shown below.

GOES-15 sounder Water Vapor band weighting functions [click to enlarge]

GOES-15 sounder Water Vapor band weighting functions [click to enlarge]

Aeroflot 270 encounters severe turbulence approaching Thailand

May 1st, 2017 |

Himawari-8 Water Vapor (6.9 µm) images, with plots of turbulence intensity along the flight path [click to enlarge]

Himawari-8 Water Vapor (6.9 µm) images, with plots of turbulence intensity along the flight path [click to enlarge]

Aeroflot Flight 270 encountered severe turbulence just off the coast of Myanmar (CNN | Aviation Herald) as it was flying toward its destination of Bangkok, Thailand on 01 May 2017. According to information from FlightRadar24 (flight map) and FlightAware (flight map | flight log) the time and location of the turbulence was around 23:54-23:56 UTC, near 16.4 N latitude, 97.4 East longitude, at the cruising altitude of 35,000 feet. Himawari-8 Water Vapor (6.9m) images (above; courtesy of Sarah Griffin, CIMSS) indicated that the aircraft made a slight course correction to fly over or through a small cluster of rapidly-developing thunderstorms — this convection was the likely cause of the turbulence.

Closer views of Himawari-8 Visible (0.64 µm), Water Vapor (6.9 µm) and Infrared Window (10.4 µm) images, centered at the location of the turbulence encounter (below), showed the rapid development of individual convective elements within this cluster of thunderstorms. Cloud-top infrared brightness temperatures were around -70º C on the 01 May / 00:10 UTC image.

Himawari-8 Visible (0.64 µm, top), Water Vapor (6.9 µm, middle) and Infrared Window (10.4 µm, bottom) images [click to enlarge]

Himawari-8 Visible (0.64 µm, top), Water Vapor (6.9 µm, middle) and Infrared Window (10.4 µm, bottom) images [click to enlarge]

Mountain waves over the Sierra Nevada

April 13th, 2017 |

GOES-16 7.3 µm (left), 6.9 µm (center) and 6.2 µm (right) Water Vapor images [click to play animation]

GOES-16 7.3 µm (left), 6.9 µm (center) and 6.2 µm (right) Water Vapor images [click to play animation]

 ** The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. **

A comparison of GOES-16 Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) revealed the presence of numerous mountain waves over parts of California and Nevada on 13 April 2017. The more pronounced of these waves were caused by strong southwesterly winds interacting with  higher terrain of the Sierra Nevada.

A 3-satellite comparison of GOES-15 (GOES-West), GOES-16 and GOES-13 (GOES-East) Water Vapor images (below) highlighted 2 factors that allowed better detection of these mountain waves by GOES-16 — improved spatial resolution (2 km for GOES-16 at satellite sub-point, vs 4 km for GOES-15/13), and a more direct satellite viewing angle (GOES-16 is positioned at 105ºW longitude, while GOES-15 is at 135ºW and GOES-13 is at 75ºW).

OES-15 (6.5 µm, left), GOES-16 (6.9 µm, center) and GOES-13 (6.5 µm, right) Water Vapor images [click to play animation]

GOES-15 (6.5 µm, left), GOES-16 (6.9 µm, center) and GOES-13 (6.5 µm, right) Water Vapor images [click to play animation]

Note that there were no Visible cloud features associated with many of the waves seen on Water Vapor imagery (below); encounters of Clear Air Turbulence (CAT) often occur with these types of mountain waves, as seen by scattered pilot reports of moderate turbulence (plotted as Category 4).

GOES-16 Visible (0.64 µm, left) and Water Vapor (6.9 µm, right) images, with pilot reports of turbulence [click to play animation]

GOES-16 Visible (0.64 µm, left) and Water Vapor (6.9 µm, right) images, with pilot reports of turbulence [click to play animation]