Gravity waves near Guadalupe Island

March 15th, 2018 |

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

GOES-16 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images [click to play 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 an interesting packet of gravity waves in the vicinity of Guadalupe Island (west of Baja California) on 15 March 2018. The mechanism forcing these waves was not entirely clear, making it a suitable candidate for the “What the heck is this?” blog category.

A similar animation of GOES-16 “Red” Visible (0.64 µm), Mid-level Water Vapor (6.9 µm) and Upper-level Water Vapor (6.2 µm) images (below) did show some smaller-scale waves on Visible imagery within the marine boundary layer stratocumulus cloud field, but they did not appear to exhibit a direct correlation with the higher-altitude waves seen in the Water Vapor imagery. Surface winds were from the northwest at 10-15 knots, as a dissipating cold front was stalled over the region.

GOES-16

GOES-16 “Red” Visible (0.64 µm, left), Mid-level Water Vapor (6.9 µm, center) and Upper-level Water Vapor (6.2 µm, right) images [click to play animation]

A larger-scale view of Mid-level Water Vapor (6.9 µm) images (below) showed that these waves were located to the north of a jet streak axis — denoted by the sharp dry-to-moist gradient (yellow to blue enhancement) stretching from southwest to northeast as it moved over Baja California.

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

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

GOES-15 (GOES-West) Water Vapor (6.5 µm) images with overlays of upper-tropospheric atmospheric motion vectors and contours of upper-tropospheric divergence (below) indicated that Guadalupe Island was located within the “dry delta” signature often associated with a jet stream break — the inflection point between 2 strong jet streaks within a sharply-curved jet stream. Upper-tropospheric winds were from the west/northwest, with upper-tropospheric convergence seen over the region of the gravity waves.

GOES-15 Water Vapor (6.5 µm) images, with water vapor wind vectors [click to enlarge]

GOES-15 Water Vapor (6.5 µm) images, with atmospheric motion vectors [click to enlarge]

GOES-15 Water Vapor (6.5 µm) images, with contours of upper-tropospheric convergence [click to enlarge]

GOES-15 Water Vapor (6.5 µm) images, with contours of upper-tropospheric convergence [click to enlarge]

An early morning Aqua MODIS Water Vapor (6.7 µm) image with NAM80 contours of 250 hPa wind speed (below) showed the two 90-knot jet streaks on either side of the jet stream break — it could be that speed convergence due to rapidly decelerating air within the exit region of the western jet streak was a possible forcing mechanism of the gravity waves seen on the GOES-16 Water Vapor imagery.

Aqua MODIS Water Vapor (6.7 µm) image, with NAM80 contours of 250 hPa wind speed [click to enlarge]

Aqua MODIS Water Vapor (6.7 µm) image, with NAM80 contours of 250 hPa wind speed [click to enlarge]

Severe turbulence over Hawai’i

January 12th, 2018 |

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

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

Numerous pilot reports of moderate to severe turbulence were received over the Hawai’i area on 12 January 2018 — and GOES-15 (GOES-West) Water Vapor (6.5 µm) images (above; also available as an MP4) showed the development of a quasi-stationary gravity wave train over the northwestern portion of the island chain which appeared to be associated with many of these pilot reports.

HNL UA /OV 2115N16010W/TM 2241/FL320/TP B767/TB CONT MOD TURB

HNL UUA /OV 2115N16048W/TM 2255/FL340/TP H/B747/TB MOD-SEV TURB

HNL UUA /OV BOARD/TM 2350/FL370/TP H/B772/TB SEVERE TURB

PHNL UUA /OV 2443N 15516W /TM 2358 /FL370 /TP B737 /TB SEV 370 /RM ZOA CWSU AWC-WEB

In spite of the large satellite viewing angle, these waves were also very evident on Himawari-8 Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (below; also available as an MP4). The 3 Water Vapor bands on the Himawari AHI are nearly identical to the 3 Water Vapor bands on the GOES-R series ABI.

Himawari-8 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and 6.2 µm, right) Water Vapor images, with hourly pilot reports of turbulence [click to play animation]

Himawari-8 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images, with hourly pilot reports of turbulence [click to play animation]

A toggle between 1-km resolution Terra MODIS Water Vapor (6.7 µm), Infrared Window (11.0 µm) and 250-meter resolution true-color Red-Green-Blue RGB images at 2106 UTC on 12 January (below) showed that no high-altitude clouds were associated with the gravity wave features — thus, these aircraft encounters were examples of Clear Air Turbulence (CAT).

Terra MODIS Water Vapor (6.7 µm) and True-color RGB images [click to enlarge]

Terra MODIS Water Vapor (6.7 µm), Infrared Window (11.0 µm) and true-color RGB images [click to enlarge]

A color-enhanced version of the Aqua MODIS Water Vapor (6.7 µm) image at 0014 UTC on 13 January is shown below (courtesy of Jordan Gerth, CIMSS).

An AWIPS screen capture (below, courtesy of Robert Bohlin, NWS Honolulu and Jordan Gerth, CIMSS) displays a High Pass filter product along with the 3 individual Himawari-8 Water Vapor band images at 0120 UTC on 13 January.

Upper-level Water Vapor (6.2 µm, upper right), Mid-level Water Vapor (6.9 µm, lower left) and Lower-level Water Vapor (7.3 µm, lower right) images [click to enlarge]

Himawari-8 High Pass filter product (6.9 µm, upper left), Upper-level Water Vapor (6.2 µm, upper right), Mid-level Water Vapor (6.9 µm, lower left) and Lower-level Water Vapor (7.3 µm, lower right) images [click to enlarge]

It bears mention that the rawinsonde data from Lihue, Hawai’i at 0000 UTC on 13 January (below) indicated significant wind shear (both speed and directional) within the 200-300 hPa layer (text listing) — the layer in which many of the turbulence reports were found.

Rawinsonde data from Lihue, Hawai'i at 00 UTC on 13 January [click to enlarge]

Rawinsonde data from Lihue, Hawai’i at 00 UTC on 13 January [click to enlarge]

The packet of gravity waves was directly over Lihue (red asterisk) at that time (below).

GOES-15 Water Vapor (6.5 µm) image at 0000 UTC on 13 January, with pilot reports of turbulence plotted. The red asterisk denotes the location of Lihue [click to enlarge]

GOES-15 Water Vapor (6.5 µm) image at 0000 UTC on 13 January, with pilot reports of turbulence plotted. The red asterisk denotes the location of Lihue [click to enlarge]

A prescribed burn in Montana, as viewed from GOES-15, GOES-16 and GOES-13

January 2nd, 2018 |

GOES-15 (left), GOES-16 (center) and GOES-13 (right) Shortwave Infrared (3.9 µm) images, with plots of hourly surface reports [click to play MP4 animation]

GOES-15 (left), GOES-16 (center) and GOES-13 (right) Shortwave Infrared (3.9 µm) images, with plots of hourly surface reports [click to play MP4 animation]

A prescribed burn the SureEnough fire — in central Montana was viewed by GOES-15 (GOES-West), GOES-16 (GOES-East) and GOES-13 Shortwave Infrared (3.9 µm) imagery on 02 January 2018. The images are shown in the native projection for each of the 3 satellites.

Due to the improved spatial resolution of the GOES-16 3.9 µm Shortwave Infrared band (2 km at satellite sub-point, vs 4 km for GOES-15 and GOES-13) and the more frequent image scans (routinely every 5 minutes over CONUS for GOES-16), an unambiguous thermal anomaly or fire “hot spot” was first evident on GOES-16 at 1707 UTC, just southeast of Lewistown (station identifier KLWT). The GOES-16 fire thermal signature was also hotter (black pixels) compared to either GOES-15 or GOES-13.

Eruption of the Bezymianni volcano

December 20th, 2017 |

Himawari-8 Ash Cloud Height product [click to play animation]

Himawari-8 Infrared Window (10.4 µm) images and Ash Cloud Height product [click to play animation]

The Bezymianni volcano on Russia’s Kamchatka Peninsula erupted at 0345 UTC on 20 December 2017 — an animation of Himawari-8 Infrared Window (10.4 µm) images and retrieved Ash Cloud Height product from the NOAA/CIMSS Volcanic Cloud Monitoring site (above) indicated that the ash reached heights of 18 km (the Tokyo VAAC estimated the ash height to be 50,000 feet or 15.2 km).

An oblique view using GOES-15 (GOES-West) Visible (0.63 µm) images (below) provided a different perspective of the volcanic cloud immediately following the eruption. The surface report from Shemya (PASY), located in the far western portion of Alaska’s Aleutian Islands, is plotted in the lower right corner of the images.

GOES-15 Visible (0.63 µm) images [click to enlarge]

GOES-15 Visible (0.63 µm) images [click to enlarge]