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]

Using GLM data to monitor convective development

March 15th, 2018 |

GOES-16 Band 13 (10.3) “Clean Window” Infrared Imagery, 0815-1400 UTC, and GLM Group Density.

Strong convection developed on 15 March over the Pampas of Argentina and Uruguay, as shown above. Full Disk imagery is available only every 15 minutes, and considerable convective development is possible during the 15 minutes between scans. If a Mesoscale sector with 1-minute imagery is not over convection, Geostationary Lightning Mapper (GLM) data from GOES-16 can be used to monitor convection during the time interval between Full Disk Scans: GLM updates every minute. The 18-minute animation below (from Real Earth) includes 3 Full-Disk images and every-minute updates of GLM Group Density. Group Density between 0700-0715 shows no sign of diminishing.  It should not surprise that cloud-tops continue to expand and cool when the 0715 UTC ABI Imagery appears at the end of the loop.

Note:  When GOES-16 or GOES-17 (GOES-S achieved Geostationary Orbit on 12 March and became GOES-17) are operating under Mode 6 (vs. the present-day Mode 3), Full Disk imagery will be available every ten minutes vs. current fifteen minutes.

GOES-16 Band 13 (10.3) “Clean Window” Infrared Imagery, and GLM Group Density 0658-0717 UTC.