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 weather in the Mid-South, and heavy snow in the Upper Midwest

February 24th, 2018 |

GOES-16 Mid-level Water Vapor (6.9 µm), with hourly plots of surface weather type [click to play Animated GIF | MP4 also available]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly plots of surface weather type [click to play Animated GIF | MP4 also available]

GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) showed the flow of moisture from the lower Mississippi Valley into the Ohio Valley on 24 February 2018 — this fueled the development of flooding rainfall and severe thunderstorms (for more details, see the Satellite Liaison Blog). A special 21 UTC sounding from Little Rock AR indicated 37.3 mm or 1.47 inches of Total Precipitable Water (TPW) within the atmospheric column.

1-minute interval Mesoscale Sector GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (below) revealed the development of a small supercell thunderstorm just north of the Kentucky/Tennessee border — this storm produced an EF-2  tornado that was responsible for 1 fatality (NWS Louisville damage survey). This (along with another in Arkansas) was the first US tornado-related death in 283 days (a new record in terms of length), with the last occurring in Wisconsin on 16 May 2017.

GOES-16 "Red" Visible<em> (0.64 µm, left)</em> and "Clean" Infrared Window <em>(10.3 µm, right)</em> images, with hourly surface reports plotted in yellow and SPC storm reports plotted in red [click to play Animated GIF | <a href="http://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2018/02/180224_goes16_visible_infrared_spc_storm_reports_KY_TN_severe_anim.mp4"><strong>MP4</strong></a> also available]

GOES-16 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.3 µm, right) images, with hourly surface reports plotted in yellow and SPC storm reports plotted in red [click to play Animated GIF | MP4 also available]

Farther to the north, bands of elevated convection (oriented generally west to east) developed across Minnesota and Wisconsin, as seen in GOES-16 Visible (0.64 µm) and Infrared Window (10.3 µm) images (below). Snowfall rates were 1-2 inches per hour at some locations, with many storm total accumulations of 7 to 9 inches. Note the small-scale “ripple structure” that was present along the tops of many of these convective bands (orthogonal to the long axis of each band).

GOES-16

GOES-16 “Red” Visible (0/64 µm) images [click to play animation]

GOES-16

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

Comparisons of Terra and Aqua MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images (below) also showed these bands of elevated convection that helped to enhance snowfall rates. The layer of instability aloft was evident on the 00 UTC sounding from Chanhassen MN.

Terra MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images [click to enlarge]

Terra MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images [click to enlarge]

Aqua MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images [click to enlarge]

Aqua MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images [click to enlarge]

Ice motion in the Great Lakes

February 14th, 2018 |
GOES-16 "Red" Visible (0.64 µm) images, with hourly plots of surface wind barbs in cyan and wind gusts (kn0ts) in red (click to play Animated GIF)

GOES-16 “Red” Visible (0.64 µm) images, with hourly plots of surface wind barbs in cyan and wind gusts (knots) in red (click to play Animated GIF | MP4 also available)

GOES-16 “Red” Visible (0.64 µm) images showed ice motion in the western Great Lakes (above) and the central/eastern Great Lakes (below) on 14 February 2018. A flow of southwesterly winds at the surface was helping to move the lake ice toward the northeast. With increasing winds and a return of warmer air, the ice coverage of Lake Superior, Lake Michigan and Lake Huron had decreased slightly from their seasonal peaks a few days earlier — while the ice coverage for Lake Erie remained neared its seasonal peak. The total ice coverage for the Great Lakes as a whole was 57.9% on this day.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly plots of surface wind barbs in cyan and wind gusts (knots) in red (click to play Animated GIF | MP4 also available)

Closer views of southern Lake Michigan and southern Lake Huron are shown below. In Lake Huron, small ice floes can be seen breaking away from the land fast ice.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly plots of surface wind barbs in cyan and wind gusts (knots) in red (click to play Animated GIF | MP4 also available)

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly plots of surface wind barbs in cyan and wind gusts (knots) in red (click to play Animated GIF | MP4 also available)

250-meter resolution Terra and Aqua MODIS True-color Red-Green-Blue (RGB) images from the MODIS Today site (below) provided more detailed views of the ice floes in southern Lake Michigan, southern Lake Huron and western Lake Erie. The Aqua satellite overpass was about 90 minutes later than that of Terra.

Terra and Aqua MODIS True-color RGB images of southern Lake Michigan [click to enlarge]

Terra and Aqua MODIS True-color RGB images of southern Lake Michigan [click to enlarge]

Terra and Aqua MODIS True-color RGB images of southern Lake Huron [click to enlarge]

Terra and Aqua MODIS True-color RGB images of southern Lake Huron [click to enlarge]

Terra and Aqua MODIS True-color RGB images of western Lake Erie [click to enlarge]

Terra and Aqua MODIS True-color RGB images of western Lake Erie [click to enlarge]

Large hail in Argentina

February 8th, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.3 µm, bottom) images, with hourly surface reports (metric units) for Córdoba, Argentina [click to play animated GIF — MP4 also available]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed the development of severe thunderstorms which produced very large hail in Córdoba, Argentina on 08 February 2018. Distinct above-anvil plumes were evident on the Visible imagery, with pulses of overshooting tops exhibiting Infrared brightness temperatures in the -70 to -80ºC range (black to white enhancement). The hail reportedly began around 1930 UTC or 4:30 PM local time.

The above-anvil plumes could also be seen in GOES-16 Near-Infrared “Snow/Ice” (1.61 µm) images (below).

GOES-16 Near-Infrared

GOES-16 Near-Infrared “Snow/Ice” (1.61 µm) images, with hourly surface reports (metric units) for Córdoba, Argentina [click to play animated GIF — MP4 also available]

An Aqua MODIS True-color Red-Green-Blue (RGB) image viewed using RealEarth (below) showed the thunderstorm just west of Córdoba around 1850 UTC.

Aqua MODIS True-color RGB image [click to enlarge]

Aqua MODIS True-color RGB image [click to enlarge]

According to the Worldview site, the coldest Aqua MODIS cloud-top infrared brightness temperature at that time was -78ºC (below).

Aqua MODIS True-color and Infrared Window (11.0 µm) images [click to enlarge]

Aqua MODIS True-color and Infrared Window (11.0 µm) images [click to enlarge]

A time series plot of surface observations at Córdoba (below) showed the warm temperatures and high dew points prior to the arrival of the thunderstorms; there were a number of hail reports between 19 UTC and 02 UTC (4 PM to 11 PM local time).

Time series of surface observations at Córdoba, Argentina [click to enlarge]

Time series of surface observations at Córdoba, Argentina [click to enlarge]