Rope Cloud over the northwest Gulf of Mexico

January 22nd, 2018 |

GOES-16 “Red Visible” 0.64 µm imagery from 1402-2142 UTC on 22 January 2018. (Click to animate)

Visible GOES-16 Satellite Imagery over the northeastern Gulf of Mexico on 22 January 2018 showed the development of a Rope Cloud. Such features have been discussed before on the CIMSS Blog — here, here, here and here! Rope Clouds are handy features in satellite analysis over the ocean because they indicate distinctly where the surface cold front exists. Note that the WPC surface analysis, shown here for 1500 UTC, has the front in the same location as the rope cloud, with convection noted out in advance of the surface cold front. The hourly animation below, showing surface observations and the GOES-16 Red Visible (0.64 µm) Imagery, confirms the windshifts that were observed when the Rope Cloud/Cold Front passed any station.

Hourly Surface Observations and GOES-16 “Red Visible” 0.64 µm imagery from 1400-2200 UTC on 22 January 2018. (Click to enlarge)

Blowing dust in Texas and Oklahoma

January 21st, 2018 |

GOES-16

GOES-16 “Moisture” Infrared brightness temperature difference (10.3-12.3 µm) images, with hourly surface reports plotted in cyan [click to play animation]

Strong winds in the wake of a cold frontal passage created large areas of blowing dust across the Panhandle Plains of northwestern Texas after 16 UTC on 21 January 2018. GOES-16 “Moisture” or “split-window difference” (10.3 µm12.3 µm) images (above) showed that the leading edge of this airborne dust moved over far southwestern Oklahoma after 20 UTC. (Note to AWIPS users: the default enhancement for this GOES-16 “Moisture” Channel Difference product was changed to “Grid/lowrange enhanced” to better highlight the dust with shades of yellow)

GOES-16 “Red” Visible (0.64 µm) and Near-Infrared “Cirrus” (1.37 µm) images (below) also displayed blowing dust signatures; the surface visibility was restricted to 2-3 miles at some locations, with Big Spring briefly reporting only 1/4 mile from 20-21 UTC. The dust signature was apparent on the Cirrus imagery because this spectral band can be used to detect any airborne particles that are effective scatterers of light (such as cirrus ice crystals, volcanic ash, dust/sand or haze).

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly reports of surface weather plotted in red and surface visibility (miles) plotted in red [click to play animation]

GOES-16 Near-Infrared

GOES-16 Near-Infrared “Cirrus” (1.37 µm) images, with hourly reports of surface weather plotted in red and surface visibility (miles) plotted in red [click to play animation]

A Cirrus band is also available with the MODIS instrument on the Terra and Aqua satellites (as well as the VIIRS instrument on Suomi NPP and NOAA-20) — a comparison of Visible (0.65 µm), Cirrus (1.37 µm), Shortwave Infrared (3.7 µm) and Infrared Window (11.0 µm) images from Terra and Aqua (below) highlighted the differing appearance of the blowing dust features as sensed by each of those spectral bands. The airborne dust exhibited a darker signature in the Shortwave Infrared images since the small dust particles were efficient reflectors of incoming solar radiation, thus appearing warmer at 3.7 µm.

Terra MODIS Visible (0.65 µm), Cirrus (1.37 µm), Shortwave Infrared (3.7 µm) and Infrared Window (11.0 µm) images, with surface reports plotted in cyan [click to enlarge]

Terra MODIS Visible (0.65 µm), Cirrus (1.37 µm), Shortwave Infrared (3.7 µm) and Infrared Window (11.0 µm) images, with surface reports plotted in cyan [click to enlarge]

Aqua MODIS Visible (0.65 µm), Cirrus (1.37 µm), Shortwave Infrared (3.7 µm) and Infrared Window (11.0 µm) images, with surface reports plotted in cyan [click to enlarge]

Aqua MODIS Visible (0.65 µm), Cirrus (1.37 µm), Shortwave Infrared (3.7 µm) and Infrared Window (11.0 µm) images, with surface reports plotted in cyan [click to enlarge]

Pilot reports within 20-45 minutes after the Terra overpass time (below) revealed Moderate to Severe turbulence at an elevation of 8000 feet, just southeast of the most dense dust plume feature (highlighted by the cooler, lighter gray infrared brightness temperatures) — this was likely due to strong wind shear in the vicinity of the rapidly-advancing cold front. Farther to the southwest, another pilot report indicated that the top of the blowing dust was at 7000 feet, with a flight-level visibility of 3 miles at 10,000 feet.

Terra MODIS Infrared Window (11.0 µm) image, with a pilot report of turbulence highlighted in red [click to enlarge]

Terra MODIS Infrared Window (11.0 µm) image, with a pilot report of turbulence highlighted in red [click to enlarge]

Terra MODIS Infrared Window (11.0 µm) image, with a pilot report of dust layer top and flight level visibility highlighted in red [click to enlarge]

Terra MODIS Infrared Window (11.0 µm) image, with a pilot report of dust layer top and flight level visibility highlighted in red [click to enlarge]

Ice dam in Lake Erie

January 19th, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly surface wind barbs plotted in yellow and wind gusts (knots) plotted in cyan [click to play animation]

Thanks to Dave Zaff (NWS Buffalo) for the email alerting us to an ice dam that had formed across the eastern portion of Lake Erie on 19 January 2018 — GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed that the northeastward drift of ice floes was effectively being blocked by this ice dam feature.

A toggle between 250-meter resolution Terra MODIS True-color and False-color Red-Green-Blue (RGB) images from the MODIS Today site (below) provided a more detailed view of the Lake Erie ice dam and upwind drift ice at 1615 UTC. Snow and ice appear as shades of cyan in the False-color image, in contrast to supercooled water droplet clouds which are shades of white.

Terra MODIS True-color and False-color RGB images [click to enlarge]

Terra MODIS True-color and False-color RGB images; red arrows denote the location of the ice dam [click to enlarge]

The Terra MODIS Visible (0.65 µm) image with an overlay of RTMA surface winds (below) showed the southwesterly flow across the long axis of the lake.

Terra MODIS Visible (0.65 µm) image with surface METAR reports and RTMA surface winds [click to enlarge]

Terra MODIS Visible (0.65 µm) image with surface METAR reports and RTMA surface winds [click to enlarge]

A toggle between 1607 UTC Terra MODIS and 1757 UTC Suomi NPP VIIRS Visible images (below) showed the motion of the lake drift ice during that time period.

Terra MODIS and Suomi NPP VIIRS Visible images, with METAR surface reports [click to enlarge]

Terra MODIS and Suomi NPP VIIRS Visible images, with METAR surface reports [click to enlarge]

Blowing snow in North Dakota and Minnesota

January 11th, 2018 |

GOES-16

1-minute GOES-16 “Red” Visible (0.64 µm, left) and Near-Infrared “Snow/Ice” (1.61 µm, right) images, with plots of hourly surface wind barbs in cyan and surface weather type in yellow [click to play MP4 animation]

Several inches of new snow followed by strong northerly winds led to widespread blizzard conditions across the Red River Valley of North Dakota and Minnesota on 11 January 2018 (NWS Grand Forks summary). A GOES-16 (GOES-East) Mesoscale Sector had been positioned over the Upper Midwest to monitor the winter storm, providing images at 1-minute intervals — and a comparison of “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (above) showed the development of horizontal convective rolls that are a common feature associated with blowing snow.