Scott Bachmeier « CIMSS Satellite Blog

Hurricane Force low pressure system off the US East Coast

April 1st, 2020 | Scott Bachmeier

GOES-16 “Red” Visible (0.64 µm), Mid-level Water Vapor (6.9 µm) and Air Mass RGB images [click to play animation | MP4]

A sequence of GOES-16 (GOES-East) “Red” Visible (0.64 µm), Mid-level Water Vapor (6.9 µm) and Air Mass Red-Green-Blue (RGB) mages (above) showed an occluding Hurricane Force low pressure system (surface analyses) off the US East Coast on 01 April 2020. In the Air Mass RGB images, darker red areas just south of the storm center indicated the presence of higher amounts of total column ozone, brought about by a lowering tropopause — RAP40 model fields of the PV1.5 pressure (representing the height of the “dynamic tropopause”) suggested that the tropopause had descended below the 500 hPa pressure level later in the day.

The hurricane-force winds at the surface were creating seas as high as 33 feet. The milky/hazy signature of a highly-agitated sea surface + sea spray — immediately south of the convection around the core of the storm — was evident in GOES-16 True Color RGB images, created using Geo2Grid (below).

GOES-16 True Color RGB images [click to play animation | MP4]

GOES-16 Visible images with an overlay of GLM Flash Extent Density (below) revealed that lightning activity gradually decreased within convection surrounding the core of the low during the day.

GOES-16 “Red” Visible (0.64 µm) images with an overlay of GLM Flash Extent Density [click to play animation | MP4]

As the storm was becoming organized near the Southeast US coast during the preceding overnight hours, a toggle between Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 0627 UTC (below) showed widespread mesospheric airglow waves in the Day/Night Band — these waves were likely generated by the approach of an upper-tropospheric jet streak.

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Addition information about this event is available on the Satellite Liaison Blog.

Posted in GLM, GOES-16, Lightning, Red-Green-Blue (RGB) images, Suomi NPP, VIIRS | No Comments »

Contrails over Wisconsin, and a mesovortex moving across Indiana

March 31st, 2020 | Scott Bachmeier

GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Cirrus” (1.37 µm), Near-Infrared “Snow/Ice” (1.61 µm), Upper-level Water Vapor (6.2 µm), Mid-level Water Vapor (6.9 µm), Low-level Water Vapor (7.3 µm), “Clean” Infrared Window (10.35 µm) and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

A sequence of GOES-16 (GOES-East) “Red” Visible (0.64 µm), Near-Infrared “Cirrus” (1.37 µm), Near-Infrared “Snow/Ice” (1.61 µm), Upper-level Water Vapor (6.2 µm), Mid-level Water Vapor (6.9 µm), Low-level Water Vapor (7.3 µm), “Clean” Infrared Window (10.35 µm) and Day Cloud Phase Distinction Red-Green-Blue (RGB) images (above) showed both circular and linear contrails over southern Wisconsin on 31 March 2020. The circular contrail was likely created by military aircraft (Wisconsin Air National Guard) performing training operations.

A toggle between GOES-16 Visible and Cirrus images at 1601 UTC (below) indicated that the darker signature seen in Visible imagery was actually the shadow from the high-altitude contrails being cast upon the top of the low-level stratus clouds.

GOES-16 “Red” Visible (0.64 µm), and Near-Infrared “Cirrus” (1.37 µm) images [click to enlarge]

Another feature of interest was revealed by 1-minute Mesoscale Domain Sector GOES-16 Visible images — a mesovortex that was moving southwestward from southwest Michigan across northwestern Indiana (below). However, the small-scale circulation of the vortex was not captured by 1-minute GOES-16 Derived Motion Winds.

GOES-16 "Red" Visible (0.64 µm) images with plots of Derived Motion Winds (yellow) [click to enlarge]

GOES-16 “Red” Visible (0.64 µm) images, with Derived Motion Winds plotted in yellow [click to play animation | MP4]

Posted in GOES-16, Red-Green-Blue (RGB) images, Satellite winds | No Comments »

Severe weather outbreak across the central US

March 28th, 2020 | Scott Bachmeier

GOES- 16 “Red” Visible (0.64 µm) images, with time-matched (+/- 4 minutes) SPC Storm Reports plotted in red [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES- 16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed widespread events of severe weather (SPC Storm Reports) associated with a large occluding low pressure system and its frontal boundaries on 28 March 2020.

The corresponding GOES-16 “Clean” Infrared Window (10.35 µm) images are shown below. The coldest cloud-top infrared brightness temperatures were in the -60 to -70ºC range (red to black enhancement). The most significant tornado produced EF-3 damage as it moved through Jonesboro, Arkansas beginning at 2157 UTC.

GOES- 16 "Clean" Infrared Window (10.35 µm) images, with time-matched SPC Storm Reports plotted in purple [click to play animation | MP4]

GOES- 16 “Clean” Infrared Window (10.35 µm) images, with time-matched (+/- 4 minutes) SPC Storm Reports plotted in purple [click to play animation | MP4]

A toggle between a Suomi NPP VIIRS Visible (0.64 µm) image (with plots of available NUCAPS soundings) and the Gridded NUCAPS CAPE values (below) revealed pockets of instability across the lower Mississippi River Valley in advance of the approaching cold front. Due to the presence of dense multi-layer cloudiness across much of Arkansas, there were no successful infrared+microwave (green) NUCAPS profiles available near Jonesboro (KJBR), except for a few microwave-only (yellow) soundings just to the south.

Suomi NPP VIIRS Visible (0.64 µm) image with plots of available NUCAPS soundings + Gridded NUCAPS CAPE [click to enlarge]

A plot of 19 UTC rawinsonde data from Little Rock, Arkansas (below) indicated a CAPE value of 2836 J/kg.

Plot of 19 UTC rawinsonde data from Little Rock, Arkansas [click to enlarge]

Additional imagery of this event is available on the Satellite Liaison Blog.

Posted in GOES-16, NUCAPS, Severe convection, VIIRS | No Comments »

High-altitude waves over the Arctic

March 27th, 2020 | Scott Bachmeier

GOES-17 “Ozone” (9.61 µm) images, with rawinsonde sites plotted in yellow [click to play animation | MP4]

GOES-17 (GOES-West) “Ozone” (9.61 µm) images (above) revealed waves propagating northwestward over northern Alaska, northern Yukon and the adjacent Beaufort Sea during the pre-dawn hours on 27 March 2020. That area was too illuminated by either aurora borealis or the rising sun — so Suomi NPP VIIRS Day/Night Band (0.7 µm) imagery could not confirm the presence of mesospheric airglow waves (see this blog post for some examples).

A plot of the GOES-17 “Ozone” spectral band weighting function — calculated using 12 UTC rawinsonde data from Fairbanks, Alaska — showed a peak contribution from within the stratosphere at the 39 hPa pressure level, corresponding to an altitude around 21 km (below).

Plot of GOES-17 “Ozone” (9.61 um) weighting function, calculated using 12 UTC rawinsonde data from Fairbanks, Alaska [click to enlarge]

The curious aspect of these waves was their northwestward propagation — rawinsonde data from 3 sites across the region (below) indicated that the winds aloft within the upper troposphere and throughout the stratosphere were strong northwesterly, which meant the waves were moving against the ambient flow. Lacking a coherent, science-based explanation for these wave features, this blog post earns its place in the “What the heck is this?” category.