On 25 January 2019 a GOES-16 (GOES-East) Mesoscale Domain Sector was positioned over Argentina in support of the RELAMPAGO-CACTI field experiment, providing imagery at 1-minute intervals. “Red” Visible (0.64 µm) images (above) showed thunderstorms that developed and moved northward over the Córdoba (SACO) area — surface observations there (plot | list) showed a sharp drop in temperatures along with wind gusts to 37 knots during the thunderstorm, which also produced hail and heavy rainfall. Two important features were revealed in the imagery: (1) an outflow boundary (from the decay of a large and long-lived Mesoscale Convective System to the southeast) which was moving slowly northward between between Rio Cuarto (SAOC) and Córdoba, likely helping to enhance boundary layer convergence and lift, and (2) a southward/southwestward flow of moist, unstable air — indicated by a plume of agitated cumulus clouds — approaching Córdoba. Toward the end of the day, the presence of an Above-Anvil Cirrus Plume also became evident in the Visible imagery.

The corresponding GOES-16 “Clean” Infrared Window (10.3 µm) images (below) showed that infrared brightness temperatures of the pulsing thunderstorm overshooting tops were frequently -90ºC or colder (yellow pixels embedded within darker purple). This indicates a significant overshoot of the tropopause, which had an air temperature of -72.1ºC at an altitude of 15.2 km on 12 UTC rawinsonde data. Also note the development of a pronounced cold/warm thermal couplet over the core region of the storm, as an enhanced-V storm top signature formed.

A side-by-side comparison of GOES-16 Visible and Infrared images is displayed below.

A toggle between NOAA-20 VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images at 1734 UTC as viewed using RealEarth (below) showed the early stage of convective development south of Córdoba, as well as the large decaying MCS to the southeast. Cloud-top infrared brightness temperatures with the developing storms were already -80–C and colder (violet enhancement), about 10ºC colder than what was observed using lower-resolution GOES-16 imagery at that same time.

We observed some of the deepest storms I’ve ever seen on ground-based radar near Córdoba, Argentina today – comparable to some of the strongest ever observed with TRMM @NSF_GEO @RELAMPAGO2018 pic.twitter.com/d0Te1BEPSl

— Steve Nesbitt (@70_dbz) January 25, 2019

URGENTE | Fuerte tormenta en Córdoba Capital

Ahora mismo se registra una fuerte tormenta con ráfagas de viento y fuertes lluvias en la ciudad de Córdoba. [Más información en: https://t.co/0573RLZtPS ] pic.twitter.com/2pwP5DdSrC

— TormentasDelLitoral (@TDLtiempo) January 25, 2019

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JMA Himawari-8 “Red” Visible (0.64 µm), Shortwave Infrared (3.7 µm) and Infrared Window (10.3 µm) images (above) showed the development of a pyroCumulonimbus (pyroCb) cloud from a bushfire that was burning in the eucalypt forests of eastern Victoria, Australia on 25 January 2019. A rapid-scan “Target” sector was positioned over the region beginning at 0522 UTC, providing images every 2.5 minutes (instead of the routine 10-minute interval). Cloud-top infrared brightness temperatures became colder than -40ºC (the threshold for pyroCb classification) after 0230 UTC, and eventually cooled to around -55ºC (orange enhancement). This temperature roughly corresponded to an altitude around 12 km, according to nearby Melbourne rawinsonde data (plot | text).

A closer view of Himawari-8 “Red” Visible (0.64 µm) and Shortwave Infrared (3.7 µm) images (below) revealed the rapid southeastward run of the fire, as shown by the growth of the “hot spot” (black to red pixels) on Shortwave Infrared images. The darker gray appearance of the pyroCb cloud is due to the presence of smaller ice crystals at the cloud top — these smaller ice crystals are more efficient reflectors of incoming solar radiation, making the cloud tops appear warmer than those of conventional cumulonimbus. Vigorous updrafts driven by the intense heat of the fire limit the in-cloud residence time for ice crystal growth, which leads to smaller particles being ejected at the pyroCb cloud top.

In a comparison of VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from Suomi NPP (at 0311 UTC) and NOAA-20 (at 0501 UTC) images viewed using RealEarth (below), cloud-top infrared brightness temperatures were in the -55 to -58ºC range (darker shades of orange).

Large bushfire in #EastGippsland producing a huge plume of smoke this afternoon stretching over eastern Bass Strait. Check out the satellite picture at https://t.co/9md40P2b4k pic.twitter.com/5ceZV5nf0T

— Bureau of Meteorology, Victoria (@BOM_Vic) January 25, 2019

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Near-Infrared (1.61 µm) images (above) displayed a long plume of horizontal convective roll (HCR) clouds across parts of the Upper Midwest on 24 January 2019. These HCR cloud features formed in the presence of strong northerly/northwesterly boundary layer winds in the wake of a cold frontal passage (surface analyses), and often highlight areas where significant blowing snow and ground blizzard conditions are likely occurring.

Animations of GOES-16 Visible and Snow/Ice images with plots of surface winds and weather type are shown below. ASOS sites report Haze (“H”) when the surface visibility — in this case, reduced by blowing snow — is less than 7 miles but greater than or equal to 4 miles. Some sites in Minnesota and Iowa reported a visibility between 0.5 and 2.0 miles at times (animation).

The signature of the HCR clouds on GOES-16 Day Cloud Phase Distinction Red-Green-Blue (RGB) images from the AOS site (below) was one that more closely resembled ice crystal clouds (light pink hues) than supercooled water droplet clouds (brighter shades of white) — suggesting a high concentration of blowing snow lofted within the boundary layer by the HRC circulations. Snow cover appears as shades of green in the RGB images.

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With a ridge of high pressure in place over the western Atlantic Ocean, GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) indicated the presence of dry air within the middle troposphere off the Southeast US coast on 23 January 2019.

GOES-16 “Red” Visible (0.64 µm) images showed that marine boundary layer stratocumulus clouds covered much of this region of the Atlantic — and due to minimal absorption by mid-tropospheric water vapor, these stratocumulus clouds were also very apparent in the corresponding GOES-16 Near-Infrared “Cirrus” (1.38 µm) images (below).

Terra MODIS Visible (0.65 µm) and Near-Infrared “Cirrus” (1.38 µm) images at 1513 UTC (below) also showed a clear signature of the stratocumulus clouds at 1.38 µm.

Cross sections of GFS90 model fields along Line I-I’ — oriented from Charleston, South Carolina to Bermuda — are shown below. Note the very dry air within the middle troposphere, with Specific Humidity values of less than 0.2 g/kg and Relative Humidity values less than 10% centered around the 500 hPa pressure level. In addition, the depth of the moist marine boundary layer was higher to the west at Charleston (2.6 km, at 746 hPa) than to the east at Bermuda (1.9 km, at 822 hPa).

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