A Super Fog event — caused by the combination of dense fog and smoke from a large swamp fire just southeast of Lake Pontchartrain — was responsible for multi-vehicle accidents along Interstate 55 (between Lake Maurepas and Lake Pontchartrain) during the early morning hours on 23 October 2023 (meda report). Before a patch of high clouds moved across the area, 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) Nighttime Microphysics RGB imagery from the CSPP GeoSphere site (above) displayed the swamp fire thermal signature as a cluster of darker purple pixels, with its brighter white smoke-filled cloud plume beginning to move west-northwest across Lake Pontchartrain (toward the I-55 accident sites). After sunrise, True Color RGB images showed the continued west-northwest transport of smoke from the swamp fire; the fog/stratus over I-55 between the 2 lakes eventually dissipated by about 1900 UTC.

Around 8-9 AM CST (1300-1400 UTC), GOES-16 Low Instrument Flight Rules (LIFR) Probability values (below) were 70% in the vicinity of the I-55 vehicle accidents — but began to decrease as the fog (and visibility) between the 2 lakes slowly improved throughout the morning hours. LIFR Probability is a component of the Fog/low stratus (FLS) Products suite.

Dense fog & smoke have combined to form what is known as Superfog (yes, it is the technical name) & this is still heavily impacting I-55 between Ponchatoula & LaPlace. The interstate was still closed according to @La_DOTD due to multiple accidents. Fog is slowly improving. pic.twitter.com/xwovJBbuco

— NWS New Orleans (@NWSNewOrleans) October 23, 2023

View only this post Read Less

GOES-16 (GOES-East) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed the formation of 2 pyrocumulonimbus (pyroCb) clouds that were created by a fire complex in northeastern Bolivia on 22 October 2023. The coldest cloud-top 10.3 µm infrared brightness temperature of the first (larger) pyroCb was around -56ºC (lighter shade of red), followed by a second (smaller) pyroCb exhibiting a minimum 10.3 µm brightness temperature around -47ºC (brighter shade of cyan). Surface analyses indicated that a large area of low pressure was expanding northward from northern Argentina to eastern Bolivia during the day — which likely brought an influx of warmer temperatures across eastern Bolivia (potentially creating a more favorable fire environment).

GOES-16 daytime True Color RGB and Nighttime Microphysics RGB images from the CSPP GeoSphere site (below) revealed a morning smoke plume drifting south-southeastward away from the fire burn scar (it is unclear whether this was a wildfire, or an intentional fire  meant to clear trees for agricultural purposes) a few hours prior to pyroCb formation.

This is likely the third confirmed case of a South American pyroCb (the first being on 29 January 2018, and the second on 18 August 2019) — in addition, it’s one of the very few pyroCb events documented so far in the tropics.

View only this post Read Less

MIMIC Total Precipitable Water (TPW) fields, below, show a band a rich moisture over the northern Indian Ocean between the Equator and 15^oN Latitude. By 17 October in the animation, cyclonic motion is diagnosed in the TPW fields between 60^o and 70^o E Longitude. By 18 October, an invest was declared. The toggle below (imagery from the CIMSS/SSEC Tropical Weather Website) shows shear values, Sea-Surface Temperatures, and low-level convergence and upper-level divergence. Shear values are favorable, and a good divergence/convergence couplet over warm waters is apparent.

Metop-B overflew the system shortly after 0500 UTC on 19 October (link) and a closed circulation was apparent near 11^oN, 63^oE. Imagery and winds derived from FY-4A, below, (from this NSMC website) show strong diffluence above the developing system at 1200 UTC on 19 October. The upper-level wind barbs (in red) and mid-tropospheric wind barbs (in green) are nearly parallel, suggesting low shear values.

By 1200 UTC on 20 October, below, a storm has formed in the region of low shear, and landfall on the southern shore of the Arabian Peninsula is forecast.

By 2100 UTC on 21 October 2023, below, a well-developed system was present. Satellite-derived winds suggest an outflow jet to the east along the northern perimeter of the storm.

RCM-2 overflew Tej shortly after 1400 UTC on 22 October 2023 (link). The SAR wind analysis, below, shows a well-defined eye structure at that time to the north of Socotra Island. The wind analysis (here) shows peak winds over 100 knots.

View only this post Read Less

Strong gap winds accelerating out of the Copper River Valley — located along the coast of southcentral Alaska — were lofting fine particles of glacial silt/sand, and transporting those aerosols southward across the Gulf of Alaska during 20-22 October 2023. 10-minute GOES-18 (GOES-West) Dust Red-Green-Blue (RGB) images created using Geo2Grid (above) displayed the plume of airborne silt/dust (shades of pink) during that 48-hour period.

During the daylight hours on 21 October, GOES-18 True Color RGB images (below) showed the long plume as it curled southeastward across the Gulf of Alaska. The hazy plume of blowing silt/dust could be seen moving down the narrow Copper River Valley before emerging from the coast.

The strong gap wind flow resulted from a tight coastal pressure gradient as a ridge of high pressure began building across southern Interior Alaska (above), which forced surface winds to accelerate down the Copper River Valley (located northeast and east of Cordova, as seen in the topography image below) toward the Gulf of Alaska.

Glacial silt from the riverbed of the Copper River has made it over the Cordova area as seen from the photos below! Credit to the Cordova Telecom Cooperative (left pic looking East from the West side of the Delta) and the FAA (right pic looking Southwest from the airport).#AKwx pic.twitter.com/Au114HULMv

— NWS Anchorage (@NWSAnchorage) October 21, 2023

Prior to sunrise on 22 October, the western edge of the plume briefly drifted across Middleton Island (PAMD), where it reduced the surface visibility to 6 miles from 1300-1500 UTC (below).

View only this post Read Less