Detection of fog during a fatal crash in Florida
A combination of fog and smoke reduced visibilities along I-95 S in southern Volusia County Florida. A series of fatal crashes (news report; this tweet suggests the accident was near Florida State Route 442; second tweet). News report suggest the smoke that helped seed the dense fog resulted from controlled burns. The Band 7 imagery (3.9 µm) above, does not show strong evidence of burns (the Fire Detection and Characterization Algorithm — FDCA — similarly showed no information in Volusia County), nor of the fire that occurred at the crash scene as vehicles burned. The first crashes occurred around 0630 UTC.
The Nighttime microphysics RGB is often used to highlight regions of fog. On this day, however, no obvious signal of fog (fog typically appears as a color between cyan and yellow, as noted here) is apparent.
The Night Fog brightness temperature difference (the ‘green’ component of the RGB above) also can be used to detect fog. GOES-R IFR Probability fields use satellite data (and model data) to outline regions of fog. The toggle below includes the night time microphysics RGB, the night fog brightness temperature difference, and the IFR Probability fields at 0631 UTC, near the time of the crash. Satellite data provided little detection for this very thin combination of smoke and fog. For this case, it would be better to rely on things like webcams.
There was a very timely Suomi-NPP overpass as shown below. The timestamp is at 0632 UTC, which is when the satellite first was broadcasting data to the Direct Broadcast antenna at CIMSS; the satellite was viewing central Florida around 0642 UTC, based on this orbit calculation (from this site). The slider does suggest a small temperature difference as might be caused by fog over southern Volusia County. (Click here to see a toggle — and here to see a very fast toggle).
A brightness temperature difference field between I05 and I04 on this date was created using McIDAS-V in this blog post.
———————————————————————————————————-A similar incident of fog — possibly enhanced by smoke — causing a multi-vehicle accident occurred in Osceola County (not far to the south of Volusia County) Florida on 13 March 2007. In that case, higher-resolution MODIS imagery was a bit more helpful in helping to highlight an area of nocturnal fog formation.