Fog and Stratus with IFR Conditions developed along the Southeast Coast of the United States on the morning of November 22. In some places, the GOES-IFR Probability fields gave a signal of the developing visibility obstructions more than an hour before the traditional brightness temperature difference signal. At 0202 UTC, below, the IFR Probability fields suggest a continuous region of enhanced probabilities of IFR conditions developing along the South Carolina coastline. Both IFR Probabilities and the brightness temperature difference fields agree that Fog/Low Stratus are already present over coastal North Carolina.
GOES-R IFR Probabilities from GOES-13 (Upper Left), GOES-13 Brightness Temperature Difference Product (10.7 µm – 3.9 µm) (Upper Right), GOES-R Cloud Thickness from GOES-13 (Lower Left), Suomi/NPP Day/Night Band (Lower Right), at 0202 UTC 22 November 2013 (click image to enlarge)
At 0315 UTC, IFR Probabilities continue to increase along the South Carolina coast. In contrast, Brightness Temperature difference fields are showing less of a signal suggestive of fog and low stratus. There was a Terra overpass at 0316 UTC that allowed MODIS data to be used in the GOES-R IFR Probability algorithm, and that field agrees well with the GOES-based field.
GOES-R IFR Probabilities from GOES-13 (Upper Left), GOES-13 Brightness Temperature Difference Product (10.7 µm – 3.9 µm) (Upper Right), GOES-R Cloud Thickness from GOES-13 (Lower Left), GOES-R IFR Probabilities computed from MODIS data (Lower Right), at ~0315 UTC 22 November 2013 (click image to enlarge)
At 0502 UTC, GOES-R IFR Probabilities are still high in a narrow corridor along the coast, despite the lack of a distinct signal from GOES-East in the brightness temperature difference field.
GOES-R IFR Probabilities from GOES-13 (Upper Left), GOES-13 Brightness Temperature Difference Product (10.7 µm – 3.9 µm) (Upper Right), GOES-R Cloud Thickness from GOES-13 (Lower Left), Suomi/NPP Day/Night Band (Lower Right), at 0502 UTC 22 November 2013 (click image to enlarge)
At 0615 UTC, the brightness temperature difference field starts to show a signal that is consistent with the presence of fog and low stratus along coastal South Carolina. GOES-R IFR Probabilities increase, as well. This is to be expected because the GOES-R algorithms use signals from both the GOES Satellite and the Rapid Refresh data to compute IFR Probabilities. Given that the Rapid Refresh data has been suggesting Fog/Low Stratus might be present (something that can be assumed to be true given the elevated probabilities that could alert any forecaster to the presence of developing fog that have been present for hours in the absence of a distinct signal from satellite), the appearance of a definitive satellite signal should only increase the probability of IFR conditions. At 0616, Suomi/NPP was viewing coastal South Carolina, and both the Day/Night band and the brightness temperature field are shown in the figure below. GOES-R IFR Probability algorithms do not yet incorporate Suomi/NPP data.
GOES-R IFR Probabilities from GOES-13 (Upper Left), GOES-13 Brightness Temperature Difference Product (10.7 µm – 3.9 µm) (Upper Right), GOES-R Cloud Thickness from GOES-13 (Lower Left), Toggle between Suomi/NPP Day/Night Band and Brightness Temperature Difference (Lower Right), at ~0615 UTC 22 November 2013 (click image to enlarge)
By 0800 UTC, below, IFR Conditions are reported at Charleston, SC, and GOES-R IFR Probabilities, brightness temperature difference field from GOES and Suomi/NPP and the Day/Night Band from Suomi/NPP all suggest the presence of fog/low stratus. To the northwest, over southeastern Tennessee, high clouds are obscuring the satellite view of any stratus/fog that is present (IFR Conditions are reported at, for example, Crossville, TN).
GOES-R IFR Probabilities from GOES-13 (Upper Left), GOES-13 Brightness Temperature Difference Product (10.7 µm – 3.9 µm) (Upper Right), GOES-R Cloud Thickness from GOES-13 (Lower Left), Toggle between Suomi/NPP Day/Night Band and Brightness Temperature Difference (Lower Right), at ~0800 UTC 22 November 2013 (click image to enlarge)
At 1145 UTC, IFR Probabilities maintain their high values along coastal South Carolina (and all of southwest Georgia) where IFR conditions are occurring. Note how the GOES-13 Brightness temperature difference product has highlighted values over central South Carolina, where IFR conditions are not reported. In this region, the Rapid Refresh model data is not showing saturation (or near-saturation) consistent with low-level stratus/fog so IFR Probabilities are reduced.
1145 UTC is the last image for GOES-R Cloud Thickness prior to twilight conditions. Data in the image can be used (in concert with this chart) to predict the dissipation time for radiation fog. GOES-R Cloud Thickness values over southeast Georgia range from 950 to 1100 feet, suggesting a dissipation time of 3 hours, or near 1445 UTC.
GOES-R IFR Probabilities from GOES-13 (Upper Left), GOES-13 Brightness Temperature Difference Product (10.7 µm – 3.9 µm) (Upper Right), GOES-R Cloud Thickness from GOES-13 (Lower Left), Suomi/NPP Day/Night Band (Lower Right), at 1145 UTC 22 November 2013 (click image to enlarge)
(Added: Later in the day)
Higher clouds allowed the low clouds to linger. By 1732 UTC, the low clouds had almost dissipated.
GOES-13 Visible Imagery, 1732 UTC 22 November 2013 (click image to enlarge)