Freezing fog in the Carolinas and Virginia

January 13th, 2021 |

GOES-16 Nighttme Microphysics, Night Fog BTD (10.3-3.9 µm) and Cloud Thickness product [click to play animation | MP4]

GOES-16 Nighttime Microphysics RGB, Night Fog BTD (10.3-3.9 µm) and Cloud Thickness product [click to play animation | MP4]

GOES-16 (GOES-East) Nighttime Microphysics RGB, Night Fog BTD (10.3-3.9 µm) and Cloud Thickness product (above) showed an arc of relatively thin fog across northern South Carolina, eastern North Carolina and southeastern Virginia — which was becoming thicker/deeper in time during the hours leading up to sunrise on 13 January 2021. In areas where the Cloud Thickness increased to 400 meters or more (lighter shades of cyan), freezing fog was observed at nearby METAR sites.

GOES-16 Nighttime Microphysics RGB images with plots of surface observations (below) indicated that air temperatures were near or just below freezing at most sites across the region.

GOES-16 Nighttime Microphysics RGB images, with plots of surface observations [click to play animation | MP4]

GOES-16 Nighttime Microphysics RGB images, with plots of surface observations [click to play animation | MP4]

The band of fog over eastern North Carolina and southeastern Virginia was being pushed eastward by a lower-tropospheric trough, as shown by the NAM40 model 925 hPa wind field at 12 UTC (below).

GOES-16 Nighttime Microphysics RGB image, with a plot of NAM40 model 925 hPa winds at 12 UTC [click to enlarge]

GOES-16 Nighttime Microphysics RGB image, with a plot of NAM40 model 925 hPa winds at 12 UTC [click to enlarge]

After sunrise, GOES-16 “Red” Visible (0.64 µm) images (below) showed that most of the fog quickly dissipated across southeastern Virginia and eastern North Carolina, while thicker fog persisted over much of South Carolina.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-R Fog/Low Stratus products are in RealEarth

January 5th, 2021 |

RealEarth instance of 1401 UTC GOES-16 IFR Probability fields, 5 January 2021, over the Mississippi River Valley (click to enlarge)

GOES-16 versions of the GOES-R Fog/Low Stratus products, such as IFR/Low IFR/Marginal VFR Probability fields, and GOES-R Cloud Thickness, are now available in RealEarth. These products are still available at the CIMSS GEOCAT site as well (link, for an image like this), but RealEarth offers pan, zoom and overlay capabilities. The RealEarth image from 1401 UTC on 5 January is shown above; the same time image from AWIPS is shown below. This link shows a more recent image in RealEarth.

AWIPS Screen Capture of IFR Probability and surface observations of ceilings and observations, 1401 UTC on 5 January 2020 (Click to enlarge)

GOES-17 IFR Probability will become available once that product is deemed Operational. Additional information on IFR Probability products is available at the Fog Blog.

Fog/stratus in the Snake River Basin of Idaho

December 29th, 2020 |

GOES-17 Night Fog BTD and “Red” Visible (0.64 µm) [click to play animation | MP4]

GOES-17 Night Fog BTD and “Red” Visible (0.64 µm) images [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-17 (GOES-West) Night Fog brightness temperature difference (BTD) and “Red” Visible (0.64 µm) images (above) showed the nighttime and daytime signature of a fog/stratus layer that had persisted throughout much of the Snake River Basin in southern Idaho on 29 December 2020. Some sites along the Interstate 84 corridor were reporting freezing fog — and the surface visibility was restricted to less than 1/4 mile at times in Boise (KBOI).

During the preceding nighttime hours, the extent of fog/stratus cloud within the Basin was well-illuminated by a nearly-full Moon (which was in the Waxing Gibbous phase, at 99% of Full) as seen in a Suomi NPP VIIRS image at 0856 UTC (below).

Suomi NPP VIIRS Day/Night Band (0.7 µm) image [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) image [click to enlarge]

GOES-17 IFR Probability fields are now being created for Alaska

October 15th, 2020 |

GOES-17 IFR Probability fields over Anchorage AK and surroundings, 0200 – 1300 UTC on 15 October 2020 (Click to animate)

CIMSS is now producing IFR Probability fields (and Low IFR Probability, Marginal VFR Probability, and Cloud Thickness fields) using GOES-17 data.  (Recall that GOES-16 IFR Probability fields  are now produced by NOAA/NESDIS and are distributed via the Satellite Broadcast Network (SBN) to National Weather Service Forecast Offices.  GOES-16, however, does not view Alaska).  GOES-17 fields will presently be available via an LDM pull.  NOAA/NESDIS will likely start processing the fields in 2021.

The animation above shows IFR Probability fields today over the Anchorage region.  The animation is preceded by a view of the topographic features, and IFR conditions on 15 October seem centered on topographic features.

GOES-17 can view the North Slope of Alaska.  This location is quite far from the GOES-17 sub-satellite point, so resolution is degraded from the nadir 2-km views. However, regions of likely IFR conditions are easily tracked (Again, the animation is preceded by topography), with a large region between the Arctic Ocean and the high terrain of the Brooks Range.

GOES-17 IFR Probability fields over northern Alaska, 0200 -1300 UTC, 15 October 2020 (Click to animate)

 

GOES-17 views of Alaska southeast, below show probabilities of low clouds and reduced visibility. As over other regions of Alaska today, highest probabilities are over high terrain. GOES-17 IFR Probability for the PACUS domain is available at this website. Work is ongoing to insert IFR Probability (from GOES-16 and GOES-17) into Real Earth.

GOES-17 IFR Probability fields over Alaska Southeast, 0200 -1400 UTC, 15 October 2020 (Click to animate)

GOES-17 fields contain artifacts in the form of horizontal stripes that can be traced to the poorly-functioning Loop Heat Pipe on GOES-17.  GOES-17 is now in a reduced-scanning mode between 0600 and 1200 UTC to enhance the ability of the satellite to shed excess heat:  fewer Mesoscale sectors are scanned, full disk sectors are not as frequent (every 15 minutes instead of every 10), and the ‘PACUS’ sector is not scanned.  This scanning strategy will continue through the end of October.


The Forecast Decision Training Division has a Quick Guide on IFR Probability fields here.  A 20-minute YouTube video explaining the product is here.