Comparing IFR Probability with NDBC BuoyCam imagery

June 2nd, 2022 |
GOES-17 IFR Probability fields, 1710 UTC on 2 June 2022 (click to enlarge)

Some National Data Buoy Center buoys do include webcams that provide sky information (link). How well do those observations compare to IFR Probability fields, as shown above in an image from RealEarth? There are three BuoyCams along the Oregon coastline, as shown in the image below, and 3 more offshore that can be compared to the IFR Probability fields above. Consider Buoy 46029, 20 nm offshore of the mouth of the Columbia River, shown below. It shows what appear to be low overcast skies in a region where IFR Probabilities are large. Proceed counterclockwise around the 6 buoys near/offshore Oregon (the one just south of the Oregon/California border is not included here), and you’ll note low clouds are present in most of the BuoyCam observations: Buoy 46089; Buoy 46005; Buoy 46002; Buoy 46015. Only Buoy 46050, along the central Oregon coast, shows multiple breaks in the clouds. This is in a region where IFR Probabilities are smaller!

Webcam observations from Buoy 46029, 1710 UTC on 2 June 2022. Note that the left-most webcam view points towards 90o. (Click to enlarge)

The animation below shows the 6 WebCam observations in sequence. Use these webcams to become more confident in using IFR Probability fields in the open ocean.

Webcam views at 1710 UTC near and offshore from the Oregon Coast (Click to enlarge)

View and animate GOES-16 and GOES-17 Full-Disk IFR/Low IFR Probability fields in RealEarth

May 25th, 2022 |

GOES-16 and GOES-17 Full-Disk IFR and Low IFR Probability fields are now available in RealEarth. IFR (Instrument Flight Rules) Probability estimates the likelihood that IFR conditions are occurring. You can view and animate real-time satellite IFR probability in RealEarth.

Finding IFR and Low IFR fields in RealEarth for GOES-16 and GOES-17 full disk.
Comparing GOES-17 IFR and Low IFR for 05-25-2022 at 15:10UTC, and animating GOES-17 IFR fields in RealEarth over Hawai’i for the last 12 available GOES-17 time steps (10-minute resolution from 13:10 to 15:20UTC).

Fog in and around the Aleutians

May 18th, 2022 |
GOES-17 Night time Microphysics RGB over the Aleutian Islands and surrounding waters, hourly from 0800 -1300 UTC on 18 May 2022 (Click to enlarge)

The hourly animation above shows the GOES-17 Night time Microsphysics RGB over and surrounding the Aleutian Islands, from 0800 – 1300 UTC on 18 May 2022. Yellowish features are low clouds in this RGB; low clouds at warmer temperatures have a blue/cyan tint because the inclusion of Band 13 infrared (10.3 µm) brightness temperatures in the ‘blue’ part of the RGB will change the color representation of low clouds. High clouds — red in the RGB — are also present along the western edge of the domain, over the Bering Sea — and are apparent as thin clouds over the low clouds over the Aleutians, visible as purple streaks.

Are the low clouds shown above fog — that is, are the clouds touching the surface? That’s hard to tell with certainty over Marine Environments. The single surface observation — at St Paul Island (PASN) in the Bering Sea, does show fog/low stratus present, and IFR conditions. An inference from that observation might be extended into the entire region. Real-time webcams and ship observations can also help with the determination of whether low clouds are actually banks of fog.

IFR Probability fields, below, for the same 6 observation times, incorporate model-derived estimates of low-level saturation, suggesting more low-level variability to the low clouds/fog over the Bering Sea (and in the Gulf of Alaska south of the Aleutians); that’s shown more clearly in this toggle between the two fields at 1200 UTC. Note also that a useful signal is produced underneath the high clouds at the western edge of the domain: even though the satellite gives no direct observations of the low-level clouds there, model estimates can nevertheless give information on low-level saturation.

GOES-17 IFR Probability fields, hourly from 0800 – 1300 UTC on 18 May 2022 (Click to enlarge)

When the sun is above the horizon, the Night time Brightness temperature difference field (10.3 µm – 3.9 µm) signal flips sign because of the large amounts of 3.9 µm solar reflectance; thus the Nighttime Microphysics RGB is less useful in low-cloud detection. The toggle below compares the Night Time Microphysics RGB and the IFR Probability field at 0400 UTC. Note that the observation at St Paul Island at this time does not show IFR conditions — and IFR Probabilities there are not quite so large as later, as displayed in the animations above.

Nighttime Microphysics RGB and IFR Probability fields, 0400 UTC on 18 May 2022, along with surface observations (Click to enlarge)

The imagery above were all captured using a National Weather Service AWIPS machine, with dataflow over the Satellite Broadcast Network (SBN) that supplies data products to the offices. What if you don’t have that resource? RealEarth contains Full-Disk IFR and Low IFR Probability fields from GOES-16 and GOES-17 (search for IFR within the search box at the RealEarth website). An animation of IFR Probability from GOES-17, from 1000 UTC – 1250 UTC, at 10-minute steps (the scanning cadence of GOES-17 Full Disk imagery) is below.

IFR Probability fields, 1000 – 1250 UTC on 18 May 2022 (click to enlarge)

GOES-17 Full-Disk Nighttime microphysics RGB imagery is available from a variety of sources. For example, it’s at the NOAA/NESDIS Imagery viewer (link); at the CIRA Slider ; the mp4 animation below is taken from a coming upgrade to the CSPP Geosphere site that shows Night time Microphysics RGB imagery at night (and true color imagery during the day).

GOES-17 Nighttime Microphysics RGB, 1000 – 1300 UTC on 18 May 2022

Persistent fog/stratus across eastern Virginia

May 3rd, 2022 |

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

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed abroad arc of fog/stratus that persisted for much of the day across parts of eastern Virginia, Chesapeake Bay and the Delmarva Peninsula on 03 May 2022. Since this fog/stratus deck — which was on the cold side of a quasi-stationary frontal boundary — was slow to dissipate, it held daytime temperatures in the 50s and 60s F (in contrast to the 70s F in cloud-free areas east of the front, and 80s F west of the front). By the end of the day, some of the colder air and stratus had sagged southward across extreme northeastern North Carolina (including the northern end of the Outer Banks).

Afternoon thunderstorms reached strong to severe levels as they approached the frontal boundary, producing 1-inch diameter hail and damaging winds (SPC Storm Reports).

1-minute GOES-16 Visible images with overlays of the 5-minute GOES-16 Fog Depth product (below) provided an estimate of the fog/stratus deck thickness, helping to highlight which portions might be slower to dissipate.

GOES-16 “Red” Visible (0.64 µm) images, with an overlay of the GOES-16 Fog/Stratus Depth product [click to play animated GIF | MP4]