IFR (Instrument Flight Rules) Probability estimates the likelihood that IFR conditions are occurring by fusing GOES-17 satellite data with model output. The satellite-derived products give output of low IFR, (LIFR), IFR, and Marginal Visual Flight Rules (MVFR). In aviation, the difference between these classifications is generally:

Low Instrument Flight Rules (LIFR): Ceilings are less than 500 feet above ground level and/or visibility is less than 1 mile.

Instrument Flight Rules (IFR): Ceilings are 500 to 1,000 feet and/or visibility 1 to 3 miles.

Marginal VFR (MVFR): Ceilings are 1,000 to 3,000 feet and/or visibility is 3 to 5 miles.

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Color-enhanced wind speeds observed from Synthetic Aperture Radar (SAR) data on the second RADARSAT Constellation Mission satellite (RCM-2), shown above in AWIPS (Click here for a similar image online at this website) show parallel lines of enhanced wind speeds, a wind structure suggestive of a bore (click here for many previous blog posts on this phenomena), over southern Lake Michigan. Peak wind values (in yellow over the water) are near 14 m/s, with minima in between the lines showing winds around 5-6 m/s. (Note that SAR wind information over land is invalid). When this kind of event happens under mostly clear skies, parallel lines of clouds (that are perpendicular to the observed wind) develop. In this case, widespread clouds prevented satellite detection of cloud bands. The toggles below show Visible (Band 2, 0.64 µm) and Infrared (Band 13, 10.3 µm) at the time of the SAR observations.

Modest convection (cloud tops are only around -48^oC) over central Lake Michigan likely generated the bore. For a bore to propagate, a strong inversion is required. Soundings at Green Bay WI and Gaylord MI likely are unrepresentative of the environment over southern Lake Michigan. The sounding at White Lake Michigan — near Detroit — (from this website) does show a surface inversion, as does the sounding at Davenport IA. The cool late-Spring waters of Lake Michigan will serve to anchor a similar low-level inversion over the Lake; bore features travel along those inversions.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) and “Red” Visible (0.64 µm) images (above) showed Tropical Storm Alex after it reached tropical storm intensity at 0900 UTC on 05 June 2022. Overshooting tops within the deep convection exhibited infrared brightness temperatures of -80ºC or colder (shades of violet).

GOES-16 Infrared Window (11.2 µm) images from the CIMSS Tropical Cyclones site (below) include contours of deep-layer wind shear at 17 UTC  — which displayed the high shear that was displacing the convection associated with Alex well northeast of the storm center.

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The MIMIC Total Precipitable Water (available at this website) animation below tracks Pacific Hurricane Agatha as it makes landfall, and then the accumulation of moisture that is incorporated into Alex.

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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!

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.

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