GOES-R Fog/Low Stratus in Alaska

GOES-R IFR Probabilities from GOES-W (Upper Left) and from MODIS (Upper Right); GOES-W color-enhanced IR Imagery (Bottom Left), Alaska Topography (Bottom Right).  Station Observations including visibilities and ceilings above ground level as indicated.

Alaska poses unique challenges in both Fog/Low stratus detection and in aviation forecasting.  For example, there are very few observation sites — airports — where verification of products can occur.  The abundance of small aircraft — bush aircraft — means that aviation support is critical in remote regions where such aircraft will operate.  Alaska is also far enough north that the GOES-West pixel footprint size is very large, making detection of small-scale fog events difficult.

The series of images above document some of these issues.  The GOES-R IFR Probabilities computed with GOES-West data (upper left) and MODIS data (upper right) show similar patterns.  But the far superior resolution inherent in polar orbiters over Alaska results in far greater detail in the MODIS product.  This is a case with multiple cloud layers over northern Alaska (as evidenced by the 10.7 window channel image, lower left);  the enhanced IFR probabilities along the Brooks Range in northern Alaska are mostly model-driven (the model used in that region is the Rapid Refresh (the boundary between the Rapid Refresh and the GFS is apparent in the upper left image over the Bering Sea and over far northern Alaska).  The model suggests IFR conditions are possible in an elevated stratus cloud that surrounds the Brooks Range.  That is, the terrain is rising up into the clouds.

Leave a Reply