AWIPS images of 4-km resolution GOES-13 6.5 Âµm “water vapor channel” data (above; click image to play animation) revealed an extensive “mountain wave signature” across much of the Mid-Atlantic region of the US on 19 February 2011. Strong winds (gusting to 71 mph in Virginia and 63 mph in Maryland and Pennsylvania) in the wake of a cold frontal passage were interacting with the terrain of the Appalachian Mountains to create the widespread mountain waves — and some of the mountain waves were responsible for pilot reports of moderate to severe turbulence.
1-km resolution MODIS 6.7 Âµm water vapor images (below) offered a more detailed view of the mountain wave structure.
On occasion, these mountain waves appear in “clear air’ with no clouds present — this can be seen from Virginia to the Delmarva Peninsula in a comparison of a MODIS 0.65 Âµm visible image with the corresponding MODIS 6.5 Âµm water vapor image (below). Aircraft sometimes encounter “clear air turbulence” under such circumstances.
It is interesting to note that the MODIS 2.1 Âµm near-IR “snow/ice channel” image (below) displayedÂ a signature of what appeared to be the effect of atmospheric gravity waves over the adjacent offshore waters. A similar signature was discussed on the MODIS Image of the Day site off the coast of New Zealand on 21 December 2010.
The combination of strong winds and dry vegetation (MODIS Normalized Difference Vegetation Index) created an environment favorable for wildfire activity — and on this day there were more than 100 wildfires reported across the state of Virginia alone. The “hot spots” signatures (black to yellow to red color enhancement) from many of the larger fires could be seen on 4-km resolution GOES-13 3.9 Âµm imagery, with many more of the smaller fires exhibiting such signatures on the corresponding 1-km resolution POES AVHRR 3.7 Âµm shortwave IR image (below).
A MODIS â€œtrue colorâ€ Red/Green/Blue (RGB) image (below; displayed using Google Earth) showed a few of the longer smoke plumes that were emanating from the largest fires located from western Virginia to the Washington, DC area.