Ongoing fire activity in parts on Idaho, Montana, and Wyoming (NOAA HMS product) was producing very large smoke plumes late in the day on 12 August 2007. A QuickTime animation of GOES-12 visible imagery (above; 3.9 MB file; 1280 x 1024 screen resolution required) shows several large and dense smoke plumes that grew quickly in size and moved rapidly northeastward during the afternoon hours. During the previous night-time hours, 1-km resolution MODIS 3.7µm IR imagery (below, left) was able to detect many more fire “hot spots” (yellow to red enhancement) than the corresponding 4-km resolution GOES-12 3.9µm IR imagery (below, right).

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Early afternoon MODIS true color imagery showed a closer view of the smoke plumes in the northwestern US (above), while another fairly large smoke plume was also evident from a fire that was burning to the northwest of Los Angeles, California (below). Thick smoke from northwestern US fire activity a day earlier had been transported as far eastward as Montana and North Dakota.

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Wave clouds downstream of mountain ridges are a fairly common sight for regular observers of satellite data. See, for example, the parallel bands of clouds over southern Virginia in this image from the Record-setting Nor’easter in April of 2007. Such clouds develop as air is forced upward by the ridges of the Appalachian mountains. A standing wave develops, usually downstream of the mountain ridge, with clouds in the region of upward motion (if moisture is sufficient to allow for condensation) and clearing in regions of downward motion.

An excellent example of Wave Clouds occurred August 9th over the Bay of Fundy, in the Canadian Maritimes. The region is not noted for its tall mountains; however, the Caledonia Hills parallel the north shore of the Bay of Fundy, and North Mountain is along the south shore of the Bay of Fundy in Nova Scotia. (As shown here). The clouds formed in the northwest flow behind a departing low pressure system and gradually dissipated during the day as downward motion behind the departing the storm increased.

(Click on the image for a loop — note how the parallel bands of clouds are stationary). Clouds of this type generally are capped by an inversion, and such was the case on this day. This link shows the upper-air sounding from Yarmouth, on the southeast coast of Nova Scotia. An inversion exists above strong north-northwesterly winds that would be perpendicular to the coastline and the mountains that parallel the coast. The Caledonian Mountains along the coast of the Bay of Fundy aren’t particularly tall (they’re mostly below 400m at their peaks). The mountains on the north shore of Nova Scotia that surround the Annapolis Valley are also of modest height (less than 400 m). They are tall enough, however, to cause the atmospheric motions that give rise to the Wave Clouds in the images.

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A Java animation of GOES-12 (above; upper panels) and GOES-13 (above; lower panels) visible channel and 3.9 µm IR images showed a smoke plume (drifting southeastward) and “hot spots” (black-enhanced IR pixels) associated with a large wildfire that was burning the the eastern portion of the Upper Peninsula of Michigan on 03 August 2007. Note the improvement evident with changes to the image navigation and registration (INR) on the GOES-13 satellite: the coastline features and the fire hot spots remain fairly steady from image to image, compared to the GOES-12 images which exhibit a good deal of “wobble” in the animation.

The smoke plume was clearly depicted on Aqua MODIS true color imagery (below), drifting southeastward across northern Lake Huron. The fire (likely started by lightning on 02 August) was reported to have burned about 5000 acres by late afternoon, and was spreading southeastward at the rate of more than 1 mile per hour through uninhabited marshland north of Newberry, Michigan.

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A cold frontal boundary was moving southeastward through the Great Lakes region on 02 August 2007; Terra MODIS true color imagery (above) showed a very hazy air mass along and ahead of the advancing frontal boundary, with a very clean air mass behind the front. The dew point temperature at Madison, Wisconsin dropped from 70º F to 42º F in the 24-hour period following the frontal passage. Also evident on the MODIS image is a thin light-colored streak (oriented southwest-to-northeast) across northeastern Wisconsin, which was the damage path from a long-track tornado that occurred nearly 2 months earlier on 07 June 2007.

The IDEA MODIS aerosol optical depth (AOD) product several days earlier (below) revealed a high AOD signal (orange to red enhancement) over the northern Rocky Mountains region, due to thick smoke from numerous wildfires that were burning in Idaho and western Montana. Much of this smoke was subsequently transported eastward along the cold frontal boundary (MODIS AOD image Java animation).

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