Large wildfires continued to burn out of control in parts of Idaho and Montana (NOAA HMS product) on 13 August 2007. GOES-13 visible imagery (above; Java animation) showed smoke (from the previous day of burning) that was trapped in the valleys during the morning hours…with a transition to rapid smoke plume growth as southwesterly boundary layer winds increased and new fire activity flared up during the afternoon and evening hours.

GOES-12 visible imagery (below; Java animation) showed that smoke from previous days of burning had been transported as far eastward as Wisconsin and the western Great Lakes region on 13 August.

The extent of the eastward transport of smoke was confirmed using the MODIS Aerosol Optical Depth (AOD) product (above), with the thick smoke exhibiting high AOD values of 0.7 to 1.0 (orange to red enhancement).

MODIS true color imagery (below) showed a closer view of the smoke (hazy areas) that was drifting over Wisconsin and surrounding states during the early afternoon hours — and the IDEA aerosol trajectory forecast suggested a continuation of smoke transport aloft across the the Upper Midwest and Great Lakes regions .

The thick smoke aloft was responsible for creating a colorful (albeit somewhat muted) sunset — the photo below was taken in Middleton, Wisconsin, looking west, around 7:45 PM local time.

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GOES-11 IR imagery from the CIMSS Tropical Cyclones site (above) depicted a nice symmetric eye structure exhibited by Hurricane Flossie as it maintained Category 4 intensity in the central Pacific Ocean on 13 August 2007. Judging from the IR imagery, Flossie appeared to be an annular hurricane — annular hurricanes tend to weaken more slowly than non-annular storms of similar intensity, which may help to explain why Flossie maintained Category 4 intensity even as it began to encounter slightly cooler sea surface temperatures and increasing environmental shear. While Hurricane Flossie was forecast to weaken somewhat as it passed just to the south of the Hawaiian Islands (below), some adverse impacts (increasing winds, high surf, heavy rainfall) were still expected as the storm approached.

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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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