A large (208,000 acre) wildfire continued to burn near Derby Mountain in southwestern Montana on 12 September. A QuickTime animation of the 3.9 micrometer shortwave IR imagery from GOES-11, GOES-12, and GOES-13 (above) shows the “hot spots” associated with this fire — on the grayscale enhancement applied to these images, the warmest temperatures are black, and the coldest temperatures are white. However, note that some GOES-12 pixels in the vicinity of the fire are white, indicating a cold pixel; there is a problem with the 3.9 micrometer detectors on GOES-12, and pixel values that should be very hot “roll over” and are actually indicated as cold temperatures. This same problem was noted on GOES-11 during the post-launch evaluation of that satellite a few years ago, but there was no GOES-11 pixel roll-over noted for these particular hot fires (and fortunately, the recently-launched GOES-13 has not yet exhibited this behavior). Because of this hot spot detection discrepancy, the GOES-12 Wildfire ABBA flagged this fire as a “saturated” pixel (yellow), while the GOES-11 Wildfire ABBA flagged it as a “processed fire” (red pixel).

An AWIPS 4-panel comparison of MODIS vs. GOES shortwave IR and visible channels (below) show that this fire also saturated the MODIS Band 20 detector (as indicated by the “NO DATA” cursor value); the visible images also reveal that a smoke plume was drifting east-southeastward from the fire source (which was very apparent on this MODIS true color image).

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Hurricane Florence passed very near Bermuda on 11 Sep (IR image | water vapor image), with a peak wind gust of 111 mph reported on the island. The radius of high winds associated with Florence was rather large, and the tight pressure gradient between the tropical cyclone and a large area of high pressure over southeastern Canada (above) was creating strong winds that prompted the issuance of high surf and other marine warnings/advisories along much of the US east coast. GOES-12 low-level visible winds (below) indicated the extent of the strong winds along the western periphery of Florence, with several targets having speeds of 34 knots or greater (bold green or cyan wind barbs on this closer view) a considerable distance from the storm center.

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Severe convection developed in eastern portions of the Texas panhandle region, which produced wind gusts to 67 mph and golf-ball size hail (1.75 inch diameter) around 20:20 to 20:30 UTC (3:20 to 3:30 PM local time) in parts of Cottle county, TX (the county outlined on the images above); a few hours later, this convection was also responsible for flash flooding in that particular county. The 16-panel image (above) shows visible and IR channel images from all 4 of the current operating GOES satellites (GOES-10, GOES-11, GOES-12, and GOES-13) at 20:30 UTC; the development of that same storm can also be viewed at 1-minute intervals from GOES-10 (below), which is still in Super Rapid Scan Operations (SRSO) as the satellite is being re-positioned to 60 W longitude. During the hours leading up to convective initiation, a curved outflow boundary from earlier thunderstorms was apparent across that region, and AWIPS GOES sounder-derived lifted index and total precipitable water depicted an axis of instability (LI = -10.4 C) and moisture (PW = 51 mm / 2.00 in) that was extending west-northwestward into Cottle county along that outflow boundary.

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Cold air was streaming southwestward across Lake Superior, behind a strong Canadian cold front (temperatures the following morning dropped to 19 F at Embarrass MN and 28 F at Hayward WI). On the MODIS true color image (below, left), the appearance of the cloud bands that formed over the lake closely resembled “lake-effect snow bands” that often form in the winter (due to the large temperature difference between the relatively warm water surface and the cold arctic air). While the air behind this particular front wasn’t cold enough for lake-effect snow, there were some areas of lake-effect rain and drizzle in the UP of Michigan and in northern Wisconsin. Once we get into the winter months, MODIS products such as the Cloud Phase and the Cloud Top Temperature (below, right) will be helpful for determining whether snow or freezing rain/drizzle will be the likely precipitation type over a given region. In this case, the MODIS Cloud Phase product indicated thatwater phase clouds (blue enhancement) covered most of Lake Superior (MODIS IR and Cloud Top Temperature values were several degrees below freezing, so it was likely supercooled water droplets these clouds); farther to the south, over northern Wisconsin and the UP, a band of more intense rain showers and thunderstorms (with some cloud to ground lightning strikes) was depicted as ice phase clouds (pink enhancement), with corresponding IR and cloud top temperature values colder than -30 C (dark blue enhancement on the MODIS CTT and IR images).

Note to AWIPS users: Jordan Gerth made a modification to the MODIS Cloud Phase product, to allow AWIPS cursor display of the actual phase category (along with a phase label in the color bar).

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