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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GOES-10 Super Rapid Scan Operations (SRSO) visible and 10.7 micrometer InfraRed (IR) imagery at 1-minute intervals shows a nice view of a small thunderstorm that developed off the Texas coast this morning. The pulsing of overshooting tops could be seen in the visible imagery, along with periods of colder cloud top temperatures (around -65 C, darker red enhancement) in the IR imagery. Toward the end of the animation, an outflow boundary can be seen moving westward away from the convection. Since the storm was offshore, there were no reports of any hail or severe weather with this particular convection…but it was interesting to watch in the 1-minute imagery. Real-time GOES-10 SRSO visible imagery can be viewed here or here.

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No shortage of satellite meteorology topics today over the Upper Midwest and Great Lakes regions! A look at the GOES-12 visible channel animation (below, left) reveals the following features: (1) fingers of morning fog in the river valleys of southwestern Wisconsin, (2) areas of smoke aloft from wildfires burning in Canada and the Pacific Northwest, and (3) afternoon lake breeze boundaries that acted as a focus for thunderstorm development in both Wisconsin and lower Michigan.

(1) As we have noted previously, these narrow fog features are often not detected using the 4 km resolution GOES fog/stratus product, but the 1 km resolution MODIS fog/stratus product (with observations overlaid) is able to resolve the river valley fog in southwestern Wisconsin.

(2) While the smoke signature is subtle on the GOES-East (GOES-12) visible imagery, we can take advantage of a more favorable forward scattering geometry using the GOES-West (GOES-11) satellite to better see the areal extent of the smoke early in the day (GOES-11 animation). The smoke is also depicted as a large plume of high MODIS aerosol optical depth (AOD) extending from southern Canada to the Upper Midwest (below, right). In addition, the thick smoke contributed to a colorful sunset (and sunrise) here in Madison (photo 1 | photo 2).

(3) Narrow pockets of instability were noted on the GOES sounder lifted index (LI) derived product (values of -7 to -8 F), in the vicinity of the lake breeze boundaries in both Wisconsin and Michigan; hail up to 1 inch in diameter was reported from the afternoon lake breeze convection in Wisconsin and Michigan.

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Tropical depression #6 in the Atlantic Basin strengthened into Tropical Storm Florence today (IR image); forecasters at the National Hurricane Center utlized a CIMSS AMSU estimate of 1003 mb central pressure and 42 knot peak wind (below, left) to aid in their intensity estimate of the large developing tropical cyclone. The CIMSS satellite-derived IR/water vapor winds product (below, right) showed the presence of a large subtropical ridge located over the North Atlantic Ocean to the northwest of Florence — this ridge will likely be an important steering mechanism in the coming days as Florence continues to intensify and move toward the US East Coast.

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