GOES-12 visible channel images (above) revealed
an interesting wave structure along the top of an extensive stratus cloud deck
that covered much of Iowa, southern Wisconsin, and northern Illinois on 20
November 2007. An AWIPS 4-panel image showing the MODIS and GOES-12
visible and IR window channels (below) demonstrated
the better wave detection capabilities of the higher spatial resolution MODIS
data. The GOES-12 and MODIS IR brightness temperatures in the region of the
wave signatures were generally in the +1ºC to +5ºC range, with the GOES
Sounder Cloud Top Height indicating tops around 4700 feet in that
area (tan enhancement); the MODIS
Cloud Phase product confirmed that the cloud in that region was
likely composed of supercooled water droplets (blue enhancement).

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Much of the wave structure on satellite imagery seemed to be located along
a southwest-to-northeast oriented baroclinic zone (indicated
by a tighter packing of the 850 mb isotherms), with the individual banding
elements oriented generally perpendicular to the axis of the baroclinic
zone (above); however, radar echoes that developed
a few hours later were generally aligned closer with the axis of the baroclinic
zone (below). A northwest-to-southeast cross section
of NAM12 model output (along
line D-D’ orthogonal to the baroclinic zone axis) revealed elevated
pockets of frontogenesis and omega (within
the 600-850 mb layer) which may have played a role in the formation of
the regions of banding seen on both satellite imagery and radar reflectivity.

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A 250-m resolution MODIS true color image (above) from
the SSEC
MODIS Today site shows the cloud top waves in great detail over
northeastern Iowa. Note that some of the wave structure and orientation (just
south of the Iowa/Minnesota border) was similar to that seen on the radar images.

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A comparison of the MODIS “true color” RGB image (Red=channel 01, Green=channel 04, Blue=channel 03) and the corresponding “false color” RGB image (Red=channel 02, Green=channel 07, Blue=channel 07) from 19 November 2007 (above) shows snow cover over parts of New York, Vermont, New Hampshire, and Maine (extending northward into portions of southern Quebec in Canada). Both snow cover and clouds appear white on the true color image, but deep snow cover appears as darker shades of red (with clouds composed of ice crystals appearing as a lighter shades of red) on the false color image — this makes it relatively easy to discriminate snow cover from supercooled water droplet clouds (which appear as shades of white on the false color image). In fact, a few small patches of supercooled water droplet cloud can be seen over the region of deeper snow clover (along and just north of the US/Canada border). Snow depth data from the NOAA National Operational Hydrologic Remote Sensing Center (NOHRSC) indicated a number of sites reporting 5-10 inches (13-25 cm) of snow on the ground that morning.

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A NOAA-17 InfraRed (IR) image (above) depicted a well-defined eye and eyewall structure associated with Category 4 Cyclone Sidr while it was located over the Bay of Bengal on 15 November 2007. The CIMSS Advanced Dvorak Technique (ADT) intensity estimate around that time was 146 knots.

Animations of the Morphed Integrated Microwave Imagery at CIMSS (MIMIC) (above) showed Cyclone Sidr as it approached the coast of Bangladesh. This CIMSS MIMIC product was also featured on The Weather Channel by their tropical weather expert Dr. Steve Lyons (below).

Meteosat-7 IR images (below) indicated that Cyclone Sidr made landfall around 14:00 UTC between Calcutta, India (station identifier VECC) and Chittagong, Bangladesh (station identifier VGEG). Media reports suggest that the death toll in Bangladesh resulting from Cyclone Sidr is now greater than 3100 people.

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Meteosat-7 IR images sourced from the CIMSS Tropical Cyclones site (above) showed Category 4 intensity Tropical Cyclone Sidr as it moved northward across the Bay of Bengal on 14 November 2007. Increasing amounts of deep layer wind shear (below) to the north of the storm may act to diminish the intensity of Sidr somewhat as it approaches land, but catastrophic storm surge flooding will still be a danger across much of the flood-prone flat river delta regions along the coast of Bangladesh. A tropical cyclone with winds of 150 mph (240 km/hr) and a storm surge of 16-32 feet (5-10 meters) killed an estimated 500,000 people in Bangladesh in November 1970.

The CIMSS Advanced Dvorak Technique (ADT) plot (above) indicated an intensity estimate of 140 knots late in the day on 14 November — this was not long after the center of Sidr passed over a region of higher Ocean Heat Content over the Bay of Bengal (below).

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