GOES-13 10.7 µm IR images (click image to play animation)

A thunderstorm complex over the northern Gulf of Mexico on the morning of September 5th is being monitored for tropical development. This cluster originated as a mesoscale convective system that emerged from the southern edge of Isaac’s decaying circulation, as shown in the animation above. The animation, starting from Isaac’s landfall over the Mississippi Delta on 29 August, shows a complex developing over northern Alabama on 3 September and dropping southward through that state on 4 September, emerging into the Gulf on 5 September. An analysis of wind shear and Sea Surface Temperatures (taken from the CIMSS Tropical Weather Website) suggests that the system is moving into an environment favorable for strengthening. A loop of 850-mb vorticity also shows the evolution of the system, and the piece of Isaac that breaks off and heads back to the Gulf of Mexico.

Further information on this system is available from the National Hurricane Center.

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Suomi NPP VIIRS 0.7 µm Day/Night Band image + Precipitation reports

An AWIPS image of the Suomi NPP VIIRS 0.7 µm Day/Night Band (above) showed a night-time view of large swaths of wet ground across much of Kansas at 07:58 UTC (2:58 AM local time) on 05 September 2012. Many parts of central Kansas received significant rainfall as thunderstorms moved eastward across the state; five sites reported over 1 inch of precipitation, with as much as 1.90 inches falling near Potwin. In southeastern Kansas, also note the bright southeast-to-northwest oriented “streak” — a signature of lightning illuminating the cloud top as the VIIRS instrument was scanning that area.

Many areas of Kansas had been experiencing extreme to exceptional drought (below). Since the moon was in the Waning Gibbous phase, moonlight from 75% of the disk was able to provide sufficient illumination to reveal the darker rain-soaked ground surfaces, which stood out in contrast to the surrounding dry ground across the state.

Kansas drought monitor

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Suomi NPP VIIRS 0.8 µm Day/Night Band image (with surface observations)

An AWIPS image of Suomi NPP VIIRS 0.8 µm Day/Night Band data with overlays of surface observations (above) revealed the “dendritic fingers” signature of river valley fog across parts of southwestern Wisconsin and the adjacent Mississippi River Valley region at 08:17 UTC (3:17 AM local time) on 04 September 2012. The moon was in the waning gibbous phase (with 83% of the Moon’s visible disk illuminated), providing ample illumination of the night-time river valley fog features in the middle portion of the image. Additional cloud features could also be seen in other parts of the satellite scene, as well as the brighter signatures of city light across the region.

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Suomi NPP VIIRS 0.64 µm visible channel images

AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel data (above) and 11.45 µm IR channel data (below) showed a close-up view of the clouds associated with a strong storm (surface analysis) that was crossing the Aleutian Islands and entering the Bering Sea on 03 September – 04 September 2012. Banded convective elements can be seen along the western edge of the high cloud deck, which marked the leading edge of the advancing occluded frontal boundary.

At the time of the images, the winds at Shemya Air Force Base (station identifier PASY) were gusting to 57 knots (66 mph), but during the previous hour the peak winds were 61 knots (70 mph).

Suomi NPP VIIRS 11.45 µm IR channel images

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