MTSAT-1R visible images (above) showed the large shadow from a solar eclipse, which could be seen moving from west to east across Asia and the Pacific Ocean on 22 July 2009. According to Wikipedia, this was the longest-lasting total solar eclipse of the 21st century, with a duration of up to 6.5 minutes in some locations.

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The National Weather Service forecast office at Cheyenne WY requested that both the GOES-11 (GOES-West) and the GOES-12 (GOES-East) satellites be placed into Rapid Scan Operations (RSO) to monitor severe convection across their County Warning Area (CWA) on 20 July 2009:

SENIOR DUTY METEOROLOGIST NWS ADMINISTRATIVE MESSAGE
NWS NCEP CENTRAL OPERATIONS CAMP SPRINGS MD
2114Z MON JUL 20 2009

GOES RSO INFO…

A GOES EAST RSO WILL BE IN EFFECT FROM 2226Z TILL 0426Z
AND GOES WEST RSO WILL BE IN EFFECT FROM 2203Z TILL
0403Z THIS EVENING AS REQUESTED BY WFO CYS /CHEYENNE/
WHO IS ON THE CUSP OF THE SATELLITE RSO COVERAGE AREAS
FOR SVR WX MONITORING SUPPORT.

While there were reports of hail up to 1.0 inch in diameter in the Cheyenne CWA, the thunderstorms that developed further to the east over western Nebraska and western Kansas were more severe (producing tornadoes in Kansas, and hail as large as 4.25 inches in diameter in both Kansas and Nebraska). A comparison of GOES-11 and GOES-12 visible images (above) shows the view of these storms from each satellite perspective. Note that some features were easier to see from the GOES-11 perspective, which allowed more of a view from the side (to reveal surface boundaries and flanking line development more clearly).

A comparison of GOES-11 and GOES-12 10.7 µm IR images (below) shows that the development of a distinct “enhanced-v” signature was apparent on imagery from both satellites from the 23:00 to 23:11 UTC period. The coldest IR brightness temperatures were -67º C (darker black color enhancement) from both GOES-11 and GOES-12.

These thunderstorms appeared to be propagating southward ahead of an advancing cold frontal boundary, and along a decaying stationary frontal boundary that was oriented northwest-to-southeast from western Nebraska into central Kansas. GOES sounder Derived Product Images (DPI) of Lifted Index (LI) and Total Precipitable Water (TPW) (below) indicated that there was an axis of instability (LI values of -4 to -6 º C) and moisture (TPW values of 20-30 mm, or 0.8 to 1.2 inches) along the stationary frontal boundary.

A few hours later, thunderstorms that developed ahead of the advancing cold front in Oklahoma and southern Kansas exhibited cloud top IR brightness temperatures as cold as -84º C (purple color enhancement) on AWIPS imagery of the MODIS 11.0 µm channel (below).

===== 21 JULY UPDATE =====

On the following day, MODIS 3.7 µm shortwave IR and MODIS Land Surface Temperature (LST) images (below) revealed a long swath of rain-cooled ground across far western Kansas. MODIS LST values were in the 75-85º F range (green colors) within the swath of rain-cooled ground, in contrast to LST values in excess of 110º F (darker orange colors) just to the west.

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An intense upper-level low developed over the Canadian Arctic Archipelago on 14 July 2009, and subsequently migrated southwestward over the Northwest Territories, Yukon, and northeastern Alaska by 16 July 2009. AWIPS images of the GOES-11 + GOES-12 water vapor channel composite (above) showed a well-defined signature of the intensifying upper low during this period, with a large area of warmer/drier air (darker blue colors) within the circulation.

What was remarkable about this warm/dry signature on the water vapor imagery is the fact that such detail could be seen, in spite of the very large satellite viewing angle of the GOES satellites. Water vapor imagery is prone to the effect of “limb brightening” as the water vapor weighting function is shifted to higher, colder altitudes over the higher latitude regions — this tends to make water vapor imagery appear rather cold and “washed out” over the Arctic much of the time. However, in this case the dynamic tropopause (taken to be the pressure of the 1.5 Potential Vorticity Unit surface) was brought downward to the 850 hPa pressure level on 14 July (below) as the low intensified — and snow was even reported at Norman Wells (station identifier CYVQ) in the Northwest Territories on 16 July.

On the GOES water vapor imagery above there was a hint of some embedded vortex structure developing within the upper low circulation. These vorticies (which were likely small stratospheric intrusion vorticies) were much easier to identify on the 1-km resolution MODIS water vapor image than on the “8-km” resolution GOES-11 water vapor image (below) — this is partly due to the upward shift of the water vapor weighting function mentioned previously, and also due to the fact that the 8-km GOES-11 water vapor pixels were effectively about 30 km in size due to the very large satellite viewing angle.

Another interesting satellite signature was the appearance of a “thermal anomaly” over the Arctic Ocean north of Alaska on the GOES-11 10.7 µm IR window channel image at 09:00 UTC (below, bottom panels). At that particular time, there is a great deal of solar reflection off the water and ice surface, which appears very bright on the visible imagery (top panels), and very hot (dark black enhancement) on the 3.9 µm shortwave IR imagery (center panels). The intense solar reflection effectively causes the IR window channel brightness temperature to “roll over” from very warm to very cold values (black to white color enhancement). This IR window channel thermal anomaly does not appear if cloud cover masks the highly reflective nature of the water and ice in the Arctic Ocean.

Later in the day, GOES-11 visible imagery showed that the southern edge of the ice in the Arctic Ocean had receded a considerable distance from the northern coast of Alaska (above). The ice edge could be seen in greater detail using 1-km resolution MODIS true color imagery (below, courtesy of the GINA, University of Alaska Fairbanks SwathViewer).

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MTSAT-1R InfraRed (IR) images from the CIMSS Tropical Cyclones site (above) showed the rapid development of a cold Central Dense Overcast (CDO) as Tropical Storm 07W (Molave) intensified east of the Philippines in the West Pacific Ocean on 16 July 2009. It is interesting to note that the CDO was centered a considerable distance to the southwest of the low-level circulation of the tropical cyclone.

4-km resolution MTSAT-1R 10.3 µm IR cloud top brightness temperatures (above) were a cold as -92.4º C (purple color enhancement) at 12:30 UTC. 1 hour and 15 minutes later, a 1-km resolution MODIS 11.0 µm IR image (below) indicated that cloud top IR brightness temperatures were still as cold as -92.1º C.

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