A devastating tornado struck Moore, Oklahoma just after 20:00 UTC or 3:00 PM local time on 20 May 2013, causing extensive (EF4 to EF5) damage and at least 24 fatalities. McIDAS images of GOES-15 (GOES-West) and GOES-13 (GOES-East) 0.63 µm visible channel data (above) showed the line of rapidly-developing thunderstorms over southern and central Oklahoma during the early afternoon hours — Moore is located about halfway between Oklahoma City (OKC) and Norman (OUN). Earlier in the day the GOES-13 satellite had been placed into Rapid Scan Operations (RSO) mode (providing images as frequently as every 5-10 minutes), while the GOES-15 satellite was placed into Super Rapid Scan Operations (SRSO) mode (providing bursts of imagery at 1-minute intervals) after 20:15 UTC. According to the preliminary NWS damage survey, the tornado began around 19:45 UTC just west of Newcastle, and ended around 20:35 UTC just east of Moore.

An AWIPS comparison of 1-km resolution Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images about an hour before the tornado arrived in Moore (above) revealed the presence of shadowing from overshooting tops and cloud-top IR brightness temperatures as cold as -68º C. About 30 minutes prior to the Moore tornado, a comparison of 1-km resolution Aqua MODIS 0.65 µm visible channel and 11.0 µm IR channel images (below) again indicated signatures of vigorous overshooting tops, with cloud-top IR temperatures as cold as -76º C.

Comparisons of the 1-km resolution VIIRS 11.45 µm IR and MODIS 11.0 µm IR images with their corresponding 4-km resolution GOES-13 10.7 µm IR images (below) demonstrated the value of higher spatial resolution to aid in the earlier and more accurate detection of the cold cloud-top IR brightness temperatures values associated with these rapidly-developing convective cells. There were significant differences in the magnitude of the coldest cloud-top IR brightness temperatures with the more northerly cell that spawned the Moore tornado:  -68 C on VIIRS vs -51 C on GOES, and -76 C on MODIS vs -62 C on GOES. The northwestward shift in the location of features on the GOES-13 images was due to parallax.

A 250-meter resolution Aqua MODIS true-color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (below; viewed using Google Earth) shows a closer view of the northernmost cell that produced the Moore tornado, along with hail as large as 3.25 inches in diameter (SPC storm reports).

GOES-13 sounder Convective Available Potential Energy (CAPE) derived product images (below; click image to play animation) showed how the atmosphere rapidly destabilized during the day, with CAPE values in excess of 5000 J/kg (lighter purple color enhancement) at 18:00 UTC east of the stationary frontal boundary just prior to convective development.

Cloud Top Temperature retrievals created using data from the IASI, CrIS, and AIRS polar-orbiting sounder instruments (below; courtesy of Elizabeth Weisz and Nadia Smith, CIMSS) showed the rapid trend in cloud-top cooling during the 15:56-19:35 UTC timeframe.

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A comparison of AWIPS images of Suomi NPP VIIRS 1.61 µm “snow/ice discrimination channel” data from 19 May and 20 May 2013 (above) revealed the areal extent of flooding along the Yukon River upstream of the Fort Yukon (station identifier PFYU) area in northeastern Alaska. Both ice and water are strong absorbers at the 1.61 µm wavelength, so they appear very dark on the images. The flooding along the Yukon River began as a surge of ice and water moved through the Eagle, Alaska (station identifier PAEG) area on 17 May, then continued downstream to produce major flooding in the Circle, Alaska area on 19 May (Circle is located about halfway between PAEG and PFYU). An ice jam had formed about 12 miles upstream of Fort Yukon, which then impounded the flow of ice and water that had flooded Circle, leading to the increased flooding seen upstream of Fort Yukon on 20 May.

A comparison of Suomi NPP VIIRS 0.64 µm visible channel, 0.86 µm “land/water discrimination channel”, and 1.61 µm “snow/ice discrimination channel” at 20:52 UTC on 20 May (below) showed how the 0.86 µm and 1.61 µm images can be used to identify the darker flooded portions of the Yukon River that are not apparent on the 0.64 µm visible image.

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The GOES-15 (GOES-West) satellite was placed into Super Rapid Scan Operations (SRSO) on 18 May 2013 (to support the IfloodS field experiment), providing bursts of imagery at 1-minute intervals. At the same time, the GOES-13 (GOES-East) satellite had been placed into Rapid Scan Operations (RSO) due to the threat of severe weather over the central US, providing images as frequently as every 5-10 minutes. A comparison of 0.63 µm visible channel GOES-15 SRSO  images with GOES-13 RSO images covering western Kansas, western Oklahoma, and the Texas Panhandle regions (above; click image to play animation; also available as a QuickTime movie) showed interesting views of the convective storm development — both from a perspective of the different satellite viewing geometries, and also the different temporal resolution from the different scanning strategies of the two GOES satellites. One of the more notable tornadoes on this day (SPC storm reports) moved through Rozel, Kansas.

About a half hour prior  to the start of the GOES-15 SRSO period, a sequence of three AWIPS images of 1-km resolution IR data from POES AVHRR (12.0 µm), Suomi NPP VIIRS (11.45 µm), and Aqua MODIS (11.0 µm) showed the rapid cooling of cloud-top IR brightness temperatures (to values of -70 F and colder, black color enhancement), even before any cloud-to-ground lightning strikes were detected (below).

A comparison of the 19:43 UTC 1-km resolution Suomi NPP VIIRS 11.45 µm IR image with the corresponding 4.km resolution GOES-13 10.7 µm IR image (below) demonstrated the value of higher spatial resolution for the earlier and more accurate detection of the cold cloud-top IR brightness temperatures values associated with the rapidly-developing convective cells over southwestern Kansas. The actual times that the two satellite were imaging the storms were very close, yet the difference in coldest IR brightness temperature values (-58 C on GOES, compared to -77 C on VIIRS) was quite striking. The northwestward shift in the location of features on the GOES-13 image was due to parallax.

On the following day (19 May 2013), GOES-15 was again placed into SRSO mode, allowing a similar GOES-15 SRSO vs GOES-13 RSO visible image comparison of the development of severe convection over Oklahoma and Kansas (below; click image to play animation; also available as a QuickTime movie). One of the more notable tornadoes on this day (SPC storm reports) moved through Shawnee, Oklahoma, causing 2 fatalities.

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In normal or “Routine” operations, GOES Imagery (from both GOES-East and GOES-West) follows a schedule that includes scans of CONUS (Continental US) nominally every 15 minutes.

For GOES-East, these are images at :02, :15, :32 and :45 after the hour. The :02 and :32 images are CONUS only: the southern boundary is the central Caribbean Sea and the eastern boundary stretches from Newfoundland to the Windward Islands. The :15 and :45 images include the entire north Atlantic Ocean and stretch southward to 20 S latitude (these are called ‘Northern Hemisphere Extended’). Full-disk images are produced every three hours (02:45, 05:45, 08:45, 11:45, 14:45, 17:45, 20:45 and 23:45 — all times UTC). The Full-Disk image takes 26 minutes to scan and that means a CONUS scan does not occur during the Full-disk scan. In routine operations, after the CONUS scan at :02 and :32 minutes past the hour, a South American scan over Chile and Argentina occurs (starting at :09 and :39 minutes past the hour). On a ‘normal’ day, nearly 130 images are produced by the Imager of GOES-13; of these, 87 are CONUS. An example of the Routine scan sectors is shown above (also available as a QuickTime movie), and a diagram of the Routine scan sectors is also shown here.

There is also daily ‘station-keeping’ during which times (00:34-00:40 and 15:30-15:45 for GOES-13) system scheduling, diagnostics and maintenance are performed.

During GOES-East Rapid Scan Operations (RSO), scanning of the Southern Hemisphere is curtailed sharply. The Northern Hemisphere Extended imagery at :15 and :45 is replaced by images that extend only to the Equator (and take 9 minutes to scan, versus 14 for the Northern Hemisphere Extended). The only Southern Hemisphere imagery scanned — other than the full disk image every three hours — is a small segment over the tropical eastern Pacific, the Southern Hemisphere Short sector that provides information for Sea surface temperature estimates. These images are produced hourly on the half-hour and take less than two minutes to scan. RSO operations yields CONUS imagery from GOES-13 at :02, :10, :15, :25, :32, :40, :45, and :55, every hour, except when the full disks are scanned at times noted above, in which cases the :55, :02 and :10 imagery are not scanned. RSO imaging produces almost 160 images; more than 120 of those are CONUS. An example of the RSO scan sectors is shown above (also available as a QuickTime movie), and a diagram of the RSO scan sectors is shown here.

During Super Rapid Scan Operations (SRSO), southern Hemisphere scanning includes only the every-three-hour Full Disk image. Northern Hemisphere scanning continues (:15 and :45), the CONUS scans are shifted slightly (:59 and :30) and small sectors are scanned at one-minute intervals (the one-minute interval determines how many lines can be scanned). These are at :04, :05, :06, :07, :08, :09, :10 or :11, :12, :25, :35, :36, :37, :38, :39, :40, :41 or :42, :43 and :55. An example of SRSO scan sectors is shown here (QuickTime movie), and a diagram of SRSO sectors is shown here. During a few days in August-October 2012 and also in June and August 2013 GOES-14 will be performing Super Rapid Scan Operations for GOES-R Super Rapid Scan Operations for GOES-R (SRSOR) scans (SRSOR image viewer).

The link for GOES-East scheduling is here.

The table below presents the schedules for GOES-East for the different operations: Routine, Rapid-Scan Operations (RSO), Super Rapid-Scan Operations (SRSO), Experimental Super Rapid-Scan Operations for GOES-R (SRSOR), and GOES-R ABI (GOES-R is scheduled to launch in 2015).

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