GOES-East “Routine” scan sectors (covering a 6-hour period from 17:45 to 23:45 UTC)

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.

GOES-East “Rapid Scan Operations (RSO)” scan sectors (covering a 6-hour period from 17:45 to 23:45 UTC)

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).

List of the attributes associated with GOES imager Routine, RSO, SRSO, SRSOR and the GOES-R ABI schedules. Sample scenes are shown at the bottom.

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MODIS 11.0 µm IR Window channel brightness temperature

Pavlof Volcano (located at about 55.5 N, 162 W) in the Aleutian Islands had been experiencing a series of small eruptions that were captured by the constellation of polar-orbiting satellites that pass over the region. For example, a MODIS 11.0 µm IR Window channel image from 08:07 UTC on 16 May (above) showed a dark (warm) pixel over the volcano. That 0º C pixel was surrounded by values closer to -15º C.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR images

A comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) and 3.74 µm shortwave IR images at 12:12 UTC on 16 May 2013 (above) showed the bright glow of the volcano on the DNB, centered over a warm thermal anomaly of 47.5º C (orange color enhancement) on the shortwave IR. These were both signatures of hot lava flows from the summit and down along the northwest flank of Pavlof.

Volcanic plume characteristics derived from Aqua MODIS at 13:50 UTC

The high spectral resolution of MODIS — 36 different channels in the visible and infrared — on board the Terra and Aqua satellites allows for creation of products that quantitatively describe the volcanic ash cloud, beyond just locating the hot spot of the volcano itself. False color imagery, shown above (top left panel, derived from the brightness temperature differences indicated in the figure) from Aqua MODIS at 13:50 UTC, nicely outlines the volcanic ash plume in shades of red. The other three figure panels show the Ash Cloud Height (very important information for aviation concerns), the Ash Cloud Particle Size (which is related to how long it will take to settle out — small particles stay in the atmosphere for a longer time) and Ash Cloud Loading (what is the mass of volcanic ash in the column?).

A later 4-panel suite of products derived from MODIS data on Terra, at 21:31 UTC, is shown below. In addition to the high spectral resolution on MODIS, the polar orbiter satellites have good horizontal resolution over Alaska as well.

Volcanic plume characteristics derived from Terra MODIS at 21:31 UTC

A comparison of Suomi NPP VIIRS 0.64 µm visible channel and 3.74 µm shortwave IR channel images at 22:08 UTC (below) showed the hazy signature of the volcanic plume on the visible image, as well as a warm thermal anomaly exhibiting a brightness temperature of 40º C (yellow color enhancement) on the shortwave IR image. A Volcanic Ash Advisory had been issued for altitudes between the surface and 15,000 feet, as the volcanic plume drifted southeastward at 15 knots.

Suomi NPP VIIRS 0.64 µm visible channel and 3.74 µm shortwave IR channel images

GOES imaging of this eruption suffers because of limited channels (5) on the GOES Imager, and because of degraded spatial resolution at the high latitudes (as result of the very large satellite viewing angle). However, the hazy signature of the volcanic plume could still be seen drifting southeastward from Pavlof on GOES-15 0.63 µm visible channel images (below; click image to play animation). The location of the Pavlof volcano is denoted by the “P” on the images. Also of interest in the animation is the motion of sea ice in the Bering Sea north of the Aleutians, which could be seen once a break in the clouds moved over that area.

GOES-15 0.63 µm visible channel images (click image to play animation)

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GOES-15 (left) and GOES-13 (right) 0.63 µm visible channel images (click image to play animation)

An outbreak of tornadoes across the Dallas/Ft. Worth area in north Texas on 15 May 2013 produced up to 16 tornadoes (NWS summary) which were responsible for 6 fatalities. Hail as large as 4.0 inches in diameter and a wind gust as high as 80 mph also accompanied these severe thunderstorms (SPC storm reports). A McIDAS image comparison of GOES-15 (GOES-West) and GOES-13 (GOES-East) 0.63 µm visible channel data (above; click image to play animation)  showed the rapid development of convection across the north Texas region, with the storms exhibiting a number of overshooting tops. The locations of Granbury (G) and Cleburne (C) were noted on the images, where EF-4 and EF-3 tornado damage occurred.

A similar comparison of GOES-15 (GOES-West) and GOES-13 (GOES-East) 10.7 µm IR channel images (below; click image to play animation) showed the cold cloud top IR brightness temperatures associated with these storms, which were as cold as -63 C (darker red color enhancement) in the vicinity of Granbury and Cleburne around the time of the tornadoes.

GOES-15 (left) and GOES-13 (right) 10.7 µm IR channel images (click image to play animation)

GOES-13 sounder Lifted Index derived product images (click image to play animation)

These storms developed along an axis of instability and moisture that was located to the east of a dryline that was bulging eastward across north Texas — the GOES-13 sounder Lifted Index (LI) derived product images (above; click image to play animation) revealed LI values as low as -12.4 C (dark purple color enhancement) at 23:00 UTC, and the GOES-13 sounder Total Precipitable Water (TPW) derived product images (below; click image to play animation) showed that TPW values were as high as 46.7 mm or 1.84 inches (darker red color enhancement) at 22:00 UTC. METAR surface reports are plotted on the sounder images (Granbury is station identifier KGDJ, and Cleburne is station identifier KCPT).

GOES-13 sounder Total Precipitable Water derived product images (click image to play animation)

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GOES-13 Sounder Derived Lifted Index (click image to play animation)

Strong convection in the late afternoon/early evening produced wind damage and heat bursts over southern Wisconsin late in the day on May 14, 2013 in a region where severe convection was not considered likely. GOES Sounder data did an excellent job of depicting the instability that developed in the late afternoon. The animation above shows strong destabilization starting shortly after 1800 UTC, and persisting as the convection moved through southern Wisconsin.

GOES-13 Sounder Derived Lifted Index

The instability associated with this convective event was very localized, and easily slipped in between the radiosonde stations. This is therefore another example of the benefit of the GOES Sounder DPI products: Not only do they provide hour-by-hour coverage, so that an evolving situation can be monitored, but they can show mesoscale features that are poorly sampled by conventional radiosonde data. The above image shows the 2346 UTC 14 May GOES Sounder DPI LI over the upper midwest; superimposed upon the image are the Lifted Indices computed from radiosondes and the LI computed from the GFS model. The strongest instability is not well sampled by the radiosonde network.

GOES-13 Sounder Derived CAPE

Convective Available Potential Energy (CAPE) can also be used to diagnose the potential for convection. In regions where CAPE values are large, convection can grow explosively. The AWIPS screen capture of CAPE computed from the sounder, above, shows values exceeding 4000 J/kg even after the convection has passed!

GOES-13 Visible (0.63 µm) Imagery (click image to play animation)

Visible imagery from GOES-13, above, shows the development of the convection as it moves into the area of diagnosed instability. The Microburst Windspeed Potential Index (MWPI) predicts maximum wind gusts that might occur given the thermal profiles associated with developing convection. Attributes that promote downbursts are steep mid-level lapse rates (to enhance convective instability) and abundant dry air (to enhance evaporative cooling). The two animations below (created using McIDAS-V and this bundle) show a maximum in MWPI (with values near 50 — the relationship between MWPI and convective gusts is here) developing over southwest WI as the convection develops. (Data are from the Rapid Refresh model run at 2200 UTC on Tuesday 14 May). The animation of model soundings over Madison (bottom) indicates strong destabilization and mid-level drying, two components that enhance the potential for microbursts. (McIDAS-V animations courtesy of Ken Pryor, NOAA/NESDIS)

Microbust Windspeed Potential Index (MWPI) from 2200 UTC 14 May-0100 UTC 15 May over Wisconsin. Data from Rapid Refresh Model

Rapid Refresh Model Soundings over Madison, WI from 2200 UTC 14 May-0100 UTC 15 May over Wisconsin

GOES Sounder DPI products are available here. YouTube videos of the convection, obtained from the cameras on the roof of SSEC, are available here (looking east) and here (looking north).

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