GOES-12 10.7 µm IR images (with overlay of surface weather type)

An intense blizzard affected much of the central US on 24 December – 25 December 2009, significantly disrupting travel and commerce from North Dakota to Texas. Oklahoma City OK received 14.1 inches of snow, which was both their greatest 24-hour snowfall and their greatest storm total snowfall on record. McIDAS images of the GOES-12 10.7 µm IR channel data (above; also available as a QuickTime animation) showed the evolution of a well-defined Trough of Warm Air Aloft (TROWAL) signature across Oklahoma and Texas — with moderate to heavy snow falling just to the north and west of the pivot point of the southern/eastern edge of the colder (-30º to -50º C, dark blue to violet color enhancement) cloud top temperatures. Surface winds gusted as high as 64 mph in Oklahoma, creating white-out conditions with blowing and drifting snow.

On the morning of 25 December, a comparison of AWIPS images of the MODIS visible channel and a false-color Red/Green/Blue (RGB) composite (below) showed the areal extent of significant snow remaining on the ground — snow cover on the RGB image was highlighted with a red color enhancement, in contrast to supercooled water droplet clouds which appeared as brighter white features. This also offers a glimpse at the type of RGB image capability that should be available with the upcoming AWIPS-2 software. For higher-resolution MODIS true color and false color images from 25 December, see the SSEC MODIS Today site.

MODIS visible image and false-color Red/Green/Blue (RGB) image

GOES-12 6.5 µm water vapor images (below; also available as a QuickTime animation) displayed the impressively large size of the circulation associated with the storm as it intensified from 25 December to 26 December. In the north-central US, entire Interstate highway systems were shut down for an extended period across the Dakotas — snowfall amounts were as high as 40.0 inches at Lead, South Dakota (with amounts over 24 inches in North Dakota and Minnesota). Significant accruals of ice (up to 0.4 inch) from freezing rain occurred in parts of Iowa, Illinois, and Indiana. Winds gusted as high as 76 mph in western South Dakota (HPC storm summary).

GOES-12 6.5 µm water vapor images

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MODIS true color image (displayed using Google Earth)

Strong winds associated with a developing storm over the southwestern US caused areas of blowing dust across southern Arizona on 22 December 2009. A MODIS true color image from the SSEC MODIS Today site  (above) showed one of the larger plumes of blowing dust which was moving northeastward across the region. On a smaller scale, there were also localized areas of very thick blowing dust that reduced visibility and caused a number of multiple-vehicle accidents along Interstate 10 between Tucson and Phoenix — fatalities were reported with one of the larger vehicle pile-ups near Casa Grande.

AWIPS images of the AVHRR Cloud Top Temperature (CTT) and Cloud Particle Effective Radius products (below) indicated that CTT values associated with the large-scale blowing dust plume were around +10 to +15º C, which was between the 921 and 850 hPa pressure levels on the Tucson AZ rawinsonde report. The dust particle effective radius values were in the 15-25 µm range — much smaller than the 50-100 µm values seen for the cloud features located in other parts of the image scene.

AVHRR Cloud Top Temperture and Cloud Particle Effective Radius products

GOES-14 visible images

As part of its ongoing NOAA Science Test, GOES-14 was emulating GOES-West operations on that day. McIDAS images of the GOES-14 visible channel data (above) showed the evolution of the large-scale dust plume as it became more organized along the Arizona/Mexico border and moved northeastward toward the Casa Grande (station identifier KCGZ) area. Also worthy of mention is the fact that the convection that moved through the Phoenix area generated a few reports of 0.25 inch diameter hail.

A clue to the approach of strong mid-tropospheric winds could be seen in a comparison of 4-km resolution GOES-14 6.5 µm water vapor and 8-km resolution GOES-11 6.7 µm water vapor images (below) — lee waves were apparent immediately downwind of the higher terrain, particularly over Baja California. Note how the improvement in spatial resolution from 8-km to 4-km improves the ability to detect the complexity and the areal extent of the lee waves on water vapor imagery. When GOES-11 is due for replacement as the operational GOES-West satellite, GOES-14 will likely take over that duty.

GOES-14 6.5 µm and GOES-11 6.7 µm water vapor images

A MODIS 11.0 µm – 12.0 µm IR difference image (below) was useful for helping to highlight the large-scale blowing dust plume at 20:09 UTC. Beginning with GOES-12, the Imager instrument 12.0 µm IR channel was replaced with a 13.3 µm channel, preventing the application of this type of IR difference blowing dust identification on the more recent GOES satellites — however, the 12.0 µm IR channel will return on the ABI instrument aboard GOES-R.

MODIS 11.0 µm - 12.0 µm IR difference image

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GOES-14 10.7 µm IR imagery (click image for a QuickTime animation)

An intense winter storm impacted a large portion of the mid-Atlantic and Northeast regions of the US on 18 December – 19 December 2009, creating blizzard conditions and setting a number of snowfall records (listing of snowfall totals). As a part of its ongoing NOAA Science Test, the GOES-14 satellite was placed into Super Rapid Scan Operations (SRSO) mode, supplying imagery at 1-minute intervals during much of the storm life cycle. McIDAS images of the GOES-14 10.7 µm IR channel data (above; click image for a 61 MB QuickTime animation) showed the formation of a large, cold cloud shield early in the period, followed by the development of a number of convective bands after about 03:00 UTC on 19 December which then helped to further enhance snowfall rates.

As the storm center was moving across the northern Gulf of Mexico on 18 December, it even exhibited an eye-like appearance on GOES-14 visible channel images (below; click image for a QuickTime animation), which is suggestive of a warm seclusion.

GOES-14 visible channel imagery (click image for a QuickTime animation)

On 19 December, a comparison of 15-minute interval GOES-12 and 1-minute interval GOES-14 visible images centered off the east coast of the Delmarva Peninsula (below; courtesy of Tim Schmit, NOAA/ASPB) offers a compelling demonstration of the value of more frequent imaging for monitoring the development and evolution of cloud features. During this 18:15 – 19:04 UTC time period, there were only 3 images available from GOES-12, compared to 44 images using GOES-14. A longer animation of GOES-14 SRSO visible imagery during the afternoon hours on 19 December can be seen here.

GOES-12 and GOES-14 visible images

On the day following the storm (20 December), a comparison of AWIPS images of the MODIS visible channel and a false-color Red/Green/Blue (RGB) image (below) demonstrates the value of using RGB imagery to help discriminate between snow cover (red-enhanced features) and supercooled water droplet clouds (brighter white features) across the mid-Atlantic states. This also offers a glimpse at the type of RGB image capability that should be available with the upcoming AWIPS-2 software.

MODIS visible and false-color Red/Green/Blue (RGB) images

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GOES-12 sounder radiance images

Beginning in September 2009, the GOES-12 sounder instrument filter wheel began to experience problems (tied to syncronization issues associated with increased friction in the filter wheel bearing) that resulted in intermittent periods of noisy data and pixel dropouts — this was previously discussed on a 25 November 2009 CIMSS Satellite Blog post. Originally the problem was primarily affecting the shortwave IR channels (sounder bands 13-18) — however, at times it had an impact on all 19 of the sounder channels, as seen on a 17 December 2009 multi-panel display of GOES-12 sounder radiance images (above) from the CIMSS Realtime GOES Derived Product Imagery site. This GOES-12 sounder filter wheel problem is currently being investigated by NOAA/NESDIS engineers.

GOES sounder Total Precipitable Water product

While this GOES-12 sounder filter wheel problem persists, AWIPS users of GOES sounder Derived Product Imagery (DPI) such as Total Precipitable Water (above) and Cloud Top Height (below) will notice periods of noisy data characterized by widespread pixel drop-outs over the eastern US and adjacent portions of the Gulf of Mexico and the western Atlantic Ocean. Note that the sounder DPI over the western US (using data from GOES-11) does not exhibit any pixel drop-outs.

GOES sounder Cloud Top Height product

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