GOES-11 (GOES-West)/ GOES-15 / GOES-13 (GOES-East) 10.7 µm IR images

Severe thunderstorms propagated southeastward across far northeastern Montana late in the day on 26 July 2010. McIDAS images of GOES-11 (GOES-West), GOES-15, and GOES-13 (GOES-East) 10.7 µm IR data (above; each image set is displayed in the naive projection of the respective satellite) showed that a subtle “enhanced-v” storm top signature first began to appear on GOES-13 imagery around 23:25 UTC, with this signature becoming more apparent by 23:45 UTC on all 3 satellite IR images. In addition, a well-defined cold/warm thermal couplet (with an IR brightness temperature difference of 11-14º C) was displayed on all three satellite IR images around 01:00 UTC. Note that more frequent images were available from GOES-11 and GOES-13, since both of those operational satellites had been placed into Rapid Scan Operations (RSO) mode. GOES-15 is providing images as part of its Post Launch Testing.

According to the SPC Storm Reports, these storms produced hail as large as 4.0 inches in diameter, and produced a tornado that was responsible for EF-3 damage and 2 fatalities. This was only the 4th EF3 damage producing tornado on record in Montana, and the deadliest tornado in that state since 1923.

The GOES-15 satellite (positioned at 89.5º West longitude) had the most direct view of the storm — and an animation of 0.63 µm visible channel images (below) showing some interesting cloud top structure, including several overshooting tops as well as a well-defined anvil plume later in the animation sequence.

GOES-15 0.63 µm visible images

The GOES-11 (GOES-West) satellite (positioned at 135º West longitude) offered a more oblique view of the severe thunderstorms (below). Viewing the storms from such a high western angle, one can see the appearance of low-level inflow feeder band clouds as the thunderstorms were intensifying. In addition, since GOES-11 was in Rapid Scan Operations (RSO) mode, more images were available compared to the normal 15-minute scan interval used with GOES-15 above.

GOES-11 0.65 µm visible images

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GOES-13 10.7 µm IR images

Several days before the largest hailstone on record in the US fell in central South Dakota, McIDAS images of 4-km resolution GOES-13 10.7 µm IR data (above) showed a cluster of severe thunderstorms that propagated southeastward across far northwestern South Dakota on 19 July 2010. From a satellite perspective, this convection did not appear to be unusually intense in terms of cold IR cloud top brightness temperatures (only as cold as -63º C, darker red color enhancement) or any “enhanced-V” or other typical severe storm top signatures, but it nonetheless produced a long-duration wind and hail event that resulted in a remarkably long and wide hail damage path.

This wind-driven hail damage path can be seen on the comparison of three 250-meter resolution MODIS true color Red/Green/Blue (RGB) images (created using bands 4/3/1) from 15 July (4 days before the event), 20 July (one day after the event), and 25 July (6 days after the event) acquired from the SSEC MODIS Today site. The hail damage swath appears as the distinct broad tan-colored feature that is oriented from northwest to southeast. According to the SPC Storm Reports, the largest hail size was 2.50 inches in diameter, and the maximum wind gust was 70 mph in that particular region. However, a number of the storm reports mentioned a wind-driven hail duration of 15-30 minutes, which exacerbated the crop damage. One storm report mentioned “1150 acres of corn stripped”.

MODIS true color RGB images from 15 July, 20 July, and 25 July 2010

According to Matt Bunkers (SOO at the NWS forecast office at Rapid City SD), this event "started with two HP supercells across southeastern Montana which then merged into a bow echo across western South Dakota". These 2 distinct storms in southeastern Montana show up with better clarity on the 1-km resolution NOAA-18 10.8 µm IR image compared to the 4-km resolution GOES-13 10.7 µm IR image (below). The cloud-top IR brightness temperatures are also significantly colder on the NOAA-18 image (-61º C) than on the GOES-13 image (-52“ C).

NOAA-18 10.8 µm IR and GOES-13 10.7 µm IR images

A false-color RGB image (created using NOAA-18 AVHRR channels 01/02/04) is shown below.

NOAA-18 false-color RGB image

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AWIPS menu of 1-km resolution MODIS products from CIMSS

July 2010 marks the 4 year anniversary of the point when CIMSS  first began to provide MODIS images and products to National Weather Service (NWS) users in an AWIPS format. These MODIS images and products are available for interested NWS offices to add to their local AWIPS workstations via Unidata LDM subscription. A screen capture of the AWIPS menu of 1-km resolution MODIS products is shown above, with a sample of those products shown below over the southeastern US on 23 July 2010 (when Tropical Storm Bonnie happened to be moving across southern Florida and weakening to a Tropical Depression). In addition, there is also a 1-km resolution fog/stratus product (available only at night).

This MODIS in AWIPS project has been a critical component of the CIMSS contribution to the GOES-R Proving Ground effort — and along with extensive user training, has been a successful demonstration of the “Research to Operations” concept.

1-km resolution MODIS images and products available from CIMSS

In addition to supplying the MODIS images and products, CIMSS also includes a MODIS Orbit Itinerary Viewer tool that is available from the AWIPS menu to assist the users in planning when to expect MODIS image availability on any given day. Also, for NWS users in Wisconsin, 250-meter resolution MODIS true color images are also available for viewing from the AWIPS menu.

AWIPS menu of 4-km resolution MODIS products from CIMSS

Similarly, a screen capture of the AWIPS menu of MODIS 4-km resolution products is shown above, with those corresponding MODIS products shown below.

4-km resolution MODIS products available in AWIPS from CIMSS

In an effort to continually improve the quality of the MODIS products being delivered, a recent development has been the correction of the “bow-tie” image artifacts that affect the outer edges of the MODIS scan swath (due to the scanning strategy of the MODIS instrument). In order to most effectively perform this bow-tie image correction, CIMSS has chosen to employ the MODIS Swath Reprojection Tool (MRTSwath) that is supported by NASA. Several examples of how the image bow-tie correction process performs are shown below. (Notice to NWS MODIS users: the bow-tie correction will be applied to all 1-km resolution MODIS images and products distributed by CIMSS beginning 27 July 2010).

MODIS visible images (with and without bow-tie correction)

MODIS IR images (with and without bow-tie correction)

MODIS Land Surface Temperature product images (with and without bow-tie correction)

MODIS Sea Surface Temperature product images (with and without bow-tie correction)

MODIS fog/stratus product images (with and without bow-tie correction)

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GOES-13 (top) and GOES-15 (bottom) 10.7 µm IR images

McIDAS images of GOES-13 and GOES-15 10.7 µm IR images (above) showed the development of severe thunderstorms that produced very large hail, tornadoes, and damaging surface winds (SPC storm reports) in central South Dakota on 23 July 2010. This storm produced the largest US hailstone on record: 8 inch diameter, 18.6 inch circumference, 1.9375 pound weight — photos of the record-setting largest hailstone were taken by staff from the Aberdeen, South Dakota NWS forecast office. The coldest cloud top IR brightness temperatures were -71º C (darker black color enhancement) at 23:25 and 23:32 UTC. Since the GOES-13 satellite had been placed into Rapid Scan Operations (RSO), images were available as often as every 5-10 minutes (as opposed to every 15 minutes via the routine image scan schedule on GOES-15).

The corresponding GOES-13 and GOES-15 0.63 µm visible channel images (below) displayed a well-defined storm top anvil with distinct overshooting tops (GOES-13 visible images only: Animated GIF). Prior to convective development, the appearance of the quasi-stationary low-level parallel cloud bands suggests that there was strong warm air advection into the region from the southwest (HPC surface forecast).

GOES-13 (top) and GOES-15 (bottom) 0.63 µm visible images

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GOES-13 Sounder Total Precipitable Water (TPW) product

AWIPS images of the GOES-13 Sounder Total Precipitable Water (above) and Lifted Index (below) depicted a broad axis of moisture and instability that extended northwestward into central South Dakota on that day.

GOES-13 Sounder Lifted Index (LI) product

A comparison of the 1-km resolution GOES-13 0.63 µm visible image and the 4-km resolution GOES-13 10.7 µm IR image at 22:45 UTC (around the time of a report of 85 mph surface winds) is seen below. The apparent offset between the location of the overshooting top and the location of the surface wind gust is due in part to parallax error (a result of the large viewing angle from the GOES-13 satellite, which is positioned over the Equator at 75º West longitude).

GOES-13 visible and IR images at 22:45 UTC (near the time of a 85 mph wind gust)

A comparison of the 1-km resolution 0.63 µm GOES-13 visible image and the 4-km resolution 10.7 µm IR image at 23:10 UTC (around the time of a report of “softball size” 4.25 inch diameter hail) is shown below.

GOES-13 visible and IR images at 23:10 UTC (near the time of 4.25 inch diameter hail)

As noted above, the coldest cloud top IR brightness temperatures observed for this storm were -71º C — according to the rawinsonde profile data from Rapid City, South Dakota (below) this temperature corresponded to an altitude of around 55,000 feet or 16,800 meters.

Rawinsonde profile from Rapid City SD at 00 UTC on 24 July

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