An isolated severe thunderstorm developed over the northern portion of the Black Hills of South Dakota around 18 UTC (Noon local time) on 27 May 2014, and moved southeastward producing hail as large as 2.75 inches in diameter and a tornado (SPC storm reports), as well as up to 3 inches of heavy rainfall. 4-km resolution GOES-13 10.7 µm IR channel images (above; click image play animation) showed the cold cloud-top IR brightness temperatures associated with the storm (which reached a minimum of -59º C at 21:40 UTC). Convective initiation was aided by convergence of a surface cold frontal boundary with the topography of the Black Hills, as seen here.

A comparison of 375-meter resolution Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 19:38 UTC (below) revealed a minimum cloud-top IR brightness temperature of -68º C. Subsequent cumulus cloud development is seen to be suppressed in the stable outflow region in the wake of the storm.

A comparison of the VIIRS IR image with the closest available GOES-13 IR image (below) demonstrated the advantage of higher spatial resolution of polar-orbiting satellite imagery, as well as the lack of parallax error associated with the geostationary-orbit GOES imagery. The coldest cloud-top IR brightness temperature on the GOES-13 image was -57º C, compared to -68º C on the VIIRS image.

The NOAA/CIMSS ProbSevere model identified this storm as a potential producer of severe weather. The animation below shows the evolution of the MRMS radar signal with ProbSevere overlain from 1812 UTC through 2000 UTC. The Radar object that is highlighted has strong satellite growth rate (observed at 1725 UTC), MUCAPE of 1750 J/kg and Effective Shear of ~19 knots. At 1810 UTC, when MESH values are 0.53″, ProbSevere is 18%; four minutes later at 1814 UTC MESH increased to 0.94″ and ProbSevere increased to 69%. The National Weather Service issued the first warning at 1905 UTC and severe hail (1.5″ in diameter) occurred at 1910 UTC (when MESH was 1.64″ and ProbSevere was 94% and less than an hour after ProbSevere increased above 50%).

ProbSevere later in the day, after 2200 UTC, continues to track the hail-producing storm in far southwestern South Dakota. Although ProbSevere is designed to show when the first severe reports might occur, it does continue to provide useful information. In time, as below at 2222 UTC, the satellite growth parameters are replaced by ‘Mature Storm’ as a reminder that this tracked feature is not new.

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Amanda became the first tropical storm of the 2014 East Pacific Basin season on 23 May 2014. 4-km resolution GOES-15 (GOES-West) 10.7 µm IR channel images from the CIMSS Tropical Cyclones site (above; click image to play animation) an increasing amount of organization to the convection associated with Amanda.

A similar trend was seen in 1-km resolution GOES-15 0.63 µm visible images (below; click image to play animation).

Given that Amanda was in an environment of low deep layer wind shear (above) and over warm sea surface temperatures (below), intensification to Category 1 hurricane intensity was forecast.

===== 24 May Update =====

McIDAS images of GOES-15 0.63 µm visible channel data (above; click image to play animation) and 10.7 µm IR channel images (below; click image to play animation) showed that Amanda began to display an eye signature as it intensified to hurricane strength later in the day on 24 May. Amanda became the second earliest major hurricane on record in the East Pacific basin.

===== 25 May Update =====

In the early hours of 25 May UTC, Amanda underwent a period of rapid intensification, reaching Category 4 intensity around 12 UTC. This trend of rapid intensification is very evident on a plot of the CIMSS Automated Dvorak Technique (above). According to a National Hurricane Center discussion, Amanda became the strongest May hurricane on record over the East Pacific basin in the satellite era.

Hurricane Amanda exhibited a small eye, which was easily seen in 0.63 µm visible channel imagery (below; click image to play animation) from GOES-15 (GOES-West), GOES-14, and GOES-13 (GOES-East). The small-diameter eye was also apparent in DMSP SSMIS 85 GHz microwave imagery at 01:43 UTC and 15:00 UTC.

A McIDAS-V nighttime comparison of  Suomi NPP VIIRS 11.45 µm IR channel and 0.7 µm Day/Night Band images (below) showed the eye of Amanda at 09:02 UTC on 25 May. A ring  of cold cloud-top IR  brightness temperatures surrounded the eye, with the coldest values on the northern, western, and southern portions. Since there was minimal illumination from the Moon (which was in the Waning Crescent phase, at about 6% of full), there was not a lot of cloud-top details seen in the Day/Night Band image.

===== 26 May Update =====

GOES-15 10.7 um IR channel images spanning the 24 May – 26 May period (above; click image to play animation; also available as an MP4 movie file) showed the development and evolution of the eye of Hurricane Amanda. Note that there were several time intervals when the IR cloud-top brightness temperature was colder than -80 C (violet color enhancement).

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GOES-14 operations in SRSOR mode deliver the ability to monitor convective development at very short time-scales. A good example of this occurred over the lower Ohio Valley/western Kentucky on May 22nd. The animation of GOES-13 Sounder Derived Product Imagery of CAPE (above) and of Lifted Index (1300 and 1700 UTC) showed considerable instability waiting to be released.

GOES-14 SRSOR animations can be used to monitor the evolving cumulus field in the search for the tower that will break the cap (Nashville, TN/Lincoln IL Soundings from 1200 UTC). The animation below shows visible imagery from 1800 UTC through 2011 UTC, at which time the convection has developed. Initial convection dissipates, but eventually develops along the Ohio River in western Kentucky (cumulus clouds continue to grow/dissipate over the Mississippi River valley throughout the animation).

By 1900 UTC, convective development over the lower Ohio Valley is vigorous enough that Cloud-Top Cooling algorithm from CIMSS (below) has flagged growing clouds, with values exceeding 20º C/15 minutes.

How does the NOAA/CIMSS ProbSevere model  then change with time as the convection intensifies? The 1904 and 1906 UTC ProbSevere products, toggled below, shows values increasing from 49% to 54% as Satellite Growth rates at 1900 UTC are incorporated at 1906 UTC. ProbSevere values then dropped (1912 UTC, 1922 UTC) as MRMS MESH decreased.

By 1936 UTC, ProbSevere has again increased above 50%, in two regions where MRMS has MESH sizes over 0.50″. MESH values are equivalent in the two regions, as are environmental values, but higher satellite predictors associated with the smaller eastern radar object drive higher ProbSevere values there.

The animation below shows the evolution of NOAA/CIMSS ProbSevere from 1948 UTC through 2000 UTC, with focus on a second cell that was warned. NOAA/CIMSS ProbSevere is designed to give an estimate of when severe weather might initially occur. Severe weather was not reported in Kentucky with these storms (link); however, observations of severe weather did occur as the storms moved near Nashville.

Related Hazardous Weather Testbed blog posts on this event can be found here, here, and here.

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McIDAS images of GOES-13 (GOES-East) 0.63 µm visible channel data (above; click image to play animation) showed the rapid growth of the smoke plume from the Slide Fire which was burning in Arizona on 21 May 2014.

As the fire continued to burn into the night, a comparison of AWIPS images of 375-meter resolution Suomi NPP VIIRS 3.74 µm and 4-km resolution GOES-13 3.9 µm shortwave IR images (below) demonstrated the advantage of improved spatial resolution (and a more direct viewing angle) of the VIIRS data for determining both the intensity and the true location of the fire hot spots around 10 UTC or 4 am local time.

On the following morning, GOES-15 (GOES-West) 0.63 µm visible channel images (below; click to play animation) the smoke plume aloft and smoke which had settled into valleys could be seen during the early morning hours.

Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from 21 May and 22 May are visualized using the SSEC RealEarth web map server (below). On 22 May, bands of high-altitude cirrus clouds were moving over the region, making the identification of the north/northwestward-moving smoke plume a bit more difficult.

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