Tornadoes and large hail in Minnesota and Wisconsin

May 16th, 2017 |

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm, bottom) images, with SPC storm reports plotted in cyan [click to play animation]

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm, bottom) images, with SPC storm reports plotted in cyan [click to play animation]

** The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. **

A significant outbreak of severe thunderstorms developed on 16 May 2017, producing damaging winds, large hail and tornadoes from Texas to Wisconsin (SPC storm reports). On the northern end of this outbreak, hail as large as 3.0 inches in diameter fell in northwestern Wisconsin, and a tornado resulted in 1 fatality and at least 25 injuries near Chetek (NWS Twin Cities MN summary). GOES-16 Visible (0.64 µm) and Infrared Window (10.3 µm) images (above) showed the development of the convective systems; surface-to-cloud-top parallax-corrected SPC storm reports are plotted on the images. Overshooting tops and above-anvil cloud plumes were evident on the visible images, with well-defined “enhanced-V” and “cold/warm thermal couplet” storm top signatures seen on the infrared imagery.

A closer view of the GOES-16 Visible and Infrared Window images (below) provided more detail of the supercell storm-top structure. Note that the pronounced enhanced-V Infrared signature began to develop near the Minnesota/Wisconsin border just before 2100 UTC, which was about 40 minutes before the first Wisconsin hail report of 2.5 inches, and about 90 minutes prior to the fatal Chetek tornado. Since the early 1980s (reference), the enhanced-V satellite signature has been recognized as a reliable predictor of supercell thunderstorms having a high potential to produce either damaging winds, large hail or tornadoes; an automated Enhanced-V / Overshooting Top product (reference) will be available using the ABI instrument on the GOES-R series of satellites..

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm, bottom) images, with plots of SPC storm reports and hourly surface reports [click to play animation]

GOES-16 Visible (0.64 µm, top) and Infrared Window (10.3 µm, bottom) images, with plots of SPC storm reports and hourly surface reports [click to play animation]

A comparison of GOES-13 (GOES-East) and GOES-16 Infrared Window images (below) demonstrated the advantage of improved spatial resolution (2-km at satellite sub-point with GOES-16, vs 4-km with GOES-13) for identifying features such as cold overshooting tops.

Infrared Window images from GOES-13 (10.7 µm, top) and GOES-16 (10.3 µm, bottom) , with SPC storm reports plotted in cyan [click to play animation]

Infrared Window images from GOES-13 (10.7 µm, top) and GOES-16 (10.3 µm, bottom) , with SPC storm reports plotted in cyan [click to play animation]

True-color Red/Green/Blue (RGB) imagery (below; courtesy of Kaba Bah, CIMSS) offered another view of the storms on a regional scale.

GOES-16 true-color RGB images [click to play animation]

GOES-16 true-color RGB images [click to play animation]


Large hail in eastern Colorado

May 8th, 2017 |

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.4 µm, right) images, with surface station identifiers in yellow and SPC reports of hail size in cyan [click to play MP4 animation]

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.4 µm, right) images, with surface station identifiers plotted in yellow and SPC reports of hail size plotted in cyan [click to play MP4 animation]

** The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. **

Severe thunderstorms developed over eastern Colorado on 08 May 2017, producing large hail (especially in the Denver area: SPC storm reports | NWS Boulder summary). Both GOES-16 Mesoscale Sectors were positioned over that region, providing 30-second interval images — Visible (0.64 µm) and Infrared Window (10.35 µm) images (above; also available as a 161 Mbyte animated GIF) showed the convection in great detail, with parallax-corrected SPC storm reports of hail size (inches; H275 = 2.75 inches in diameter) plotted in cyan. Several of the storms exhibited well-defined overshooting tops in the Visible imagery, as well as “enhanced-V” and/or cold-warm “thermal couplet” signatures on the Infrared imagery.



A comparison of 30-second interval GOES-16 Mesoscale Sector and 15-minute interval GOES-13 (GOES-East) Routine Scan visible images (below; also available as a 179 Mbyte animated GIF) demonstrated the clear advantage of rapid-scan imagery for monitoring convective development. Also note the degradation of GOES-13 visible imagery (the cloud features do not appear as bright), due to the age of that satellite — the GOES-R series ABI instrument features on-board visible detector calibration, so this type of visible image degradation over time will not occur.

GOES-16 Visible (0.64 µm, left) and GOES-13 Visible (0.63 µm, right) images, with surface station identifiers in yellow [click to play MP4 animation]

GOES-16 Visible (0.64 µm, left) and GOES-13 Visible (0.63 µm, right) images, with surface station identifiers plotted in yellow [click to play MP4 animation]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images (below; actual satellite overpass time 1943 UTC) provided a high-resolution (375 meter) view of the developing thunderstorms, about 17 minutes before the first report of hail northeast of Trinidad (KTAD) at 2000 UTC — a number of these storms exhibited cloud-top infrared brightness temperatures of -70 to -73º C (black enhancement). The VIIRS instrument will also be on the JPSS series of satellites, the first of which is scheduled to be launched in the 4th quarter of 2017.

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images, with surface station identifiers plotted in cyan [click to enlarge]

NOAA/CIMSS ProbTor with a Severe Thunderstorm over Florida

April 6th, 2017 |

GOES-16 “Red” Band (0.64 µm) from 1222 through 1517 UTC on 6 April 2017 (Click to animate)

GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing.

GOES-16 Visible Imagery early on 6 April 2017 showed a strong thunderstorm developing north of Lake Okeechobee and proceeding east towards the Atlantic Coast near Vero Beach (1-minute or 30-second imagery was not available over Florida because the GOES-16 Mesoscale Sectors were in their default locations; routine 5-minute CONUS imagery is shown above).

Clean Infrared  Window channel (10.33 µm) imagery from 1400-1500 UTC, taken from AWIPS, below, shows a well-developed albeit weakening storm that is moving off the coast. A pronounced Overshooting Top/Thermal Couplet is present at 1402 UTC; the brightness temperature of the overshoot is -77º C, and the downwind warm trench is -62º C.

GOES-16 Clean Infrared Window Band (10.3 µm) from 1402 through 1457 UTC on 6 April 2017 (Click to animate)

The NOAA/CIMSS ProbTor product was monitoring this storm as it moved eastward through central Florida. The animation below shows the cell strengthening rapidly after 1310 UTC, and maintaining large ProbTor values for about an hour, after which time values collapsed.

NOAA/CIMSS ProbTor product from 1256 through 1444 UTC on 6 April 2017 (Click to animate)

The time series below shows ProbTor as a function of time (1232-1444 UTC). The different parameters that are used in the computation of ProbTor are plotted as well. The times of the Severe Weather Warnings issued by the National Weather Service are drawn along the horizontal axis. The three wind events noted as vertical magenta lines (wind events taken from the Storm Prediction Center Storm Reports) occur within the envelope of highest ProbTor probabilities.

Plot of NOAA/CIMSS ProbTor values from 1232 through 1444 UTC on 6 April 2017. Vertical magenta lines are wind damage reports from SPC (Click to animate)

Note: NOAA/CIMSS ProbSevere Products — ProbHail, ProbWind, ProbTornado and the 2016 version of ProbSevere are all run using legacy GOES data (GOES-13 and GOES-15). GOES-16 data can be incorporated into this tool only after the statistical model has been trained on GOES-16 data, and that has not yet happened; A GOES-16 version is planned for the 2018 convective season.

With 16 Channels, the ABI on GOES-16 allows many different views of the same event. The animation below includes the 1/2-km resolution 0.64 µm “Red” Visible channel, the Snow/Ice channel (1.61 µm, 1-km resolution) that distinguished between clouds made of water droplets and clouds made of ice because ice strongly absorbs radiation at 1.61 µm and hence reflectances are smaller and the cloud appears less white, the Cirrus channel (1.378 µm, 2-km resolution) that highlights high clouds because radiation at the wavelength is very strongly absorbed by water vapor so reflectance from low-level clouds cannot escape to space before it is absorbed, and the Clean Infrared Window channel (10.33 µm, 2-km resolution) that affords a view that is least affected by water vapor absoption. In the animation below, the coastline does not become visible in the Cirrus channel because of strong absorption of radiation at that wavelength by water vapor. The Cirrus clouds in the 1.61 µm channel are considerably darker because of absorption by ice of radiation at that wavelength; a few water-based clouds do appear in the scene and are bright: 1.61 µm radiation is reflected quite well by water droplets.

GOES-16 “Red” Visible Band (0.64 µm), Snow/Ice Band (1.61 µm), Cirrus Band (1.378 µm) and Clean Infrared Window (10.33 µm) from 1222 through 1517 UTC on 6 April 2017 (Click to animate)

The GOES-R website has Quick Guide information on the Red Visible Band (0.64 µm), the Snow/Ice Band (1.61 µm), the Cirrus Band (1.378 µm) and the Clean Infrared Window Band  (10.33 µm) at this site.

Severe Weather over the southern United States

April 5th, 2017 |

GOES-16 “Red” Band (0.64 µm) from 1900 through 2100 UTC on 5 April 2017 (Click to animate)

GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing.

On 5 April 2017, The Storm Prediction Center in Norman OK issued a Day 1 Convective Outlook that included Moderate and High Risk areas over much of the southeastern United States. Mesoscale discussion 442 and 448 on 5 April discuss the area shown above. One of two GOES-16 Mesoscale Sectors on 5 April viewed this scene, and a 2-hour animation spanning the outbreak of convection is shown above. It is difficult to predict which particular towering cumulus is going to grow into a cumulonimbus based on the visible imagery alone.

GOES-16 Low-Level Water Vapor Band (7.34 µm) from 2002 through 2127 UTC on 5 April 2017 (Click to animate)

Water Vapor Imagery from GOES-16 might help in that prediction. The animation above, from 2000 UTC to 2130 UTC, shows multiple subtle gradients in the low-level water vapor field that could be associated with impulses influencing convective initiation. Convection appears to form along those subtle gradients. The 16 channels on ABI offer far more information than legacy GOES.


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CIMSS Scientists have been refining the NOAA/CIMSS ProbSevere product to account for individual threats (Hail, Wind, Tornado), and a screen capture of that product is shown below. Radar Objects are outlined in colors that relate to the Probability of a severe event. These outlines allow a forecaster to determine which cell is potentially most threatening based on the inputs into the determination of probability.

NOAA/CIMSS ProbSevere for All Hazards at 2130 UTC on 5 April (click to enlarge)

At 2130 UTC, shown above, a cell over Tennessee has the highest ProbTor probability; the readout (below) shows the variables that are used in computing all the hazard probabilities — ProbHail, ProbWind, and ProbTor (Not all variables are used for all products; for example, ProbTor does not use Satellite-derived growth rates; ‘PS‘ in the output is the value of the 2016 version of ProbSevere). ProbTor of 70% for the cell over Tennessee (compared to smaller values at nearby cells) suggests that particular cell deserves special attention from anyone monitoring the cell for development. The ProbTor for the warned cell in Alabama — a cell that produced Tennis Ball-sized hail near Heflin , showed a ProbTor value at this time of 43% — a larger value than for the storms on either side of it — again suggestive that it should be of most concern. Ten minutes later, at 2140 UTC, ProbTor for the Tennessee storm had dropped to 34%, and that of the Alabama storm had increased to 55%.

ProbTor will be one of the CIMSS products demonstrated at the Hazardous Weather Testbed in June and July this year.

NOAA/CIMSS ProbSevere for All Hazards at 2130 UTC on 5 April; The readout for the indicated cell is shown (Click to enlarge)

Note: ProbSevere products are computed using legacy GOES imagery only. GOES-16 data can be incorporated into this tool only after the statistical model has been trained on GOES-16 data, and that has not yet happened; A GOES-16 version is planned for the 2018 convective season.