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]

Cyclone Donna in the South Pacific Ocean

May 7th, 2017 |

Himawari-8 Infrared Window (10.4 µm) images [click to play MP4 animation]

Himawari-8 Infrared Window (10.4 µm) images [click to play MP4 animation]

Cyclone Donna (18P) formed in the South Pacific Ocean (northeast of Vanuatu) on 02 May 2017. Himawari-8 Infrared Window (10.4 µm) images during the 03-06 May period (above) revealed the formation of multiple convective bursts, many exhibiting cloud-top IR brightness temperatures of -90º C and colder.

On 07 May, Cyclone Donna rapidly intensified from a Category 2 to a Category 4 storm (SATCON | ADT) — and Himawari-8 Infrared Window images (below) showed the presence of a large eye for a few hours. Environmental factors favoring rapid intensification included warm sea surface temperatures and light vertical wind shear.

Himawari-8 Infrared Window (10.4 µm) images [click to play MP4 animation]

Himawari-8 Infrared Window (10.4 µm) images [click to play MP4 animation]

A comparison of GMI Microwave (85 GHz) and Himawari-8 Infrared Window (10.4 µm) images from the CIMSS Tropical Cyclones site (below) showed that the actual diameter of the eye was much larger on microwave imagery around 1400 UTC on 07 May.

GMI Microwave (85 GHz) and Himawari-8 Infrared Window (10.4 µm) images [click to enlarge]

GMI Microwave (85 GHz) and Himawari-8 Infrared Window (10.4 µm) images [click to enlarge]

Small Eddy and coastal jet off the coast of Northern California

May 4th, 2017 |

GOES-16 Visible (0.64 µm) from 1245 through 2200 UTC on 4 May 2017 (Click to play mp4 animation)

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

One of the two GOES-16 Mesoscale Sectors was moved from its default position over the eastern United States and placed over the west coast of the United States on 4 May 2017. This allowed 1-minute imagery of a small-scale coastal eddy between Cape Mendocino and Pt. St. George near Crescent City, above, and an associated coastal jet. (Click here to play 300-meg Animated Gif; alternatively, this animation shows the eddy from 1600-1900 UTC as displayed in AWIPS (courtesy Dan Miller, WFO DLH))

A zoomed-in Visible animation of the coastal eddy is shown below; NWS Eureka described it as “one of the best examples of these coastal eddies seen in quite a while”.

GOES-16 Visible (0.64 µm) images, with hourly surface reports plotted in yellow (Click to animate)

GOES-16 Visible (0.64 µm) images, with hourly surface reports plotted in yellow (Click to animate)

GOES-16 Visible 0.64 µm imagery is able to capture not only the eddy, but also the northerly low-level jet that develops off the coast of Cape Mendocino, swiftly moving clouds southward around that feature. A small eddy also develops south of Cape Mendocino. Note also the abundance of cirrus clouds flowing northward along the coast.

The dimensions of this eddy are approximately 70 km in the along-shore direction and 55 km perpendicular to the shore, yet GOES-16 is able to capture and resolve many small-scale cloud bands. The small cloud band streaming south around Cape Mendocino, for example, is only about 6 km wide and is well-resolved; if GOES-16 becomes GOES-East at 75 W Longitude, this is the type of resolution that can be expected in Salt Lake City.

It should be noted that none of the models (including the hourly RTMA, below) resolved this eddy feature.

Suomi NPP VIIRS Visible (0.64 µm) image, with RTMA surface winds {Click to enlarge)

Suomi NPP VIIRS Visible (0.64 µm) image, with RTMA surface winds {Click to enlarge)

Thanks to Dan Miller, Science and Operations Officer (SOO) in Duluth for calling this awesome feature to our attention!

Using GOES-16 to view clouds over snow

May 1st, 2017 |

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

A late-season snow storm dropped a band of heavy snow over Colorado, western Kansas and western Nebraska on 29-30 April 2017. In the visible image above from sunrise on 1 May 2017, it is difficult to guess where the cloud features sit on top of the snow (Click here for a visible image with a map), even with the knowledge that they are casting shadows in this early morning imagery. GOES-16 includes a 1.61 µm channel, however; radiation at that wavelength is absorbed strongly by ice — either in the form of cirrus clouds, or snow, so that reflectance is small over ice features. The toggle below between the 1.61 µm “Snow/Ice” Channel and the 0.64 µm “Red Visible” channel shows ice and snow as dark. Clouds that are made up of water droplets are highly reflective in the 1.61 µm and in the 0.64 µm channels; such water clouds (there are only a few of them!) show up as very bright against the dark background of snow in the 1.61 µm channel.

Note in the toggle above that shadows are much darker in the 1.61 µm channel. Why?

Atmospheric scattering is stronger at shorter wavelengths in the atmosphere; there is more scattering of 0.64 µm radiation than of 1.61 µm radiation. In the shadow regions, more 0.64 µm radiation than 1.61 µm is being scattered back towards the satellite for detection. Shadows in the 0.47 µm “Blue Visible” band should be even less distinct. Non-annotated versions of imagery are available here for 0.64 µm and here for 1.61 µm.

During the subsequent late morning and early afternoon hours, the edges of the long swath of snow cover were seen to melt quickly — due to heating from the high May sun angle — on GOES-16 Visible (0.64 µm) and Snow/Ice (1.61 µm) images, below. The Snow/Ice images helped to highlight bright cumulus clouds (composed of supercooled water droplets) drifting southeastward across the snow cover.

GOES-16 Visible (0.64 µm, left) and Snow/Ice (1.61 µm, right) images [click to animate]

GOES-16 Visible (0.64 µm, left) and Snow/Ice (1.61 µm, right) images [click to animate]

Animations of GOES-16 Visible vs Snow/Ice images from the previous day (when the southwestern portion of the swath of fresh snow cover first became evidentt as clouds from the parent storm departed) are available here: Animated GIF | MP4.