Bore over Kansas

June 3rd, 2015
GOES-13 Imager 0.63 µm visible channel images (click to play animation)

GOES-13 Imager 0.63 µm visible channel images (click to play animation)

Visible imagery after sunrise on 3 June 2015 over Kansas, above, shows the parallel lines of low clouds that characterize a bore feature. As the bore penetrated southward, winds initially shifted before becoming more variable. Bore propagation requires the presence of an inversion, and 1200 UTC Soundings from both Dodge City and from Topeka contain inversions. Because inversions are present, it is unusual for convection to form in the presence of a bore.

The initial southward push the became the bore may have emerged from strong convection over central Nebraska early in the morning of 3 June. Suomi NPP VIIRS imagery captured that convection; the Day Night Band (under near-Full Moon conditions) and 11.45 µm infrared imagery, below, show the strong convection at 0848 UTC on 3 June 2015).

Suomi NPP VIIRS 0.70 µm visible Day Night Band and 11.45 µm infrared imagery at 0848 UTC on 3 June 2015 (click to enlarge)

Suomi NPP VIIRS 0.70 µm visible Day Night Band and 11.45 µm infrared imagery at 0848 UTC on 3 June 2015 (click to play animation)

GOES-14 was performing SRSO-R observations over Kansas on 3 June. One-minute imagery of the bore evolution is available here in animated gif format (74 M in size) and here in mp4 format (2.8M in size). The YouTube video is embedded below.



Tornadic Thunderstorm over eastern Colorado

May 28th, 2015

NOAA/CIMSS ProbSevere Product, 1902-1922 UTC on 27 May 2015 [click to play very very large animation]

GOES-14 Visible Imagery (0.626 µm) animation, 1708 UTC 27 May 2015 – 0059 UTC 28 May 2015 [click to play very very large animation]

A tornado was reported near Yuma, CO, (SPC Storm Reports) at 1910 UTC on 27 May 2015. GOES-14 was in SRSO-R scanning mode, and a storm-centered animation of the visible imagery (0.626 µm) is shown above (Warning: the animation above is 270M; click here for an mp4, or view it on YouTube). Note that GOES-14 produces no imagery from 1900-1915 UTC when the satellite is performing daily station-keeping maneuvers. The tornado occurred early in the life of the supercell on which the animation centers.

The NOAA/CIMSS ProbSevere output for this storm is shown below. ProbSevere increased above 50% at 1904 UTC. The satellite information for the storm object was derived from GOES-13 data between 1730 and 1745 UTC, when strong growth occurred, and from 1745-1815 UTC when weak glaciation occurred (how the reduced time resolution at that time, when GOES-13 is scanning a full-disk image, affected the Glaciation estimates is not certain — ‘weak’ is probably a lower bound).

NOAA/CIMSS ProbSevere Product, 1902-1922 UTC on 27 May 2015 [click to play animation]

NOAA/CIMSS ProbSevere Product, 1902-1922 UTC on 27 May 2015 [click to play animation]

GOES-14 SRSO-R imagery: severe thunderstorms in Texas and Oklahoma

May 25th, 2015


GOES-14 remained in Super Rapid Scan Operations for GOES-R (SRSO-R) mode on 25 May 2015, providing 1-minute 0.63 µm visible channel imagery of severe thunderstorms that produced widespread damaging winds, large hail, and tornadoes  (SPC storm reports) across much of Texas (above; also available as an MP4 movie file). One fatality and four injuries were reported at 2104 UTC in Pettibone, Texas (denoted by the asterisk in this GOES-14 visible/IR comparison).

The animation below (YouTube 1080p HD version; also available as an MP4 movie file) is centered a bit farther north, to cover storms that developed in Oklahoma. The enhancement is also tailored to help highlight the thunderstorm overshooting tops and storm-top gravity wave features.


GOES-14 SRSO-R imagery: “mystery feature” over eastern Tennessee

May 21st, 2015


 

GOES-14 remained in Super Rapid Scan Operations for GOES-R (SRSO-R) demonstration mode on 21 May 2015, providing 1-minute images for much of the eastern US (see this blog post) — and another interesting feature was seen over eastern Tennessee that was rather perplexing. Since this easily qualified for the “What the heck is this?” blog category, we thought it might be fun to have a contest of sorts and invite readers to submit their wild guesses and/or educated explanations. We will post more imagery later in the day on 22 May as to our explanation — but in the meantime, leave a comment on the blog (comments are moderated, so they will not appear until approved), or send your thoughts to our Twitter account.

—– 22 May Update —–

Thanks to all who submitted their suggestions here and on Twitter of an explanation of the “What the heck is this” feature; Here is our best guess:

GOES-13 (GOES-East) visible, 3.9 µm shortwave IR, 6.5 µm, and 10.7 µm IR images [click to play animation]

GOES-13 (GOES-East) visible, 3.9 µm shortwave IR, 6.5 µm, and 10.7 µm IR images [click to play animation]

The first step in trying to understand what might be causing this interesting feature was to examine 4-panel images showing imagery from other GOES channels (or spectral bands): in this case, the 3.9 µm “shortwave IR” channel, the 6.5 µm “water vapor” channel, and the 10.7 µm “IR window channel” (above; click image to play animation). The 3.9 µm IR brightness temperatures of cloud features were in the +20 to +25º range, while the 10.7 µm IR brightness temperatures were in the +3 to +5º C range — the significantly warmer shortwave IR temperatures indicates that the clouds were comprised of liquid or supercooled cloud droplets. Otherwise, no significant clues were seen on the IR (or the water vapor) images.

However, the METAR surface reports offer an important clue: a rain shower moved from southwest to northeast through the region during the preceding overnight hours with the passage of a weak low pressure system (surface analyses), with Knoxville (station identifier KTYS) receiving 0.23″ and Oak Ridge (KOQT) receiving 0.10″ of rainfall (radar-estimated 24-hour precipitation). Therefore, one plausible explanation of the feature seen on visible imagery is that it was a shallow pool of stable, rain-cooled air near the surface that was spreading out and flowing downslope (westward) into the Great Valley of East Tennessee during the morning and early afternoon hours.

While the outer edges of this rain-cooled stable air feature remained generally cloud-free, the inner core exhibited a good deal of cloud development (including what appeared to be a more dense northwest-to-southeast oriented cloud band through the middle). An overlay of hourly RTMA surface winds (below; click image to play animation) indicated that there was convergence within the feature (to the lee of higher terrain within the Cumberland Plateau), which along with daytime heating of the moist soil would have helped to promote such shallow cloud development.

GOES-13 0.63 µm visible channel images, with RTMA surface winds [click to play animation]

GOES-13 0.63 µm visible channel images, with RTMA surface winds [click to play animation]

For clouds within expanding the rain-cooled boundary at 1534 UTC, the CLAVR-x POES AVHRR Cloud Type was liquid, with Cloud Top Height values of 1-3 km and Cloud Top Temperature values of +2 to +10º C (below).

CLAVR-x POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature products

CLAVR-x POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature products