Suomi NPP VIIRS and POES AVHRR IR brightness temperature difference “fog/stratus product” images

An AWIPS comparison of nighttime Suomi NPP VIIRS and POES AVHRR IR brightness temperature difference “fog/stratus product” images (above) exhibited signals of fog and/or stratus forming in river valleys straddling the West Virginia and Virginia border on 13 May 2014.

The GOES-14 satellite continued to be operated in Super Rapid Scan Operations for GOES-R (SRSOR) mode, providing images at 1-minute intervals. Early morning 0.63 µm visible channel images (below; click image to play an MP4 animation; also available as a QuickTime movie) showed the narrow fingers of river valley fog/stratus, which began to burn off as heating and mixing increased during the morning hours. There was then a rapid transition to the formation of cumulus clouds across the region, some of which became organized areas of deep convection that produced hail and damaging winds (SPC storm reports).

GOES-14 0.63 µm visible channel images (click to play MP4 animation)

A 3-panel comparison showing the difference between standard or routine 15-minute interval, 5-7 minute interval Rapid Scan Operations (RSO), and 1-minute interval SRSO GOES-14 0.63 µm visible channel images (below; click image to play an MP4 animation; also available as a very large Animated GIF) demonstrated the clear advantage of higher temporal resolution for monitoring the rate of dissipation of river valley fog/stratus features, as well as subsequent convective initiation and development.

GOES-14 0.63 µm visible channel images: Standard, RSO, and SRSOR scan strategies (click to play MP4 animation)

Consecutive overpasses of the Suomi NPP satellite provided a look at the rapid rate of convective cloud development on VIIRS 0.64 µm visible channel images (below).

Suomi NPP VIIRS 0.64 µm visible channel images, with surface observations and frontal boundaries

On a 18:59 UTC MODIS 11.0 µm IR channel image (below), the coldest cloud-top IR brightness temperature was -78º C near the West Virginia/Virginia border.

MODIS 11.0 µm IR channel image

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Automated detection of Overshooting Tops (blue symbols) from GOES-14 during SRSO Operations, 1400-1545 UTC on 12 May 2014

Detection of overshooting tops is important because the overshoot occurs with very strong updrafts that can punch through the tropopause. These strong updrafts can suspend large hydrometeors, and overshooting tops are associated with heavy rain and severe weather (principally hail and high winds, but also tornadoes). See this link for more information, and this link for other case studies. On Monday May 12th, eastward-moving morning convection over southern Wisconsin produced many overshooting tops as shown in the animation above (SPC Storm Reports are here). The overshooting tops were detected using an Automated Detection Algorithm developed for GOES-R by scientists at NASA Langley and UW-CIMSS. The steadiness of the OT production reflects the persistent strength of the thunderstorm complex. What did this storm look like in visible and infrared imagery from GOES-14, which was operating in SRSO mode? The animations below, from 1345 through 1545 UTC, shows GOES-14 in SRSO mode (left — 1-minute imagery), RSO mode (center — images every 7-15 minutes), and standard mode (right — images usually every 15 minutes) using visible images (top animation) and infrared images (bottom animation). Click on the images to see the animations as YouTube videos. The 1-minute imagery alone captures the very dynamic and rapidly-evolving cloud-top structures associated with the strong convection.

GOES-14 Visible Imagery (0.62 µm) Animations from 12 May 2014. SRSO (Left), RSO (Center) and Standard (right) Scan Strategies are presented. Click to Animate

GOES-14 IR Imagery (10.7 µm) Animations from 12 May 2014. SRSO (Left), RSO (Center) and Standard (right) Scan Strategies are presented. Click to Animate

In both of the animations above, note how well the OTs observed in the satellite imagery match the auto-detected OTs. Auto-detection can miss detecting some tops, but the false alarm rate is low. Both image animations are also available as mp4 downloads (Visible, Infrared) and as YouTube videos (Visible and Infrared).

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GOES-14 0.63 µm visible channel images (click to play animation)

The GOES-14 satellite continued to be in Super Rapid Scan Operations for GOES-R (SRSOR) mode on 11 May 2014, capturing the development of thunderstorms along a dryline that stretched from the Texas Panhandle into far southwestern Kansas. As a southward-moving cold front intersected this dryline, McIDAS images of 1-minute interval GOES-14 0.63 µm visible channel data (above; click image to play animation; also available as an MP4 movie file) showed that the narrow line of storms later developed into large discrete supercell thunderstorms over Kansas, with widespread reports of tornadoes, large hail, and damaging winds (SPC storm reports).

Farther to the northeast, other large supercell thunderstorms could be seen growing over eastern Nebraska along a warm frontal boundary — these storms exhibited numerous signatures of vigorous overshooting tops. Near the end of the animation, winds gusted to 82 mph at Omaha, Nebraska at 00:51 UTC.

GOES-13 sounder Convective Available Potential Energy (CAPE) derived product imagery (click to play animation)

AWIPS images of GOES-13 sounder Convective Available Potential Energy or CAPE (above; click image to play animation) and Total Precipitable Water or TPW (below; click image to play animation) with surface frontal analyses revealed the sharp gradient of both instability and moisture across the dryline — just to the east of the dryline, CAPE values exceeded 4000 J per kg (darker purple color enhancement), while TPW values were generally in the 30-40 mm or 1.2-1.6 inch range (shades of yellow). In addition, GOES-13 sounder Lifted Index values were in the -8 to -10º C range across parts of Kansas into southeastern Nebraska prior to convective initiation.

GOES-13 sounder Total Precipitable Water (TPW) derived product imagery (click to play animation)

A 19:36 UTC Suomi NPP VIIRS 11.45 µm IR channel image (below) showed the early stages of convective development along the dryline in far southwestern Kansas; the coldest cloud-top IR brightness temperature value at that time was -80º C, just west of Dodge City, Kansas KDDC (corresponding GOES-14 visible image).

Suomi NPP VIIRS 11.45 µm IR channel image, with METAR surface reports

A comparison of POES AVHRRR 12.0 µm IR channel images (below) showed the explosive convective growth over Kansas and Nebraska in the 3-hour period between 19:56 UTC and 22:53 UTC.

POES AVHRR 12.0 µm IR channel images

Additional details on this event can be found on the RAMMB GOES-R Proving Ground Blog.

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AWIPS-2 display of a strong thunderstorm over Texas, including ProbSevere Readouts at 1400 UTC

A hail-producing storm (cick here for Storm reports from SPC) moved through Edwards, Real and Bandera counties of Texas after sunrise on May 9th. This storm gives a nice opportunity to compare ProbSevere and GOES-14 SRSO-R depictions of a severe storm. The 1400 UTC image, above, shows ProbSevere > 95%, with a MESH just over 1″. Within the next 10 minutes, MESH increased to 1.48″ at 1406 UTC (when ProbSevere was 96%), and to 1.92″ at 1408 UTC (see image below, when ProbSevere was 99%). A Severe Thunderstorm Warning was issued at 1408 UTC.

AWIPS-2 display of a strong thunderstorm over Texas, including ProbSevere Readouts at 1408 UTC

The storm maintained its strength over the following half hour. Imagery from 1436 shows MESH values near 1.50″ and ProbSevere is at 99%. At 1442 UTC, the radar shapefile vanishes from the display, a result of processing errors, but it is back at 1444 UTC. Note that the Satellite Predictors have flipped at 1444 UTC from values derived at 1015 UTC to ‘Mature Storm‘ (this change has nothing to do with the missed processing at 1442 UTC). Recall that ProbSevere is designed to probabilistically determine whether or not a storm will produce severe weather in the next 60 minutes. ‘Mature Storm’ designations serve as a reminder that Probabilities have been elevated for a long period of time.

At 1458 UTC, below, near the end of the Severe Thunderstorm warning, the MESH value that is incorporated into the ProbSevere computation has decreased to 1.17″, and ProbSevere has dropped to “only” 97%. At 1502 UTC, however, MESH has started to increase again, to 1.21″ (and ProbSevere remains high); a second severe thunderstorm warning is issued at 1504 UTC when MESH is at 1.53″ (and ProbSevere is at 99% again). ProbSevere remains high through 1530 UTC.

AWIPS-2 display of a strong thunderstorm over Texas, including ProbSevere Readouts at 1458 UTC

GOES-14 was in SRSO-R mode during this hail event, allowing an opportunity to see the storm evolution at very high temporal resolution. (The storm initially was right at the edge of the domain). The animation below shows cloud-tops warming around 1440 UTC, before cooling again, consistent with changing updraft speeds that can be inferred by changes in MESH. Cold temperatures occurred at 1501 UTC, 209.1 K. Temperatures were cooler than 210 K only at 1500 and 1501 UTC — that is, for two minutes — demonstrating the importance of 1-minute imagery in resolving without aliasing the coldest features at cirrus level. A second very cold event occurred between 1507 and 1509 UTC (brightness temperatures were cooler than 208 K); it was gone by 1511 UTC (when brightness temperatures were all warmer than 211 K). One-minute imagery is necessary to resolve these very rapid changes at cirrus level.

GOES-14 Visible (0.62 µm) (top) and GOES-14 IR (10.7 µm) (bottom) from 1401 UTC through 1530 UTC on 9 May. Edwards, Real and Bandera Counties are highlighted

The plot below shows the coldest IR Brightness Temperature observed in the GOES-14 10.7 µm channel over the hail-producing storm. Tic-marks along the x-axis are at 5-minute intervals, and there are large differences that occur with time-scales shorter than 5 minutes. This is consistent with the findings of Cintineo et al. in the September 2013 issue of Journal of Applied Meteorology and Climatology (link).

Minimum cloud-top IR Brightness Temperature over hail-producing storm, from 1411-1530 UTC. Tic marks on x-axis every 5 minutes.

During the following hours, 1-minute interval GOES-14 0.63 µm visible channel images (below; click image to play animation; also available as an MP4 movie file) showed other areas of convection which produced damaging winds across parts of southeastern Texas.

GOES-14 0.63 µm visible channel images (click to play animation)

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