Long-track Tornado over southwestern Manitoba

July 27th, 2015

Color-enhanced Infrared (10.7 µm) imagery from GOES-15 (left) and GOES-13 (right), times as indicated  [click to play animation]

Color-enhanced Infrared (10.7 µm) imagery from GOES-15 (left) and GOES-13 (right), times as indicated [click to play animation]

A strong tornado (rated a high-end EF-2) touched down near Pierson, Manitoba at around 0130 UTC on 28 July or 8:30 pm local time on 27 July (Press Report) and persisted until about 0355 UTC or 10:55 pm local time (near Virden Manitoba). The animation above shows GOES-15 (left) and GOES-13 (right) Infrared imagery from 0000 UTC through 0430 UTC. The strong storm lifting northward over southwestern Manitoba is apparent, with an enhanced-V signature especially noticeable in the GOES-13 imagery.

A closer view of the tornadic supercell is shown below, with overlays of surface reports (metric units). The pulsing nature of the overshooting tops is evident in the fluctuation of the coldest cloud-top IR brightness temperatures (the coldest of which was -69º C, darker black color enhancement, on the 0300 UTC GOES-15 and 0315 UTC GOES-13 images). There are different apparent positions of the storms based on the satellite that views them because of parallax shifts. Such shifts are especially pronounced at higher latitudes with very tall storms.

GOES-15 (left) and GOES-13 (right) 10.7 µm Infrared images, with surface reports [click to play animation]

GOES-15 (left) and GOES-13 (right) 10.7 µm Infrared images, with surface reports [click to play animation]

A 1-km resolution Terra MODIS 11.0 µm Infrared image at 0331 UTC is shown below; the minimum cloud-top IR brightness temperature was -73º C.

Terra MODIS 11.0 µm Infrared image [click to enlarge]

Terra MODIS 11.0 µm Infrared image [click to enlarge]

GOES-13 Visible (0.63 µm) imagery, times as indicated  [click to play animation]

GOES-13 Visible (0.63 µm) imagery, times as indicated [click to play animation]

Visible imagery from GOES-13 (above) and GOES-15 (below) showed the overshooting tops associated with the tornadic thunderstorm, as well as the rapidly expanding cirrus shield.

GOES-15 Visible (0.62 µm) imagery, times as indicated  [click to play animation]

GOES-15 Visible (0.62 µm) imagery, times as indicated [click to play animation]

A closer view of the tornadic supercell from GOES-15 vs GOES-13 is shown below, with overlays of surface reports (metric units). The overshooting tops are again apparent on the images, along with an above-anvil plume (which is easier seen on the GOES-13 images, due to a more favorable forward-scattering viewing geometry). The robust convective development was first seen on the 2030 UTC images, in the vicinity of the Saskatchewan/Manitoba/North Dakota border region.

GOES-15 (left) and GOES-13 (right) 0.63 µm visible channel images, with surface reports [click to play animation]

GOES-15 (left) and GOES-13 (right) 0.63 µm visible channel images, with surface reports [click to play animation]

As an area of low pressure was deepening over eastern Montana, warm and humid air was surging northward into far southern Saskatchewan and Manitoba (surface analyses). GOES sounder derived product images (available from this site) of Convective Available Potential Energy (CAPE), Lifted Index, and Total Precipitable Water (below) showed that the environment across southern Manitoba was becoming increasingly unstable and moist leading up to the time of convective initiation.

GOES sounder CAPE derived product images [click to play animation]

GOES sounder CAPE derived product images [click to play animation]

GOES sounder Lifted Index derived product images [click to play animation]

GOES sounder Lifted Index derived product images [click to play animation]

GOES sounder Total Precipitable Water derived product images [click to play animation]

GOES sounder Total Precipitable Water derived product images [click to play animation]

Severe thunderstorms causing damaging winds across Missouri and Arkansas

July 14th, 2015
GOES-13 sounder CAPE derived product images (click to play animation)

GOES-13 sounder CAPE derived product images (click to play animation)

GOES-13 sounder Convective Available Potential Energy (CAPE) derived product images (above; click to play animation) showed a large cluster of of severe thunderstorms that developed in eastern Kansas and moved southeastward across southern Missouri into northern Arkansas during the day on 14 July 2015. Due to strong surface heating and ample low-level moisture ahead of the storms, the atmosphere became quite unstable with GOES sounder CAPE values reaching the 5800-6000 J/kg range (lighter violet color enhancement) by 16 UTC. A long swath of damaging winds (SPC storm reports) was produced by these storms.

The visible and infrared images below show snapshots of this severe convective cluster at 3 different times, using high-resolution data from instruments on polar-orbiting satellites: Terra MODIS at 1657 UTC, Suomi NPP VIIRS at 1851 UTC, and POES AVHRR at 1916 UTC. The coldest cloud-top IR brightness temperatures were -83º C on the MODIS image, -86º C on the VIIRS image, and -87º C on the AVHRR image.

Terra MODIS 0.65 µm visible channel and 11.0 µm IR channel images (with SPC storm reports) at 1657 UTC [click to enlarge]

Terra MODIS 0.65 µm visible channel and 11.0 µm IR channel images (with SPC storm reports) at 1657 UTC [click to enlarge]

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images (with SPC storm reports) at 1851 UTC [click to enlarge]

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images (with SPC storm reports) at 1851 UTC [click to enlarge]

POES AVHRR 0.86 µm visible channel and 12.0 µm IR channel images (with SPC storm reports) at 1916 UTC [click to enlarge]

POES AVHRR 0.86 µm visible channel and 12.0 µm IR channel images (with SPC storm reports) at 1916 UTC [click to enlarge]

Strong Convection over the Upper Midwest

July 13th, 2015
MODIS 11 µm infrared imagery and GOES Sounder DPI Lifted Index, 0400 UTC (Click to enlarge)

MODIS 11 µm infrared imagery and GOES Sounder DPI Lifted Index, 0400 UTC 13 July 2015 (click to enlarge)

A strong mesoscale convective system (MCS) moving southeastward through the Upper Midwest from late 12 July 2015 into early morning 13 July caused numerous severe wind reports across Minnesota and Wisconsin. This MCS was forecast to drop southeastward and continue to produce severe weather during the day on 13 July 2015 (Storm Prediction Center outlook). The toggle above shows the 0420 UTC Terra MODIS 11.0 µm image and the 0400 UTC GOES-13 Sounder DPI Lifted Index product (which is available in realtime here). As the MCS moved over southern Wisconsin, the coldest cloud-top IR brightness temperature on the 0826 UTC MODIS 11.0 µm IR image was -85º C. The strong system continued to move southeastward as very unstable air as diagnosed by the Sounder fed into it (click here for 850-mb RAOB plots). The 0746 UTC Suomi NPP VIIRS 11.45 µm IR image, below, also toggled with a GOES-13 Sounder Lifted Index product, showed a similar story: very strong convection downwind of a source of strong instability. The GOES Sounder can also diagnose Convective Available Potential Energy (CAPE), with values from 5000-6000 J/kg seen over southern Minnesota and eastern Iowa.

Suomi NPP VIIRS 11.45 µm infrared imagery and GOES Sounder DPI Lifted Index, 0746/0800 UTC (Click to enlarge)

Suomi NPP VIIRS 11.45 µm infrared imagery and GOES Sounder DPI Lifted Index, 0746/0800 UTC 13 July 2015 (click to enlarge)

The Suomi NPP VIIRS Day/Night Band, below, which is a source of visible imagery at night, depicted signatures of the active lightning that accompanied this system: numerous along-scan bright streaks over southern Wisconsin were caused by lightning illuminating the cloud as the VIIRS instruments scanned the cloud top. This toggle showed a comparison of Day/Night Band and 11.45 µm Infrared imagery.

Suomi NPP VIIRS Day/Night Band 0.70 µm visible imagery 0746 UTC (Click to enlarge)

Suomi NPP VIIRS Day/Night Band 0.70 µm visible imagery 0746 UTC 13 July 2015 (click to enlarge)

A closer view comparing the 0746 UTC VIIRS IR and Day/Night Band images, below, includes overlays of METAR reports and both 15-minute and 1-hour cloud-to-ground lightning strikes. The coldest VIIRS cloud-top IR brightness temperature was -78º C.

Suomi NPP VIIRS 11.45 µm IR and 0.7 µm Day/Night Band images, with overlays of METAR surface reports and cloud-to-ground lightning strikes (click to enlarge)

Suomi NPP VIIRS 11.45 µm IR and 0.7 µm Day/Night Band images, with overlays of METAR surface reports and cloud-to-ground lightning strikes (click to enlarge)

At 0805 UTC, the coldest CLAVR-x POES AVHRR Cloud Top Temperature value was -81º C, with maximum Cloud Top Height values of 15 km along the southwestern portion of the MCS.

POES AVHRR Cloud Top Temperature and Cloud Top Height products at 0805 UTC (click to enlarge)

POES AVHRR Cloud Top Temperature and Cloud Top Height products at 0805 UTC (click to enlarge)

This image of Radar Composites of the main line of storms was produced by Greg Carbin of SPC and was posted on Facebook on 13 July 2015.

Severe Thunderstorms over Northern Illinois

June 10th, 2015

GOES-14 Visible (0.6263 µm, top) and GOES-13 Visible (0.63 µm, bottom) imagery centered over Illinois, 10 June 2015 [Click to animate]

GOES-14 Visible (0.6263 µm, top) and GOES-13 Visible (0.63 µm, bottom) imagery centered over Illinois, 10 June 2015 [Click to animate]

GOES-14, in SRSO-R mode, captured the quick development of severe thunderstorms over northern Illinois late in the afternoon on 10 June 2015. Many of these storms produced large hail — especially in Will County and in Grundy County, where the second largest hailstone on record for the state of Illinois was measured (NWS Chicago summary). This event is also discussed on the GOES-R Hazardous Weather Testbed (HWT) Blog: before initiation, during convective initiation, lightning jumps and ProbSevere (first post, second post), and Overshooting top detection. The animation above compares GOES-14 SRSO-R imagery (top) with GOES-13 in Routine Scanning mode (until 2045 UTC) and in Rapid Scan Operations (RSO) mode after 2115 UTC on 10 June 2015 (a smaller version of this large animated gif is also available as an mp4).

The GOES-14 SRSO-R imagery depicts the convection evolving in a fluid atmosphere. Even the relatively fast GOES-13 RSO time-step cannot capture the full evolution and decay of overshooting tops.  On the 1-minute GOES-14 images, note the development of prominent cloud-top plumes which spread out southeastward away from the more robust overshooting top regions, and also cloud-top gravity waves which form along the southeastern flank of some of the larger thunderstorm anvils. Another advantage of SRSO-R compared to the routine scanning strategy using visible imagery is discussed here.

A wider-scale view of the evolution of the atmosphere on 10 June over the Upper Midwest is available here as a YouTube video, here as an mp4, and here as an animated gif image (warning: 300+ Megabyte file). A closer-scale view of the developing convection with GOES-14 visible images is available as an mp4 movie file, or on YouTube; an animation of GOES-14 10.7 µm IR images is available as an mp4 file.

POES AVHRR 12.0 µm IR channel image, with SPC storm reports of large hail and damaging winds

POES AVHRR 12.0 µm IR channel image, with SPC storm reports of large hail and damaging winds

The line of severe thunderstorms developed just ahead of a cold frontal boundary (animation) that was sagging southward and stalling across northern Illinois during the day on 10 June. About an hour before the 4.75-inch diameter hail was reported in Minooka IL (located about 12 miles southwest of Joliet, KJOT), a 1-km resolution POES AVHRR 12.0 µm IR image at 2316 UTC (above) showed that particular cluster of thunderstorms just southwest of the Chicago area around the time of initial hail report (1.25 inch diameter at 2318 UTC); less than a half hour later there was a report of 2.00 inch hail at 2345 UTC. Farther to the southwest, the larger thunderstorm complex was also producing hail and damaging winds, near and to the southwest of the region of coldest cloud-top IR brightness temperatures (-77º C) exhibited by the overshooting tops.

GOES-13 sounder Lifted Index derived product images [click to play animation]

GOES-13 sounder Lifted Index derived product images [click to play animation]

Hourly derived product images (DPI) of GOES-13 sounder Lifted Index (above) and Total Precipitable Water (below) revealed that a broad axis of instability and moisture existed across northern Illinois ahead of the approaching cold frontal boundary. Lifted Index values reached the -8º to -10º C range (red colors); Total Precipitable Water values were generally in the 40 to 50 mm or 1.6 to 2.0 inch range (red colors), with some locations as high as 53 mm or 2.1 inches (violet colors). The presence of this instability and moisture helped to create an environment favorable for the rapid growth of strong to severe convection.

GOES-13 sounder Total Precipitable Water derived product images [click to play animation]

GOES-13 sounder Total Precipitable Water derived product images [click to play animation]