Midwest derecho

July 19th, 2017 |

GOES-16 Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play MP4 animation]

GOES-16 Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play MP4 animation]

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

A long-lived mesoscale convective system (MCS) known as a derecho produced swath of damaging winds — as well as some large hail and a couple of tornadoes — that stretched from north-central South Dakota to northwestern Indiana on 19 July 2017 (SPC storm reports | TWC summary). GOES-16 “Clean” Infrared Window (10.3 µm) images (above) showed the southeastward propagation of the storm system.

Closer views of the early stages of the derecho as it moved across central and eastern South Dakota are shown below, using GOES-16 “Red” Visible (0.64 µm) and Infrared Window (10.3 µm) images. The highest measured wind gust was 100 mph near Polo (1522 UTC), with 83 mph recorded at Huron (1636 and 1730 UTC). Hail of 2.50 inches in diameter fell near Cavour (1703 UTC). Note that most of the severe reports were in the general vicinity of the persistent cold overshooting top (black to white enhancement) seen on the Infrared imagery; due to parallax, the apparent location of this storm-top feature was shifted slightly north of its true location.

GOES-16 Visible (0.64 µm) images, with SPC storm reports plotted in red [click to play MP4 animation]

GOES-16 Visible (0.64 µm) images, with SPC storm reports plotted in red [click to play MP4 animation]

GOES-16 Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play MP4 animation]

GOES-16 Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play MP4 animation]

1-km resolution Terra MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images at (below) showed the MCS over the Huron (KHON) area at 1656 UTC. Since there is minimal parallax associated with polar-orbiter satellite imagery, the cluster of SPC storm reports (occurring within +/- 30 minutes of the time of the MODIS image) was much closer to the cold (-70 to -73º C, lighter gray enhancement) overshooting top. Another feature of interest seen on the Infrared image was a “warm trench” (exhibiting brightness temperatures as warm as -60º C, red enhancement) immediately surrounding the cold overshooting top — perhaps a result of compensating subsidence?

Terra MODIS Visible and Infrared Window (11.0 µm) images, with SPC storm reports [click to enlarge]

Terra MODIS Visible and Infrared Window (11.0 µm) images, with SPC storm reports [click to enlarge]

375-meter resolution Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images at 1846 UTC (below) provided a detailed view of the MCS as it was centered near the South Dakota / Minnesota border. The coldest cloud-top IR brightness temperature was -83º C (violet enhancement).

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images, with SPC storm reports [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images, with SPC storm reports [click to enlarge]

The Memphis Derecho of July 22 2003

July 31st, 2013 |
GOES-12 10.7 µm IR imagery (Click Image to play animation)

GOES-12 10.7 µm IR imagery (Click Image to play animation)

On the morning of July 22, 2003, a strong derecho moved through metropolitan Memphis, TN, with winds exceeding hurricane-force. The most significant impact of this storm was a loss of power caused in part by the many trees that were downed by the winds. The Storm Report for the day from the Storm Prediction Center shows a cluster of wind reports in and around Memphis and Shelby County. The National Weather Service office in Memphis produced a report on this event that includes radar imagery and a discussion of surface and upper-air observations. More information on this derecho is here. What do satellite data show for this event?

The animation of 10.7 µm imagery, above, shows the development of convection in southeast Kansas and northwest Arkansas that then moves eastward into the mid-South, hitting Memphis around 1200 UTC. Several overshooting tops are evident as the storms pass near Memphis, with the coldest brightness temperatures at 196K! Past derechosdiscussed on this blog (such as the one that hit the East Coast in 2012) were characterized by a channel of moisture and instability aligned with the storm motion, allowing the propagating thunderstorm complex access to a rich source of moisture and instability. This event in 2003 was no different. GOES-12 Sounder retrievals — during that year, 3×3 fields-of-view were used (versus single pixels now) — of Total Precipitable Water, Convective Available Potential Energy (CAPE) and Lifted Index (LI), show abundant moisture and instability aligned west-to-east across northern Arkansas. CAPE values exceeded 3000 J/kg, Total Precipitable Water was greater than 2 inches, and Lifted Indices were near -10.

GOES-10/GOES-12 Sounder-Derived Total Precipitable Water (3x3 Field of View) (Click Image to play animation)

GOES-10/GOES-12 Sounder-Derived Total Precipitable Water (3×3 Field of View) (Click Image to play animation)

GOES-10/GOES-12 Sounder-Derived Convective Available Potential Energy (CAPE) (3x3 Field of View) (Click Image to play animation)

GOES-10/GOES-12 Sounder-Derived Convective Available Potential Energy (CAPE) (3×3 Field of View) (Click Image to play animation)

GOES-10/GOES-12 Sounder-Derived Lifted Index (3x3 Field of View) (Click Image to play animation)

GOES-10/GOES-12 Sounder-Derived Lifted Index (3×3 Field of View) (Click Image to play animation)

GOES-12 Visible Imagery (Click Image to play animation)

GOES-12 Visible Imagery (Click Image to play animation)

Visible imagery, above, from GOES-12 shows the convection continuing to develop as it moves across the Mississippi River into Memphis. Several Overshooting tops are evident, as well as parallel cloud lines at the cirrus level that are usually associated with turbulence. GOES-10, as GOES-West, was also able to capture the convection as it moved through Memphis (below).

GOES-10 Visible Imagery (Click Image to play animation)

GOES-10 Visible Imagery (Click Image to play animation)

GOES-14 Super Rapid Scan (1-minute interval) images of eastern US low-end derecho

June 13th, 2013 |
GOES-14 0.63 µm visible channel images (click image to play animation)

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

For the second consecutive day, the GOES-14 satellite was placed into Super Rapid Scan Operations for GOES-R (SRSOR) mode to monitor the ongoing severe bow echo/low-end derecho event that was moving across the eastern US on 13 June 2013. GOES-14 0.63 µm visible channel images at 1-minute intervals (above; click image to play animation; also available as a QuickTime movie) revealed the emergence of a well-defined shelf cloud across Virginia and North Carolina, which marked the leading edge of the gust front moving out ahead of the line of severe thunderstorms. According to the SPC storm reports, these storms produced a wide swath of damaging winds (with gusts as high as 78 mph in Virginia), along with some large hail (up to 2.75 inches in diameter in Maryland).

Derecho moving southeastward from the Midwest to the East Coast

June 29th, 2012 |
POES AVHRR 10.8 µm IR channel image + cumulative SPC storm reports

POES AVHRR 10.8 µm IR channel image + cumulative SPC storm reports

An AWIPS image of 1-km resolution POES AVHRR 10.8 µm IR channel data with overlays of cumulative SPC storm reports (above) showed a strong mesoscale convective system (MCS) as it was moving southeastward across northern Indiana at 18:23 UTC or 12:23 PM local time on 29 June 2012 — this MCS evolved into a long-lived progressive derecho event, producing a broad swath of wind damage across the Ohio River Valley and into the Mid-Atlantic states (SPC storm reports). A peak wind gust of 91 mph was recorded at Fort Wayne, Indiana, with hail as large as 3.0 inches in diameter falling near Danville, Illinois. At least 12 fatalities have been attributed to this derecho.

Two ingredients helping to fuel the development and upscale growth of this derecho event were convergence/lift along a quasi-stationary frontal boundary, and rich moisture pooled along and just south of the frontal boundary. 10-km resolution GOES-13 sounder Total Precipitable Water (TPW) derived product imagery (below; click image to play animation) showed TPW values in the 50 to 65 mm (2.0 to 2.4 inch) range.

GOES-13 sounder Total Precipitable Water derived product imgery (click image to play animation)

GOES-13 sounder Total Precipitable Water derived product imgery (click image to play animation)

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GOES-13 sounder Lifted Index derived product imagery (click image to play animation)

GOES-13 sounder Lifted Index derived product imagery (click image to play animation)

There was also extreme instability present along and just south of this frontal boundary, as seen on GOES-13 sounder derived product images of Lifted Index or LI (above; click image to play animation) and Convective Available Potential Energy or CAPE (below; click image to play animation). AWIPS cursor sampling of these instability products showed widespread LI values of -14.8º C, and CAPE values of 6000 J per kg (denoted by the lighter purple color enhancements on each sounder product).

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

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

Clear sky single-field-of-view (SFOV) GOES-13 sounder temperature and moisture profiles within this axis of extreme instability (below) showed an LI value of -16.8º C at Point A in far eastern Illinois at 16 UTC. Note that the locations of some of these available GOES sounder temperature/moisture profiles were situated between the standard rawinsonde sites of Lincoln, Illinois (KILX) and Wilmington, Ohio (KILN) — this demonstrates the potential value of using GOES sounder data in regions (or at times of the day) between conventional rawinsonde launches.

GOES-13 sounder vertical profiles of temperature and dew point

GOES-13 sounder vertical profiles of temperature and dew point

3 comparisons of 1-km resolution POES AVHRR and MODIS visible channel and IR channel imagery with plots of cloud-to-ground lightning strikes (below) depicted the storm structure at 18:18 UTC, 19:17 UTC, and 19:48 UTC. Thunderstorms on the 19:48 UTC POES AVHRR image exhibited a minimum cloud top IR brightness temperature of -90 C.

POES AVHRR 0.86 µm visible, 12.0 µm IR, and cloud-to-ground lightning strikes

POES AVHRR 0.86 µm visible, 12.0 µm IR, and cloud-to-ground lightning strikes

MODIS 0.65 µm visible, 11.0 µm IR, and cloud-to-ground lightning strikes data

MODIS 0.65 µm visible, 11.0 µm IR, and cloud-to-ground lightning strikes data

POES AVHRR 0.86 µm visible, 12.0 µm IR, and cloud-to-ground lightning data

POES AVHRR 0.86 µm visible, 12.0 µm IR, and cloud-to-ground lightning data

4-km resolution GOES-13 10.7 µm IR channel images with overlays of SPC storm reports (below) showed the southeastward progression of the MCS and the attendant hail and damaging winds reports. The GOES-13 IR images also exhibited unusually cold IR brightness temperatures, at times as low as -81º C (at 20:45 UTC).

GOES-13 10.7 µm IR images + SPC storm reports (click image to play animation)

GOES-13 10.7 µm IR images + SPC storm reports (click image to play animation)

During the following overnight hours, the core of the derecho continued to move southeastward across West Virginia, Virginia, and eventually to the East Coast and the adjacent offshore waters of the Atlantic Ocean. In addition to creating a widespread swath of damging winds at the surface, the MCS was also responsible for a number of reports of high-altitude turbulence, as seen on 4-km resolution GOES-13 10.7 µm IR images with overlays of pilot reports of turbulence (below; click image to play animation). Severe turbulence was reported over or near the periphery of the storm at 01:00 UTC, 02:16 UTC, and 02:45 UTC.

GOES-13 10.7 µm IR channel images + Pilot reports of turbulence (click image to play animation)

GOES-13 10.7 µm IR channel images + Pilot reports of turbulence (click image to play animation)

Better storm-top structure can be seen on a sequence of 1-km resolution POES AVHRR 12.0 µm and MODIS 11.0 µm IR images (below), including a very detailed view of the transverse banding that formed along the northern edge of the dissipating MCS.

POES AVHRR 12.0 µm IR + MODIS 11.0 µm IR images

POES AVHRR 12.0 µm IR + MODIS 11.0 µm IR images

An overlay of 1-hour cloud-to-ground lightning strikes (ending at 07:00 UTC) on the Suomi NPP VIIRS 11.45 µm IR channel image at 07:14 UTC (below) showed a decreasing amount of lightning activity as the parent MCS began to slowly dissipate as it moved out over the waters of the western Atlantic Ocean. The corresponding 07:14 UTC VIIRS 0.7 µm Day/Night Band image did manage to reveal a few bright white pixels resulting from cloud-top illumination by clusters of lightning.

Suomi NPP VIIRS 11.45 µm IR image + VIIRS 0.7 µm Day/Night Band image

Suomi NPP VIIRS 11.45 µm IR image + VIIRS 0.7 µm Day/Night Band image

The strong surface winds downed a large number of trees and powerlines, causing widespread power outages that affected over 3 million people. One area especially hard-hit was West Virginia and adjacent portions of Virginia and Ohio, where a before/after comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) images around 07 UTC (4 AM local time) on 29 June and 30 June (below; courtesy of Jordan Gerth, CIMSS) revealed the large areas of darkness (lack of city lights) on 30 June after the derecho had moved through. The large dark areas seen on the DNB images over Pennsylvania on 29 June (VIIRS IR image) and Ohio/Michigan on 30 June (VIIRS IR image) were due to strong thunderstorms obscuring the view of the city lights below.

Suomi NPP VIIRS 0.7 µm Day/Night Band images on 29 June and 30 June

Suomi NPP VIIRS 0.7 µm Day/Night Band images on 29 June and 30 June

UPDATE: GOES-13 10.7 µm IR channel images of the entire derecho event (below; also available as a QuickTime movie). The GOES-13 satellite had been placed into Rapid Scan Operations (RSO). providing images as frequently as every 5-10 minutes during much of the life cycle of the storm.

GOES-13 10.7 µm IR channel images (click image to play animation)

GOES-13 10.7 µm IR channel images (click image to play animation)

In addition, a McIDAS-V combination of GOES-13 10.7 µm IR images and CAPE derived from overpasses of the Suomi NPP CrIS and the Aqua AIRS instruments (below; image courtesy of Joleen Feltz) showed that the derecho was moving toward pockets of instability that were in place along the trough axis that was oriented from southwest to northeast along the East Coast. Plotted in yellow are the surface wind gusts of 80 mph or greater associated with the derecho.

GOES-13 IR + CAPE from Suomi NPP CrIS and Aqua AIRS

GOES-13 IR + CAPE from Suomi NPP CrIS and Aqua AIRS