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

 

Upper Midwest Derecho, and a Seiche in southern Lake Michigan

July 11th, 2011 |
GOES-13 10.7 µm IR images (click image to play animation)

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

AWIPS images of GOES-13 10.7 µm IR data (above; click image to play animation) showed the progression of two long-lived Mesoscale Convective Systems (or “derechos”) on 11 July 2011 — one moving southeastward from the Dakotas and Minnesota, and another moving northeastward from Nebraska. These two MCS features were responsible for a large number of severe weather reports (SPC: 10 July reports | 11 July reports).

Note the elongated band of cirrus that developed  behind the departing MCS feature, curving across parts of Iowa, Nebraska, Kansas, and Colorado toward the end of the IR image animation above — this striated cloud band marked the location of a well-defined deformation zone. Areas of light to moderate turbulence aloft are often present in association with such deformation zones, as was seen by the number of pilot reports overlaid on a GOES-13 6.5 µm water vapor channel image at 17:45 UTC (below).

GOES-13 6.5 µm water vapor channel image + pilot reports of turbulence

GOES-13 6.5 µm water vapor channel image + pilot reports of turbulence

The GOES-13 sounder Total Precipitable Water (TPW) derived product (below; click image to play animation) showed that abundant moisture (TPW values of 50-60 mm or 2.0 to 2.4 inches, violet color enhancement) was in place ahead of the storms as they moved rapidly eastward.

 

 

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

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

A closer view of GOES-13 10.7 µm IR images with overlays of the Automated Overshooting Top Detection product (below; click image to play animation) revealed a number of overshooting tops, with the minimum cloud top IR brightness temperature of -81ºC occurring over eastern Iowa at 09:45 UTC. The overshooting tops were very evident after sunrise on GOES 0.63 µm visible channel imagery, as they cast shadows upon the thunderstorm anvil tops below (11:45 UTC visible image + overshooting top detection product comparison).

GOES-13 10.7 µm IR images + Overshooting Top Detection (click to play animation)

GOES-13 10.7 µm IR images + Overshooting Top Detection (click to play animation)

A set of three comparisons of 1-km resolution POES AVHRR 10.8 µm IR images with their corresponding 4-km resolution GOES-13 10.7 µm IR images (below) demonstrated the value of improved spatial resolution for more accurate detection of the location and magnitude of the coldest cloud tops on severe thunderstorms. On the 08:22 UTC, 08:47 UTC, and 11:37 UTC POES AVHRR images, the coldest cloud top IR brightness temperatures were -84ºC, -90ºC, and -85ºC, respectively (the coldest GOES-13 IR brightness temperatures were -78ºC for all three of those times). Note that the apparent northwestward displacement of cloud features on the GOES-13 images is a result of parallax error due to the large viewing angle from the geostationary satellite.

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

Very strong surface winds were observed along and in the wake of the well-defined bow echo seen on radar — peak wind gusts included 74 mph at Dubuque, Iowa, 75 mph at Chicago Midway Airport, and 85 mph at Michigan City, Indiana. These strong winds created a seiche across southern Lake Michigan (Seiche Warning | NWS Chicago event summary), with oscillations in water levels seen at Calumet Harbor, Illinois, Milwaukee, Wisconsin, and Holland, Michigan.

Intense derecho event

May 8th, 2009 |
GOES-12 10.7 µm IR window images

GOES-12 10.7 µm IR window images

An unusually-large derecho event formed over Kansas during the pre-dawn hours on 08 May 2009, and then moved rapidly eastward across Missouri and Illinois during the morning hours. GOES-12 10.7 µm IR window images (above) showed the large areal coverage of cold cloud tops (which were as cold as -79º C in southeastern Kansas).

The impressive derecho left a long swath of storm reports (below), which included several tornadoes and wind gusts to 87 knots (100 mph) at 11:30 UTC in Kansas, 81 knots (93 mph) at 12:15 UTC in Missouri, and 92 knots (106 mph) at 18:25 UTC in Illinois. Hail as large as 2.75 inch in diameter was reported in Missouri at 14:34 UTC.

MODIS 11.0 IR window image + storm reports

MODIS 11.0 IR window image + storm reports

As the storm matured toward mid-day, it began to display transverse banding on both the northern periphery and the  southern periphery of the cloud shield (below). This transverse banding is often a signature of high-altitude turbulence — and there were indeed a number of pilot reports of turbulence along the edges of the convective complex.

MODIS 6.7 µm water vapor image + pilot reports of turbulence

MODIS 6.7 µm water vapor image + pilot reports of turbulence

The storm was also a prolific producer of lightning: at one point, it was producing over 4000 cloud-to-ground strikes every 15 minutes (below).

GOES-12 IR image + cloud to ground lightning strikes

GOES-12 IR image + cloud to ground lightning strikes

Upper Midwest Derecho

August 14th, 2007 |

ir_lightningmovie.gif

Derechos are long-lived convectively-driven wind storms. In the upper midwest, they typically form in northwesterly flow just poleward of very warm and moist air and then surge southward. Convection overnight on 13-14 August 2007 developed into a long-lasting complex with a bow echo that propagated from north of Minneapolis to Illinois. Although wind speeds weren’t as strong in historic events such as July 1983, numerous wind damage reports nevertheless were reported to SPC.

070813_rpts.gif

Monday August 13 was characterized by strong moisture contrasts over the upper midwest (see the 2100 UTC dewpoint plot here; the 2100 UTC temperature plot is here). Excessive heat and humidity over the high plains extended northeastward into central Minnesota where cooler and dryer air prevailed. Predictably, this was a region for the development of strong thunderstorms, and the 0000 UTC sounding for 14 August at Chanhassen (here) showed the potential for very strong convection.

The AQUA satellite carrying the MODIS instrument flew directly over the mature thunderstorm complex at 7:50 UTC 14 August, and the color-enhanced IR window channel (10.8 micrometers) is below. Plotted on top of the clouds are the 15-minute cloud to ground lightning data. Two active regions of lightning are present; one is over south-central Wisconsin, near Madison, and a second stretches as an arc along the front of a southward-propagating bow echo over western Wisconsin, immediately in front of the coldest cloud tops. The vertex of the arc corresponds to the line of wind damage reports from SPC. This correspondence is even more striking when viewing animations of lightning data and satellite data (or the combination, at the top of this blog entry), or the radar loop with lightning superposed on top that is here. Note the striking roll-up at the eastern edge of the devloping bow echo that was captured in extreme western Wisconsin — next to the St. Croix River — in the radar image at 0554 UTC (here).

The propagating thunderstorm had a predictable influence on surface pressures. Pressures rose as the first region of lightning moved through Madison just before 08z, and again as the second region of lightning associated with the weakening bow echo moved across Dane County.

rigmeteorogram.jpg

Note also the presence of a 38-knot wind gust from the southeast at 10:10 UTC as the mesolow moved through after most of the rain had fallen.