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.

1 week of Upper Midwest MCS activity: a GOES-16 overview

July 26th, 2017 |
GOES-16 Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 Infrared Window (10.3 µm) images [click to play MP4 animation]

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

During the week of 19 July26 July 2017, the Upper Midwest was affected  by a number of strong to severe Mesoscale Convective System (MCS) events, as shown in an animation of GOES-16 “Clean” Infrared Window (10.3 µm) images (above).

At the beginning of that time period, a derecho moved across the region on 19 July producing widespread damaging winds, large hail and a few tornadoes (blog post).

Following the derecho, a separate outbreak of thunderstorms exhibited well-defined “enhanced-V” storm top signatures in western Wisconsin (below).

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

Another MCS produced tornadoes and damaging winds across eastern Iowa and northern Illinois on 21 July (SPC storm reports) — at one point a storm in northern Illinois exhibited a seldom-seen “warm trench” surrounding an overshooting top (below).

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

Early in the day on 23 July, “transverse banding” — a signature indicating the likelihood of high-altitude turbulence — was seen around the northern periphery of an MCS that was centered in southern Illinois (below).

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

A pattern of mesoscale banding was displayed by thunderstorms that produced localized 1-2″ amounts of rainfall across southern Wisconsin on 26 July (below).

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

GOES-16 Infrared Window (10.3 µm) image [click to enlarge]

Also noteworthy was the swath of very heavy rainfall during this 1-week period across eastern Iowa, far southwestern Wisconsin and northern Illinois (below), which was responsible for flash flooding in those areas.

7-day total precipitation, departure from normal and percent of normal [click to enlarge]

7-day total precipitation, departure from normal and percent of normal [click to enlarge]