Large “hole punch cloud” over Wisconsin

July 18th, 2014

GOES-13 0.63 µm visible (upper left), 3.9 µm shortwave IR (upper right), 10.7 µm IR (lower left), and 6.5 µm water vapor (lower right) images [click to play animation]

GOES-13 0.63 µm visible (upper left), 3.9 µm shortwave IR (upper right), 10.7 µm IR (lower left), and 6.5 µm water vapor (lower right) images [click to play animation]

A large (approximately 50-mile diameter) “hole punch cloud” or “fall steak cloud” was seen over northwestern Wisconsin during the morning hours of 18 July 2014. An AWIPS 4-panel comparison of GOES-13 0.63 µm visible channel, 3.9 µm shortwave IR channel, 10.7 µm IR window channel, and 6.5 µm water vapor channel images (above; click image to play animation) showed that 10.7 µm IR cloud top brightness temperatures were not particularly cold with this feature (generally in the 0º C to -4º C range), and while 3.9 µm shortwave IR brightness temperatures warmed within the broad cloud deck surrounding the hole punch cloud after sunrise (due to reflection of solar radiation off of water cloud droplets), the center of the feature continued to exhibit colder (lighter gray enhancment) IR brightness temperatures which suggests cloud glaciation.

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature products at 09:32 UTC

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature products at 09:32 UTC

A comparison of CLAVR-x POES AVHRR Cloud Type, Cloud Top Height (CTH), and Cloud Top Temperature (CTT) products at 09:32 UTC or 4:32 am Central time (above) showed patches of water droplet clouds with CTH values in the 3-4 km range and CTT values in the 0º C to -4º C range.

A similar comparison at 12:05 UTC or 7:05 am Central time (below) revealed two areas of “cirrus” cloud type (orange color enhancement) exhibiting CTT values in the -35º to -40º C range (darker blue color enhancement) along the northern and southern periphery of the forming hole punch cloud.

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature prodcts at 12:05 UTC

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature prodcts at 12:05 UTC

These ranges of AVHRR Cloud Top Temperature and Cloud Top Height values agreed well with the regional rawinsonde data from Davenport IA (KDVN), Minneapolis MN (KMPX) and Green Bay WI (KGRB) shown below.

Davenport IA, Minneapolis MN, and Green Bay WI rawinsonde data at 12 UTC

Davenport IA, Minneapolis MN, and Green Bay WI rawinsonde data at 12 UTC

Terra MODIS visible and Cloud Phase products at 17:07 UTC or 12:07 pm Central time (below) indicated that a large area of glaciated ice cloud (salmon color enhancement) existed in the center portion of the hole punch cloud feature.

Terra MODIS 0.65 µm visible image and Cloud Phase products

Terra MODIS 0.65 µm visible image and Cloud Phase products

The cause of this large hole punch or fall streak cloud feature — and the other similar but smaller features seen across the region — was likely aircraft that had either ascended or descended through the cloud layer; particles in the aircraft exhaust acted as ice condensation nuclei, causing the process of cloud glaciation to begin.

GOES-15 0.62 µm visible images [click to play animation]

GOES-15 0.62 µm visible images [click to play animation]

GOES-15 imagery (above) shows the Hole Punch cloud from an oblique angle, and highlights how the region was overrun by smoke from wildfires in Canada. Smoke is most easily seen in visible satellite imagery when the sun is low in the sky, allowing for forward scatter. The smoke becomes less apparent in the imagery as the Sun rises. A similar animation for GOES-13 is below. Smoke is not quite so evident in this image because there is less forward scatter to GOES-13 over 75º W. Animations from both satellites show a hole punch cloud in Iowa as well.

GOES-15 0.62 µm visible images [click to play animation]

GOES-15 0.62 µm visible images [click to play animation]

Mesoscale Convective Systems over the Upper Midwest, and a Mesoscale Convective Vortex over Wisconsin

June 18th, 2014
Suomi NPP VIIRS 11.45 µm IR channel and 0.7 µm Day/Night Band images, with cloud-to-ground lightning strikes

Suomi NPP VIIRS 11.45 µm IR channel and 0.7 µm Day/Night Band images, with cloud-to-ground lightning strikes

A comparison of AWIPS images of Suomi NPP VIIRS 11.45 µm IR channel and 0.7 µm Day/Night Band data (above) showed very large areas of cold cloud-top IR brightness temperatures associated with Mesoscale Convective Systems (MCSs) over the Upper Midwest region of the US at 08:00 UTC (3:00 AM Central time) on 18 June 2014. The coldest IR brightness temperature was -88º C over far southern  Minnesota.  Numerous bright white “streaks” were seen on the Day/Night Band (DNB) image, which indicated portions of the cloud that were illuminated by intense lightning activity. Cloud-to-ground lightning strikes are also plotted on the DNB image, showing how electrically-active these storms were at the time. The western MCS initially formed over eastern South Dakota during the previous evening, producing a few tornadoes there (SPC storm reports). The eastern MCS began to form later along the Wisconsin/Illinois border region — one aircraft flying near the northern edge of a rapidly-developing thunderstorm encountered severe turbulence.

Shortly after the time of the Suomi NPP satellite overpass, a 08:21 UTC overpass of the NOAA-19 POES satellite provided AVHRR-derived CLAVR-x Cloud Top Temperature (CTT), Cloud Top Height (CTH), and Cloud Type products (below). The minimum CTT value was -84º C, and the maximum CTH value was 14 km; much of the MCS cloud shield was classified as the Overshooting Top type (magenta color).

POES AVHRR Cloud Top Temperature, Cloud Top Height, and Cloud Type products

POES AVHRR Cloud Top Temperature, Cloud Top Height, and Cloud Type products

After sunrise, McIDAS  images of GOES-13 0.63 µm visible channel data (below; click image to play animation; also available as an MP4 movie file) showed that the eroding MCS cirrus shield aloft exposed a middle-tropospheric Mesoscale Convective Vortex (MCV) which continued moving eastward across Wisconsin during the day.

GOES-13 0.63 µm visible channel images (click to play animation)

GOES-13 0.63 µm visible channel images (click to play animation)

Consecutive overpasses of the Terra and Aqua satellites provided MODIS 0.65 µm visible channel images of the region (below). The convective outflow boundary from the earlier MCS activity had acted to push the warm frontal boundary (which had been acting as a focus for convective development) south of the Wisconsin/Illinois border, leaving a relatively stable boundary layer with a weak capping inversion aloft over Wisconsin — as a result, the MCV circulation did not play a role in initiating any new convective development.

MODIS 0.65 µm visible channel images, with surface reports and surface fronts

MODIS 0.65 µm visible channel images, with surface reports and surface fronts

GOES-14 SRSOR: from morning fog/stratus to afternoon convection

May 13th, 2014
Suomi NPP VIIRS and POES AVHRR IR brightness temperature difference

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)

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)

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

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

MODIS 11.0 µm IR channel image

GOES-14 SRSOR: severe thunderstorms over the central Plains

May 11th, 2014
GOES-14 0.63 µm visible channel images (click to play animation)

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)

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)

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

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

POES AVHRR 12.0 µm IR channel images

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