GOES-13 6.5 µm "water vapor channel" images (click image to play animation)

We received the following in an email message from Paul Fuentes at the National Weather Service forecast office at Key West, Florida:

“Just though you might be interested in a peculiar little feature we noticed at the WFO Key West on AWIPS from GOES-13 IR imagery on 4/23/11 starting at about 22:301Z over Andros Island (24.21N, 77.7W) and persisted to into the afternoon on 4/24/11. The feature looked almost like a smoke ring (several miles across) that was drifting off to the Northeast that emanated off of Andros Island and was also apparent in VIS/WV.”

McIDAS images of 4-km resolution GOES-13 6.5 µm “water vapor channel” data (above) showed the feature in question, as it first appeared along the east coast of Andros Island (the large island in the lower left corner of the images) at 22:45 UTC on 24 April 2011 — and then propagated northeastward, grew in size, exhibited progressively colder brightness temperatures, and at times took on a ring-like shape.

A closer look using 1-km resolution GOES-13 0.63 µm visible channel images (below) again revealed the ring-like structure that was evident at various times during the day on 25 April 2011.

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

The feature (as seen on 10.8 µm POES AVHRR IR imagery, below) seemed to follow the CRAS model 300 hPa wind flow — and southwesterly winds were not found until the 375 hPa pressure level on the 12 UTC rawinsonde report from Nassau in the Bahamas.

POES AVHRR 10.8 µm IR images + CRAS model 300 hPa wind flow

A comparison of the MODIS 0.65 µm visible channel, the 11.0 µm IR window channel, the 6.7 µm water vapor channel, and the 1.3 µm cirrus detection channel images at 15:57 UTC (below) seem to support the idea that this was a high ice cloud feature.

MODIS visible, IR window, water vapor, and cirrus detection channel images

So what exactly was this interesting satellite feature? Until an explanation is found, this blog posting shall remain in the “What the heck is this?” Category…

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MODIS false color image comparison between 11 April and 24 April 2011

A comparison of MODIS false color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above) shows the increase in areal coverage of flooding along the Red River of the North, from north of Grand Forks, North Dakota into southern Manitoba. Also evident is the melting of most of the snow cover across northeastern North Dakota, and the melting of portions of Devils Lake (snow and ice appear as cyan features on the false color images, while water has a darker blue appearance).

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

AWIPS images of GOES-13 10.7 µm IR data (above; click image to play animation) showed a large line of severe thunderstorms that moved eastward across the middle Mississippi River Valley region during the evening of 22 April 2011. This storm produced a significant number of large hail, damaging wind, and tornado reports (including one that did damage to the St. Louis airport). The initial storm damage survey has found EF-4 damage in the northern St. Louis county area.

A 1-km resolution POES AVHRR image very close to the time that the tornado was moving through the St. Louis area is shown below, with an overlay of the SPC hail, damaging winds, and tornado reports. Though the time stamp of the AWIPS image was “01:00 UTC”, the actual time that the NOAA-16 satellite was making its overpass of that region was about 01:12 UTC. Note that the storm exhibited a very well-defined “enhanced-v” signature near St. Louis (with a minimum cloud top IR brightness temperature of -83º C) — this enhanced-v IR storm top signature is often observed with areas of strong convection that are producing (or are about to produce) either large hail, damaging winds, or tornadoes.

POES AVHRR 12.0 µm IR image + severe weather reports

On a larger-scale view, a comparison of the 1-km resolution POES AVHRR 12.0 µm IR image with the corresponding 4-km resolution GOES-13 10.7 µm IR image (below) demonstrated two things: (1) how an improvement in spatial resolution can aid in the detection of small-scale cloud top features and signatures, and (2) the parallax shift of the high cloud top features on the GOES-13 image (features are shifted farther to the northwest compared to the POES AVHRR image, due to the large viewing angle from GOES-13). In spite of the AWIPS time stamps of the 2 images being different, the times of the images are actually about the same: the GOES image began scanning southward from southern Canada at 01:10 UTC, while the Miami ground station began to receive to NOAA-16 AVHRR image over the Gulf of Mexico at 01:00 UTC. Both images are scanning the St. Louis region around 01:12 UTC.

POES AVHRR 10.8 µm IR image + GOES-13 10.7 µm IR image

As the line of convection was organizing across western Missouri during the afternoon hours, GOES-13 sounder derived product images (below) of Convective Available Potential Energy (CAPE), Lifted Index (LI), and Total Precipitable Water (TPW) showed that the air mass south of the warm frontal boundary across eastern Missouri was moist (TPW values of 30-40 mm or 1.2 to 1.6 inches) and unstable (CAPE values exceeding 4000 J/kg and LI values of -5 to -9 C).

GOES-13 sounder Convective Available Potential Energy derived product image

GOES-13 sounder Lifted Index derived product image

GOES-13 sounder Total Precipitable Water derived product image

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Global montage of geostationary satellite images (click to play animation)

The “spinning globe” satellite image montage (above; click image to play animation) showed the cloud formations around the planet on Earth Day (22 April 2011). This product is created by combining data from 5 of the currently operational geostationary orbiting meteorological satellites (GOES-East at 75º West longitude, GOES-West at 135º West longitude, Meteosat at 0º longitude, Meteosat at 63º East longitude, and MTSAT at 145º East longitude), polar orbiting satellites, and a topographic background map of the Earth. The spinning globe product is created every 3 hours, and is available for either the latest time period or an animation covering the last 3 weeks.

MODIS IR image atmospheric motion vectors over the Arctic region

Polar-orbiting satellites such as the NASA Terra and Aqua platforms also provide us with valuable information over the polar regions of the Earth (which are not sampled well by geostationary satellites, due to the very large viewing angles). Cloud-tracked winds (or “atmospheric motion vectors”) can be calculated by comparing the location of features on successive images — examples of Terra and Aqua MODIS winds from 22 April 2011 over the Arctic region (above) and the Antarctic region (below) provide valuable input into numerical weather prediction models.

MODIS IR image atmospheric motion vectors over the Antarctic region

These are just a few examples of the diverse array of real-time satellite data and products that are available from the Space Science and Engineering Center at the University of Wisconsin – Madison every day.

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