General interpretation « CIMSS Satellite Blog

Tracking a Lunar Umbra (solar eclipse shadow) across the Atlantic Ocean

November 3rd, 2013

Meteosat-10 0.635 µm visible channel images (click to play animation)

A rare “hybrid” solar eclipse occurred on 03 November 2013 (photos), which began over the western Atlantic Ocean as an annular eclipse and transitioned into a full total solar eclipse for observers along the narrow path of totality in the far eastern Atlantic and over parts of Africa (map of eclipse path). The Lunar Umbra (or solar eclipse shadow) could be seen tracking rapidly southeastward across the Atlantic Ocean on EUMETSAT Meteosat-10 0.635 µm visible channel images from 10:45-14:30 UTC (above; click image to play animation).

The dark solar eclipse shadow could also be seen near the edge of the Full Disk scan of the GOES-13 satellite at 11:45 UTC, just south and southwest of the Cape Verde Islands (below). Since the current generation of GOES only perform a full disk scan once every 3 hours, the eclipse shadow could not be followed in time as it was using the 15-minute interval images from Meteosat-10.

GOES-13 0.63 µm visible channel images

With the next-generation GOES-R series, a full disk scan will occur once every 5 minutes. As a part of the GOES-14 Super Rapid Scan for GOES-R (SRSOR) testing, full disk scans were performed every 30 minutes on 14 September 2012.

Posted in General interpretation, GOES-13, GOES-R, Meteosat | No Comments »

Possible Sting Jet Associated with strong storm in Europe

October 28th, 2013

Meteosat-10 6.2 µm WV channel images (click to play animation)

Sting jets are wind maxima near the end of bent-back fronts in cases of strong cyclones. As noted earlier on this blog, they can acquire a characteristic look in water vapor imagery, vaguely reminiscent of a scorpion’s stinger. In addition, strongly sinking air around the jet, usually associated with both a tropopause fold and a maximum in ozone, is manifest as a warm (dry) patch in the water vapor (WV) imagery. In the animation above, the sting jet is apparent moving across northern Denmark into southern Sweden between 1500 and 1800 UTC. This is in association with the ‘St. Jude’ storm that killed more than a dozen across northern Europe (Reuters news story; Sky News story).

The strong sinking near a sting jet can transport momentum down to the surface. You should therefore expect to see strong surface wind gusts near the water vapor satellite signature, and that was the case on October 28, as shown below.

Hourly Meteosat-10 6.2 µm WV channel images and Observed Surface Wind Gusts (click to play animation)

Suomi/NPP viewed this storm early in the day on 28 October. The toggle between the VIIRS Day/Night Band and the 11.45 µm IR data, below, shows a developing baroclinic leaf over the British Isles.

Toggle between VIIRS Day/Night Band and 11.45 µm IR imagery at 0220 UTC on 28 October (click to enlarge)

A comparison of Aqua MODIS 0.65 µm visible, 11.0 µm IR, and 6.7 µm water vapor channel images visualized using the SSEC Web map Server (below; courtesy of Russ Dengel and Kathy Strabala, SSEC) showed the storm at 12:14 UTC on 28 October. The warm/dry signature of strongly-subsiding middle to lower tropospheric air was particularly evident on the water vapor image (yellow to orange color enhancement) as it was beginning to move eastward over Denmark.

Aqua MODIS 0.65 µm visible, 11.0 µm IR, and 6.7 µm water vapor channel images

For additional satellite images of this event, see the EUMETSAT Image Library and the Wide World of SPoRT.

Posted in General interpretation, Meteosat, MODIS, Suomi NPP, VIIRS, Web Map Server | No Comments »

Widespread power outages across Syria

October 23rd, 2013

Suomi NPP VIIRS 0.7 µm Day/Night Band images

McIDAS-V “before” (22 October 2013) and “after” (23 October 2013) night-time images of Suomi NPP VIIRS 0.7 µm Day/Night Band data (above; courtesy of William Straka, CIMSS) showed the coverage of power outages across much of Syria, caused by a rebel attack on a gas pipeline (near Damascus International Airport) that supplied the Tashrin power generating station in the southern part of the country. As can be seen in the “after” image on 23 October, full or partial power outages affected all provinces of Syria — in particular, parts of the Euphrates River valley, the northern Mediterranean coast near Latakia, and areas south of the capitol city of Damascus (map of Syria).

Posted in General interpretation, McIDAS-V, Suomi NPP, VIIRS | No Comments »

Flooding rains in southern Texas

October 14th, 2013

GOES-15/GOES-13 6.5 µm water vapor channel images (click to play animation)

Flooding rains have occurred over south Texas during the past two days, and the animation of GOES water vapor imagery, above, and of MIMIC Total Precipitable Water, below, shows two airstreams moving moisture into that region. The GOES-15/GOES-13 Water Vapor image animation, above, shows upper-level moisture moving in from the tropical Pacific south of Mexico (much of it likely outflow from Tropical Storm Octave). MIMIC Total Precipitable Water animation (available from this site), below, shows a concomitant lower-level moisture source, the Gulf of Mexico. Plots at 925 mb, and 850 mb, show moist, easterly flow around a High centered over the mid-Mississippi valley. As a result, total precipitable water values exceeded 200% of normal over a wide region. (Blended Total Precipitable Water products are available here). The high values of Total Precipitable Water persist into the day on 14 October. (Link, analysis from SPC).

MIMIC Total Precipitable Water (click to play animation)

VIIRS 11.45 µm IR image (click to enlarge)

A Suomi-NPP VIIRS 11.45 µm IR image from late in the day on 13 October (above) showed strong convection near Laredo, TX, with very cold cloud tops (brightness temperature values over Mexico are as cold as -92º C!). Applying a different color enhancement, a comparison of this 1-km resolution VIIRS IR image at 20:11 UTC with the corresponding 4-km resolution GOES-13 10.7 µm IR image (below) highlights two advantages of polar orbiter imagery over geostationary imagery: (1) with the higher spatial resolution, the magnitude of the coldest overshooting cloud tops can be assessed: the -92º C minimum cloud-top IR brightness temperature on the VIIRS image was 14º C colder than the -78º C value seen on the GOES-13 image, and (2) with the minimal parallax error of polar orbiter imagery, the exact location of such cloud-top features can be more accurately determined.

Suomi NPP VIIRS 11.45 µm IR and GOES-13 10.7 µm IR channel images

The result of the strong convection near 2100 UTC, and from other convection apparent in the water vapor animation at top, was a broad region of heavy rains, (obtained from this site) shown below. Some of these rains fell over regions of Texas in drought (as shown here), so where damage was minimal, the heavy rains could be considered beneficial.