Mesovortices within a mid-latitude cyclone

February 25th, 2014
Meteosat-10 0.75 µm visible channel and 10.8 µm IR channel images (click to play animation)

Meteosat-10 0.75 µm visible channel and 10.8 µm IR channel images (click to play animation)

Twitter follower @PedroCFernandez alerted us to an interesting case of mesovortices (original Spanish language blog post | Google translate version) which developed within the circulation of a strong mid-latitude cyclone over the northeastern Atlantic Ocean (moving toward the British Isles) on 24-25 February 2014. McIDAS images of EUMETSAT Meteosat-10 daytime 0.75 µm high resolution visible channel and night-time 10.8 µm IR channel data (above; click to play animation) revealed the series of mesovortices that spun up along the “bent-back” occluded frontal boundary (surface analyses); this storm was producing hurricane force winds during the 12-18 UTC period on 24 February, according to the NWS Ocean Prediction Center. Mesovortex cloud-top IR brightness temperatures were around -40º C (green color enhancement), indicating significant vertical development of the cloud structure associated with these features.

Meteosat-10 0.75 µm visible channel and 10.8 µm IR channel images at 18:00 UTC

Meteosat-10 0.75 µm visible channel and 10.8 µm IR channel images at 18:00 UTC

A comparison of the 18:00 UTC Meteosat-10 visible and IR images (above) showed two well-developed mesovortices at that time: #1, located southwest of the storm center, and #2, located west of the storm center;  a new mesovortex #3 was just in the process of forming to the northwest of the storm center (below).

Meteosat-10 10.8 µm IR channel image at 18:00 UTC

Meteosat-10 10.8 µm IR channel image at 18:00 UTC

Yet another powerful storm strikes the British Isles

February 5th, 2014
Meteosat-10 0.635 µm visible channel images (click to play animation)

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

McIDAS images of EUMETSAT Meteosat-10 0.635 µm visible channel data (above; click image to play animation) showed the cloud structure associated with a powerful midlatitude cyclone that was moving northeastward toward the British Isles on 04 February 2014. This storm — the latest in a series of intense North Atlantic Ocean storms to batter the region during the winter of 2013/2014 — produced very strong winds (gusting to 92 mph on the Isle of Scilly), heavy rain, and flooding; power was cut to over 40,000 customers, and rail service was disrupted.

The evolution of the storm could be seen on hourly composites of geostationary and polar-orbiting satellite water vapor channel imagery covering the 03-05 February period (below), visualized using the SSEC RealEarth web map server. As the large storm began to dissipate, another system could be seen developing upstream over the North Atlantic Ocean. Also of note are the subtle wave structures that could be seen in the water vapor imagery downwind of the Azores, caused by strong winds interacting with the high terrain of the islands (the tallest point is Pico, at 2,351 meters or 7,713 ft).

Composite of water vapor channel imagery (click to play animation)

Composite of water vapor channel imagery (click to play animation)

Chaparrastique erupts in El Salvador

December 29th, 2013
GOES-13 0.63 µm visible imagery during Chaparrastique eruption (click to play animation)

GOES-13 0.63 µm visible imagery during Chaparrastique eruption (click to play animation)

The volcano Chapparastique in eastern El Salvador near the city of San Miguel experienced a brief eruption on Sunday the 29th of December (YouTube video). Half-hourly 0.63 µm visible channel imagery from GOES-13 or GOES-East (the most frequent imagery available at 13.5º N, the latitude of the volcano), above, plainly shows the appearance of the volcanic ash cloud between 16:15 and 16:45 UTC (media sources reported that the time of the eruption was 16:32 UTC). Most of the ash cloud then moved westward across the coast and over the adjacent waters of the Pacific Ocean, although parts of the ash cloud also moved eastward over Honduras. This is the first complete Chapparastique advisory from the VAAC in Washington DC on this eruption. The most recent volcanic ash advisories can be found here.

GOES-15 or GOES-West, positioned at 135º W, was also able to view the ash cloud, and that animation is below. El Salvador is near the eastern edge of the satellite view. Routine scanning that was taking place on Sunday 29 December only viewed El Salvador every three hours.

GOES-15 0.63 µm visible imagery during Chaparrastique eruption (click to play animation)

GOES-15 0.63 µm visible imagery during Chaparrastique eruption (click to play animation)

It happens occasionally that useful information about volcanic eruptions can be gleaned from extreme limb views from geostationary satellites (see here, for example, or this animation from this blog post). In the present case, the MTSAT-2 visible imagery, below, was a bit too far to the west to view the atmosphere over central America.

MTSAT-2 0.73 µm visible imagery during Chaparrastique eruption (click to play animation)

MTSAT-2 0.73 µm visible imagery during Chaparrastique eruption (click to play animation)

Meteosat-10 data possibly saw the eruption; however, the remapped imagery that is broadcast does not include pixels for which a latitude/longitude value can be computed, such as pixels that are at the extreme edge of the limb, in outer space. To ascertain the presence of a signal in the satellite data would require access to the raw data from the satellite, and that is not routinely available. Meteorsat-10 visible images surrounding the eruption time are shown below.

METEOSAT-10 0.6 µm visible imagery during Chaparrastique eruption (click to play animation)

METEOSAT-10 0.6 µm visible imagery during Chaparrastique eruption (click to play animation)

Note that when GOES-R ABI is broadcasting data, its limb edge will resemble the METEOSAT-10 data above rather than the more complete MTSAT-2 data. Level 0 data from ABI includes space looks at the limb; that level 0 data will be calibrated, navigated and remapped and distributed as level 1 GOES-R series ReBroadcast (GRB) data that will not include points at the limb that are un-navigable (but that nevertheless can include interesting data).

As part of CIMSS/ASPB participation in GOES-R Proving Ground activities, various volcanic ash detection and analysis products have been developed. Below is an animation of GOES-13 multi-spectral false-color Red/Green/Blue (RGB) images that also show the dispersion of the volcanic ash cloud.

GOES-13 multi-spectral RGB images (click to play animation)

GOES-13 multi-spectral RGB images (click to play animation)

Examples of some of the quantitative volcanic ash products are shown below, using MODIS data from an overpass of the Aqua satellite at 18:50 UTC. The maximum ash height appeared to be around 10 km along the eastern end of the cloud; the maximum ash loading approached 6 g/m2 on the western edge of the plume; the maximum ash particle effective radius was in the 14-16 µm range along the edges of the cloud.

Aqua MODIS Ash/Dust Cloud Height product

Aqua MODIS Ash/Dust Cloud Height product

Aqua MODIS Ash/Dust Loading product

Aqua MODIS Ash/Dust Loading product

Aqua MODIS Dust/Ash Particle Effective Radius product

Aqua MODIS Dust/Ash Particle Effective Radius product

Winter Storm Xaver

December 5th, 2013
Meteosat-10 6.25 µm water vapor channel images (click to play animation)

Meteosat-10 6.25 µm water vapor channel images (click to play animation)

Winter Storm Xaver (EUMETSAT Image Library) affected much of northern Europe on 05 December 2013, causing widespread power outages, storm surge flooding, and adverse impacts to transportation in several countries. As many as nine deaths have been blamed on the storm. Many areas experienced hurricane-force winds, with the highest wind gust of 142 mph (229 km per hour) reported at Aonach Mor in Scotland. EUMETSAT Meteosat-10 6.25 µm water vapor channel images (above; click image to play animation) showed the rapid intensification of the storm as the center moved  from south of Iceland late in the day on 04 December to southern Sweden late in the day on 05 December.

Meteosat-10 water vapor channel images with overlays of surface wind gusts (in knots) are shown below (click to play animation).

Meteosat-10 6.25 µm water vapor channel images with surface wind gusts (click to play animation)

Meteosat-10 6.25 µm water vapor channel images with surface wind gusts (click to play animation)

Meteosat-10 0.7 µm broadband high resolution visible channel images (below; click image to play animation) offered a closer look at the center of the storm as it moved eastward across the North Sea and over southern Norway during the daytime hours on 05 December.

Meteosat-10 0.7 µm visible images (click to play animation)

Meteosat-10 0.7 µm visible images (click to play animation)