Airborne glacial silt over the Gulf of Alaska

November 16th, 2013 |
GOES-15 0.63 µm visible channel images (click to play animation)

GOES-15 0.63 µm visible channel images (click to play animation)

Hat tip to Mark Ruminski (NOAA/NESDIS) for directing our attention to a pair of airborne glacial silt plumes that were being drawn southward over the far northern Gulf of Alaska on 16 November 2013. McIDAS images of GOES-15 0.63 µm visible channel data (above; click image to play animation) showed the two distinct hazy plumes as they were being advected offshore east of the Cordova, Alaska (PACV) area. The tight cyclonic circulation of a mesoscale area of low pressure may have helped to increase the speed of the gap winds that were lofting the glacial silt particles from the Copper River Delta and Icy Bay regions.

Suomi NPP VIIRS 0.64 µm visible channel images

Suomi NPP VIIRS 0.64 µm visible channel images

AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel data (above) showed a better view of the 2 plumes at 21:23 and 23:04 UTC. The airborne glacial silt plumes appeared darker on the corresponding 3.74 µm shortwave IR images (below) due to enhanced solar reflection off the small particles.

Suomi NPP VIIRS 3.74 µm shortwave IR images

Suomi NPP VIIRS 3.74 µm shortwave IR images

MODIS Volcanic Ash Height product

MODIS Volcanic Ash Height product

MODIS-based products designed to monitor volcanic ash plumes were also able to detect the glacial silt plumes and provide quantitative information about these features. The mean plume height (above) was around 5000 feet, with a maximum around 9000 feet at some locations. The mean particle effective radius (below) was generally in the 4-7 µm range, with a maximum size of 9-10 µm.

MODIS Volcanic Ash Particle Effective Radius product

MODIS Volcanic Ash Particle Effective Radius product

 

Occluding storm in the East Pacific Ocean

November 11th, 2013 |
GOES-15 6.5 µm water vapor channel images (click to play animation)

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

A rapidly occluding mid-latidude cyclone over the East Pacific Ocean on 11 November 2013 exhibited a classic “dry swirl” signature on McIDAS images of 4-km resolution GOES-15 6.5 µm water vapor channel data (above; click image to play animation).

The dry swirl signature was beginning to form after about 11 UTC, as seen on an AWIPS image of 1-km resolution MODIS 6.7 µm water vapor channel data (below). There were no buoy reports near the storm center, but one bouy was reporting easterly winds gusting to 37 knots well to the northeast (just north of the occluded front).

MODIS 6.5 µm water vapor image, with surface analysis and buoy reports

MODIS 6.5 µm water vapor image, with surface analysis and buoy reports

Shortly after the time of the MODIS water vapor image, a comparison of 1-km resolution Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images (below) showed similar details in the cloud structure as the occlusion process continued. Since it was still local night-time, the clouds were illuminated primarily by airglow (the Moon was in the waxing gibbous phase, at 68% of full; however, it was below the local horizon at that particular time) — this provides an example of the “visible image at night” capability of the VIIRS Day/Night Band.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR images, with surface analysis and buoy reports

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR images, with surface analysis and buoy reports

Super Typhoon Haiyan

November 7th, 2013 |
COMS-1 10.8 µm IR channel images (click to play animation)

COMS-1 10.8 µm IR channel images (click to play animation)

Super Typhoon Haiyan (31W) formed as a tropical depression at low latitudes in the West Pacific Ocean on 03 November 2013 — and by 18 UTC on 07 November was estimated to have peaked at an intensity of sustained 170 knot winds with gusts to 205 knots (Storm track map | ADT plot | JTWC warning text). McIDAS images of 15-minute interval 10.8 µm IR channel data from the Korean COMS-1 satellite (above; click image to play animation; a YouTube video is also available) showed the intense tropical cyclone as it moved westward and made landfall in the Philippines on 07 November. There was a large, nearly symmetric ring of very cold cloud-top IR brightness temperatures in the -80 to -90º C range (violet colors) — and at times there were a few isolated pixels colder than -90º C (yellow enhancement). For comparison, a YouTube video of MTSAT-1 10.8 µm IR imagery is also available.

As the eye was still east of the Philippines, a McIDAS-V image comparison of 375-m resolution Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) and 11.45 µm IR channel data at 16:15 UTC on 07 November (below; courtesy of William Straka, CIMSS) revealed intricate banding structures within the eyewall region on the IR image, as well as bright streaks on the DNB image due to cloud illumination by intense lightning activity.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images

The eye and eyewall of Haiyan moved over the eastern Philippine islands of Samar and Leyte (near the city of Tacloban) during the early morning hours, as can be seen in COMS-1 0.675 µm visible channel images (below; click image to play animation; a YouTube video is also available)

COMS-1 0.675 µm visible channel images (click to play animation)

COMS-1 0.675 µm visible channel images (click to play animation)

 

DMSP SSMIS 85 GHz microwave brightness temperature image

DMSP SSMIS 85 GHz microwave brightness temperature image

The nearly annular structure of the eyewall at 21:08 UTC on 07 November was revealed on a DMSP SSMIS 85 GHz microwave image (above) from the CIMSS Tropical Cyclones site. In addition, a sequence of eyewall replacement cycles can be seen during the 06-07 November period using the MIMIC-TC product (below). It appears as though Super Typhoon Haiyan was in the process of undergoing another eyewall replacement cycle as it was making landfall in the Philippines.

MIMIC-TC morphed microwave imagery (click image to play animation)

MIMIC-TC morphed microwave imagery (click image to play animation)

Regarding the size of and very cold cloud-top IR brightness temperatures seen with Super Typhoon Haiyan, the IR images below (courtesy of Rick Kohrs, SSEC) show a side-by-side comparison with Category 5 Hurricane Katrina (Haiyan has been artifically superimposed at the same location over the Gulf of Mexico). Note the significantly colder cloud-top IR brightness temperatures associated with Haiyan (-80 to -89 C, violet colors), due to its location in the tropics (near 10 N latitude) where the tropopause was much higher and much colder.

IR image comparison of Haiyan (left) and Katrina (right)

IR image comparison of Haiyan (left) and Katrina (right)

It is interesting to note that during the previous daytime hours (on 06 November), a series of mesovortices could be seen within the eye of Haiyan on COMS-1 visible images (below; click image to play animation; a YouTube video is also available). For more discussion on these mesovortices, see the From the Lee Side blog.

COMS-1 0.675 µm visible channel images (click to play animation)

COMS-1 0.675 µm visible channel images (click to play animation)

 

Sea Surface Temperature analysis (with track of Haiyan)

Sea Surface Temperature analysis (with track of Haiyan)

As pointed out in the Joint Typhoon Warning Center prognostic reasoning bulletin, factors that favored the intensification of Super Typhoon Haiyan included warm sea surface temperatures (above) and low values of deep layer wind shear (below).

MTSAT IR images with overlay of Deep Layer Wind Shear contours

MTSAT IR images with overlay of Deep Layer Wind Shear contours

11 November Update: A McIDAS-V image comparison of  “before Haiyan” (31 October) and “after Haiyan” (09 November) night-time Suomi NPP VIIRS 0.7 µm Day/Night Band data (below; courtesy of William Straka, SSEC/CIMSS) showed the extent of the power outages in the Tacloban City area and other towns in the northern portion of Leyte province, caused by devastating damage sustained during the landfall of the powerful typhoon.

Suomi/NPP Day/Night Band Imagery before and after Haiyan

Suomi/NPP Day/Night Band Imagery before and after Haiyan

21 November update: Rick Kohrs (SSEC) created a large (72 megabyte) animation of hourly MTSAT-1 6.75 µm water vapor channel imagery — covering the life span of Haiyan during the 03-11 November period — superimposed on a Sea Surface Temperature background (below; click image to play animation; a YouTube video is also available).

MTSAT-1 6.75 µm water vapor images, superimposed on a Sea Surface Temperature background (click to play animation)

MTSAT-1 6.75 µm water vapor images, superimposed on a Sea Surface Temperature background (click to play animation)

GOES-13 Sounder Anomalies continue

November 4th, 2013 |
Composite of GOES-15/GOES-13 3.9 µm shortwave IR images (click image to play animation)

Composite of GOES-15/GOES-13 3.9 µm shortwave IR images (click image to play animation)

The GOES-13 Sounder has been experiencing anomalies that manifest themselves as missing pixels since mid-Summer. The missing pixels apparently arise because of slight fluctuations in the speed of the sounder instrument filter wheel. The number of missing pixels per Sounder image peaked in late September, just after the Equinox, with up to 700 missing pixels (out of 63000) per Sounder image over CONUS. At present, missing pixels vary between 100 and 250, with a maximum typically around 2200 UTC and a minimum between 0600 and 1000 UTC. In the animation above, the missing pixels show as black; the GOES-15 Sounder data have no missing pixels.

Realtime GOES Sounder imagery is available at this link. The Sounder anomalies are present in all 19 of the GOES-13 spectral bands, as evident in the toggle below between an image in late September (when error counts were highest) and early November (when error counts were lower). GOES Engineers continue to monitor this situation and investigate possible solutions.

GOES-13 Sounder 19-band display, 1800 UTC 27 September and 1600 UTC 4 Nov 2013 (click image to enlarge)

GOES-13 Sounder 19-band display, 1800 UTC 27 September and 1600 UTC 4 Nov 2013 (click image to enlarge)