Typhoon Neoguri threatens Okinawa

July 7th, 2014
COMS-1 0.675 µm and MTSAT-2 0.73 µm Visible channel images (Click to enlarge)

COMS-1 0.675 µm and MTSAT-2 0.73 µm Visible channel images (Click to enlarge)

Typhoon Neoguri is forecast to move west of Okinawa later today. The visible images above, from COMS-1 (left) and MTSAT-2 (right) show the storm at around 0800 UTC on 7 July 2014. A distinct eye filled with low-level clouds is apparent.

COMS-1 (left) and MTSAT-2 (right) visible channel images [click to play animation]

COMS-1 (left) and MTSAT-2 (right) visible channel images [click to play animation]

Magnified views of the storm center (above; click image to play animation; also available as an MP4 movie file) revealed the presence of mesovortices within the eye of Neoguri. The more frequent imaging schedule of COMS-1 (generally every 15 minutes, compared to every 30 minutes with MTSAT-2) allowed the cyclonic circulation of the mesovortices to be more easily identified. Another curious feature seen on the early morning visible imagery was a northwest-to-southeast oriented “cloud cliff” shadow just north of the eye, which was cast by the taller clouds of an eyewall convective burst just to the east. This same signature was seen again on the following morning, in nearly the same location relative to the eye (MTSAT-2 visible/IR image comparison).

METOP-B ASCAT winds over Neoguri and Observed SSTs (Click to toggle)

METOP-B ASCAT winds over Neoguri and Observed SSTs (Click to toggle)

ASCAT winds from METOP-B (above) show the structure of the typhoon, with 70-knot winds indicated. The Sea Surface Temperature (SST) image (taken from the CIMSS Tropical Cyclones site) also shows the extreme warmth of the western Pacific Ocean.

COMS-1 10.8 µm and MTSAT-2 10.8 µm Infrared channel images (Click to animate)

COMS-1 10.8 µm and MTSAT-2 10.8 µm Infrared channel images (Click to animate)

Infrared imagery from the past 24 hours show a decline in the satellite structure of the storm. Cold cloud tops have eroded from the northern and western quadrants of the storm, and a circular ring of cold cloud tops around the eye is no longer apparent.

Suomi NPP VIIRS 11.45 µm  Infrared channel image (Click to enlarge)

Suomi NPP VIIRS 11.45 µm Infrared channel image (Click to enlarge)

Suomi NPP overflew the storm on Saturday 5 July at 1620 UTC. The color-enhanced VIIRS 11.45 IR image, above (courtesy William Straka, SSEC/CIMSS), shows very cold cloud tops (185 K) southeast of a developing eye.

Eruption of the Sangeang Api volcano in Indonesia

May 30th, 2014
MTSAT-2 0.63 µm visible channel and 10.8 µm IR channel images at 08:32 UTC

MTSAT-2 0.63 µm visible channel and 10.8 µm IR channel images at 08:32 UTC

A comparison of McIDAS images of MTSAT-2 0.63 µm visible channel and 10.8 µm IR channel data at 08:32 UTC on 30 May 2014 (above) showed the volcanic cloud from the first in a series of eruptions of the Sangeang Api volcano in Indonesia (aircraft photos). The coldest cloud-top IR brightness temperature at that time was -74.5º C; note that the tall volcanic cloud was casting a large shadow toward the east-southeast in the visible image.

An animation of MTSAT-2 10.8 µm IR images (below; click image to play animation; also available as an MP4 movie file) revealed that there were a number of smaller eruptions that followed the initial, larger eruption.

MTSAT-2 10.8 µm IR channel images (click to play animation)

MTSAT-2 10.8 µm IR channel images (click to play animation)

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MTSAT-2 false-color RGB images (click to play animation

MTSAT-2 false-color RGB images (click to play animation)

The NOAA/CIMSS Volcanic Cloud Monitoring MTSAT-2 false-color Red/Green/Blue (RGB) images (above; click image to play animation) showed the southeastward spread of volcanic ash cloud from the first 2 eruptions, while the Volcanic Ash Height product (below; click image to play animation) indicated that the ash may have reached altitudes of at least 12-14 km. Pilot reports in the vicinity placed the height of the volcanic cloud at 65,000 feet or 19.8 km.

NOAA/CIMSS Volcanic Ash Height product (click to play animation)

NOAA/CIMSS Volcanic Ash Height product (click to play animation)

Night-time McIDAS-V images of Suomi NPP VIIRS 11.45 µm IR, 3.9 µm shortwave IR, and 0.7 µm Day/Night Band (DNB) images of one of the secondary eruptions at 17:43 UTC on 30 May (below; courtesy of William Straka, SSEC) showed a cloud-top IR brightness temperature as cold as -77º C, along with the yellow-enhanced “hot spot” on the shortwave IR and the bright glow on the DNB image from the hot volcano vent and lava flows.

Suomi NPP VIIRS 11.45 µm IR, 3.9 µm shortwave IR, and 0.7 µm Day/Night Band images

Suomi NPP VIIRS 11.45 µm IR, 3.9 µm shortwave IR, and 0.7 µm Day/Night Band images

A composite of Suomi NPP VIIRS true-color RGB images from 31 May, viewed using the SSEC RealEarth web map server (below) showed the widespread extent of the volcanic ash cloud from the ongoing eruption.

Suomi NPP VIIRS true-color RGB image composite

Suomi NPP VIIRS true-color RGB image composite

Due to the southeastward drift of the primary volcanic ash plume toward Australia, flights were cancelled at the Darwin airport. MTSAT-2 visible and IR images with polygons of Volcanic Ash Advisories are shown below (click image to play animation).

MTSAT-2 visible and IR images, with Volcanic Ash Advisory polygons

MTSAT-2 visible and IR images, with Volcanic Ash Advisory polygons

===== 01 June Update =====

A comparison of Suomi NPP VIIRS true-color images from 31 May and 01 June (below) showed that while the eruption was still ongoing, the amount of ash output had dramatically decreased.

Suomi NPP VIIRS true-color images

Suomi NPP VIIRS true-color images

Severe Tropical Cyclone Ita

April 10th, 2014
MTSAT-2 10.8 µm IR channel images (click to play animation)

MTSAT-2 10.8 µm IR channel images (click to play animation)

McIDAS images of MTSAT-2 10.8 µm IR channel data (above; click image to play animation) showed the development of a distinct eye associated with Intense Cyclone Ita (23P) as it moved southwestward across the Coral Sea toward the coast of Queensland, Australia on 10-11 April 2014. Cyclone Ita exhibited a period of rapid intensification (Advanced Dvorak Technique plot) early on 10 April, reaching Category 4 intensity (JTWC advisory) on the Saffir-Simpson scale (or a Category 5 on the Australian intensity scale: BOM advisory). Ita had been moving through an environment with weak deep layer wind shear and over warm sea surface temperatures, which aided in its intensification.

A timely overpass of a Metop polar-orbiting satellite provided ASCAT surface scatterometer winds at 11:26 UTC, as seen on an image from the CIMSS Tropical Cyclones site (below).

MTSAT-1 10.8 IR image with Metop ASCAT surface scatterometer winds

MTSAT-1 10.8 IR image with Metop ASCAT surface scatterometer winds

The structure of the eye of Ita was nicely displayed on a TRMM satellite TMI 85 GHz microwave image at 14:32 UTC (below).

TRMM TMI 85 GHz microwave image

TRMM TMI 85 GHz microwave image

A McIDAS-V image comparison of Suomi NPP VIIRS 11.45 µm IR and 0.7 µm Day/Night Band data at 14:58 UTC (below; courtesy of William Straka, SSEC/CIMSS) showed great detail of the eye and surrounding eyewall region of Ita.

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

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

The first available early-morning MTSAT-2 0.675 µm visible channel image at 20:32 UTC (below) revealed a convective tower within the northeastern portion of the eyewall region, with a distinct overshooting top (10-11 April animation of MTSAT-2 visible images).

MTSAT-2 0.675 µm visible channel image

MTSAT-2 0.675 µm visible channel image

The MTSAT InfraRed/Water Vapor difference product (below; click image to play animation) indicated that overshooting tops were likely around a large area surrounding the core of Ita.

MTSAT IR/WV Difference product (click to play animation)

MTSAT IR/WV Difference product (click to play animation)

===== 11 April Update =====

A TRMM satellite TMI 85 GHz microwave image at 05:23 UTC showed that Ita had a double-eyewall structure as it was close to making landfall, indicating that the cyclone was undergoing an eyewall replacement cycle — this suggests that Ita was in a weakening phase as it made landfall.

TRMM TMI 85 GHz microwave image

TRMM TMI 85 GHz microwave image

Cyclone Gillian in the Indian Ocean

March 24th, 2014
MTSAT-2 10.8 µm IR channel images (click to play animation)

MTSAT-2 10.8 µm IR channel images (click to play animation)

McIDAS images of MTSAT-2 10.8 µm IR channel data (above; click image to play animation) showed the southward motion of Cyclone Gillian as it intensified over the far eastern Indian Ocean to Category 5 intensity on 23 March 2014 (Joint Typhoon Warning Center advisory). A Category 5 tropical cyclone in the Southern Hemisphere (and in the Indian Ocean basin) is a relatively rare event.

An MTSAT-2 IR image from the CIMSS Tropical Cyclones site with an overlay of Metop ASCAT surface scatterometer winds at 14:20 UTC (below) showed the tight radius of high winds around the center of circulation.

MTSAT-2 10.8 µm IR image with Metop ASCAT surface scatterometer winds

MTSAT-2 10.8 µm IR image with Metop ASCAT surface scatterometer winds

MTSAT-2 0.675 µm visible channel images (below; click image to play animation) revealed the formation of a well-defined eye on 23 March.

MTSAT-2 0.675 µm visible channel images [click to play animation]

MTSAT-2 0.675 µm visible channel images [click to play animation]

A plot of the Advanced Dvorak Technique (ADT) satellite-based intensity estimate (below) showed the period of rapid intensification on 23 March, with tropcial cyclone Gillian reaching its peak intensity late on 23 March.

Advanced Dvorak Technique (ADT) plot for Cyclone Gillian

Advanced Dvorak Technique (ADT) plot for Cyclone Gillian

A comparison of MTSAT-2 10.8 µm IR channel data and DMSP SSMIS-16 85 GHz microwave brightness temperature data (below) demonstrated the ability of microwave imagery to show important storm details (such as the closed eyewall, and curved spiral bands) that might be obscured by clouds on conventional IR images.

MTSAT-2 10.8 µm IR image and DMSP SSMIS-16 85 GHz microwave brightness temperature image

MTSAT-2 10.8 µm IR image and DMSP SSMIS-16 85 GHz microwave brightness temperature image

The MIMIC Total Precipitable Water (TPW) product (below; click image to play animation) showed the circulation of high TPW values as Cyclone Gillian began to move southward from Indonesia on 21 March. As the tropical cyclone began to encounter an environment of increasing vertical wind shear poleward of about 20º S latitude, the storm began to rapidly decrease in intensity — and on 26 March Gillian was downgraded to a tropical low.

MIMIC Total Precipitable Water product (click to play animation)

MIMIC Total Precipitable Water product (click to play animation)