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)

Monsoon low over northwestern Australia

January 21st, 2014
MTSAT-2 0.675 µm visible channel and 10.8 µm IR channel images (click to play animation)

MTSAT-2 0.675 µm visible channel and 10.8 µm IR channel images (click to play animation)

McIDAS images of MTSAT-2 daytime 0.675 µm visible channel data and night-time 10.8 µm IR channel data (above; click image to play animation; also available as an MP4 animation) showed a monsoon low which exhibited a well-defined circulation for several days as it slowly tracked southwestward across the northwestern portion of Australia during the 15-21 January 2014 time period.

The mean seal level pressure analyses from the Australian Bureau of Meteorology (below; click image to play animation) indicated that the monsoon low deepened to a pressure of 988 hPa at 12 UTC on 19 January.

Mean sea level pressure analyses (click image to play animation)

Mean sea level pressure analyses (click image to play animation)

MTSAT-2 visible images and surface observations during the 17-18 January period are shown below (click image to play animation), visualized using the SSEC RealEarth web map server.

MTSAT-2 0.675 µm visible channel images (click to play animation)

MTSAT-2 0.675 µm visible channel images (click to play animation)

Cyclone Ian in the South Pacific Ocean

January 11th, 2014
Global IR image composite

Global IR image composite

Looking at a global composite of IR imagery from the SSEC RealEarth web map server (above), Cyclone Ian (07 P) in the South Pacific Ocean was a rather compact storm — however, a time series plot of the Advanced Dvorak Technique (below) showed that Cyclone Ian experienced a period of rapid intensification to Category 4 strength on 10 January 2014 (21 UTC Joint Typhoon Warning Center advisory).

Advanced Dvorak Technique (ADT) plot for Cyclone Ian

Advanced Dvorak Technique (ADT) plot for Cyclone Ian

IR images of Cyclone Ian (click to play animation)

IR images of Cyclone Ian (click to play animation)

SSEC RealEarth IR imagery (above; click image to play animation) and visible imagery (below; click image to play animation) showed the well-defined eye that was exhibited by Cyclone Ian during this period of rapid intensification on 10 January, as the storm moved slowly south-southeastward across the island nation of Tonga.

Visible images of Cyclone Ian (click to play animation)

Visible images of Cyclone Ian (click to play animation)

On 11 January, water vapor channel imagery from the CIMSS Tropical Cyclones site (below) showed the continuation of the impressive channel of poleward outflow from Cyclone Ian, which was enhanced by the presence of a mid-latitude trough passing to the south of the tropical cyclone.

Water vapor channel imagery

Water vapor channel imagery