Tropical cyclones « CIMSS Satellite Blog

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)

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)

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)

Posted in MTSAT, Tropical cyclones, Web Map Server | No Comments »

Cyclone Ian in the South Pacific Ocean

January 11th, 2014

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

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)

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

Posted in Tropical cyclones, Web Map Server | 1 Comment »

Super Typhoon Haiyan

November 7th, 2013

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

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)

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)

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)

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)

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

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

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)

Posted in COMS, DMSP, McIDAS-V, MTSAT, Suomi NPP, Tropical cyclones, VIIRS | 6 Comments »

Super Typhoon Francisco

October 19th, 2013

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

Super Typhoon Francisco became the third Category 5 tropical cyclone of 2013 on 19 October 2013, as it intesified over the West Pacific Ocean northwest of Guam. 4-km resolution MTSAT-2 10.8 µm IR channel images (above; click image to play animation) showed the evolution and track of the eye of Francisco during the 17-19 October period (the island of Guam is in the lower right corner of the images). Note the trochoidal motion or “wobble” that is exhibited by the eye of the tropical cyclone as it tracked northwestward – this is caused by changes within the inner core structure of the storm, such as convective asymmetries.

1-km resolution MTSAT-2 0.73 µm visible channel images (below; click image to play animation) revealed better details of the eye and eyewall structure during the daylight portion of 18-19 October. The lowering October sun angle tended to more brightly illumimate the sloped surface of the northern quadrant of the eye.

MTSAT-2 0.73 µm visible channel images (click to play animation)

A McIDAS-V comparison of 375-meter resolution Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm thermal IR channel images at 15:48 UTC on 18 October (below; images courtesy of William Straka, CIMSS) showed a good example of the so-called “stadium effect”: the eye diameter appeared larger on the VIIRS IR image than on the corresponding “visible image at night” from the VIIRS Day/Night Band, because the clouds along the edges of the eye were steeply sloping outward with height.