Typhoon Maysak in the West Pacific Ocean

March 30th, 2015
Himawari-8 AHI 0.64 µm visible channel images (click to play animation)

Himawari-8 AHI 0.64 µm visible channel images (click to play animation)

McIDAS-V images of Himawari-8 AHI 0.64 µm visible channel data (above; click image to play animation; images courtesy of William Straka, SSEC) showed the evolution of Category 2 Typhoon Maysak over the West Pacific Ocean on 30 March 2015. A number of large convective bursts can be seen surrounding the eye, along with more subtle features such as transverse banding.

An 11:01 UTC MTSAT-2 10.8 µm IR image with an overlay of 11:11 UTC Metop ASCAT surface scatterometer winds from the CIMSS Tropical Cyclones site (below) revealed the wind field in the eastern semicircle of the tropical cyclone.

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

Several hours later, a comparison of a 19:01 UTC MTSAT-2 10.8 µm IR image with a 19:00 UTC DMSP SSMIS 85 GHz microwave image (below) showed that the microwave instrument was able to “see” through the clouds surrounding the eye to depict the larger size of the eyewall structure.

MTSAT-2 10.8 µm IR image + DMSP SSMIS 85 GHz microwave image

MTSAT-2 10.8 µm IR image + DMSP SSMIS 85 GHz microwave image

During the later hours of 30 March, Typhoon Maysak underwent a period of rapid intensification from a Category 2 to a Category 4 storm, as depicted on a plot of the Advanced Dvorak Technique (ADT) intensity estimate (below). Rapid intensification occurred as the tropical cyclone was moving over an area of relatively high ocean heat content.

Advanced Dvorak Technique (ADT) intensity estimate plot for Typhoon Maysak

Advanced Dvorak Technique (ADT) intensity estimate plot for Typhoon Maysak

MTSAT-2 10.8 µm IR channel images during this period of rapid intensification are shown below (click image to play animation).

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

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

The MIMIC Total Precipitable Water (TPW) product (below; click image to play animation) depicted TPW values in excess of 60 mm or 2.36 inches (darker red color enhancement) associated with Maysak as the tropical cyclone moved between the islands of Guam (PGUM) and Yap (PTYA). Yap recorded over 4 inches of rainfall.

MIMIC Total Precipitable Water product (click to play animation)

MIMIC Total Precipitable Water product (click to play animation)

31 March 2015 Update: Maysak intensified to a Category 5 Super Typhoon (ADT plot). Full-resolution visible imagery from Himawari-8 AHI is shown below; a faster animation is available here. A number of mesovortices could be seen within the eye of Maysak; these mesovortices were also evident in photos of the eye of the typhoon taken by an astronaut on the International Space Station, as posted on Twitter here and here.

Himawari-8 AHI 0.64 µm visible channel images (click to play animation)

Himawari-8 AHI 0.64 µm visible channel images (click to play animation)

Images from all 16 channels from the Himawari-8 AHI can be combined into one animation, showing the different information provided by each of the spectral bands — such an animation is shown below, using data from 0600 UTC on 31 March 2015. The Infrared data is shown at full (2-km) resolution; Visible/near Infrared imagery is scaled down by a factor of 2 (0.46 µm, 0.51 µm, 0.85 µm) or by a factor of 4 (0.64 µm). A similar animation, but without annotation or color enhancement, is available here.

Himawari-8 AHI images for all 16 channels at 0600 UTC (click to enlarge)

Himawari-8 AHI images for all 16 channels at 0600 UTC (click to enlarge)

Maysak had remained in an environment of relatively low deep-layer wind shear (below; click image to play animation), which was favorable for its trend of continued intensification.

MTSAT-2 10.8 µm IR channel images, with deep-layer wind shear (click to play animation)

MTSAT-2 10.8 µm IR channel images, with deep-layer wind shear (click to play animation)

However, in a comparison of MTSAT-2 10.8 µm IR channel and TRMM TMI 85 GHz microwave images around 14 UTC (below), it can be seen that the microwave image indicated that an eyewall replacement cycle might be underway (which would suggest a subsequent decrease in the typhoon’s intensity within the coming hours). This was supported by the ADT intensity estimate plot, which dropped the intensity of Maysak just below 140 knots after 18 UTC on 31 March.

MTSAT-2 10.7 µm IR image and TRMM TMI 85 GHz microwave image

MTSAT-2 10.7 µm IR image and TRMM TMI 85 GHz microwave image

01 April Update: A nighttime comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR images at 16:58 UTC on 01 April (below; images courtesy of William Straka, SSEC) showed the eye of Typhoon Maysak after it had weakened to a Category 4 storm.

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

Category 5 Cyclone Pam in the South Pacific

March 12th, 2015
MTSAT-2 10.8 µm IR images (click to play animation)

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

Cyclone Pam in the South Pacific Ocean was rated at Category 5 intensity by the Joint Typhoon Warning Center at 18 UTC on 12 March 2015. MTSAT-2 10.8 µm IR channel images (above; click image to play animation; also available as an MP4 movie file) showed the well-defined eye as the storm moved southwestward across the Vanuatu archipelago during the 12-13 March time period.

The corresponding MTSAT-2 0.7 µm visible channel images (below; click image to play animation) revealed a complex structure of gravity waves and transverse banding surrounding the eye.

MTSAT-2 0.7 µm visible channel images (click to play animation)

MTSAT-2 0.7 µm visible channel images (click to play animation)

A comparison of the 12 March 21:32 UTC MTSAT-2 visible image and the 21:44 UTC Metop ASCAT surface scatterometer winds from the CIMSS Tropical Cyclones site is shown below.

MTSAT-2 visible image and Metop ASCAT surface scatterometer winds

MTSAT-2 visible image and Metop ASCAT surface scatterometer winds

Just prior to the time when Pam was beginning to enter a period of rapid intensification (ADT intensity estimate plot), a nighttime comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm Infrared images at 13:37 UTC on 11 March is shown below.

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

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

Tropical Storm Niko (07P) in the South Pacific Ocean

January 20th, 2015
MIMIC Total Precipitable Water product, with Tropical Surface Analyses (click to play animation)

MIMIC Total Precipitable Water product, with Tropical Surface Analyses (click to play animation)

AWIPS images of the MIMIC Total Precipitable Water product (above; click image to play animation) showed a broad moist plume in the equatorial South Pacific Ocean, within which Tropical Storm Niko began to develop during the 19 January – 20 January 2015 period. By the end of the animation, Gale Force winds were being analyzed within the eastern semicircle of the developing cyclone. Metop ASCAT surface scatterometer winds at 08:01 UTC (below) showed winds as strong as 42 knots (though the direction of the stronger yellow wind barbs was suspect, likely due to rain contamination).

MIMIC TPW product, with Metop ASCAT surface scatterometer winds

MIMIC TPW product, with Metop ASCAT surface scatterometer winds

After daybreak on 20 January, McIDAS images of GOES-15 (GOES-West) 0.63 µm visible channel data (below; click image to play animation) showed the development of spiral banding wrapping into the central low-level circulation center as the system reached tropical storm intensity by 18 UTC.  In addition, a few strong convective pulses with distinct overshooting tops could be seen near the core of Niko.

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

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

An animation of GOES-15 10.7 µm IR channel images from the CIMSS Tropical Cyclones site (below) included an overlay of contours of the deep layer (200 – 850 hPa) wind shear at 18 UTC — Tropical Storm Niko developed in a region characterized by low wind shear, which enabled the storm to rapidly intensify.

GOES-15 10.7 µm IR channel images, with contours of deep layer wind shear

GOES-15 10.7 µm IR channel images, with contours of deep layer wind shear

Tropical Cyclone Bansi in the Indian Ocean

January 13th, 2015
Advanced Dvorak Technique (ADT) intensity estimate

Advanced Dvorak Technique (ADT) intensity estimate

A plot of the Advanced Dvorak Technique intensity estimate for Tropical Cyclone Bansi (above) showed that the storm experienced a period of rapid intensification late in the day on 12 January 2015, reaching Category 4 intensity by 00 UTC on 13 January.

EUMESAT Metosat-7 11.5 µm IR channel images (below; click to play animation; also available as an MP4 movie file) revealed the formation of a well-defined eye, which also exhibited a notable amount of trochoidal motion or “wobble” as it moved across the southwest Indian Ocean (north of Reunion and Mascarene Island).

Meteosat-7 11.5 µm IR channel images (click to play animation)

Meteosat-7 11.5 µm IR channel images (click to play animation)

A more detailed view of Tropical Cyclone Bansi was provided by McIDAS-V images of Suomi NPP VIIRS 11.45 µm IR and 0.7 µm Day/Night Band data (below; credit: William Straka, SSEC) — deep convection with overshooting tops could be seen in the southern quadrant eyewall region, with gravity waves propagating radially outward across the northeastern and eastern portion of the cirrus canopy.

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

A DMSP SSMIS 85 GHz microwave image from the CIMSS Tropical Cyclones site (below) showed that a prominent “moat” of warm brightness temperatures (darker blue color enhancement) existed around the center of Bansi at 14:24 UTC on 13 January. The presence of such a moat usually signifies that the secondary (outer) eyewall formation process has completed, and an eyewall replacement cycle is underway (also signalling that the period of rapid intensification has ended). The moat feature is sustained by subsidence from the eyewall secondary circulations.

DMSP SSMIS 85 GHz microwave image

DMSP SSMIS 85 GHz microwave image

Note that there was no well-defined eye evident on the conventional Meteosat-7 IR image during this eyewall replacement cycle (below).

Meteosat-7 11.5 µm IR channel and DMSP SSMIS 85 GHz microwave images

Meteosat-7 11.5 µm IR channel and DMSP SSMIS 85 GHz microwave images