Internal Waves in the Banda Sea

October 30th, 2015
Himawari-8 Band 3 Visible (0.64 µm) images from 29 October [click to play animation]

Himawari-8 Band 3 Visible (0.64 µm) images from 29 October [click to play animation]

Himawari-8 (Imagery courtesy of JMA) captured the northward march of three sets of Internal Waves in the Banda Sea in late October, as shown above (MODIS True Color Imagery showed the waves as well). Because the internal waves affect the ocean surface, sun glint can make them visible via methods described here. The fine spatial and temporal resolution of Himawari-8 (0.5 km for Band 3/0.64µm, 10-minute imagery) allows for a good description of the northward speed of the waves: approximately 10 km/hour.

MTSAT-2 (scheduled to become the backup satellite on Friday 4 December 2015 as Himawari-8 takes over operational duties; MTSAT-1 is to be decommissioned that day because of fuel limitations) and COMS-1 also viewed the waves, as shown below. Sun glint allowed MTSAT-2 to view only three scenes (3:32, 4:32 and 5:32 UTC). COMS-1, above the Equator at 128º E, farther west than MTSAT-2 (at 145º E), viewed the waves earlier (because sunglint was present over the scene earlier). Both MTSAT-2 and COMS-1 visible channels have nominal resolution of only 1 km.

MTSAT-2 Visible (0.73 µm) images from 29 October, 0232-0632 UTC [click to play animation]

MTSAT-2 Visible (0.73 µm) images from 29 October, 0232-0632 UTC [click to play animation]

COMS-1 Visible (0.675 µm) images from 29 October, 0100-0630 UTC [click to play animation]

COMS-1 Visible (0.675 µm) images from 29 October, 0100-0630 UTC [click to play animation]

Hat Tip to Mike Ziobro, NWS Guam, for showing us these very interesting waves!

Cyclone Chapala in the Arabian Sea

October 30th, 2015
Day Night Band Imagery from Suomi NPP VIIRS (0.70 µm) 2102 UTC, 29 October 2015

Day Night Band Imagery from Suomi NPP VIIRS (0.70 µm) 2102 UTC, 29 October 2015 (Click to enlarge)

Tropical Cyclone Chapala is poised to make an unusual landfall on the Arabian Penisula over the weekend. The Suomi NPP VIIRS Day Night Band Imagery (courtesy William Straka, SSEC/CIMSS), above, from 2102 UTC on 29 October, shows a compact storm with curved bands of strong convection around an apparent eye. A more zoomed-in version of the storm in the infrared (A Zoomed in version of the Day Night band is here), shows very cold cloud tops.

Total Precipitable Water and Projected Storm Path for Chapala, 1200 UTC on 30 October 2015 (Click to enlarge)

Data from the CIMSS Tropical Page shows the environment in which Chapala strengthened will become progressively less favorable as the storm approaches land. The MIMIC Total Precipitable Water, above, shows the storm with dry air to the north and west. Tropical cyclones that approach the Arabian peninsula are rare. Those that do approach are invariably weakened as they ingest the dry air that is typically over Arabia. Diagnostics of wind shear also suggest that Chapala is moving towards a more highly sheared environment.

Microwave imagery, below, shows a very intense eye around 0100 UTC on 30 October. After that time, however, the eye becomes less distinct.

Microwave Imagery over the Eye of Chapala, 0100-1245 UTC on 30 October 2015 (Click to enlarge)

Storm-centered animation of 11.2 µm imagery from Kalapana-1 (Click to enlarge)

Data from the Indian Satellite Kalpana-1 (data courtesy of the Indian Space Research Organization) shows a peak intensity — as measured by the warmest pixel in the eye — occurred around 1015 UTC on 30 October 2015. The warmest brightness temperature warmed 15 K between 1015 UTC and 1345 UTC.

Meteosat-10 viewed the storm as well, and all 11 channels from 0300 to 1500 UTC, including 0600 and 1200 UTC, are shown below. The water vapor channels, in particular, show the very dry air over the Arabian Peninsula. In addition, the animation shows gradual warming of the coldest cloud tops. Data from Meteosat-7, (source) viewing the Indian Ocean, shows the rapid intensification of this small storm. (See also this Meteosat-7 Visible imagery courtesy of the British Met Office).

Multispectral imagery from Meteosat-10 for 0300 to 1500 UTC, 30 October 2015. Row 1: 0.6 µm, 0.8 µm, 1.6 µm ; Row 2: 3.9 µm, 6.2 µm, 7.3 µm ; Row 3: 8.7 µm, 9.7 µm, 10.8 µm; Row 4: 12.0 µm, 13.4 µm, RGB Composite of 0.6 µm, 0.8 µm and 1.6 µm (Click to enlarge)

See also this blog post on this rare event.

Cyclone Gonu in 2007 also affected the Arabian Peninsula (and Iran). The toggle below shows Meteosat-7 imagery of the two storms near their respective peak intensities (Chapala’s intensity plot with time is shown here). Gonu was a far more symmetric storm with more expansive cold clouds tops, but the overall sizes of both storms were similar.

Meteosat-7 11.5 µm imagery over Cyclone Gonu at 1730 UTC on 4 June 2007, and over Cyclone Chapala at 0900 UTC on 30 October 2015 (Click to enlarge)

INSAT-3D viewed the storm as well. The near-infrared 0.86 µm imagery, above, highlights the land-sea differences very well as well as showing a compact eye.

INSAT-3D 0.86 µm imagery Cyclone Chapala at 1030 UTC on 30 October 2015 (Click to enlarge)

A Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image of Cyclone Chapala is shown below.

Suomi NPP VIIRS true-color image [click to enlarge]

Suomi NPP VIIRS true-color image [click to enlarge]

Smoke over Indonesia and the western tropical Pacific Ocean

October 26th, 2015
H8_RGB_08-26October2015_0200_anim

RGB Composites from Himawari-8 (0.47 µm, 0.51 µm and 0.64 µm used for blue, green and red, respectively) 0200 UTC from 08-26 October 2015. (Click to animate)

Many of the islands in Indonesia have been shrouded in smoke for much of October. RGB composites from Himawari-8, above, for 0200 UTC on each day from 08-26 October 2015 testify to the dense smoke, especially over the island of Borneo. News reports suggest the haze will persist through the end of the year. This is in part due to the strong El Nino event ongoing; El Nino events typically suppress rainfall over the western tropical Pacific basin.

Smoke detection using visible channels, such as those combined in the true color imagery above, is straightforward. At night, however, visible imagery is not available. The animation below shows the difficulty in detecting smoke using infrared imagery. Although parts of the smoke plume show up, the widespread pall of smoke is not captured. Hot spots can be detected using the 3.9 µm (and 2.3 µm) bands on Himawari-8, but viewing the transport of the resultant smoke is a challenge. Except for the VIIRS Day/Night Band imagery from Suomi NPP, then, nighttime smoke detection relies on model output (Source).

H8_RGB_08-26October2015_0200_anim

16-panel Himawari-8 multispectral animation, hourly from 0000 UTC/20 October to 0100/21 October. Top row: 0.47µm, 0.51µm, 0.64µm, 0.86µm ; Second Row: 1.6µm, 2.3µm, 3.9µm, 6.2µm; Third Row: 6.9µm, 7.3 µm, 8.6 µm, 9.6 µm; Bottom Row: 10.4µm, 11.2 µm, 12.4µm, 13.3µm (Click to animate)

The SSEC RealEarth web map server can be used to take a closer look at the islands of Borneo and Sumatra from 20-26 October. Daily comparisons of Suomi NPP VIIRS fire detections and true-color RGB images shown below revealed that although there was a gradual decreasing trend in the number and areal coverage of fires by 26 October, a great deal of smoke still remained over much of the region.

Daily comparisons of Suomi NPP VIIRS fire detections and true-color RGB images, from 20-26 October [click to animate]

Daily comparisons of Suomi NPP VIIRS fire detections and true-color RGB images, from 20-26 October [click to animate]

A daily time series plot of weather conditions at the major airport of Kuala Lumpur, below, showed that the surface visibility was often restricted to less than 1 mile during the 20-26 October period.

Daily time series of surface reports from Kuala Lumpur [click to animate]

Daily time series of surface reports from Kuala Lumpur [click to animate]

Suomi NPP VIIRS Day/Night Band Visible Imagery (0.70 µm) 1837 UTC on 26 October 2015 [click to enlarge]

Suomi NPP VIIRS Day/Night Band Visible Imagery (0.70 µm) 1837 UTC on 26 October 2015 [click to enlarge]

The Suomi NPP VIIRS instrument contains a day-night sensor that produces useful visible imagery when illuminated by the Moon (and a full Moon occurred on 27 October 2015). The image above from 1837 UTC on 26 October (Courtesy William Straka, SSEC) shows a pall of smoke from Borneo to Sumatra. Thunderstorms are also present over the South China Sea and Borneo. An toggle of the Day Night Band, the 3.9 µm infrared and the 1.6 µm infrared imagery shows that hot spots associated with fires can be detected (enhanced as orange in the 3.9 µm and white in the 1.6 µm), but the associated smoke is mostly undetected in the infrared.

Two sites, one NASA and one NOAA, can give additional information about the smoke. The toggle below, taken from imagery at the NASA site, shows MODIS True-Color imagery, Aeorosol Optical Depth (AOD) (in NASA Worldview, with units) (in cloud-free regions) and retrieved Carbon Monoxide concentrations (in NASA Worldview, with units). AODs are very large, and CO concentrations are off the scale.

MODIS True Color Imagery, Aerosol Optical Depth and CO Concentrations on 26 October 2015 [click to enlarge]

MODIS True Color Imagery, Aerosol Optical Depth and CO Concentrations on 26 October 2015 [click to enlarge]

Hurricane Patricia

October 23rd, 2015

GOES-15 Infrared (10.7 µm) images [click to play animation]

GOES-15 Infrared (10.7 µm) images [click to play animation]

GOES-15 (GOES-West) Infrared (10.7 µm) images (above; also available as an MP4 animation) displayed the formation of a ring of cold eyewall cloud-top IR brightness temperatures (in the -80 to -90º C range, violet colors) during the period of rapid intensification of Hurricane Patricia on 22 October 2015; the storm reached Category 5 intensity around 00 UTC on 23 October. Patricia then continued to intensify, reaching maximum sustained surface winds estimated at 175 knots with a minimum central pressure of 878.4 hPa or 25.94 inches of mercury (making this the strongest tropical cyclone on record for the National Hurricane Center area of responsibility, which is the North Atlantic Ocean and the eastern North Pacific Ocean). The storm weakened somewhat prior to making landfall (although still as a Category 5 hurricane) around 2315 UTC on 23 October.

Multi-day YouTube animations showing the formation of Patricia are available here (0.63 µm visible imagery from GOES-13) and here (10.7 µm infrared imagery from GOES-13). The multi-day location of Patricia’s 850 hPa relative vorticity signature (derived from satellite atmospheric motion vector data) can be seen here.

A plot of the Advanced Dvorak Technique intensity estimate (below) showed the rate of rapid intensification on 22-23 October. At one point Patricia’s central pressure deepened 100 hPa in 24 hours, and 73 hPa in 12 hours, making it the fastest-intensifying tropical cyclone on record in the Western Hemisphere.

Advanced Dvorak Technique (ADT) intensity estimate plot [click to enlarge]

Advanced Dvorak Technique (ADT) intensity estimate plot [click to enlarge]

GOES-15 Visible (0.63 µm) images (below; also available as an MP4 animation) revealed the small “pinhole” eye of Patricia during rapid intensification on 22 October.

GOES-15 Visible (0.63 µm) images [click to play animation]

GOES-15 Visible (0.63 µm) images [click to play animation]

As Patricia was rapidly intensifying from a Category 1 to Category 5 intensity, the tropical cyclone was moving over a region of high Ocean Heat Content (below), and Sea Surface Temperature values were as high as 31º C.

Ocean Heat Content on 22 October

Ocean Heat Content on 22 October

A comparison of Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images at 0741 UTC on 23 October is shown below (courtesy of William Straka, SSEC). With ample illumination from the Moon (which was in the Waxing Gibbous phase, at 78% of Full), the “visible image at night” capability of the Day/Night Band provided a detailed view of cloud-top gravity waves surrounding the eye.

Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images at 0741 UTC

Suomi NPP VIIRS Infrared (11.45 µm) and Day/Night Band (0.7 µm) images at 0741 UTC

A later VIIRS Infrared (11.45 µm) image at 0920 UTC is shown below.

Suomi NPP VIIRS Infrared (11.45 µm) image at 0920 UTC

Suomi NPP VIIRS Infrared (11.45 µm) image at 0920 UTC

A comparison of GOES-15 (GOES-West) and GOES-13 (GOES-East) Visible (0.63 µm) images (below) showed the eye of Patricia from sunrise on 23 October until landfall along the west coast of Mexico around 2315 UTC. A mesonet station at the Chamela-Cuixmala Biosphere Reserve (located approximately 10 miles northwest of the eye landfall position) reported maximum sustained winds of 185 mph at 2350 UTC, with a peak wind gust of 210.9 mph at 2310 UTC.

GOES-15 (left) and GOES-13 (right) 0.63 µm visible images [click to play animation]

GOES-15 (left) and GOES-13 (right) 0.63 µm visible images [click to play animation]

MIMIC morphed microwave imagery (below) showed the development and motion of the very compact eye during the 22-23 October period. There was also a signature of the formation of a secondary outer eyewall, suggesting that an eyewall replacement cycle was underway as Patricia was approaching the west coast of Mexico.

MIMIC morphed microwave imagery [click to enlarge]

MIMIC morphed microwave imagery [click to enlarge]

View a 23 October weather briefing held at CIMSS to discuss Hurricane Patricia here.

===== 25 October Update =====

Following the landfall of Patricia late in the day on 23 October, and increase in offshore sediment could be seen in Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images (from the RealEarth web map server) on 24 and 25 October (below), a result of runoff from heavy rains inland.

Suomi NPP VIIRS true-color images from 23, 24, and 25 October [click to enlarge]

Suomi NPP VIIRS true-color images from 23, 24, and 25 October [click to enlarge]