Cyclone Chapala approaches Yemen

November 2nd, 2015
METOP-B Imagery (0.63 µm Visible and 10.8 µm Infrared) over Chapala, ~0615 UTC on 2 November 2015

METOP-B Imagery (0.63 µm Visible and 10.8 µm Infrared) over Chapala, ~0615 UTC on 2 November 2015 (Click to enlarge)

Cyclone Chapala continued its unusual approach towards Yemen on the southwestern edge of the Arabian Peninsula. Early on 2 November, the storm has passed just north of the Island of Socotra and entered the Gulf of Aden. METOP-B overflew the storm at ~0615 UTC on 2 November; Visible and Infrared data, above, show a still-compact storm with an obvious eye ringed by cold cloud tops (the coldest brightness temperatures are near -75º C) tucked into the mouth of the Gulf of Aden. Wind shear in the region is very low and sea-surface temperatures are warm. The morphed microwave imagery, below (taken from this site), indicates that the eyewall brushed the island of Socotra as it passed (a comparison of Meteosat-7 Infrared and DMSP SSMIS microwave images around 15 UTC on 01 November can be seen here).

Morphed Microwave Imagery ending 1645 UTC 01 November 2015

Morphed Microwave Imagery ending 1645 UTC 01 November 2015 (Click to enlarge)

Subsequent microwave imagery, below, for the 24 hours ending 1200 UTC on 2 November (the image below overlaps the one above) show a decrease in the eyewall structure and intensity.

Morphed Microwave Imagery ending 1200 UTC 02 November 2015

Morphed Microwave Imagery ending 1200 UTC 02 November 2015 (Click to enlarge)

Satellite-based intensity estimates at around 0000 UTC on 2 November (link) suggest a central mean sea-level pressure around 940 mb with sustained winds near 120 knots. The 0000 UTC Meteosat-7 image is shown below.

Meteosat-7 Window Channel Infrared (11.5 µm) 0000 UTC, 2 November 2015

Meteosat-7 Window Channel Infrared (11.5 µm) 0000 UTC, 2 November 2015 (Click to enlarge)

Suomi NPP overflew the region shortly after 2100 UTC on 1 November, and the Day/Night Band imagery from VIIRS is shown below, toggled with the 11.45 µm Infrared imagery. The storm is centered just northwest of Socotra; mesovortices are evident within the eye, as are overshooting tops in the eyewall convection; the bright streak seen on the Day/Night Band image is a region of the western eyewall illuminated by intense lightning activity. Zoomed-out versions of the imagery are available here for Day/Night Band and here for 11.45 µm Infrared. (VIIRS Imagery courtesy William Straka, SSEC/CIMSS).

Suomi NPP VIIRS Day/Night Band Visible Image and 11.45 µm Infrared Image 2149 UTC, 2 November 2015

Suomi NPP VIIRS Day/Night Band Visible Image and 11.45 µm Infrared Image 2149 UTC, 2 November 2015 (Click to enlarge)

A comparison of Meteosat-7 Infrared and DMSP SSMIS Microwave images around 1530 UTC on 2 November, below, showed the northern edge of the eyewall very near to the coast of Yemen.

Meteosat-7 Infrared and DMSP SSMIS Microwave images {click to enlarge)

Meteosat-7 Infrared and DMSP SSMIS Microwave images (click to enlarge)

At landfall, below, as viewed by Suomi NPP’s VIIRS instrument and a timely overpass, the eye of the storm had filled. The change in storm structure prior to landfall was very apparent in this toggle of two METOP Infrared images, at 0558 and 1644 UTC on 2 November. However, Meteosat-7 Infrared images showed that there was a large convective burst that developed as Chapala made landfall. Chapala was the first tropical cyclone on record to make landfall in Yemen while still at hurricane intensity.

Suomi NPP VIIRS I05 (11.45 µm) Infrared Image, 2127 UTC on 2 November [click to enlarge]

Suomi NPP VIIRS I05 (11.45) Infrared Image, 2127 UTC on 2 November (click to enlarge)

A 6-day animation of the storm using VIIRS true-color imagery from RealEarth can be seen here. Cyclone Chapala is also discussed in this blog post.

===== 05 November Update =====

A 14-day animation of UK Met Office OSTIA Sea Surface Temperature, below, reveals the cold wake of upwelling water (yellow color enhancement) following the passage of Hurricane Chapala.

UK Met Office OSTIA Sea Surface Temperature analyses [click to enlarge]

UK Met Office OSTIA Sea Surface Temperature analyses [click to enlarge]

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]

Typhoon Koppu hits the Philippines

October 18th, 2015

Himawari-8 Infrared Imagery, 0400-2030 UTC 17 October 2015 [click for mp4 animation]

Himawari-8 Infrared Imagery, 0400-2030 UTC 17 October 2015; 6.2 µm (Upper Left), 6.9 µm (Upper Right), 7.3 µm (Lower Left), 10.35 µm (Lower Right) [click for mp4 animation]

Typhoon Koppu hit the northern Philippines island of Luzon on Saturday 18 October. The 4-panel mp4 animation above (Click here for an animated gif) shows the 3 water vapor infrared channels (6.2 µm, 6.9 µm and 7.3 µm) and the window infrared channel (10.35 µm) from the Himawari-8 satellite. There is value in three water vapor channels because the shorter wavelength (6.2 µm) better captures high-level moisture whereas the longer wavelength better captures mid-level moisture. Cirrus is readily apparent in the 6.2 µm channel; tropical cumulus is more readily apparent underneath cirrus in the 7.3 µm channel. Compare the two channels in this animation, for example, or in this one. The three water vapor channels on Himawari-8 (similar to the 3 that will fly on the GOES-R ABI instrument) give a three-dimensional view of atmospheric moisture. All four channels above show the approach of Koppu towards Luzon, with the ragged eye filling rapidly at landfall.

Morphed Microwave Imagery showing Koppu's Eyewall [click to enlarge]

Morphed Microwave Imagery showing Koppu’s Eyewall [click to enlarge]

The structure of Koppu’s eyewall is depicted above in a 24-hour morphed animation of microwave data (Source, as referred to from here). The nearly complete eyewall rapidly loses its integrity as the storm moves onshore. Total Precipitable Water (below, taken from the MIMIC Total Precipitable Water Site) shows Koppu on the northern edge of the rich moisture source that is the Intertropical Convergence Zone (Typhoon Champi is to Koppu’s east). Notably, the storm stalled over Luzon after making landfall; flooding rainfalls occurred.

MIMIC Total Precipitable Water over the Western North Pacific Basin [click to enlarge]

MIMIC Total Precipitable Water over the Western North Pacific Basin [click to enlarge]

Himawari-8 also captured the evolution of the storm in visible imagery. The full-resolution animation from 0100-0930 UTC on 17 October is shown below (a slower animation is available here). Periodic bursts of deep convection are apparent in the curved bands near the storm center. These convective bursts are better resolved with the 10-minute imagery from Himawari-8 than from 15-minute data from MTSAT-2 (or COMS-1).

Himawari-8 Visible Imagery (0.63) from 0100 through 0930 UTC on 17 October [click to animate]

Himawari-8 Visible Imagery (0.63) from 0100 through 0930 UTC on 17 October [click to animate]

Moisture from Central Pacific Hurricane Oho moving into British Columbia and Alaska

October 9th, 2015
GOES-15 Infrared Water Vapor (6.5 µm) Imagery, 0000 UTC 5 October through 0900 UTC 9 October 2015 [click to animate]

GOES-15 Infrared Water Vapor (6.5 µm) Imagery, 0000 UTC 5 October through 0900 UTC 9 October 2015 [click to animate]

The rocking animation* above shows central Pacific Hurricane Oho forming south of Hawai’i and then moving quickly northeast; moisture associated with the remains of the storm is now moving onshore in British Columbia and Alaska Southeast. It is unusual for central Pacific Hurricanes to influence directly the weather in the Pacific Northwest as Oho will (link). Because of the record number of central Pacific Hurricanes this year (in the satellite era at least), however, it’s perhaps not surprising that this is occurring.

The moisture is also trackable via microwave data as shown in the MIMIC Total Precipitable Water animation below.

MIMIC Total Precipitable Water for 72 hours ending 0700 UTC 09 October 2015 [click to enlarge]

MIMIC Total Precipitable Water for 72 hours ending 0700 UTC 09 October 2015 [click to enlarge]

Scatterometer winds from 0630 UTC (below) show a region of 40+-knot winds both in the warm sector of the storm and behind the cold front.

GOES-15 Water Vapor Imagery and ASCAT Scatterometer Winds, 0630 UTC on 9 October 2015 [click to enlarge]

GOES-15 Water Vapor Imagery and ASCAT Scatterometer Winds, 0630 UTC on 9 October 2015 [click to enlarge]

*You may notice some full disk imagery missing in this loop (at 0900 and 2100 UTC in the animation). At 2100 UTC the Sun is behind the ground antenna acquiring the data. This happens for a few days each year. The 0900 UTC imagery is missing because of GOES-15 Keep-Out Zone Operations.