Mount Rinjani volcanic ash plume

November 4th, 2015 |

Suomi NPP VIIRS true-color RGB images [click to enlarge]

Suomi NPP VIIRS true-color RGB images [click to enlarge]

The Mount Rinjani volcano in Indonesia began a period of eruptions on 25 October 2015; the ash plume became very apparent on Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from RealEarth on 03 and 04 October (above). The volcanic ash disrupted flights at Denpasar Airport in Bali (the red dot at the southern tip of the island) for several days.

A GOES-R volcanic ash height product (derived using Himawari-8 AHI data) from the SSEC Volcanic Cloud Monitoring site indicated that the plume reached heights of 10 km (dark blue color enhancement) at times during the 03-04 October period (below).

Himawari-8 Volcanic Ash Height product [click to play animation]

Himawari-8 Volcanic Ash Height product [click to play animation]

McIDAS-V images of Suomi NPP VIIRS Day/Night Band (0.7 µm), near-IR (1.6 µm), shortwave IR (3.74 µm), and IR (11.45 µm) images (below, courtesy of William Straka, SSEC) showed the hot spot and nighttime glow of the summit of the Rinjani volcano at 1733 UTC on 04 November.

Suomi NPP VIIRS Day/Night Band (0.7 µm), near-IR (1.6 µm), shortwave IR (3.74 µm), and IR (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm), near-IR (1.6 µm), shortwave IR (3.74 µm), and IR (11.45 µm) images [click to enlarge]

Advection of fog/stratus across western Lake Superior

November 3rd, 2015 |

GOES-13 Visible (0.63 µm) image, Metop ASCAT and RTMA surface winds, METAR surface reports, and surface frontal analysis [click to enlarge]

GOES-13 Visible (0.63 µm) image, Metop ASCAT and RTMA surface winds, METAR surface reports, and surface frontal analysis [click to enlarge]

A GOES-13 Visible (0.63 µm) image (above) showed a bank of fog and low stratus (FLS) covering much of the western portion of Lake Superior at 1600 UTC on 03 November 2015. Overlays of Metop ASCAT and Real-Time Mesoscale Analysis (RTMA) surface winds showed the long fetch of northeasterly winds that were moving this FLS feature toward the southwest; this southwestward (and eventual inland) advection could be followed on GOES-13 Visible images (below).

GOES-13 Visible (0.63 µm) images with METAR surface reports [click to play animation]

GOES-13 Visible (0.63 µm) images with METAR surface reports [click to play animation]

A more detailed view of the FLS deck was provided by a 375-meter resolution Suomi NPP VIIRS Visible (0.64 µm) image at 1848 UTC, with overlays of METAR surface reports, RTMA surface winds, and surface frontal analysis (below).

Suomi NPP VIIRS Visible (0.64 µm) image with METAR surface reports, RTMA surface winds, and surface frontal analysis [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) image with METAR surface reports, RTMA surface winds, and surface frontal analysis [click to enlarge]

The GOES-R Low Cloud Thickness product shown below (derived using GOES-13 data) indicated that the maximum depth of the FLS feature was around 2200 feet (yellow color enhancement).

GOES-13 Low Cloud Thickness product [click to enlarge]

GOES-13 Low Cloud Thickness product [click to enlarge]

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]