GOES-14 SRSO-R: Tropical Disturbance near the Caribbean

August 25th, 2016

GOES-14 Visible (0.63 µm) images [click to play animated gif]

GOES-14 Visible (0.63 µm) images [click to play animated gif]

GOES-14 SRSO-R Imagery is being produced over the Greater Antilles on 25 August 2016 to monitor a tropical wave (Invest 99L) that is moving towards Florida and the southeast United States. The visible animation above shows a highly sheared system: a low-level circulation center (LLCC) is evident north of Hispaniola and east of the Turks and Caicos, but strong convection (overshooting tops are readily apparent) is displaced well to the east of the system. There is also considerable convection over Hispaniola.

A 2-panel comparison of GOES-14 Visible and Infrared Window images, below (also available as a large 200 Mbyte animated GIF), provided a slightly closer view of the LLCC feature.

GOES-14 0.63 µm Visible (top) and 10.7 µm Infrared Window (bottom) images [click to play MP4 animation]

GOES-14 0.63 µm Visible (top) and 10.7 µm Infrared Window (bottom) images [click to play MP4 animation]

Wind shear analyses from the CIMSS Tropical Weather site, below, show the surface circulation is within a small ribbon of relatively strong shear. Development chances will increase if the wind shear relaxes. A GOES-13 Visible image with overlays of satellite winds and wind shear is available here.

Wind Shear Analysis, 1200 UTC on 25 August 2016 [click to play animated gif]

Wind Shear Analysis, 1200 UTC on 25 August 2016 [click to enlarge]

Metop-A overflew the system at about 0200 UTC on 25 August (link to orbit path), and winds near Tropical Storm Force cover a wide swath of the southwestern Atlantic. Even if this system does not develop into a Tropical Depression, gusty winds and abundant moisture (see the animation of MIRS Total Precipitable Water from this site, below) herald a weekend when it’s appropriate to pay attention to the weather because of the potential for rain and winds.

Morphed Observations of Total Precipitable Water from MIRS, 0000 UTC 24 August - 1500 UTC 25 August [click to play animated gif]

Morphed Observations of Total Precipitable Water from MIRS, 0000 UTC 24 August – 1500 UTC 25 August [click to play animated gif]

===== 28 August Update =====

GOES-14 0.63 µm Visible (top) and 10.7 µm Infrared Window (bottom) images [click to play MP4 animation]

GOES-14 0.63 µm Visible (top) and 10.7 µm Infrared Window (bottom) images [click to play MP4 animation]

Invest 99L developed into Tropical Depression 09 around 21 UTC on 28 August. A comparison of 1-minute GOES-14 Visible (0.63 µm) and Infrared Window (10.7 µm) images, above (also available as a large 94 Mbyte animated GIF), showed the tropical depression as it moved westward through the Florida Straits.

Heavy rainfall and flash flooding in Maryland

July 30th, 2016

GOES-13 0.63 µm Visible (top) and 10.7 µm Infrared Window (bottom) images [click to play animation]

GOES-13 0.63 µm Visible (top) and 10.7 µm Infrared Window (bottom) images [click to play animation]

A 2-panel comparison of GOES-13 (GOES-East) Visible (0.63 µm) and Infrared Window (10.7 µm) images (above) showed a band of thunderstorms oriented southwest-to-northeast across northern Virginia and northern Maryland late in the day on 30 July 2016. Cells within this band produced very heavy rainfall and extreme flash flooding at Ellicott City, Maryland — located northwest of Baltimore/Washington International Airport KBWI, and marked with a cyan * symbol — with a total of 6.60 inches of rain in just over 2 hours (NWS Baltimore/Washington Public Information Statement | Event summary). The coldest cloud-top IR brightness temperature was -67º C at 0045 UTC on 31 July (8:45 pm local time).

The MIMIC Total Precipitable Water product at 3-hour intervals (below) indicated the presence of TPW values in the 2.0 to 2.5 inch range over parts of the region.

MIMIC Total Precipitable Water product [click to enlarge]

MIMIC Total Precipitable Water product [click to enlarge]

Upstream rawinsonde data profiles from Washington Dulles International Airport in northern Virginia (below) showed TPW values of 46.8 mm or 1.83 inches at 12 UTC on 30 July, and 49.2 mm or 1.94 inches at 00 UTC on 31 July (although the later data looks suspect, given the balloon was launched as strong thunderstorms were approaching).

Washington Dulles VA rawinsonde profiles [click to enlarge]

Washington Dulles VA rawinsonde profiles [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]

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]