Bonnie

May 29th, 2016
GOES-13 6.5 µm Infrared images [click to play animation]

GOES-13 6.5 µm Infrared images[click to play animation]

Tropical Storm Bonnie became a minimal tropical storm at 2100 UTC on Saturday 28 May, the second named storm of the Atlantic Season (Hurricane Alex, which storm formed in January, was the first named storm). The water vapor animation above shows that Bonnie’s initial spin may be traced to a front associated with an occluded system crawled through the eastern United States, exiting on about 23 May 2016. It’s not uncommon for vorticity associated with extratropical cyclone fronts to sow the seed of a tropical cyclone, especially early (or late) in the season. In this case, the cold front failed to pass Bermuda, and by 27 May, persistent thunderstorms about halfway between Bermuda and the Bahamas suggested tropical cyclogenesis was underway.

MIMIC Total Precipitable Water derived from Microwave imagery, 1800 UTC 28 May - 1700 UTC 30 May [click to enlarge]

MIMIC Total Precipitable Water derived from Microwave imagery, 1800 UTC 28 May – 1700 UTC 30 May [click to enlarge]

Total Precipitable Water fields, from the microwave MIMIC product, above, show the system was embedded deep within tropical moisture. Tropical moisture associated with the storm moved up the east coast of the United States into the mid-Atlantic States with local flooding reported. This longer animation (from 21 through 28 May) shows that persistent westward motion of moisture occurred over the tropical Atlantic well in advance of Bonnie’s formation.

Rapidscat Scatterometer Winds, 1012 UTC on 27 May [click to enlarge]

Rapidscat Scatterometer Winds, 1012 UTC on 27 May [click to enlarge]

The tropical wave the produced Bonnie showed a closed circulation as early as 1012 UTC on 27 May according to rapidscat scatterometer winds (above), and MODIS Sea Surface Temperatures, below, showed very warm water over the Gulf Stream.

MODIS-based Sea Surface Temperatures, 1848 UTC on 27 May [click to enlarge]

MODIS-based Sea Surface Temperatures, 1848 UTC on 27 May [click to enlarge]

Suomi NPP Day Night Band (0.70 µm Visible) and Infrared (11.45 µm) Imagery at 0621 UTC on 27 May 2016 [click to enlarge]

Suomi NPP Day Night Band (0.70 µm Visible) and Infrared (11.45 µm) Imagery at 0621 UTC on 27 May 2016 [click to enlarge]

Suomi NPP overflew this tropical systems at various times during its lifecycle. Shortly after midnight on 27 May 2016, above, strong convection was centered just north of the apparent surface circulation (as inferred by the curved bands of low-level clouds, clouds made visible by moonlight in this night-time visible imagery). Twenty-four hours later, at 0742 UTC on 28 May, below, in a more zoomed-in view, the (then) tropical depression Number 2 is supporting strong convection that is obscuring the low-level circulation center.

Suomi NPP Day Night Band (0.70 µm Visible) and Infrared (11.45 µm) Imagery at 0742 UTC on 28 May 2016 [click to enlarge]

Suomi NPP Day Night Band (0.70 µm Visible) and Infrared (11.45 µm) Imagery at 0742 UTC on 28 May 2016 [click to enlarge]

Suomi NPP Day Night Band (0.70 µm Visible) and Infrared (11.45 µm) Imagery at 0723 UTC on 29 May 2016 [click to enlarge]

Suomi NPP Day Night Band (0.70 µm Visible) and Infrared (11.45 µm) Imagery at 0723 UTC on 29 May 2016 [click to enlarge]

Finally, at 0723 UTC on 29 May, (above) after strong shear has displaced all convection well north of the center, the low-level circulation of Tropical Storm Bonnie is southeast of the the South Carolina Coast. Strong convection is over North Carolina. This shear was noted in the 0300 UTC and 0900 UTC (29 May) Discussions from the National Hurricane Center. The effect of shear is apparent in the two GOES-13 Infrared Images below, from 2045 UTC on 28 May when convection was close to the center, and from 1045 UTC on 29 May, shortly before landfall, when convection was stripped from the center and displaced well to the north.

GOES-13 Infrared (10.7 µm) Imagery at 2045 UTC on 28 May and at 1045 UTC 29 May 2016;  the Yellow Arrow points to the low-level circulation center [click to enlarge]

GOES-13 Infrared (10.7 µm) Imagery at 2045 UTC on 28 May and at 1045 UTC 29 May 2016; the Yellow Arrow points to the low-level circulation center [click to enlarge]

Cyclone Roanu, and a new all-time high temperature record set in India

May 21st, 2016

INSAT-3D Infrared Window (10.8 µm) images, with hourly surface weather symbols [click to play MP4 animation]

INSAT-3D Infrared Window (10.8 µm) images, with hourly surface weather symbols [click to play MP4 animation]

Cyclone Roanu (01B) was the first tropical cyclone of the 2016 North Indian Ocean season, with a northeastward track just off the east coast of India during the 18-21 May period. The storm moved over very warm waters, with sea surface temperature values of 30-31º C, but moderate amounts of deep-layer wind shear prevented the storm from rapidly intensifying (ADT | SATCON). INSAT-3D Infrared Window (10.8 µm) images (above; also available as a large 79 Mbyte animated GIF) showed that the storm exhibited a number of convective bursts with a large areal coverage of cloud-top IR brightness temperatures colder than -90ºC. Cyclone Roanu brought very heavy rainfall to Sri Lanka, coastal India, and Bangladesh.

As Roanu was moving along the east coast, very hot surface air temperatures were seen in the western portion of India on 19 May, with many sites reporting temperatures in excess of 110ºF. The animation below shows hourly Infrared images with surface METAR reports, as viewed using RealEarth.

Hourly Infrared satellite images, with METAR surface reports [click to play animation]

Hourly Infrared satellite images, with METAR surface reports [click to play animation]

INSAT-3D Visible (0.65 µm) images, with hourly surface wind barbs (knots) and temperatures (ºF) [click to play animation]

INSAT-3D Visible (0.65 µm) images, with hourly surface wind barbs (knots) and temperatures (ºF) [click to play animation]

INSAT 3D Visible (0.65 µm) images with hourly surface temperatures in ºF (above) revealed temperatures as warm as 122ºF at Ahmadabad, at 10 UTC and 12 UTC; a plot of the time series of weather condition at Ahmadabad is shown below. Farther to the north at the city of Phalodi (whose location is denoted by the gray * symbol) a temperature of 123.8ºF or 51.0ºC was recorded, which set an all-time record for the highest temperature officially measured in India (the previous record was 50.6ºC, set in 1886 at Pachpadra)..

Time series plot of surface data for Ahmadabad, India [click to enlarge]

Time series plot of surface data for Ahmadabad, India [click to enlarge]

Cyclone Fantala in the Indian Ocean

April 16th, 2016

Advanced Dvorak Technique intensity plot for Cyclone Fantala [click to enlarge]

Advanced Dvorak Technique intensity plot for Cyclone Fantala [click to enlarge]

A plot of the Advanced Dvorak Technique (ADT) hurricane intensity estimate (above) revealed that Indian Ocean Cyclone Fantala (19S) exhibited a period of rapid intensification on 15 April 2016, reaching Category 4 intensity with maximum sustained winds of 135 knots at 14 UTC.

EUMETSAT Meteosat-7 Infrared Window (11.5 µm) images (below) showed the formation of a well-defined eye after about 03 UTC.

Meteosat-7 Infrared (11.5 µm) images [click to play animation]

Meteosat-7 Infrared (11.5 µm) images [click to play animation]

A comparison of Meteosat-7 Infrared (11.5 µm) and DMSP-18 SSMI Microwave (85 GHz) images from the CIMSS Tropical Cyclones site (below) showed the eye structure around 15 UTC.

Meteosat-7 Infrared (11.5 µm) and DMSP-18 SSMI Microwave (85 GHz) images [click to enlarge]

Meteosat-7 Infrared (11.5 µm) and DMSP-18 SSMI Microwave (85 GHz) images [click to enlarge]

===== 18 April Update =====

Meteosat-7 Infrared Window (11.5 µm) images [click to play animation]

Meteosat-7 Infrared Window (11.5 µm) images [click to play animation]

During the 17-18 April period Cyclone Fantala reached Category 5 intensity (ADT plot), with maximum sustained winds of 150 knots (making it the strongest tropical cyclone on record in the South Indian Ocean); Fantala also became the longest-lived hurricane-strength tropical cyclone on record for that ocean basin. Meteosat-7 Infrared Window (11.5 µm) images (above) showed the storm reaching peak intensity as it moved just north of the island of Madagascar.

A comparison of Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images (below) offered a detailed nighttime view of the eye of Fantala at 2249 UTC on 17 April. Side lighting from the Moon (in the Waxing Gibbous phase, at 81% of full) helped to cast a distinct shadow within the eye, and also provided a good demonstration of the “visible image at night” capability of the Day/Night Band.

 

Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm images [click to enlarge]

Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm images [click to enlarge]

Severe Cyclone Emeraude in the Indian Ocean

March 17th, 2016

Advanced Dvorak Technique intensity plot for Cyclone Emeraude [click to enlarge]

Advanced Dvorak Technique intensity plot for Cyclone Emeraude [click to enlarge]

A plot of the Advanced Dvorak Technique intensity estimate for Cyclone Emeraude in the Indian Ocean (above) shows that the storm rapidly intensified to Category 4 intensity on 17 March 2016.

Himawari-8 AHI Visible (0.64 µm) and Infrared Window (10.4 µm) images (below; also available as a large 31-Mbyte animated GIF) revealed the formation of a well-defined eye during the day.

Himawari-8 Visible (0..64 µm, top) and Infrared Window (10.4 µm, bottom) images [click to play MP4 animation]

Himawari-8 Visible (0..64 µm, top) and Infrared Window (10.4 µm, bottom) images [click to play MP4 animation]

Nighttime images of Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) data at 1859 UTC (below, courtesy of William Straka, SSEC) showed the ragged appearance of the eye at that time, with an isolated convective burst that had developed well west of the eye.

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]