Tropical Cyclone Bansi in the Indian Ocean

January 13th, 2015
Advanced Dvorak Technique (ADT) intensity estimate

Advanced Dvorak Technique (ADT) intensity estimate

A plot of the Advanced Dvorak Technique intensity estimate for Tropical Cyclone Bansi (above) showed that the storm experienced a period of rapid intensification late in the day on 12 January 2015, reaching Category 4 intensity by 00 UTC on 13 January.

EUMESAT Metosat-7 11.5 µm IR channel images (below; click to play animation; also available as an MP4 movie file) revealed the formation of a well-defined eye, which also exhibited a notable amount of trochoidal motion or “wobble” as it moved across the southwest Indian Ocean (north of Reunion and Mascarene Island).

Meteosat-7 11.5 µm IR channel images (click to play animation)

Meteosat-7 11.5 µm IR channel images (click to play animation)

A more detailed view of Tropical Cyclone Bansi was provided by McIDAS-V images of Suomi NPP VIIRS 11.45 µm IR and 0.7 µm Day/Night Band data (below; credit: William Straka, SSEC) — deep convection with overshooting tops could be seen in the southern quadrant eyewall region, with gravity waves propagating radially outward across the northeastern and eastern portion of the cirrus canopy.

Suomi NPP VIIRS 11.45 µm IR and 0.7 µm Day/Night Band images

Suomi NPP VIIRS 11.45 µm IR and 0.7 µm Day/Night Band images

A DMSP SSMIS 85 GHz microwave image from the CIMSS Tropical Cyclones site (below) showed that a prominent “moat” of warm brightness temperatures (darker blue color enhancement) existed around the center of Bansi at 14:24 UTC on 13 January. The presence of such a moat usually signifies that the secondary (outer) eyewall formation process has completed, and an eyewall replacement cycle is underway (also signalling that the period of rapid intensification has ended). The moat feature is sustained by subsidence from the eyewall secondary circulations.

DMSP SSMIS 85 GHz microwave image

DMSP SSMIS 85 GHz microwave image

Note that there was no well-defined eye evident on the conventional Meteosat-7 IR image during this eyewall replacement cycle (below).

Meteosat-7 11.5 µm IR channel and DMSP SSMIS 85 GHz microwave images

Meteosat-7 11.5 µm IR channel and DMSP SSMIS 85 GHz microwave images

Storm “Nina” affects the northern British Isles and Norway

January 10th, 2015
Meteosat-10 6.25 µm water vapor channel images (click to play animation)

Meteosat-10 6.25 µm water vapor channel images (click to play animation)

The intense extratropical cyclone referred to in Norway as “Extreme Weather Nina” was described as the strongest storm to hit the western part of that country in 20 years, bringing high winds that caused widespread tree and property damage, disrupted power for an estimated 170,000 people, and halted some forms of transportation on 10 January 2015 (The Nordic Page). EUMETSAT Meteosat-10 6.25 µm water vapor channel images (above; click image to play animation; also available as an MP4 movie file) showed the well-defined circulation of the storm, which included a “scorpion tail” signature (10 UTC image) over the North Sea west of Norway suggesting that a sting jet feature may have been present. About 3 hours after the leading edge of this middle-tropospheric sting jet signature moved over Haugesund, winds there gusted to 71 knots/36.5 meters per second. Winds gusted as high as 89 knots/45.7 meters per second at the offshore oil platform Gullfax, and the Flesland airport at Bergen was briefly closed due to strong winds (which peaked at 65 knots/33.4 meters per second). In the northern British Isles, wind gusts as strong as 70 knots/36 meters per second were reported on Shetland Island, along with thunderstorms (water vapor image with 4-letter station identifier locations).

Meteosat-10 0.8 µm High Resolution Visible images (below; click image to play animation; also available as an MP4 movie file) revealed the development of numerous showers and thunderstorms across the southern sector of the storm.

Meteosat-10 0.8 µm High Resolution Visible images (click to play animation)

Meteosat-10 0.8 µm High Resolution Visible images (click to play animation)

A SSEC RealEarth Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image around 12:00 UTC (below) showed the storm center just off the west coast of Norway.

Suomi NPP VIIRS true-color image

Suomi NPP VIIRS true-color image

Strong winds in parts of northern Scotland and southern Norway

January 2nd, 2015
EUMETSAT Meteosat-10 6.25 µm water vapor channel images (click to play animation)

EUMETSAT Meteosat-10 6.25 µm water vapor channel images (click to play animation)

A band of strong westerly/northwesterly winds moved across northern Scotland and southern Norway on 02 January 2015 (surface analyses), with a number of locations reporting wind gusts in excess of 50-60 knots. The highest wind gust seen was 64 knots at the Gullfax Platform (ENGC) in the North Sea at 16 UTC, with a wind gust to 63 knots at Oslo Fornebu airport (ENFB) at 21 UTC; in the morning hours, an aircraft was blown off the runway at Stornoway Airport, Isle of Lewis, in the Outer Hebrides of Scotland (EGPO). Ferry services between Kristiansand and Denmark as well as those between Sandefjord and Sweden were cancelled due to the strong winds. EUMETSAT Meteosat-10 6.25 µm water vapor channel images (above; click image to play animation; also available as an MP4 movie file) showed that most of the stronger wind gusts occurred beneath a ribbon of drier air aloft, in which instability rain/snow showers (and even thunderstorms) were developing.

A Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image at 10:57 UTC visualized using the SSEC RealEarth web map server (below) showed a more detailed view of the instability showers and thunderstorms as they were developing over the North Sea. Along the west coast of Norway, thunderstorms were reported at Haugesund, Ålesund, Florø, and Bergen.

Suomi NPP VIIRS true-color image

Suomi NPP VIIRS true-color image

Super Typhoon Nuri in the West Pacific Ocean

November 3rd, 2014
Advanced Dvorak Technique (ADT) intensity estimate for Super Typhoon Nuri

Advanced Dvorak Technique (ADT) intensity estimate for Super Typhoon Nuri

A plot of the Advanced Dvorak Technique (ADT) intensity estimation for Super Typhoon Nuri (above) shows that the tropical cyclone went through a period of rapid intensification early in the day on 02 November 2014, reaching Super Typhoon strength with sustained winds of 155 knots later in the day.

During this period of rapid intensification, MTSAT-2 10.8 µm IR channel images (below; click image to play animation; also available as an MP4 movie file) showed the development of a small “pinhole” eye (with a diameter of about 15 km); as the storm began to recurve to the north and northeast, a bit of trochoidal motion or “wobble” of the eye was also evident. The coldest cloud-top IR brightness temperatures were -88º C (darker violet color enhancement).

MTSAT-2 10.8 µm IR channel images (click to play animation)

MTSAT-2 10.8 µm IR channel images (click to play animation)

A 375-meter resolution Suomi NPP VIIRS 11.45 µm IR channel image (below; courtesy of William Straka, SSEC) showed great detail in the storm top temperature structure within the eyewall region of Nuri at 17:12 UTC or 2:12 am local time.

Suomi NPP VIIRS 11.45 µm IR channel image

Suomi NPP VIIRS 11.45 µm IR channel image

During the daylight hours,  the COMS-1 satellite provided 15-minute interval 0.675 µm visible channel images (below; click image to play animation; also available as an MP4 movie file) which revealed the presence of mesovortices within the eye of Super Typhoon Nuri.

COMS-1 0.675 µm visible channel images (click to play animation)

COMS-1 0.675 µm visible channel images (click to play animation)

============================= Added 11/04/2014 =====================

Suomi NPP VIIRS 0.7 µm Day Night Band and 11.45 µm Infrared imagery during the overnight hours (16:49 UTC or 1:49 am local time) on 03 November showed a strong, well-organized system. Ample illumination from the Moon in a Waxing Gibbous phase (94% of full) helped to highlight the “visible image at night” capability of the Day/Night Band.

Suomi NPP VIIRS Day Night Band and 11.45 µm Infrared images of the typhoon eye (click to enlarge)

Suomi NPP VIIRS Day Night Band and 11.45 µm Infrared images of the typhoon eye (click to enlarge)

Suomi NPP VIIRS Day Night Band and 11.45 µm Infrared images of the typhoon (click to enlarge)

Suomi NPP VIIRS Day Night Band and 11.45 µm Infrared images of the typhoon (click to enlarge)