Cyclone Gita in the South Pacific Ocean

February 12th, 2018 |

Himawari-8

Himawari-8 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.4 µm, bottom) images, with hourly plots of surface reports [click to play Animated GIF | MP4 also available]

Himawari-8 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.4 µm) images (above) showed Cyclone Gita as it moved toward Tonga in the South Pacific Ocean during 11 February – 12 February 2018. The tropical cyclone reached Category 4 intensity (ADT | SATCON) near the end of the animation period.

A longer animation of Himawari-8 Infrared images (below) revealed that the center of Gita moved just south of the main island of Tongatapu. Surface observations from Fua’Amotu (NFTF) ended after 0735 UTC.

Himawari-8

Himawari-8 “Clean” Infrared Window (10.4 µm) images, with hourly surface plots [click to play Animated GIF | MP4 also available]

MIMIC-TC morphed microwave imagery (below) showed that Gita underwent an eyewall replacement cycle after moving to the southwest of Tongatapu — a small eyewall was replaced by a larger eyewall, which was very apparent in DMSP SSMIS Microwave (85 GHz) images at 1533 and 1749 UTC.

MIMIC-TC morphed microwave imagery

MIMIC-TC morphed microwave imagery

Metop ASCAT scatterometer surface winds (below) showed Gita around the time that the storm center was just south of Tongatapu at 0850 UTC.

Metop ASCAT scatterometer surface winds [click to enlarge]

Metop ASCAT scatterometer surface winds [click to enlarge]

Cyclone Numa in the Mediterranean Sea

November 19th, 2017 |

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

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

A toggle between Terra MODIS and Suomi NPP VIIRS Red-Green-Blue (RGB) images, viewed using RealEarth (above), revealed the well-defined eye structure of Cyclone Numa over the Ionian Sea (between Italy and Greece) on 18 November 2017. Tracing its origin back to the remnants of Tropical Storm Rina (track), Cyclone Numa had acquired subtropical characteristics, making it a relatively rare Medicane.

EUMETSAT Meteosat-10 High Resolution Visible (0.8 µm) images (below) showed the evolution of the storm on 18 November. Plots of hourly surface reports (in metric units) are plotted on the images.

Meteosat-10 Visible (0.8 µm) images, with plots of hourly surface reports [click to play MP4 animation]

Meteosat-10 Visible (0.8 µm) images, with plots of hourly surface reports [click to play MP4 animation]

Meteosat-10 Infrared Window (10.8 µm) images (below) showed cloud-top infrared brightness temperatures around -60ºC (darker red enhancement) associated with some of the convective bursts during the 18-19 November period, as the system eventually moved inland across Greece.

Meteosat-10 Infrared Window (10.8 µm) images, with plots of hourly surface reports [click to play MP4 animation]

Meteosat-10 Infrared Window (10.8 µm) images, with plots of hourly surface reports [click to play MP4 animation]


Super Typhoon Lan in the West Pacific

October 21st, 2017 |

Advanced Dvorak Technique (ADT) plot for Typhoon Lan [click to enlarge]

Advanced Dvorak Technique (ADT) plot for Typhoon Lan [click to enlarge]

A plot of the Advanced Dvorak Technique for Typhoon Lan (above) showed that the tropical cyclone underwent a period of rapid intensification during the 00-12 UTC period on 20 October 2017.

A 24-hour animation of Himawari-8 rapid-scan (2.5 minute interval) Infrared Window (10.4 µm) images (below) revealed the development of a very large eye during the 20 October/06 UTC to 21 October/06 UTC period.

Himawari-8 Infrared Window (10.4 µm) images [click to play MP4 animation]

Himawari-8 Infrared Window (10.4 µm) images [click to play MP4 animation]

A nighttime comparison of Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 1700 UTC or 2:00 AM kocal time (below; courtesy of William Straka, CIMSS/SSEC) provided a good visualization of the “stadium effect” — an eye that was more narrow at the surface, with a larger diameter at higher altitudes. A packet of mesospheric airglow waves (reference) was also evident on the Day/Night Band image, propagating south-southeastward away from the eye.

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (10.4 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (10.4 µm) images [click to enlarge]

A 2-panel comparison of Himawari-8 Visible (0.64 µm) and Infrared Window (11.45 µm) images (below) showed the eye of Lan after it attained Super Typhoon status at 18 UTC on 20 October. Mesovortices could  be seen within the eye on the rapid-scan images.

Himawari-8 Visible (0.64 µm, left) and Infrared Window (10.4 µm, right) images [click to play MP4 animation]

Himawari-8 Visible (0.64 µm, left) and Infrared Window (10.4 µm, right) images [click to play MP4 animation]

A large amount of moisture was associated with this tropical cyclone, as depicted by hourly images of the MIMIC Total Precipitable Water product (below) — note the large area with TPW values of 70 mm or greater (light violet color enhancement).

MIMIC Total Precipitable Water product [click to play animation]

MIMIC Total Precipitable Water product [click to play animation]

A TPW value of 72.5 mm (2.87 inches) was derived from the Minamidaitojima, Japan rawinsonde data at 12 UTC on 21 October (below). Minamidaitojima is the largest island in the Daito Islands group southeast of Okinawa, Japan  — this station was just to the northeast of Lan around 12 UTC.

Rawinsonde data from Minamidaitojima, Japan [click to enlarge]

Rawinsonde data from Minamidaitojima, Japan [click to enlarge]

Hurricane Ophelia

October 14th, 2017 |

GOES-13 Visible (0.63 µm, left) and Infrared Window (10.7 µm, right) images, with hourly surface reports (in metric units) plotted in yellow [click to animate]

GOES-13 Visible (0.63 µm, left) and Infrared Window (10.7 µm, right) images, with hourly surface reports (in metric units) plotted in yellow [click to animate]

Hurricane Ophelia — the record-tying 10th consecutive Atlantic basin hurricane of the 2017 season — reached a satellite-estimated Category 3 intensity at 15 UTC on 14 October 2017. GOES-13 (GOES-East) Visible (0.63 µm) and Infrared Window (10.7 µm) images (above) showed a well-defined circular eye as the storm moved well south of the Azores. The tweet below underscores the unusual nature of the intensity and location of Ophelia (which also occurred over unusually-cold waters).

A DMSP-17 SSMIS Microwave (85 GHz) image (below) also revealed a circular eye structure.

DMSP-17 SSMIS Microwave (85 GHz) image [click to enlarge]

DMSP-17 SSMIS Microwave (85 GHz) image [click to enlarge]

One factor that might have aided this increase of intensity was the recent passage of Ophelia through an environment of higher Maximum Potential Intensity (reference), where maximum wind speed values of 100 knots resided (below).

Maximum Potential Instability wind speed plot from 13 October, with the track of Ophelia as of 18 UTC on 14 October [click to enlarge]

Maximum Potential Instability wind speed plot from 13 October, with the track of Ophelia as of 18 UTC on 14 October [click to enlarge]