Pyrocumulonimbus cloud in eastern Russia

April 30th, 2019 |

Himawari-8

Himawari-8 “Red” Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, middle) and “Clean” Infrared Window (10.4 µm, bottom) [click to play animation | MP4]

On 30 April, JMA Himawari-8 “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.4 µm) images (above) showed the formation of the first known pyrocumulonimbus (pyroCb) cloud of the 2019 Northern Hemisphere wildfire season. The pyroCb developed within the warm sector of an approaching midlatitude cyclone (surface analyses) in the Russian Far East, between still-ice-covered Lake Bolon and the Amur River. The cloud-top infrared brightness temperature first reached the -40ºC “pyroCb threshold” at 0310 UTC; note that the pyroCb cloud top appears warmer (darker shades of gray) than those of surrounding thunderstorms in the Shortwave Infrared images — a characteristic of enhanced solar reflection off the smaller ice crystals that are found in pyroCb cirrus anvils.

A faster animation revealed the rapid northeastward run of the large pyroCb-producing fire on Shortwave Infrared imagery.

VIIRS True Color RGB and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP [click to enlarge]

VIIRS True Color RGB and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP [click to enlarge]

In a sequence of three VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP as viewed using RealEarth (above), the coldest cloud-top infrared brightness temperature of the pyroCb was -59ºC — which closely corresponded to the tropopause temperature on 00 UTC rawinsonde data from Habarovsk (below), located just southwest of the fire region.

Plot of 00 UTC rawinsonde data from Habarovsk [click to enlarge]

Plot of 00 UTC rawinsonde data from Habarovsk [click to enlarge]

Storm Hannah moves across the British Isles

April 26th, 2019 |

True Color RGB and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 [click to play animation]

VIIRS True Color RGB and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 [click to play animation]

A sequence of VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 as viewed using RealEarth (above) showed “Storm Hannah” as it approached Ireland and the United Kingdom on 26 April 2019. The midlatitude cyclone had peaked in intensity as a Hurricane Force low around that time (surface analyses).

EUMETSAT Meteosat-11 Water Vapor (6.25 µm) images (below) showed winds gusting to 40-65 knots at several sites in southern Ireland and southern England, as the dry slot air stream moved across the region. In Ireland the peak wind gust was 66 knots at Mace Head, with 64 knots at Shannon — wind gusts in southern England included 71 knots at Aberderon, 68 knots at Pembrey Sands and 52 knots at Valley.

Meteosat-11 Water Vapor (6.25 µm) images with plots of surface winds and gusts [click to play animation | MP4]

Meteosat-11 Water Vapor (6.25 µm) images with plots of surface winds and gusts [click to play animation | MP4]

Cyclone Kenneth makes landfall in Mozambique

April 25th, 2019 |

Meteosat-8 Visible (0.8 µm) images [click to play animation | MP4]

Meteosat-8 Visible (0.8 µm) images [click to play animation | MP4]

EUMETSAT Meteosat-8 Visible (0.8 µm) images (above) and Infrared Window (10.8 µm) images (below) showed Category 4 Cyclone Kenneth (12 UTC JTWC advisory) making landfall along the northeast coast of Mozambique (north of Pemba FQPB: surface observations) on 25 April 2019. Kenneth had been moving over warm water and through an environment of low deep-layer wind shear, factors favorable for its rapid intensification (ADT | SATCON). After making landfall, Kenneth rapidly weakened to Category 1 intensity by 18 UTC — but Metop-A ASCAT winds of 40-49 knots were still sampled along the coast on the rear periphery of the storm. The slow inland movement of the remnants of Kenneth combined with copious amounts of tropical moisture as depicted by MIMIC TPW posed a concern for potential flooding problems.

Meteosat-8 Infrared Window (10.8 µm) images [click to play animation | MP4]

Meteosat-8 Infrared Window (10.8 µm) images [click to play animation | MP4]

VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20, viewed using RealEarth (below), provided higher-resolution views of Kenneth a few hours prior to landfall. This was the strongest tropical cyclone landfall on record for the northern portion of Mozambique, as discussed here.

VIIRS True Color RGB and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 [click to enlarge]

VIIRS True Color RGB and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 [click to enlarge]

GCOM-W1 AMSR2 Microwave (89 GHz) image (below, courtesy of William Straka, CIMSS) showed the eye and spiral band structures near the Mozambique coast at 1030 UTC on 25 April. The evolution of the eye since its initial formation on 23 April was evident in the MIMIC TC product.

GCOM-W1 AMSR2 Microwave (89 GHz) image [click to enlarge]

GCOM-W1 AMSR2 Microwave (89 GHz) image [click to enlarge]

A longer animation of Meteosat-8 Infrared images (below) during the later half of its storm track showed the formation of an eye as Kenneth began its period of rapid intensification on 24 April. Cloud-top infrared brightness temperatures were -90ºC and colder (yellow pixels embedded with darker shades of purple) during the 1030-1800 UTC period on 24 April. Note that the center of Kenneth passed just north of the island of Grande Comore soon after the eye had developed — at Prince Said Ibrahim International Airport FMCH in Moroni, southeast winds gusted to 65 knots at 21 UTC 0n 24 April as the southern eyewall passed over the island.

Meteosat-8 Infrared Window (10.8 µm) images [click to play animation | MP4]

Meteosat-8 Infrared Window (10.8 µm) images [click to play animation | MP4]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (below, courtesy of William Straka, CIMSS) showed Kenneth at 2232 UTC on 24 April, shortly before the tropical cyclone had reached Category 4 intensity. Ample illumination from the Moon — in the Waning Gibbous phase, at 73% of Full — provided an excellent example of the “visible image at night” capability of the VIIRS Day/Night Band.

NOAA-20 Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Ship tracks in the East Pacific, and eddy circulations near the California coast

April 24th, 2019 |

GOES-17 "Red" Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

GOES-17 “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

GOES-17 (GOES-West) “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images (above) showed a number of ship condensation trails (or “ship tracks”) over the East Pacific Ocean on 24 April 2019. Aerosols from the exhaust of ships cause a “cloud seeding effect”, which results in a higher concentration of smaller cloud droplets compared to the surrounding unperturbed clouds. These smaller cloud droplets are more effective reflectors of sunlight, leading to a warmer (darker red) 3.9 µm signature.

GOES-17 Visible images (below) revealed a few eddy circulations within the marine boundary layer stratocumulus off the coast of southern California, along with other interesting Channel Island cloud interactions — some of the eddy circulations exhibited a small cloud-free center. Surface winds were light and variable over the Channel Islands (surface analyses), with a thermal low situated well inland over the Desert Southwest (the national high temperature on 24 April was 106ºF at Death Valley, California).

GOES-17

GOES-17 “Red” Visible (0.64 µm) images [click to play animation | MP4]