Pyrocumulonimbus cloud in Bolivia

August 18th, 2019 |

GOES-16

GOES-16 “Red” Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, middle) and “Clean” Infrared Window (10.35 µm, bottom) images [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed the formation of a pyrocumulonimbus (pyroCb) cloud over far southeastern Bolivia on 18 August 2019. The small anvil cloud briefly surpassed the -40ºC pyroCb threshold from 1800-1820 UTC, attaining a minimum cloud-top infrared brightness temperature of -45.2ºC along the Bolivia/Paraguay border at 1800 UTC. This pyroCb formed over the hottest southern portion of an elongated fire line, as seen in the Shortwave Infrared imagery.

A 1.5-day animation of GOES-16 Shortwave Infrared images (from 12 UTC on 17 August to 2350 UTC on 18 August) revealed the rapid southeastward run of the fire to the Bolivia/Paraguay border on 17 August, followed by the eastward expansion of the fire line on 18 August (below).

GOES-16 Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

GOES-16 Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

A toggle between Suomi NPP VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images as viewed using RealEarth (below) showed the large and dense smoke plume streaming southeastward, with the small pyroCb along the Bolivia/Paraguay border at 1745 UTC — the brighter white tops of the pyrocumulus and pyrocumulonimbus clouds reached higher altitudes than the tan-colored smoke plume. The coldest cloud-top infrared brightness temperature was about -55ºC (orange enhancement), which corresponded to an altitude around 9 km according to rawinsonde data from Corumbá, Bolivia.

Suomi NPP VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images [click to enlarge]


Strong northerly to northwesterly surface winds were blowing across the region, in advance of an approaching cold front (surface analyses) — at Robore, Bolivia (located just north-northwest of the fires), winds were gusting to 25-28 knots during much of the day (below).

Time series of surface report data from Robore, Bolivia [click to enlarge]

Time series of surface report data from Robore, Bolivia [click to enlarge]

This is likely the second confirmed case of a South American pyroCb (the first being on 29 January 2018) — in addition, it’s the second pyroCb documented in the tropics and the first pyroCb documented during a winter season. Thanks to Mike Fromm (NRL) for bringing this case to our attention!

Swan Lake Fire in Alaska

August 17th, 2019 |

GOES-17

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

1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images (above) revealed thick smoke and a pronounced thermal anomaly (hot pixels, darker black) associated with the Swan Lake Fire on the Kenai Peninsula in south-central Alaska on 17 August 2019. Later in the day, a few pyrocumulus jumps could be seen in Visible imagery over the fire source region, as fire behavior increased (another day when pyrocumulus jumps were apparent with this fire was 30 June, during a period when southerly winds were transporting dense smoke to the Anchorage area).

Strong northerly-northwesterly winds were transporting smoke from the Swan Lake Fire southward across the Kenai Peninsula and the Seward area — a time series of surface report data from Seward (below) showed that this smoke had reduced the visibility to less than 1 mile by 03 UTC (7 PM local time). South-central Alaska was experiencing drought conditions, which had worsened from the preceding week; the strong winds on this day acted to dry fuels even further, leading to a re-invigoration of the long-lived fire.

Time series of surface reports from Seward, Alaska [click to enlarge]

Time series of surface report data from Seward, Alaska [click to enlarge]

Seward Airport webcam image at 2358 UTC [click to enlarge]

Seward Airport webcam image at 2358 UTC [click to enlarge]

The PM2.5 Air Quality Index reached 427 at Cooper Landing, and 358 farther downwind at Seward (below).

Air Quality Index at Copper Landing and Seward [click to enlarge]

Air Quality Index at Copper Landing and Seward [click to enlarge]

The southward transport of smoke across the Seward area and out over the adjacent offshore waters of the Gulf of Alaska was evident in VIIRS True Color Red-Green-Blue (RGB) images from NOAA-20 and Suomi NPP, as viewed using RealEarth (below).

VIIRS True Color RGB images from NOAA-20 and Suomi NPP [click to enlarge]

VIIRS True Color RGB images from NOAA-20 and Suomi NPP [click to enlarge]

Super Typhoon Lekima in the West Pacific Ocean

August 8th, 2019 |

Himawari-8

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

JMA 2.5-minute rapid scan Himawari-8 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.4 µm) images (above) showed the eye and eyewall region of Category 4 Super Typhoon Lekima on 07-08 August 2019. Features of interest included surface mesovortices within the eye, eyewall cloud-top gravity waves, and a quasi-stationary “cloud cliff” notch extending northwestward from the eye (infrared brightness temperature contours). This cloud cliff feature has been observed with other intense tropical cyclones (for example, Typhoon Neoguri in 2014).

VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 as viewed using RealEarth are shown below.

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]

The trochoidal motion (or wobble) of the eye of Lekima became very pronounced as it crossed the Ryukyu Islands, as seen in an animation of 2.5-minute rapid scan Himawari-8  Infrared images (below). The center of the tropical cyclone moved between Miyakojima (ROMY) and Ishigakijima (ROIG), which reported wind gusts to 67 knots and 64 knots respectively.

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

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

Himawari-8 Infrared images with contours and streamlines of deep-layer wind shear at 15 UTC from the CIMSS Tropical Cyclones site (below) indicated that Lekima was moving through an environment of very low shear, which was a factor aiding its intensification.

Himawari-8 "Clean" Infrared Window (10.4 µm) images, with contours and streamlines of deep-layer wind shear at 15 UTC [click to play animation]

Himawari-8 “Clean” Infrared Window (10.4 µm) images, with contours and streamlines of deep-layer wind shear at 15 UTC [click to play animation]

Milepost 97 Fire in southwestern Oregon

July 26th, 2019 |

GOES-17 Fire Temperature RGB,

GOES-17 Fire Temperature RGB, “Red” Visible (0.64 µm), CIMSS Natural Color RGB and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

An animation that cycles through GOES-17 (GOES-West) Fire Temperature Red-Green-Blue (RGB), “Red” Visible (0.64 µm), CIMSS Natural Color RGB and Day Cloud Phase Distinction RGB images (above) showed the thermal anomaly (darker red pixels) and smoke associated with the Milepost 97 Fire in southwestern Oregon on 26 July 2019. In this particular case, dense smoke appeared as darker shades of green in the Day Cloud Phase Distinction RGB images.

A time series of surface data from Sexton Summit (immediately downwind of the fire) indicated that smoke reduced the surface visibility at that location to 1/4 mile at times; farther from the fire, the visibility was in the 2-3 mile range at times in Medford (below).

Time series of surface data from Sexton Summit [click to enlarge]

Time series of surface data from Sexton Summit [click to enlarge]

Time series of surface data from Rogue Valley International Airport in Medford [click to enlarge]

Time series of surface data from Rogue Valley International Airport in Medford [click to enlarge]

===== 27 July Update =====

GOES-17 True Color RGB images [click to play animation | MP4]

GOES-17 True Color RGB images [click to play animation | MP4]

GOES-17 True Color RGB images from the AOS site (above) showed the increased coverage of smoke from the Milepost 97 Fire, spreading across southern Oregon and into Northern California on 27 July. Some of the smoke had been lofted to higher altitudes, being transported as far northeastward as Montana.

Later in the day, GOES-17 True Color RGB images showed that the smoke had moved a significant distance southward along and just off the California coast (below).

GOES-17 True Color RGB images [click to play animation | MP4]

GOES-17 True Color RGB images [click to play animation | MP4]