Cape Newenham, Alaska bow shock waves

June 10th, 2018 |

GOES-15 Visible (0.63 µm) images, with hourly plots of wind barbs [click to play animation]

GOES-15 Visible (0.63 µm) images, with hourly plots of wind barbs [click to play animation]

GOES-15 (GOES-West) Visible (0.63 µm) images (above) showed patches of fog and low stratus moving southwestward off Southwest Alaska and across the adjacent offshore waters of the Bering Sea on 10 June 2018.

A closer look using 250-meter resolution Terra/Aqua MODIS and 375-meter resolution Suomi NPP VIIRS true-color Red-Green-Blue (RGB) images from RealEarth (below) revealed a packet of “bow shock waves” created as the shallow fog/stratus interacted with the relatively rugged terrain of the narrow Cape Newenham land feature (Google Maps). Other examples of similar bow shock wave cloud features have been documented here, here and here.

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

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

A 30-meter resolution Landsat-8 false-color RGB image (below) provided a more detailed view of the bow shock wave structure. Snow cover (cyan) could be seen on some of the higher-elevation land features.

Landsat-8 false-color RGB image [click to enlarge]

Landsat-8 false-color RGB image [click to enlarge]

A time series plot of Cape Newenham surface observations (below) showed the fluctuations in visibility as northerly winds brought patches of fog over the site.

Time series plot of Cape Newenham surface observations [click to enlarge]

Time series plot of Cape Newenham surface observations [click to enlarge]

Lava flow from Kilauea in Hawai’i

June 6th, 2018 |

GOES-15 Shortwave Infrared (3.9 µm) images, with hourly plots of surface reports [click to play MP4 animation]

GOES-15 Shortwave Infrared (3.9 µm) images, with hourly plots of surface reports [click to play MP4 animation]

The Kilauea volcano on the Big Island of Hawai’i continued to be active into early June 2018 — and GOES-15 (GOES-West) Shortwave Infrared (3.9 µm) imagery (above) showed the thermal anomaly or “hot spot” (black to yellow to red enhancement) associated with lava flows from active fissures in the East Rift Zone on 06 June.

GOES-15 Visible (0.63 µm) images (below) showed clouds of steam from the East Rift Zone drifting to the south-southwest; a hazy plume of volcanic fog or “vog” was also evident, which was being transported farther to the southwest by the northeasterly trade wind flow.

GOES-15 Visible (0.63 µm) images, with hourly plots of surface reports [click to play MP4 animation]

GOES-15 Visible (0.63 µm) images, with hourly plots of surface reports [click to play MP4 animation]

A Suomi NPP VIIRS Visible (0.64 µm) image at 2307 UTC (below) showed clear skies over Kapoho on the eastern tip of the Big Island, with steam plumes from the active East Rift Zone fissures flowing southwestward.

Suomi NPP VIIRS Visible (0.64 µm) image [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) image [click to enlarge]

The corresponding VIIRS Shortwave Infrared (3.74 µm) image (below) helped to discriminate between the hot brightness temperatures of recent (and old) lava flows and the cooler brightness temperatures exhibited by regions of vegetation.

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) image [click to enlarge]

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) image [click to enlarge]

A closer look at the Kilauea East Rift Zone (below) provided a detailed view of the recent lava flow and active fissures, including the lava field that entered and covered Kapoho Bay a few days earlier. Note the appearance of numerous multi-colored pixels in the center of the lava field — the 3.74 µm I04 band detectors on the VIIRS instrument saturate around 385 K, so the hottest lava features which exceeded that brightness temperature threshold ended up being displayed as cold pixels (the so-called “wrap-around” effect). There is a Moderate-resolution M13 band (4.05 µm) on VIIRS which saturates at a much hotter 700 K; while it is a lower spatial resolution (750 meters, vs 375 meters for the I04 band), the M13 band can be useful for sampling the actual temperature of very hot features such as lava flows or wildfires.

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) image [click to enlarge]

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) image [click to enlarge]

Thanks to Jordan Gerth (CIMSS) and Eric Lau (NWS Pacific Region Headquarters) for providing the VIIRS imagery for this case.

Update: This link shows Landsat-8 and Sentinel-2 imagery before and after the Kapoho Bay lava flow.

Kilauea effects stretch to Guam

June 1st, 2018 |

Suomi-NPP Views of the eastern tip of the island of Hawai’i at 1155 UTC on 1 June 2018. VIIRS Day Night Band Visible (0.70) and Shortwave Infrared (3.75) and Longwave Infrared (11.45) (Click to enlarge)

Early on 1 June 2018, clear skies allowed an unobstructed view of the still-erupting Kilauea from Suomi-NPP. (Orbit paths from this link).   The image above steps through the Day Night Band 0.7 µm Visible Image, the 3.75 µm Shortwave Infrared, and the 11.45 µm Longwave Infrared. The warm signatures of the lava extend all the way into the ocean.


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Photo showing Volcanic Haze on the Island of Guam (photo courtesy Brandon Aydlett, NWS GUM)

On 30 May 2018, hazy skies were widespread over the Mariana Islands, haze that could be traced back to Hawaii. (The picture above looks northeast from Nimitz Hill on the island of Guam).

The visible imagery below shows a pall of haze entrenched within the tropical easterlies from south and west of Hawai’i all the way across the Pacific Basin to Guam — a distance of some 4000 miles! (Himawari imagery courtesy Brandon Aydlett, NWS GUM, where the National Weather Service day begins!)

Himawari-8 Band 3 (0.64 µm) Imagery on Wednesday 30 May 2018 (Click to enlarge)

Suomi NPP and NOAA-20 view Tropical Depression Alberto over the lower Ohio River Valley

May 30th, 2018 |

Day Night Band Visible (0.7 µm) Imagery from Suomi NPP (0722) and NOAA-20 (0812 UTC) over Tropical Depression Alberto (Click to enlarge)

Suomi-NPP and NOAA-20 overflew tropical depression Alberto, at 0722 and 0812 UTC, respectively (orbit paths from this site), on 30 May 2018, and the near-Full moon provided ample illumination for the Day Night Band imagery, shown above.  A motion to the northeast is apparent.  Convection developed far to the north of the storm as well, south of Chicago, and a streak of lightning occurs over Oklahoma in the later image.  (For individual Day Night Band images in the loop, click here for Suomi NPP and here for NOAA-20) A similar loop, below, shows the Window Channel (11.45 µm) from the VIIRS instrument on Suomi NPP and NOAA-20. A tip of the Hat to Will Straka, CIMSS, for the imagery.

VIIRS Window Channel (I05) Infrared (11.45 µm) Imagery from Suomi NPP (0722) and NOAA-20 (0812 UTC) over Tropical Depression Alberto (Click to enlarge)

Added: NOAA-20 was declared Operational on 30 May 2018. Welcome NOAA-20!