Eruptions of Popocatépetl in Mexico

November 23rd, 2017 |

GOES-16 Visible (0.64 µm, left) and Infrared Window (10. µm, right) images, with plots of hourly surface reports [click to play animation]

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.3 µm, right) images, with plots of hourly surface reports [click to play animation]

* GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing *

An eruption of Mexico’s Popocatépetl volcano — the largest since 2013 — occurred on 23 November 2017. The volcanic cloud was evident in GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) as it drifted southward. However, due to the relatively thin nature of the cloud (a result of low values of ash loading), 10.3 µm infrared brightness temperatures were quite warm (greater than -20ºC), making a height determination from the single-band infrared imagery alone rather difficult.

This example demonstrates the value of using multi-spectral image techniques to derive retrieved products — available from the NOAA/CIMSS Volcanic Cloud Monitoring site — such as Ash Height (below). In this case, the retrieved ash cloud height was 7 km or 24,000 feet (darker green enhancement0, even for portions of the cloud with relatively low ash loading.

Ash Cloud Height product [click to play animation]

Ash Cloud Height product [click to play animation]

During the following nighttime hours, another eruption occurred, this time sending ash to a slightly higher altitude of 8 km or 26,000 feet (below).

Ash Cloud Height product [click to play animation]

Ash Cloud Height product [click to play animation]

A GOES-16 GeoColor animation can be seen here.

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Two of the channels on GOES-16 detect radiation in parts of the electromagnetic spectrum where sulfur dioxide (SO2) absorbs radiation: Band 10 (7.3 µm, the low-level Water Vapor channel) and Band 11 (8.4 µm, the Infrared Cloud Phase channel, see in particular the figure on the first page of the Quick Guide). The SO2 Red-Green-Blue (RGB) Composite was designed to highlight volcanic plumes, using the Brightness Temperature Difference between the mid-level and low-level Water Vapor Channels (6.9 µm7.3 µm) as the Red Component, the Brightness Temperature Difference between the Clean Infrared Window (Band 13, 10.3 µm) and the Infrared Cloud Phase (Band 11, 8.4 µm) as the Green Component, and the Clean Infrared Window (Band 13, 10.3 µm) as the Blue Component.  The eruption is obvious in the SO2 RGB imagery, below, with magenta and blue values apparent.  The volcanic plume’s appearance differs markedly from that of the convection along the Pacific coast of Mexico south and west of the eruption.

GOES-16 SO2 RGB, 2023 UTC 23 November 2017 – 2148 UTC 23 November 2017 (Click to animate)

Interesting contrail in North Dakota

November 21st, 2017 |

* GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing *

As mentioned in a Tweet from NWS Grand Forks (above), an interesting contrail was seen over eastern North Dakota on 21 November 2017. They noted that the contrail was most easily seen using imagery from the water vapor bands.

A comparison of GOES-16 ABI Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (below) showed the formation and motion of the contrail feature (which was likely caused by military aircraft, based in Grand Forks and/or Minot, performing training exercises).

GOES-16 Lower-level (10.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images, with surface station identifiers plotted in cyan [click to play animation]

GOES-16 Lower-level (10.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images [click to play animation]

A comparison of three of the GOES-16 Near-Infrared bands (below) showed that the high-altitude ice crystal contrail feature was also very apparent in “Cirrus” (1.37 µm) images; the contrails themselves were very subtle in the “Vegetation” (0.86 µm) and “Snow/Ice” (1.61 µm) images, but their darker shadows which were cast upon the surface (to the east-northeast) were more obvious — for example, on the 2132 UTC images.

GOES-16 Vegetation (0.86 µm, left), Cirrus (1.37 µm, center) and Snow/Ice (1.61 µm, right) images [click to play animation]

GOES-16 Vegetation (0.86 µm, left), Cirrus (1.37 µm, center) and Snow/Ice (1.61 µm, right) images [click to play animation]

A similar contrail feature was noted over North Dakota in March 2011.

 

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]


Alaska’s first -40º temperature of the 2017-2018 winter season

November 19th, 2017 |

NOAA-18 Infrared Window (10.8 mm) image, with surface identifiers and air temperatures plotted in red [click to enlarge]

NOAA-18 Infrared Window (10.8 mm) image, with surface identifiers and air temperatures plotted in red [click to enlarge]

Alaska’s first (official) surface air temperature of -40º or colder for the 2017-2018 winter season was reported by the Cooperative Observer at Chicken (-43ºF) on 19 November 2017. A NOAA-18 Infrared Window (10.8 µm) image at 0320 UTC (above) showed cold air drainage into river valleys, with the coldest infrared brightness temperatures around -40ºC/-40ºF (darker blue color enhancement). Chicken is located about midway between Eagle (PAEG) and Northway (PAOR), where 03 UTC surface air temperatures were -17ºF and -24ºF, respectively. However, PAEG reached their minimum temperature around 11 UTC after additional hours of cloud-free radiational cooling.

An automated RAWS site at Chicken reached a minimum temperature of -34ºF at 1120 UTC — the dew point at that time was -42ºF. However, a MesoWest map (below) shows that the RAWS tower is located on a small hill (at an elevation of 2060 feet) — and the Cooperative Observer instrument shelter was likely located in the lower elevations of the settlement.

MesoWest map showing the location of the Chicken RAWS site [click to enlarge]

MesoWest map showing the location of the Chicken RAWS site [click to enlarge]

For comparison, note the 2011-2012 and 2010-2011 winter seasons.