Ex-hurricane Ophelia over Ireland and the United Kingdom

October 16th, 2017 |

Meteosat-10 Water Vapor (6.25 µm) images, with hourly surface wind gusts (knots) plotted in red [click to play MP4 animation]

Meteosat-10 Water Vapor (6.25 µm) images, with hourly surface wind gusts (knots) plotted in red [click to play MP4 animation]

After reaching Category 3 intensity over the eastern Atlantic Ocean on 14 October, Hurricane Ophelia (storm track) rapidly underwent transition to an extratropical storm which eventually spread high winds across much of Ireland and the United Kingdom on 16 October 2017. EUMETSAT Meteosat-10 upper-level Water Vapor (6.25 µm) (above) and lower-level Water Vapor (7.35 µm) images (below) revealed the familiar “scorpion tail” signature of a sting jet (reference). Hourly wind gusts (in knots) from primary reporting stations are plotted in red.

Meteosat-10 Water Vapor (7.35 µm) images, with hourly surface wind gusts (knots) plotted in red [click to play MP4 animation]

Meteosat-10 Water Vapor (7.35 µm) images, with hourly surface wind gusts (knots) plotted in red [click to play MP4 animation]

Two sites with notable wind gusts were Cork, Ireland (67 knots at 0930 UTC) and Valley, UK (70 knots at 1500 UT), shown below. In fact, a wind gust of 103 knots (119 mph or 191 km/hour) was reported at the Fastnet Rock Lighthouse off the southwest coast of Ireland.

Time series plot of surface data from Cork, Ireland [click to enlarge]

Time series plot of surface data from Cork, Ireland [click to enlarge]

Time series plot of surface data from Valley, United Kingdom [click to enlarge]

Time series plot of surface data from Valley, United Kingdom [click to enlarge]

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Terra and Aqua MODIS true-color images [click to enlarge]

Terra and Aqua MODIS true-color images [click to enlarge]

In a toggle between Terra MODIS (overpass time around 1159 UTC) and Aqua MODIS (overpass time around 1345 UTC) true-color Red/Green/Blue (RGB) imagery (above), a somewhat hazy appearance was seen over the Irish Sea on the Terra MODIS image. This was due to an airborne plume of sand from the Sahara Desert (UK Met Office story).

In fact, blowing sand was observed about 3 hours later at Isle of Man, from 1520-1620 UTC — during that time period their surface winds gusted to 68 knots (78 mph), and surface visibility was reduced to 2.2 miles (below).

Time series plot of surface data from Isle of Man [click to enlarge]

Time series plot of surface data from Isle of Man [click to enlarge]

42-year anniversary of the GOES program

October 16th, 2017 |

A sample Visible (0.65 µm) image from GOES-1 is shown below (courtesy of Tim Schmit, NOAA/NESDIS/ASPB and the SSEC Data Center), after the satellite had been positioned over the Indian Ocean to support the Global Atmospheric Research Program. The first GOES-1 image was broadcast on 25 October 1975.

GOES-1 Visible (0.65 µm) image, 0930 UTC on 01 January 1979 [click to enlarge]

GOES-1 Visible (0.65 µm) image, 0930 UTC on 01 January 1979 [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]

GOES-16 Tools to Observe and Monitor Fires

October 9th, 2017 |

GOES-16 Visible (0.64 µm) Imagery, 1522-2017 UTC on 9 October 2017 (Click to animate)

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

GOES-16 provides many tools to the Operational Meteorologist, and to National Weather Service Incident Meteorologists (IMETs), to monitor fires when they occur, such as those over Napa and Sonoma Counties in California (Blog Post). Visible (0.64 µm) and Shortwave Infrared (3.9 µm) channels, above and below, respectively, are available routinely at 5-minute intervals over the Continental United States. During daytime, the Visible Imagery is useful for highlighting smoke palls and for alerting meteorologists to any wind changes. The Shortwave Infrared has long been used to detect fires; the shortwave infrared channel on GOES-16 can detect hotter and smaller fires than previous GOES Satellites because of improved spatial resolution and improved bit depth in the imagery.

GOES-16 Shortwave Infrared (3.9 µm) Imagery, 1522-2017 UTC on 9 October 2017 (Click to animate)

GOES-16 Channels can be combined to create Red Green Blue (RGB) Composites that also help identify fires qualitatively. The Fire RGB, below, combines the shortwave IR (3.9 µm) with the 2.2 µm and 1.6 µm channels; as fires get warmer, radiation is emitted at shorter and shorter wavelengths. When this RGB shows white values, you can be certain that the fire is very hot. At some times in the RGB animation, the 3.9 µm imagery is missing where the fire is exceptionally hot, meaning the ‘red’ component of the RGB has no value, and the RGB acquires a blue and green hue.

GOES-16 Fire Temperature RGB, 1522 – 2017 UTC on 9 October 2017 (Click to animate)

The Fire Temperature RGB like the visible imagery shown above offer qualitative information about fire. More quantitative information is available in GOES-16 Baseline Products that are an extension and refinement of the WF-ABBA products available for GOES-13 and GOES-15 (and other satellites). Fire-related products for GOES-16 include Fire Area and Fire Temperature, shown below. The products give the size of the fire within the pixel, and its temperature. These products are valuable in quickly evolving fires to monitor how things change, and the products are available every 5 minutes.

GOES-16 Fire Area Derived Product, 1522-2017 UTC on 9 October 2017 (Click to animate)

GOES-16 Fire Temperature, 1522-2017 UTC on 9 October 2017 (Click to animate)

Finally, GOES-16 has 1-minute Mesoscale Sectors that can be used to closely monitor quickly-evolving fire situations. The 3.9 µm shortwave infrared and Fire RGB images are shown below for a two-hour period. There can be significant changes to a fire in 1 minute, as was seen in this Blog Post! Note again that missing points in the 3.9 µm imagery will show up as green or blue regions in the RGB.

Fire RGB Product, 1931-2130 UTC on 9 October 2017 (Click to animate)

GOES-16 Shortwave Infrared (3.9 µm), 1933 – 2132 UTC on 9 October 2017 (Click to animate)