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 rapidly underwent transition to an extratropical storm which 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) images (above) revealed the familiar “scorpion tail” signature of a sting jet (reference). Hourly wind gusts (in knots) from primary reporting stations are plotted in red.

The sting jet signature was also seen on Meteosat-10 lower-level Water Vapor (7.35 µm) images (below).

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]

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.

Of particular interest was the observation of blowing sand 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]

Hurricane Irma in the eastern Atlantic Ocean

September 1st, 2017 |
Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images (Click to enlarge)

Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images (Click to enlarge)

A toggle between nighttime images of Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) data at 0347 UTC (courtesy of William Straka, SSEC/CIMSS) showed a high-resolution view of the eye of Category 3 Hurricane Irma.

 

Toggle of CIMSS True Color, GOES-16 Split Window Difference (10.3 µm – 12.3 µm) field, and GOES-16 Dust RGB Product, 1315 UTC on 1 September 2017 (Click to enlarge)

GOES-16 data (ABI and GLM) posted on this page are preliminary, non-operational and are undergoing testing

The animation above cycles through imagery from 1315 UTC on 1 September, showing CIMSS GOES-16 True Color Imagery, The GOES-16 Split Window Difference (10.3 µm – 12.3 µm), and the GOES-16 Dust RGB (Red-Green-Blue) Product. The Split Window Difference field highlights moist air (bright red in the enhancement) to the south of Irma, and also dryer air (blue in the color enhancement), to the north. The Saharan Air Analysis, below, from the CIMSS Tropical Weather Website, corroborates the placement of the dry air to the north of Irma, and Total Precipitable Water estimates (from here) also show dry air. This dry air could influence further strengthening of the storm in the short term.

Saharan Air Layer analysis on 01 September 2017 (Click to animate)

Irma is near the eastern edge of the GLM Domain for GOES-16 in the central Test position at 89.5 W Longitude; the animation below, with GLM Group information (every 10 minutes) over ABI Band 13 (10.3 µm, every 30 minutes from the Full Disk Domain), shows little lightning near the center of Irma on 30/31 August. Lightning was more active on 1 September.

GOES-16 ABI “Clean Window” 10.3 µm Infrared Imagery, every half hour, with GLM Group Data plotted in 10-minute increments from 0000 UTC on 30 September through 1200 UTC on 1 September 2017 (Click to animate)

Satellite trends with Irma show the development of an eye structure, as seen below in the screen capture from the GOES-13 Floater (source) at 1745 UTC, and DMSP-16 SSMIS Microwave (85 GHz) at 1829 UTC on 1 September.

GOES-13 10.7 µm Infrared Imagery, 1745 UTC, 1 September 2017 (Click to enlarge)

The evolution of the eye is also apparent in the GOES-16 Visible Imagery (0.64 µm), below, from 1315-1815 UTC on 1 September 2017.

GOES-16 Visible (0.64 µm) Imagery, 1315-1815 UTC, 1 September 2017 (Click to animate)

For more information on Irma, consult the webpages of the National Hurricane Center or the CIMSS Tropical Weather Website.

GOES-16 and Tropical Depression #4 in the Atlantic Ocean

July 6th, 2017 |

GOES-16 “Cirrus Channel” (1.38 µm) near-infrared imagery, 0900-2100 UTC on 6 July 2017 (Click to play animated gif)

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

Tropical Depression #4 formed in the tropical Atlantic on 5 July 2017 (Click here for National Hurricane Center advisories on the system). The Depression is not forecast to strengthen, and two GOES-16 products give evidence to its weakened state. The animation of GOES-16 Band 4 (1.38 µm “Cirrus Channel”), above, shows a general decrease in the high clouds associated with this system (located north of 10º North Latitude and between 40º and 50º West Longitude), meaning convection is not strong. A closer view reveals intricate cirrus transverse banding around the periphery of the system during the early part of the day. In addition, the 10.3 µm “Clean Window” image, below, overlain on top of the GOES-16 Baseline Total Precipitable Water (TPW) Product, shows dry air west of the circulation. A Saharan Air Layer (SAL) analysis from here that uses Meteosat data, shows dry air moving towards the system from the east as well (Link). A toggle between GOES-13 Infrared Window, Meteosat-10 SAL product, and MIMIC TPW imagery can be seen here.

Refer to the National Hurricane Center website, or the CIMSS Tropical Weather website, for more information on this sytem.

GOES-16 “Clean Window” Band (10.33 µm) and GOES-16 Total Precipitable Water, 2100 UTC on 6 July 2017 (Click to enlarge)

Deadly Fire in Portugal

June 18th, 2017 |

Suomi NPP VIIRS Day/Night Band Visible Imagery (0.70 µm) at 0240 UTC on 18 June 2017 (Click to enlarge)

(Images in this blog post were created by William Straka, SSEC. Thanks William!!)

Parts of Pedrogao Grande in central Portugal (northeast of Lisbon) burned over the weekend in a massive forest fire. At least 62 people were killed (News Link; Youtube Video 1, 2). Suomi NPP overflew the region shortly after the fire started, and annotated VIIRS (Visible Infrared Imaging Radiometer Suite) Day/Night Band imagery is shown above (Click here for an image without annotation).  The size of the bright light signature from the fire (overlain with thin clouds) rivals that of Lisbon.

Suomi NPP VIIRS Shortwave Infrared imagery ( 3.75 µm) at 0240 UTC on 18 June 2017 (Click to enlarge)

Shortwave Infrared channels on Suomi NPP also testify to the intensity of the fire. The 3.75 µm above (Click here for an image with no labels) shows a saturated pixel (exceeding 367 K) over the hottest part of the fire.  The 1.61 µm channel in the near infrared also had a strong signal.   The 4.05 µm imagery (Click here for an image without annotation) shown below had a maximum brightness temperature exceeding 550 K! (This channel was specifically designed for fire detection).

Suomi NPP VIIRS Shortwave Infrared Imagery (4.05 µm) at 0240 UTC on 18 June 2017 (Click to enlarge)

Meteosat-10 Severi Infrared Imagery (3.9 µm) from 0000 to 0400 UTC on 18 June 2017 (click to enlarge)

The SEVERI Instrument on Meteosat-10 also detected this fire, and because Meteosat is geostationary, it provided better temporal coverage vs. the single snapshot from Suomi NPP. The animation above shows considerable cloud cover over Portugal, but very warm pixels are present starting after 0145 UTC. The toggle below compares 3.9 µm SEVIRI at 0245 UTC with 3.75 µm Suomi NPP VIIRS at 0240 UTC. The better spatial resolution of the VIIRS instrument is apparent, as are much warmer temperatures as expected given the smaller pixel size on VIIRS.  Note also a slight parallax shift.

Shortwave Infrared Imagery (3.9 µm from Meteosat-10 SEVIRI at 0245 UTC and 3.75 µm from Suomi NPP VIIRS at 0240 UTC) over Portugal (Click to enlarge)


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Suomi NPP VIIRS Day/Night Band visible (0.70 µm) imagery at 0145 UTC on 19 June 2017 (Click to enlarge)

Data from the 0145 UTC 19 June overpass on Suomi NPP show that the fire continues, although with less intensity. The Day/Night Band (above) and the 3.75 µm Shortwave Infrared (below) show the fire locations.

Suomi NPP VIIRS Shortwave Infrared (3.75 µm) imagery at 0145 UTC on 19 June 2017 (Click to enlarge)