Tropical Storm Cindy

June 24th, 2017 |

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.3 µm, right) images, with hourly surface//ship/buoy reports plotted in yellow [click to play MP4 animation]

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.3 µm, right) images, with hourly surface//ship/buoy reports plotted in yellow [click to play MP4 animation]

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

As Tropical  Storm Bret was forming off the coast of South America, Potential Tropical Cyclone 3 (PTC3) was becoming more organized as it moved from the western Caribbean Sea across the Yucatan Peninsula of Mexico and into the Gulf of Mexico on 19 June 2017 (MIMIC TPW). On 20 June, one of the GOES-16 Mesoscale Sectors was positioned  over PTC3 and  provided 1-minute imagery — Visible  (0.64 µm)  and  Infrared Window (10.3  µm) images (above) showed deep convective bursts moving northward to reveal an exposed Low Level Circulation Center (LLCC).

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.3 µm, right) images, with hourly surface/buoy/ship reports plotted in yellow [click to play MP4 animation]

GOES-16 Visible (0.64 µm, left) and Infrared Window (10.3 µm, right) images, with hourly surface/buoy/ship reports plotted in yellow [click to play MP4 animation]

Early in the day on 21 June, 1-minute GOES-16 Visible and Infrared Window images (above) showed multiple LLCC features associated with PTC3, with deep convection remaining well to the north/northwest. In addition, Mid-level Water Vapor (6.9  µm) images (below) indicated that a large amount of dry air had wrapped into the southern and eastern portions of the storm circulation.

GOES-16 Visible (0.64 µm, left) and Water Vapor (6..9 µm, right) images [click to play MP4 animation]

GOES-16 Visible (0.64 µm, left) and Water Vapor (6..9 µm, right) images [click to play MP4 animation]

However, by mid-day a more consolidated central circulation had developed, as seen on Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images (below) — and PTC3 was upgraded to Tropical Storm Cindy.

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images, with surface pressure plotted in yellow and station identifiers plotted in cyan [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images, with surface pressure plotted in yellow and station identifiers plotted in cyan [click to enlarge]

Hourly images of the MIMIC Total Precipitable Water product covering the 19-24 June period (below) showed  the northward transport of rich tropical moisture into the Gulf  Coast states, which then moved northeastward toward the Northeast US bringing heavy rainfall and flooding to many locations (WPC storm summary).

MIMIC Total Precipitable Water [click to play animation]

MIMIC Total Precipitable Water [click to play animation]

Maps of daily rainfall during the 21-24 June period (along with 7-day rainfall totals, departure from normal and percent of normal) are shown below.

21-24 June daily precipitation, along with 7-day Precipitation Total, 7-day Departure from Normal and 7-day Percent of Normal [click to enlarge]

21-24 June daily precipitation, along with 7-day Precipitation Total, 7-day Departure from Normal and 7-day Percent of Normal [click to enlarge]

Tropical Storm Bret

June 19th, 2017 |

GOES-16 “Veggie” Band (0.86 µm) animation of Tropical Storm Bret, 1545-2030 UTC on 19 June 2017 (Click to animate)

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

The fast-moving tropical system in the southern Caribbean Sea has developed a closed circulation and has been named Bret.  Tropical Storm Bret, shown above in an animation of GOES-16 Near-Infrared (0.86 µm) imagery that highlights land/water contrasts (the Orinoco River in Venezuela and Caribbean Islands — some with cloud streamers in their lee — north of Venezuela stand out clearly), is forecast to remain very close to the South American coastline.  Such proximity to land will likely hinder development. Further, wind shear in the atmosphere over the storm is predicted to increase.

Bret is embedded within a ribbon of very moist air (associated with the ITCZ) that stretches from Africa to the northwest Caribbean, as shown in the animation below (taken from this site) that shows morphed microwave observations of total precipitable water.

Microwave estimates of Total Precipitable Water for the 24 hours ending 1900 UTC on 19 June 2017 (Click to enlarge)

For more information on Bret, refer to the National Hurricane Center and the CIMSS Tropical Cyclones sites (where you can also follow the future of the system emerging into the Gulf of Mexico).

Scattering and Shadows

June 19th, 2017 |

GOES-16 Imagery over New England from 1022 through 1117 UTC on 19 June 2017. Blue Band (0.47 µm), upper left; Red Band (0.64 µm), upper right; ‘Veggie’ Band (0.86 µm), lower left; ‘Snow/Ice’ Band (1.61 µm), lower right. Click to enlarge.

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

The animation of GOES-16 imagery, above, showing, clockwise from upper left, the GOES-16 0.47 µm, 0.64 µm, 1.61 µm and 0.86 µm channels, shows lows clouds over southeast New England, with a few mid-level clouds aloft. The moving mid-level clouds are casting shadows on the lower clouds beneath. Note that the shadows appear darkest at the longest wavelength. This is shown in the AWIPS cursor readout below as well — for the point selected, the 1.61 µm reflectance is 5.4%, and it increases to 18.9% at 0.47 µm. Why does it change by wavelength?

AWIPS read-out of reflectance in a shadow east of Cape Cod. Note the reflectance increases as wavelength decreases. (Click to enlarge)

Rayleigh scattering in the atmosphere is a function of wavelength: scattering is more effective at shorter wavelengths. Thus, the atmosphere is scattering the greatest amount of 0.47 µm radiation (compared to the longer wavelengths shown here). Shadows are darker (there is less detected reflectance) at longer wavelengths because less longer-wavelength radiation is scattered towards the satellite sensor.

The tweet from the National Weather Service in Melbourne, below, shows another shadow scene with 0.86 µm imagery.


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)