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

GOES-16 Shortwave Infrared (3.9 µm) images (above) showed the “hot spot” signatures (black to yellow to red pixels) associated with numerous wildfires that began to burn in Northern California’s Napa County around 0442 UTC on 09 October 2017 (9:42 PM local time on 08 October). A strong easterly to northeasterly Diablo wind (gusts) along with dry fuels led to extreme fire behavior, with many of the fires quickly exhibiting very hot infrared brightness temperature values and growing in size at an explosive rate (reportedly burning 80,000 acres in 18 hours).

A comparison of nighttime GOES-16 Shortwave Infrared (3.9 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (below) offered another example of nocturnal fire signature identification — the bright glow of the fires showed up well on the 1-km resolution 1.61 µm imagery. Especially noteworthy was the very rapid southwestward run of the Tubbs Fire, which eventually moved just south of station identifier KSTS (Santa Rosa Sonoma County Airport; the city of Santa Rosa is located about 5 miles southeast of the airport). These Northern California fires have resulted in numerous fatalities, destroyed at least 3500 homes and businesses, and forced large-scale evacuations (media story).

A toggle between 1007 UTC (3:07 AM local time) Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images (below) provided a view of the fires at an even higher spatial resolution. Since the Moon was in the Waning Gibbous phase (at 82% of Full), it provided ample illumination to highlight the dense smoke plumes drifting west-southwestward over the adjacent offshore waters of the Pacific Ocean.

A closer VIIRS image comparison (with county outlines) is shown below.

A comparison of Suomi NPP VIIRS true-color and false-color Red-Green-Blue (RGB) images from RealEarth (below) helped to discriminate between smoke and cloud features offshore over the Pacific Ocean.

===== 10 October Update =====With the switch to southwesterly surface winds on 10 October, smoke plumes could be seen moving northeastward on RealEarth VIIRS true-color imagery, while the burn scars of a number of the larger fires became apparent on VIIRS false-color RGB imagery (above).

===== 11 October Update =====

A toggle (above)  between 30-meter resolution Landsat-8 false-color RGB images from 04 October (before the Tubbs Fire) and 11 October (after the Tubbs Fire) showed the size of the fire burn scar (shades of brown) which extended southwestward from the fire source region into Santa Rosa.

===== 12 October Update =====A transition back to northerly winds on 12 October helped to transport the wildfire smoke far southward over the Pacific Ocean (above). Smoke was reducing surface visibility and adversely affecting air quality at locations such as San Francisco (below).

Suomi NPP VIIRS Aerosol Optical Depth values were very high — at or near 1.0 — within portions of the dense smoke plume (below).

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

October is typically not a month when tornadoes are expected in Wisconsin. (And in fact, the month ranks fourth in the numbers of fewest tornadoes nationwide). Nevertheless, a brief tornado occurred on the east side of Madison WI late in the afternoon on 7 October (NWS Milwaukee/Sullivan). The visible animation, above, from GOES-16, shows a thin line of weak convection moving through the central part of the state. A slower animation centered on the reported time of the tornado (2200 UTC), is below. The dynamic state of the thunderstorm tops is apparent, and the 5-minute time-step may not be sufficient to resolve the small time-scale changes in the tornadic storm (the two GOES-16 Mesoscale sectors that provide 1-minute imagery were covering the pending landfall of Hurricane Nate at this time, and were giving severe weather support to Puerto Rico, radar-less in the wake of Hurricane Maria).

The Clean Window Channel, below, with the default AWIPS enhancement, shows little cloud-top structure.

Coldest cloud-top brightness temperatures with this event were in the -15º to -20º C range, and the default enhancement (with a range from -109º to 55º) showed little gradation in that range. By changing the coldest temperature in the enhancement from -109º C to -43º C, however, a structure in the cold clouds emerged, as shown below. Do not be afraid to change enhancements!

The NOAA/CIMSS ProbSevere products for this event is shown below (from this site). ProbTor values were negligible; however, ProbWind values for the tornadic cell were around 20-24% leading up to the event. In addition, the cell that produced the tornado had the highest probabilities in the identified cells along the line of convection. The single exception occurred at 2235 UTC, after the severe weather event, when the cell to the north briefly (for only five minutes) showed Probabilities exceeding 40%.

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The National Weather Service in Milwaukee/Sullivan WI determined that the tornado was an EF-0 based on a damage assessment. They provided radar imagery at the start of the tornado, during the tornado, at its end, and after dissipation.

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

1-minute interval Mesoscale Sector GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed the large central dense overcast (which exhibited cloud-top infrared brightness temperatures of -80ºC and colder, violet colors, and at times -90ºC and colder, yellow enhancement) and subsequent smaller convective bursts associated with Hurricane Nate on 07 October 2017.

After having moved north-northwestward at speeds up to 24 mph — quite possibly the fastest-moving tropical cyclone on record in the Gulf of Mexico — Nate made its initial landfall (as a Category 1 storm) in Louisiana near the mouth of the Mississippi River at 00 UTC on 08 October 2017 [note: Nate’s second landfall was around 0530 UTC near Biloxi, Mississippi]. A few reports of damaging winds and tornadoes were noted ahead of and during Nate’s landfall; a listing of other wind gusts can be seen here.

Earlier in the day, DMSP-17 SSMIS Microwave (85 GHz) imagery was hinting at the development of a closed eye structure beneath the central dense overcast seen on GOES-13 Infrared Window (10.7 µm) imagery (below).

Even though Nate passed over very warm water in the Gulf of Mexico (below), the fast forward motion of the storm limited its ability to take advantage of those warm waters and rapidly intensify.

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An email from SSEC/CIMSS employee Shane Hubbard discussed details of a weak tornado in San Juan, Puerto Rico on 06 October 2017:

While I was working in San Juan last week a tornado formed close to the shoreline of Lake (Lagoon) Los Corozos, moved over the water, and then damaged homes in a neighborhood named ‘Playita’ where I was working. The tornado formed near 18.439089, -66.041962 on October 6th around 4:25pm AST. 10+ roofs were damaged from the event. Many of those roofs had already been repaired by residents or by the carpenters that were volunteering in the community. It was a very depressing event to say the least.

Here are links to the tornado.

https://www.youtube.com/watch?v=Oc8j4uLPQvg

Approximate tornado path (courtesy of Shane Hubbard)

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

A GOES-16 Mesoscale Sector remained positioned over Puerto Rico (to support their lack of weather radars, which were destroyed by Hurricane Maria; click here for a Tweet from NWS San Juan showing their radar damage) — “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed the region around San Juan (station identifier TJSJ).  An Infrared animation covering the time from 1915 UTC to 2054 UTC, displayed at the GOES-16 ABI full 12-bit depth (created using SIFT) is shown here; a visible animation is available here.

Convective initiation occurred over the far eastern end of the island about an hour before the tornado — cloud-top infrared brightness temperatures cooled to around -70ºC (black enhancement) around the time of the tornado (2025 UTC) during a second burst of convection.

Of particular note is the speed with which the second convective storm grew.  Between 2020 UTC and 2025 UTC, the cloud-top infrared brightness temperatures cooled 20ºC in the region of thunderstorm development!  The bar graphs below show the brightness temperature distribution in the region of convective development.

The animation below shows GOES-16 10.3 µm Clean Infrared Window images for 10 minutes: 2017-2026 UTC on 6 October. Very strong convective development is apparent, overlapping with the 2025 UTC time of the tornado.

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